Science Operations Specialist Michael Hoenig makes sure the telescope is operating smoothly from the Hilo Base Facility.
Scientist and project lead, Atsuko Nitta (colorful dress); Associate Director of Operations, Andy Adamson; and Director, Markus Kissler-Patig (left to right) congratulate staff for the success of BFO implementation, and their appreciation for the hard work that went into the BFO project at Gemini North.
Base Facility Operations (BFO) are now fully implemented for the Gemini North telescope. All operations are now routinely conducted each night from the Hilo Base Facility.
The implementation of BFO at Gemini North is the culmination of several years of work by most of Gemini's staff. This includes significant infrastructure improvements at the telescope and base facilities, software upgrades, staff training, and changes at all levels of operations. The result is a milestone that has revolutionized the way Gemini operates and acquires data.
Observing crews at Gemini North have been testing the BFO mode since September of 2015. The night crews report that observing is much more efficient in this mode, and the science staff were thrilled to see the system go live from Hilo as our standard operations model.
Gemini's Director Markus Kissler-Patig adds that in addition to this being a first for an 8-10 meter-class telescope, Gemini is also integrating the use of visitor instruments into BFO operations. "The recent visit of the Differential Speckle Survey Instrument (DSSI) produced a record number of observations when it observed up to 130 targets per night during its run operated remotely! This bodes well for the remarkable efficiency we can achieve with Base Facility Operations."
Based on the experience at Gemini North, Gemini South is now preparing for a similar switch to BFO by the end of this year.
For more details on Gemini's switch to BFO see the post on our public blog.
Gemini South Telescope with the Milky Way above.
Today, in the journal Science, Australian scientist Keith Bannister announced findings that might help solve a 30-year old mystery.
Bannister and his team used Gemini to provide baseline optical observations of a quasar (PKS 1939-315) which has displayed wild fluctuations in its radio emissions. The Gemini Director’s Discretionary Time program, using the Gemini Multi-Object Spectrograph at the Gemini South telescope, confirmed that the optical light is constant, while the radio emission changes. The steady optical light, concurrent with the radio variations, means that earlier optical surveys for dark clouds would not have found these. Also, these lenses must not be dusty, because dust would have reddened the quasar’s light.
The researchers conclude that the radio waves from the quasar (observed with Australia’s CSIRO Compact Array) are likely being focused and defocused by a thin “atmosphere” of electrically charged particles in our Milky Way Galaxy. According to the team, these clumps of gas are thought to take on shapes that are similar to lasagna noodles seen edge- on. The team speculates that the clumps could take on a variety of shapes from hazelnuts to noodles with sizes comparable to the diameter of the Earth’s orbit around the Sun.
Left: GPI J band (top) and K1 band (bottom) polarized intensity (Qr) images of the TW Hya disk. Right: Qr(i; j) scaled by r2(i; j), where r(i; j) is the distance (in pixels) of pixel position (i; j) from the central star, corrected for projection effects. All images are
shown on a linear scale. The coronagraph is represented by the black filled circles and images are oriented with north up and east to the left.
Image Credit: Gemini Observatory/AURA, Valerie Rapson - Rochester Institute of Technology (PI)
TW Hydrae (TW Hya) is one of the best-studied young stars in the galaxy.At just 180 light years from Earth and a ripe young age of roughly 8 million years, this nearly solar-mass star and its orbiting, circumstellar disk of dust and gas are prime targets to better understand the processes involved in star and planet formation. The most sensitive telescope systems available, accessing wavelengths from radio to X-ray, have observed the TW Hya system. Astronomers have now used the Gemini Planet Imager (GPI) on Gemini South to image infrared light from TW Hya that is scattered off dust grains in its surrounding disk. The new GPI images confirm the presence of a darkened ring or gap in the disk at 23 AU (i.e., 23 times the earth-Sun distance) -- and GPI brings this gap into the sharpest focus yet. Comparison with detailed numerical simulations of planets forming in circumstellar disks indicates that the 5-AU-wide gap's observed structure could be generated by a sub-Jupiter-mass planet orbiting within the disk at a position roughly equivalent to that of Uranus in our solar system. "These GPI data reveal tell-tale disk structure in the giant-planet-forming region around TW Hya at higher resolution than any other measurements to date," says Dr. Valerie Rapson of Rochester Institute of Technology, who led the research team. “The results will help us piece together the story of how giant planets form around sun-like stars.”
The paper is published in The Astrophysical Journal.
We present Gemini Planet Imager (GPI) adaptive optics near-infrared images of the giant-planet-forming regions of the protoplanetary disk orbiting the nearby (D = 54 pc), pre-main-sequence (classical T Tauri) star TW Hydrae. The GPI images, which were obtained in coronagraphic/polarimetric mode, exploit starlight scattered off small dust grains to elucidate the surface density structure of the TW Hya disk from ~80 AU to within ~10 AU of the star at ~1.5 AU resolution. The GPI polarized intensity images unambiguously confirm the presence of a gap in the radial surface brightness distribution of the inner disk. The gap is centered near ~23 AU, with a width of ~5 AU and a depth of ~50%. In the context of recent simulations of giant-planet formation in gaseous, dusty disks orbiting pre-main-sequence stars, these results indicate that at least one young planet with a mass ~0.2 MJ could be present in the TW Hya disk at an orbital semimajor axis similar to that of Uranus. If this (proto)planet is actively accreting gas from the disk, it may be readily detectable by GPI or a similarly sensitive, high-resolution infrared imaging system.
Figure 1. The massively star-forming galaxies analyzed in this study have clumpy, turbulent gas shown on the left (Hubble Telescope data). Through a unique combination of Gemini-GMOS and Keck-OSIRIS observations, the scientists were able to measure the velocity of these galaxies in each point, such as shown on the right in false colors.
Figure 2. Kinematic fits for the four clumpy targets. Column 1: Emission line fluxes of the Paα (OSIRIS) and Hβ (GMOS) lines, as indicated in parentheses; Hβ is shown in cyan for distinction from Paα. Columns 2&3: Density+velocity maps of data and models, respectively. Lightness represents the continuum surface brightness and hue represents the rest-frame line-of-sight velocity of the emission lines. A greyscale is used where only continuum data is available. White dashed lines show the best-fit major axes and half-mass ellipses. Columns 4&5: Maps of the line-of-sight velocity residuals ∆v 0 = v 0 − v 0 model and stellar density residuals ∆Σs = Σs – Σ models. Image Credit: Obreschkow, D. et. al.; ICRAR
A team of Australian researchers used two Maunakea-based observatories – Gemini North and W. M. Keck Observatory – to discover why some galaxies are clumpy rather than spiral in shape and it appears that low spin is to blame. The finding challenges an earlier theory that high levels of gas cause clumpy galaxies, and sheds light on the conditions that brought about the birth of most of the stars in the Universe. The finding was published today in The Astrophysical Journal.
A combination of integral field spectroscopy data from Keck Observatory and Gemini Observatory was the key to obtaining measurements for a galaxy’s spin. Keck Observatory’s OSIRIS instrument collected data high spatial resolution in the galaxy centers, and the Gemini Multi-Object Spectrograph (GMOS) collected data for high surface brightness sensitivity out to large radii.
The rest of the text is adapted from the International Centre for Radio Astronomy Research press release, which can be found here.
Lead author Dr. Danail Obreschkow, from The University of Western Australia (UWA) node of the International Centre for Radio Astronomy Research (ICRAR), said that ten billion years ago the Universe was full of clumpy galaxies, but these developed into more regular objects as they evolved; the majority of stars in the sky today, including our five billion-year-old Sun, were probably born inside these clumpy galaxies.
"The clumpy galaxies produce stars at phenomenal rates," Dr. Obreschkow said. "A new star pops up about once a week, whereas spiral galaxies, like our Milky Way, only form about one new star a year."
The research team – a collaboration between ICRAR and Swinburne University of Technology – focused on a few rare galaxies known as the DYNAMO galaxies, which still look clumpy even though they’re seen "only" 500 million years in the past. Obreschkow said looking at galaxies 500 million years ago was like looking at a passport photo taken a year ago.
"We see that galaxy the way it probably looks now… something could have happened to it, but it’s very unlikely," Obreschkow said. "The galaxies that are 10 billion light years away are comparable to a picture from when you were three or four years old; that’s very different."
The team combined high-resolution and large-radius spectroscopic maps taken from the Keck Observatory and Gemini Observatory in Hawai‘i to measure the spin of the galaxies and millimeter and radio telescopes to measure the amount of gas they contained. "We used Keck adaptive optics to probe the fine details of galaxy rotation and Gemini to look at the large scale distribution. This made possible a result that was not before known about the spin of early primitive galaxies. It is one of the most exciting results of my career," said Swinburne University astronomer Professor Karl Glazebrook, co-author and leader of the survey team. He said the finding was exciting because the first observation that galaxies rotate was made exactly 100 years ago.
Obreschkow said the DYNAMO galaxies had a low spin, which was the dominant cause of their clumpiness, rather than their high gas content as previously thought. "While the Milky Way appears to have a lot of spin, the galaxies we studied here have a low spin, about three times lower," he said.
"Today we are still revealing the important role that the spin of the initial cloud of gas plays in galaxy formation," Glazebrook said. "This novel result suggests that spin is fundamental to explaining why early galaxies are gas-rich and lumpy while modern galaxies display beautiful symmetric patterns."
Observations using the Gemini Planet Imager are featured prominently at the Extreme Solar Systems III meeting ongoing this week (Nov. 29 - December 4) in Waikoloa Hawai‘i. Below are two results from a press conference on December 1, 2015.
University of California Berkeley astronomer Paul Kalas and Abhijith Rajan (Arizona State University) kicked things off with a summary of their team’s work entitled “Resolving the HD 106906 Disk with the Gemini Planet Imager.” See the UC Berkeley press release.
Following the presentation by Kalas and Rijan, Subaru astronomer Thayne Currie presented his work on an early forming exoplanet system around the star HD 100546. For more details on this work see the Gemini Webfeature story “Astronomers Spy a Nursery of Baby Exoplanets.”
Figure 1. Image of Cheshire Cat gravitationally lensed galaxies produced by combining Chandra X-ray data with Hubble Space Telescope optical data. Gemini spectroscopy provided critical spectroscopic data for characterizing the foreground lensing cluster and understanding its history and likely fate as a "fossil group." Image Credit: Hubble Space Telescope and Chandra X-ray Observatory
Figure 2. Color–magnitude diagram of all galaxies detected in the GMOS images with r' brighter than 24.5 mag (595 galaxies, black dots). Blue circles and red squares are the spectroscopically confirmed members of the G1 and G2 groups respectively, with filled and open symbols representing which of these galaxies lie inside and outside of 0.5 r200 of the group. Red short dash and blue long dash vertical lines represent a two magnitude gap from the E and W eye galaxies, respectively. The black triangles represent spectroscopically confirmed background and foreground galaxies, while black dots represent objects without spectroscopic redshifts. The two central galaxies of the groups, SDSS J103843.58+484917.7 and SDSS J103842.68+484920.2 (the "eyes" of the Cheshire Cat) are represented by a letter (E and W) in the CMD.
Gemini observations provide a key scientific context for a striking new image of the gravitationally lensed galaxy group popularly known as the Cheshire Cat. The image, released by NASA’s Chandra X-ray Observatory, combines X-ray data with optical images from the Hubble Space Telescope to paint a remarkable likeness to the famously devious smiling cat in Lewis Carrol’s Alice in Wonderland.
Behind the scenes, Gemini played a critical role in the image’s scientific story by taking the spectral fingerprints of many of the galaxies that make up the foreground cluster which bends the distant galactic light. For more details on the image, and how gravitational lenses work, see the Chandra press release here.
Gemini South astronomer Rodrigo Carrasco, a co-author on the paper which spawned the image, adds that Gemini provided the core spectroscopic data that allowed the team to fully characterize the cluster of foreground galaxies which serves as the lens. "With the Gemini data we were able to study the individual members of the cluster which we expect will eventually become fossil groups," says Carrasco. Fossil groups consist of a giant elliptical central galaxy which is the end-product of interactions with other galaxies over billions of years, and surrounded by smaller, less bright galaxies. "Our results indicate that merging of fossil groups – in this case, the Cheshire Cat – could be one of the ways that a large fraction of fossil groups in the nearby Universe formed."
The paper, published in The Astrophysical Journal, is available here.
Abstract: The Cheshire Cat is a relatively poor group of galaxies dominated by two luminous elliptical galaxies surrounded by at least four arcs from gravitationally lensed background galaxies that give the system a humorous appearance. Our combined optical/X-ray study of this system reveals that it is experiencing a line of sight merger between two groups with a roughly equal mass ratio with a relative velocity of ∼1350 km s-1. One group was most likely a low-mass fossil group, while the other group would have almost fit the classical definition of a fossil group. The collision manifests itself in a bimodal galaxy velocity distribution, an elevated central X-ray temperature and luminosity indicative of a shock, and gravitational arc centers that do not coincide with either large elliptical galaxy. One of the luminous elliptical galaxies has a double nucleus embedded off-center in the stellar halo. The luminous ellipticals should merge in less than a Gyr, after which observers will see a massive 1.2 − 1.5 x 1014 M⊙ fossil group with an Mr = −24.0 brightest group galaxy at its center. Thus, the Cheshire Cat offers us the first opportunity to study a fossil group progenitor. We discuss the limitations of the classical definition of a fossil group in terms of magnitude gaps between the member galaxies. We also suggest that if the merging of fossil (or near-fossil) groups is a common avenue for creating present-day fossil groups, the time lag between the final galactic merging of the system and the onset of cooling in the shock-heated core could account for the observed lack of well-developed cool cores in some fossil groups.
Figure 1. Color composite-image of IMS J2204+0111 at z=6 (about 1 billion years after the Big Bang). IMS J2204+0111 is the red object at the center and its distance from us is 12.8 billion light years. Because of the expansion of the universe, distant objects like IMS J2204+0111 move away from us almost at the speed of the light, making their light to shift into near-infrared wavelength (phenomenon, called “redshift”). This makes them look very red in comparison to other objects, and this special color feature enabled the team to identify distant quasar candidates.
Full resolution JPEG
Figure 2: GMOS spectrum of IMS J2204+0111. A prominent break in the spectrum is visible at the wavelength of about 8500 Å. The feature corresponds to the Hydrogen Lyman-α line which has a wavelength of 1216 Å at rest. It is now shifted to 8500 Å, suggesting that this object is moving away from us at the redshift of 5.944. The sharp break is caused because neutral hydrogen around the quasar absorbed the light at the wavelength below the Lyman-α line.
The following is based on a translation of the Korean press release.
A team of Korean astronomers discovered a faint quasar in the early Universe which sheds light on the main sources of illumination about 1 billion years after the Big Bang. The team used the Gemini South telescope in Chile, and several telescopes on Maunakea in Hawai‘i, to make the discovery. This is the first published scientific result from the Korean astronomical community since the Korea Astronomy and Space Science Institute (KASI) joined in a limited partnership with Gemini at the beginning of 2015.
The history of objects we see today in the Universe started when the first stars formed a few hundred million years after the Big Bang. However, it has been unclear what types of objects illuminated the intergalactic medium in order to ionize neutral atoms (called the re-ionization of the universe).
Quasars, because they are so bright, have been suggested as one of the main “culprits” for the source of re-ionizing energy. Quasars shine when supermassive black holes at the centers of galaxies vigorously accrete gas and stars – they can blaze at up to 100 times the total brightness of their host galaxies. Knowing the number of quasars in the early Universe with moderate luminosity (from about a few to 10 times more luminous than our Milky Way galaxy) can provide an important clue to solving this puzzle, since moderate luminosity quasars dominate the available illumination provided by quasars.
However, moderate luminosity quasars are faint (because they are so distant), and rare, so it is challenging to find them. So far, only two or three such objects have been identified. In order to find moderate luminosity quasars at a redshift of 6 (or about one billion years after the Big Bang), the team performed a moderately wide and deep imaging survey, called the Infrared Medium-deep Survey (IMS) using the data taken with telescopes on Maunakea, including the United Kingdom Infrared Telescope, and the Canada-France-Hawai‘i Telescope. In a subset of these data, the team identified 7 faint quasar candidates. Subsequently, the spectrum of one of these quasars, obtained with the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South telescope in July 2015, revealed that the object is indeed a much sought-after moderate luminosity quasar in the early Universe.
The newly discovered quasar, named as IMS J220417.92+011144.8, is expected to harbor a black hole of about 10 million to 100 million solar masses. Its distance is about 12.8 billion light-years from us. The discovery of IMS J2204+0111 and the statistical results of the survey suggest that quasars can only contribute up to about 10% of the re-ionizing flux in the early Universe. This value is lower than expected and doesn’t provide enough energy to fully account for the re-ionization of the Universe. Additionally, the redshifts of the other quasar candidates are still unknown; if they turn out not to be quasars, this number would be reduced even further. Therefore, it is unlikely that quasars are the dominant sources of illumination in the early Universe: 90% or more of the light must originate from other objects.
The discovery was made possible thanks to the GMOS’s high sensitivity to infrared light where most of the light of such high-redshift quasars is concentrated. This work was carried out by Yongjung Kim (lead author), Myungshin Im (Principal Investigator), and Yiseul Jeon of Seoul National University, Minjin Kim at Korea Astronomy and Space Science Institute, and 14 other collaborators. The result was published in the November 10 issue of The Astrophysical Journal Letters, and the paper is available on the astro-ph.
Gemini South optical engineers inspect the primary mirror after 7-hour coating process.
The 8.1 meter primary mirror suspended on the 4th floor, before descending to the stripping/coating area on the first floor of the observatory building.
After 18 days of hard work during the recent scheduled maintenance shutdown, the Gemini South telescope is back on the sky! During maintenance, which took place October 13th - 30th, the 8.1-meter primary mirror received a fresh multi-layer protected silver coating - a key task for the shutdown.
Read more details about the Gemini South telescope's scheduled shutdown on the Gemini blog! http://www.gemini.edu/blog/blog/2015/11/02/back-on-the-sky-at-gemini-south/
30"x30" color composite g+r+i image using data from both Gemini and the NOT, highlighting the three brighter lensed quasar images for which time delays have now been measured. Image C leads all other images of the quasar by several years, and hence predicts the future behaviour. Lensing of quasars is achromatic, but the NOT data (r,i) and Gemini data (g) were taken at different times, and hence image C appears in this composite to be a different color than images A and B.
A team of Norwegian and US astronomers, using data from Gemini North and the Nordic Optical Telescope (NOT), have measured the time delay in images of a quasar lensed by a foreground cluster of galaxies. The Gemini observations are the first published result obtained with the innovative Fast Turnaround (FT) mode of observing.
A distant quasar may have its light split into multiple images by a foreground galaxy cluster that acts as a gravitational lens. The light travels along different paths of differing lengths to form each of these images. Quasars themselves are intrinsically variable, so the observed fading and brightening of each image happens at different observed times. Measuring these “time delays” yields tight constraints on the mass distribution in the lensing cluster, as well as the lensing geometry, and hence cosmology.
The team monitored the redshift z=2.82 quasar SDSS J2222+2745 over the course of three years, using the NOT and Gemini+GMOS-N. They found a time delay of 48 and 722 days for two pairs of the quasar’s lensed images. The Gemini data were instrumental in refining the time delay measurements for the quasar image that leads the other image by ~ 2 years and hence predicts the behavior of other images of the quasar; continuing monitoring of the system will now allow further observations that take advantage of that 2 year peek into the future.
Under Gemini’s FT mode, users can submit proposals every month and (if accepted) receive data 1-4 months after their initial proposal idea. The mode can be used for any kind of scientifically valuable project that needs just a few hours of observing time. Since the program’s launch in January, it has been used to follow up discoveries of new solar system objects, obtain data sets needed to complete projects, and also for short, self-contained programs. For more information, see the FT web pages: http://www.gemini.edu/sciops/observing-gemini/observing-modes/fast-turnaround.
This work is available on Astro-ph at: http://arxiv.org/abs/1505.06187.
We report first results from an ongoing monitoring campaign to measure time delays between the six images of the quasar SDSS J2222+2745, gravitationally lensed by a galaxy cluster. The time delay between A and B, the two most highly magnified images, is measured to be τAB=47.7±6.0 days (95% confidence interval), consistent with previous model predictions for this lens system. The strong intrinsic variability of the quasar also allows us to derive a time delay value of τCA=722±24 days between image C and A, in spite of modest overlap between their light curves in the current data set. Image C, which is predicted to lead all the other lensed quasar images, has undergone a sharp, monotonic flux increase of 60-75% during 2014. A corresponding brightening is firmly predicted to occur in images A and B during 2016. The amplitude of this rise indicates that time delays involving all six known images in this system, including those of the demagnified central images D-F, will be obtainable from further ground-based monitoring of this system during the next few years.
A special addition to this year’s programming is a week-long visit by the renowned science entertainers, Big Van “Scientists on Wheels.”
Credit: Gemini Observatory/AURA
Following his presentaiton to students, Gemini Astronomer Erich Wenderoth explains cosmological concepts to a group of students from San Nicolas school.
Viaje al Universo Coordinator, Maria Antonieta García provides directions to a group of students at the San Joaquin school during a Family Astro session.
Gemini Astronomer Rodrigo Carrasco shares his passion for astronomy with high school students at the San Joaquín school.
Gemini Observatory kicked off its week-long program Viaje al Universo with an opening ceremony at the University of La Serena. The annual program is an immersive week of fun, hands-on learning focusing on local students and teachers.
Gemini’s invited international guests also joined in the celebration, highlighting their program: The Big Van “Science on Wheels.” “We are thrilled to be able to engage local students and make them laugh, and even though they might not know it, learn science!”, said Alberto Vivó of of the three members of the Big Van troupe. More information about this group can be found at: www.thebigvantheory.com
“Gemini is thrilled that we have many new partners in our effort this year,” said Gemini Deputy Director Nancy Levenson. “It is indeed a sign that we are having an impact when our community steps up to participate actively in our work.”
The University of La Serena’s Deputy Director Jorge Catalán Ahumada emphasized the long-standing ties with Gemini in Chile, highlighting the importance of having a local Physics and Astronomy Department.
Gemini astronomer Erich Wenderoth, who is a regular visitor to local classrooms, adds that his experiences in area classrooms inspires him. “I find sharing what I do with local students so energizing. I look forward to someday when a young astronomer approaches me and reminds me of a talk I gave to their classroom in La Serena!” For the rest of this week classroom programs led by observatory engineers, scientists, and The Big Van troupé are scheduled in many area schools. These visits feature presentations and hands-on activities by staff from the Association of Universities for Research in Astronomy (AURA) observatories in Chile (Gemini, Cerro Tololo), Las Campanas, the Giant Magellan Telescope (GMT), The Office for the Protection of the Northern Sky Of Chile (OPCC), and the University of La Serena. In addition the week’s activities include StarLab portable planetarium programs, family activities, and educational workshops.
Along with schools visits, a special, limited engagement of the Big Van troupé at the Lighthouse CoffeeShop (Matta #570 La Serena) on Tuesday October 20th is planned for the public although tickets are completely sold out to attend the “Café ConCiencia” performance . Nevertheless, a public presentation by The Big Van at St. Mary’s School – El Milagro on Wednesday October 21st (registration at the school), a discussion panel of observatory professional and technical careers at Colegio San Joaquín on October 22nd and a workshop for the Department of Tourism of the Municipality of La Serena called “How to Communicate Effectively about Astronomy” scheduled for Friday 23rd are some of the activities that will happen outside schools.
Participating dignitaries included: La Serena’s Mayor representative, City Council Member Robinson Hernández; Gemini Deputy Director Nancy Levenson; University of La Serena’s representative Jorge Ahumada Catalán, and local officials who joined teachers along with other community leaders who participated in the ribbon-cutting ceremony.
For more on Viaje al Universo, please visit: www.gemini.edu/viaje
Figure 1. Color composite image of the central region of NGC 253, from Flamingos 2 images using the filters J (blue), H (green) and Ks (red). This region of the edge-on viewed galaxy appears completely veiled in optical images due to the presence of large amounts of dust (so dense that it is still obscuring some regions at the near-infrared spectral range). The wavelength range covered by F-2 goes from 1 to 2.5 μm. The field of view is 420 x 144 arcseconds.
Figure 2. Color composite image of the core region of NGC 253, from T-ReCS images using the filters Si-2 (blue), [NeII] (green) and Qa (red). The nucleus candidate IRC appears as the brightest object in the infrared. The wavelength range covered by T-ReCS images goes from 8 to 20 μm. The field of view is 32 x 23 arcseconds.
The nearest spiral galaxy with a nuclear starburst (greatly enhanced star formation near a galaxy’s center) is also the site of a long-standing astronomical mystery. Designated NGC 253, or by amateurs as the Silver Dollar Galaxy, the core of this galaxy is so shrouded by gas and dust that the exact location of its core has remained unresolved for years. Now, thanks to research by Guillermo Günthardt of the National University of Cordoba (Argentina), Gemini South infrared data appear to have unambiguously pinpointed the galaxy’s core. In the process, evidence for a lowish-mass, but rapidly growing, black hole as the starburst’s trigger is painting a new picture of this enigmatic galaxy (Figure 1).
NGC 253 is the nearest spiral galaxy with a nuclear starburst. The nuclear region is so veiled by large amounts of dust associated to the star formation process that it has been unclear, until now, where this galaxy’s true galactic nucleus lies. Guillermo Günthardt, from the National University of Cordoba (Argentina), and an international team suggest that the brightest near- and mid-infrared source in the central region, named the IRC (Infrared Core) by the authors, is the galaxy’s core. Long considered just a large young star cluster, Günthardt et al. present several features leading to the conclusion this source is the genuine galactic nucleus. This contradicts the previous idea that a source called TH2 (a bright fuzzy radio source catalogued by Turner and Ho in 1985) is the best candidate for the nucleus.
In the team’s paper, to appear in the next issue of The Astronomical Journal the team presents kinematic, spectrophotometric, and morphological evidence that support the hypothesis that the IRC is NGC 253's galactic nucleus. This includes the fact that the IRC is the most massive object in NGC 253's central region, the major source of the nuclear starburst outflow, the molecular gas rotation center, and it is almost coincident with the galactic bar symmetry center.
Günthardt’s team obtained near-infrared observations with Flamingos 2 (F2) on the Gemini South telescope, including spectroscopy and images in four bands. In order to penetrate the veil of dust deeper, F2 observations were complemented by mid-infrared images obtained at Gemini South with T-ReCS (Thermal-Region Camera Spectrograph) in 2011, again, using four filters. At near- and mid-infrared wavelengths the IRC, TH7 in the radio source catalogue, appears an order of magnitude brighter than any other objects in the central region of NGC 253, moreover, there is no infrared source detected at the previous candidate position (TH2). The T-ReCS high-spatial-resolution images show a shell-like structure around the IRC, and F2 spectra show the largest turbulence motions in the ionized gas at this location, with expanding velocities over 500 km per second. This observation reveals that the IRC is also the main present source of the galaxy-wide gaseous winds detected in 2013 with ALMA by Bolatto et al.
The innermost radial velocity measures of the molecular gas do not exclude the possible presence of a few million solar masses black hole at the center of the IRC. Considering that NGC 253 is a large spiral galaxy with a mass of more than 7 x 1011 times the mass of our Sun, the IRC is an unexpectedly lightweight core, but which might be growing rapidly as it co-evolves with the violent star-formation process taking place in the galaxy’s nuclear region.
The off-center position of the IRC and of the nuclear disk, with respect to the galaxy’s bulge of stars, also contributed to the historic uncertainty in the nucleus location and implies a decoupling of the central gas and nuclear cluster from the older galactic structure. In 2015 Emsellem et al. theorized just such a decoupling using numerical simulation models in which a small nuclear core oscillates around the center of symmetry of a barred galaxy. In such a scenario, the small black hole in NGC 253 would not only grow rapidly while it accretes the dense nuclear gas, but also would efficiently trigger star formation due to its dance around the galaxy’s geometrical center.
This work is available on Astro-ph at: http://arxiv.org/abs/1509.00330
NGC253 is the nearest spiral galaxy with a nuclear starburst, which becomes the best candidate to study the relationship between starburst and AGN activity. However, this central region is veiled by large amounts of dust, and it has been so far unclear which is the true dynamical nucleus. The near infrared spectroscopy could be advantageous in order to shed light on the true nucleus identity. Using Flamingos 2 at Gemini South we have taken deep K-band spectra along the major axis and through the brightest infrared source. We present evidence showing that the brightest near infrared and mid infrared source in the central region, already known as radio source TH7 and so far considered just a stellar supercluster, in fact, presents various symptoms of a genuine galactic nucleus. Therefore, it should be considered a valid nucleus candidate. It is the most massive compact infrared object in the central region, located at 2.0 arcseconds of the symmetry center of the galactic bar. Moreover, our data indicate that this object is surrounded by a large circumnuclear stellar disk and it is also located at the rotation center of the large molecular gas disk of NGC 253. Furthermore, a kinematic residual appears in the H2 rotation curve with a sinusoidal shape consistent with an outflow centered in the candidate nucleus position. The maximum outflow velocity is located about 14 parsecs from TH7, which is consistent with the radius of a shell detected around the nucleus candidate observed at 18.3 μm (Qa) and 12.8 μm ([NeII]) with T-ReCS. Also, the Brγ emission line profile is blue-shifted and this emission line has also the highest equivalent width at this position. All these evidences point out TH7 as the best candidate to be the galactic nucleus of NGC 253.
Left: (Ks, F606W-Ks) color–magnitude diagram of NGC 1851; the detail of the double SGB is shown in the inset. Right: same as the left panel with average photometric (random) uncertainties indicated. Overlaid is the fiducial line with the approximate locations of the main sequence turnoff and main sequence knee highlighted by red dots.
Expecting to resolve stars deep into the crowded field of a globular cluster is a tall order for ground-based telescopes. However, Paolo Turri (University of Victoria, Canada) and colleagues have used the Gemini Multi-conjugate adaptive optics System (GeMS) with the Gemini South Adaptive Optics Imager (GSAOI) to do just that. Their data present the most accurate and deepest near-infrared photometry from the ground of a crowded field. It also illustrates the remarkable potential of MCAO-equipped Extremely Large Telescopes of the future.
Their Ks measurements of the Galactic globular cluster NGC 1851 are combined with HST photometry and the resulting color-magnitude diagram demonstrates that the ground-based data is of an unprecedented depth and precision for crowded field observations. The delivered image quality approaches Gemini’s diffraction limit, with an average measured full-width at half-maximum (FHWM) of 0.09 arcsecond. The work is published in The Astrophysical Journal Letters.
The Extremely Large Telescopes currently under construction have a collecting area that is an order of magnitude larger than the present largest optical telescopes. For seeing-limited observations the performance will scale as the collecting area, but with the successful use of adaptive optics (AO), for many applications it will scale as D4 (where D is the diameter of the primary mirror). Central to the success of the ELTs, therefore, is the successful use of multi-conjugate adaptive optics (MCAO) which applies a high degree of correction over a field of view larger than the few arcseconds that limits classical AO systems. In this Letter, we report on the analysis of crowded field images taken on the central region of the galactic globular cluster NGC 1851 in the Ks band using the Gemini Multi-conjugate Adaptive Optics System (GeMS) at the Gemini South Telescope, the only science-grade MCAO system in operation. We use this cluster as a benchmark to verify the ability to achieve precise near-infrared photometry by presenting the deepest Ks photometry in crowded fields ever obtained from the ground. We construct a color–magnitude diagram in combination with the F606W band from the Hubble Space Telescope/Advanced Camera for Surveys. As well as detecting the “knee” in the lower main sequence at Ks '20.5, we also detect the double subgiant branch of NGC 1851, which demonstrates the high photometric accuracy of GeMS in crowded fields.
The HH 24 jet complex emanates from a dense cloud core that hosts a small multiple protostellar system known as SSV63. The nebulous star to the south is the visible T Tauri star SSV59. Color image based on the following filters with composite image color assignments in parenthesis: g (blue), r (cyan), I (orange), hydrogen-alpha (red), sulfur II (blue)) images obtained with GMOS on Gemini North in 0.5 arcsecond seeing, and NIRI. Field of view is 4.2x5.1 arcminutes, orientation: north up, east left. Image produced by Travis Rector.
A new Gemini Observatory image reveals the remarkable “fireworks” that accompany the birth of stars. The image captures in unprecedented clarity the fascinating structures of a gas jet complex emanating from a stellar nursery at supersonic speeds. The striking new image hints at the dynamic (and messy) process of star birth. Researchers believe they have also found a collection of runaway (orphan) stars that result from all this activity..
Gemini Observatory has released one of the most detailed images ever obtained of emerging gas jets streaming from a region of newborn stars. The region, known as the Herbig-Haro 24 (HH 24) Complex, contains no less than six jets streaming from a small cluster of young stars embedded in a molecular cloud in the direction of the constellation of Orion.
"This is the highest concentration of jets known anywhere," says Principal Investigator Bo Reipurth of the University of Hawaii’s Institute for Astronomy (IfA), who adds, "We also think the very dynamic environment causes some of the lowest mass stars in the area to be expelled, and our Gemini data are supporting that idea."
Reipurth along with co-researcher, Colin Aspin, also at the IfA, are using the Gemini North data from the Gemini Multi-Object Spectrograph (GMOS), as well as the Gemini Near-Infrared Imager, to study the region which was discovered in 1963 by George Herbig and Len Kuhi. Located in the Orion B cloud, at a distance of about 400 parsecs, or about 1,300 light-years from our Solar System, this region is rich in young stars and has been extensively studied in all types of light, from radio waves to X-rays.
"The Gemini data are the best ever obtained from the ground of this remarkable jet complex and are showing us striking new detail," says Aspin. Reipurth and Aspin add that they are particularly interested in the fine structure and "excitation distribution" of these jets.
"One jet is highly disturbed, suggesting that the source may be a close binary whose orbit perturbs the jet body," says Reipurth.
The researchers report that the jet complex emanates from what is called a Class~I protostar, SSV63, which high-resolution infrared imaging reveals to have at least five components. More sources are found in this region, but only at longer, submillimeter wavelengths of light, suggesting that there are even younger, and more deeply embedded sources in the region. All of these embedded sources are located within the dense molecular cloud core.
A search for dim optical and infrared young stars has revealed several faint optical stars located well outside the star-forming core. In particular, a halo of five faint Hydrogen-alpha emission stars (which emit large amounts of red light) has been found with GMOS surrounding the HH 24 Complex well outside the dense cloud core. Gemini spectroscopy of the hydrogen alpha emission stars show that they are early or mid-M dwarfs (very low-mass stars), with at least one of which being a borderline brown dwarf.
The presence of these five very low-mass stars well outside the star-forming cloud core is puzzling, because in their present location the gas is far too tenuous for the stars to have formed there. Instead they are likely orphaned protostars ejected shortly after birth from the nearby star-forming core. Such ejections occur when many stars are formed closely together within the same cloud core. The crowded stars start moving around each other in a chaotic dance, ultimately leading to the ejection of the smallest ones.
A consequence of such ejections is that pairs of the remaining stars bind together gravitationally. The dense gas that surrounds the newly formed pairs brakes their motion, so they gradually spiral together to form tight binary systems with highly eccentric orbits. Each time the two components are closest in their orbits they disturb each other, leading to accretion of gas, and an outflow event that we see as supersonic jets. The many knots in the jets thus represent a series of such perturbations.
For release on September 16th, 2015
Contacts at end of release
See the Dunlop Observatory/University of Toronto version of this release here.
A team of astronomers has given us our best view yet of an exoplanet moving in its orbit around a distant star. A series of images captured between November 2013 to April 2015 shows the exoplanet β Pic b as it moves through 1 ½ years of its 22-year orbital period.
First discovered in 2008, β Pic b is a gas giant planet ten to twelve times the mass of Jupiter, with an orbit roughly the diameter of Saturn’s. It is part of a dynamic and complex system that includes comets, orbiting gas clouds, and an enormous debris disk that in our Solar System would extend from Neptune’s orbit to nearly two thousand times the Sun/Earth distance. Because the planet and debris disk interact gravitationally, the system provides astronomers with an ideal laboratory to test theories on the formation of planetary systems beyond ours.
Maxwell Millar-Blanchaer, a PhD-candidate in the Department of Astronomy & Astrophysics, University of Toronto, is lead author of a paper to be published September 16th in the Astrophysical Journal. The paper describes observations of the β Pictoris system made with the Gemini Planet Imager (GPI) instrument on the Gemini South telescope in Chile.
"The images in the series represent the most accurate measurements of the planet’s position ever made," says Millar-Blanchaer. "In addition, with GPI, we're able to see both the disk and the planet at the exact same time. With our combined knowledge of the disk and the planet we’re really able to get a sense of the planetary system’s architecture and how everything interacts."
The paper includes refinements to measurements of the exoplanet’s orbit and the ring of material circling the star which shed light on the dynamic relationship between the two. It also includes the most accurate measurement of the mass of β Pictoris to date and shows it is very unlikely that β Pic b will pass directly between us and its parent star.
"It’s remarkable that Gemini is not only able to directly image exoplanets but is also capable of effectively making movies of them orbiting their parent star," said Chris Davis, astronomy division program director at the National Science Foundation, which is one of five international partners that funds the Gemini twin telescopes’ operation and maintenance. "Beta Pic is a special target. The disk of gas and dust from which planets are currently forming was one of the first to be observed and is a fabulous laboratory for the study of young solar systems.”
Astronomers have discovered nearly two thousand exoplanets in the past two decades but most have been detected with instruments – like the Kepler space telescope – that use the transit method of detection: astronomers detect a faint drop in a star’s brightness as an exoplanet transits or passes between us and the star, but do not see the exoplanet itself.
With GPI, astronomers image the actual planet – a remarkable feat given that an orbiting world typically appears a million times fainter than its parent star. This is possible because GPI's adaptive optics sharpen the image of the target star by cancelling out the distortion caused by the Earth’s atmosphere; it then blocks the bright image of the star with a device called a coronagraph, revealing the exoplanet.
Laurent Pueyo is with the Space Telescope Science Institute and a co-author on the paper. "It’s fortunate that we caught β Pic b just as it was heading back – as seen from our vantage point – toward β Pictoris," says Pueyo. "This means we can make more observations before it gets too close to its parent star and that will allow us to measure its orbit even more precisely."
GPI is a groundbreaking instrument that was developed by an international team led by Stanford University’s Prof. Bruce Macintosh (a U of T alumnus) and the University of California Berkeley’s Prof. James Graham (former director of the Dunlap Institute for Astronomy & Astrophysics, University of Toronto). In August 2015, the team announced its first exoplanet discovery: a young Jupiter-like exoplanet designated 51 Eri b. It is the first exoplanet to be discovered as part of the GPI Exoplanet Survey (GPIES) which will target 600 stars over the next three years.
Continuing Gemini Observatory’s commitment to the positive stewardship of our planet, Gemini leads in the use of renewable energy sources on Maunakea.
Gemini Observatory in Hilo, Hawai‘i has finished the installation of photovoltaic (PV) solar panels on the roof of its telescope on Maunakea this week. The PV panels were installed by Maui Pacific Solar and took about six weeks to complete.
"The PV panels [on Maunakea] are the second highest in the world by about 200 feet [~61 meters]. The highest are in Tibet." says Maui Pacific Solar Founder and President Mike Carroll. "However, it is the highest rooftop mounted PV system in the world that is connected to the utility."
The solar panels will (conservatively) generate about 10% of the power required to operate the Maunakea facility, and will be roughly 70% more energy productive than the panels planned for installation on the roof of the observatory’s base facility in Hilo.
The table below shows a side-by-side comparison of PV panel installation at the Hilo Base Facility versus the Gemini North telescope on Maunakea. The reason for this productivity boost on Maunakea is a combination of clear skies, lower temperatures, and less absorption in the atmosphere.
|Peak Sun Hours||4.6 hours||6.4 hours||39%|
|Average Ambient Temperature||80℉/26.7℃||45℉/7.2℃||10%|
|Elevation||Sea-level||13,790 feet/4,203 meters||10%|
Employees of Maui Pacific Solar braved elevation fatigue and adverse weather to install the panels ahead of the anticipated November deadline.
"There are lots of challenges working at that high elevation. Not only are you working at about 60% of sea-level oxygen levels," says Carroll, “but it also snowed in July!"
Gemini Observatory continues to explore new ways to improve operational efficiency. "While PV panels require a significant investment," says Gemini Lead Engineer Chas Cavedoni, "we predict that the investment will be recovered in less than four years."
The solar panels are scheduled for connection to the electrical grid within a month.
Figure 1. Discovery image of 51 Eri b with the Gemini Planet Imager taken in the near-infrared light on December 18, 2014. The bright central star has been mostly removed by a hardware and software mask to enable the detection
of the exoplanet one million times fainter. Credits: J. Rameau (UdeM) and C. Marois (NRC Herzberg).
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Figure 2. An artistic conception of the Jupiter-like exoplanet, 51 Eri b, seen in the near-infrared light that shows the hot layers deep in its atmosphere glowing through clouds. Because of its young age, this young cousin of our own Jupiter is still hot and carries information on the way it was formed 20 million years ago. Credits: Danielle Futselaar & Franck Marchis, SETI Institute.
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Fly-by video in AVI (600MB)
The simulated fly-by of the 51 Eridani star and planet system begins with the view of the sky showing the location of the star near the constellation Orion visible in the northern hemisphere winter. The young star 51 Eridani is 100 light-years from the Sun and a Jupiter-like planet is directly imaged in the infrared in an orbit similar in size to the Sun-Saturn distance. The star also has indirect evidence of belts of rocky debris orbiting closer and farther to the the star than the new planet. The fly-by ends with a view back toward the Sun from the newly discovered planet.Credits: J. Patience & J. Cornelison (ASU).
The Gemini Planet Imager utilizes an integral field spectrograph, an instrument capable of taking images at multiple wavelengths – or colors – of infrared light simultaneously, in order to search for young self-luminous planets around nearby stars. The left side of the animation shows the GPI images of the nearby star 51 Eridani in order of increasing wavelength from 1.5 to 1.8 microns. The images have been processed to suppress the light from 51 Eridani, revealing the exoplanet 51 Eridani b (indicated) which is approximately a million times fainter than the parent star. The bright regions to the left and right of the masked star are artifacts from the image processing algorithm, and can be distinguished from real astrophysical signals based on their brightness and position as a function of wavelength. The spectrum of 51 Eridani b, on the right side of the animation, shows how the brightness of the planet varies as a function of wavelength. If the atmosphere was entirely transmissive, the brightness would be approximately constant as a function of wavelength. This is not the case for 51 Eridani b, the atmosphere of which contains both water (H2O) and methane (CH4). Over the spectral range of this GPI dataset, water absorbs photons between 1.5 and 1.6 microns, and methane absorbs between 1.6 and 1.8 microns. This leads to a strong peak in the brightness of the exoplanet at 1.6 microns, the wavelength at which absorption by both water and methane is weakest.Robert De Rosa (UC Berkeley), Christian Marois (NRC Herzberg, University of Victoria).
Going beyond the discovery and imaging of a young Jupiter, astronomers using the Gemini Observatory's new Planet Imager (GPI) have probed a newly discovered world in unprecedented detail. What they found is a planet about two times the mass of Jupiter, and the most Solar System-like planet ever directly imaged around another star.
The planet, known as 51 Eridani b, orbits its host star at about 13 times the Earth-Sun distance (equivalent to being between Saturn and Uranus in our Solar System). The system is located about 100 light years away. The Gemini data also provide scientists with the strongest-ever spectroscopic detection of methane in the atmosphere of a planet outside of our Solar System, adding to its similarities to giant planets in our Solar System.
"Many of the exoplanets astronomers have imaged before have atmospheres that look like very cool stars" said Bruce Macintosh, of Stanford University who led the construction of GPI and now leads the planet-hunting survey. "This one looks like a planet."
The research is published in the August 13, 2015 issue of the journal Science.
"This superb result is a clear demonstration of the remarkable imaging and spectroscopic capabilities of GPI," said Chris Davis, the US National Science Foundation (NSF) Astronomy Division program officer who oversees Gemini Observatory funding. "The exoplanet surveys now possible with Gemini will undoubtedly lead to a far better understanding of the numbers of gas giants orbiting neighboring stars, the characteristics of their atmospheres, and ultimately the way in which giant planets like Jupiter and Saturn are formed."
The discovery is part of the team's broader effort to find and characterize new planets called the GPI Exoplanet Survey (GPIES). The survey expects to explore over 600 stars that could host planetary systems; so far they've looked at almost a hundred stars. "This is exactly the kind of system we envisioned discovering when we designed GPI", says James Graham, professor at UC Berkeley and Project Scientist for GPI.
"GPI is capable of dissecting the light of exoplanets in unprecedented detail so we can now characterize other worlds like never before," says Christian Marois of the National Research Council of Canada (NRC). Marois, one of almost 90 researchers on the team, pioneered many of the observation strategies and data reduction techniques that played a critical role in the detection and analysis of the new planet. The light from the planet is very faint – a million times fainter than the star – but GPI can see it clearly. "The planet is so faint and located so close to its star, that it is also the first directly imaged exoplanet to be fully consistent with Solar System-like planet formation models," adds Marois.
The Gemini observations were also followed up by the W.M. Keck Observatory on Maunakea in Hawaii to verify the discovery.
GPI Instrument Scientist, Fredrik Rantakyro, added, "Since I was a child, I dreamed about planets around other stars and the possible lives that could be out there. As an astronomer, it's common to work with state-of-the-art telescopes but not to make your heart beat faster. This is exactly what happened with this dream-come-true discovery of this brother to Jupiter!"
51 Eridani is young – only 20 million years old – and this is exactly what made the direct detection of the planet possible. When planets coalesce, material falling into the planet releases energy and heats it up. Over the next hundred million years they radiate that energy away, mostly as infrared light, and gradually cool.
In addition to being what is likely the lowest-mass planet ever imaged, its atmosphere is also very cool – 430 degrees C (800 degrees Fahrenheit). It also features the strongest spectroscopic atmospheric methane signal, similar to the heavy methane dominated atmospheres of the gas giant planets in our Solar System.
GPI Exoplanet Survey (GPIES) is currently less than 20% through the 600 targets slated for observations during the 3-year campaign. The targets were selected because of their youth and relatively close proximity to our Solar System (within about 300 light years). The results of this survey will be remarkable, as it is probing a regime of exoplanet mass and separation that have never been properly surveyed before. It is expected to provide the first detailed census and demography of gas giant exoplanets, to find several multi-planet systems, and to perform detailed spectral characterization of many new exoplanets.
GPI was made possible with funding by the US National Science Foundation and Gemini partnership to support the work of an international team from the US and Canada. Lawrence Livermore National Laboratory constructed GPI's adaptive optics system and worked to match it to the Gemini telescope. Engineers with the National Research Council of Canada (NRC) designed and built GPI's optical-mechanical structure, and wrote the top level and mechanical control software. UCLA produced GPI's infrared spectrograph. The American Museum of Natural History developed starlight-blocking masks. JPL was responsible for a precision wavefront sensor. University of Montreal, the Space Telescope Science Institute, and other members of the GPI team produced the data analysis software.
Figure 1. NIR Spectral type histogram of all known low-gravity dwarfs and those presented in this work. Green bars delimited by dashed lines represent the known population prior to BASS, purple bars delimited by dash-dotted lines represent known dwarfs for which low-gravity features were identified here for the first time, and orange bars delimited by solid lines represent new discoveries from BASS. The BASS survey has contributed significantly in increasing the number of known low-gravity M6–L5 dwarfs.
An international team of astronomers from Canada and the United States recently discovered 42 new brown dwarfs using data from the near-infrared imager and spectrograph Flamingos-2 at Gemini South and other telescopes in Chile and Hawai’i. The team used Flamingos-2’s near-infrared spectroscopic capabilities to study a total of 101 targets from 2013 to 2015.
The work, led by Jonathan Gagne, from the University of Montreal, confirmed signs of low-gravity for 42 of the objects with estimated masses between 8 to 75 times that of Jupiter. Further, the team identified previously unrecognized signs of low gravity for 24 known brown dwarfs.
This kind of object has an important role in explaining part of the process of star formation, as current stellar formation models include the production of a non-negligible fraction of free-floating planets. Additionally, the research shows that some objects, that were thought to be brown dwarfs, were indeed much less massive, and similar to planetary mass objects.
Gagne’s research also provides a context for ongoing work with the Gemini Planet Imager (GPI) because these objects are easier to observe without the glare from a nearby host star of GPI targets. “One big question that remains unanswered is whether these isolated planets significantly differ from objects in orbit around stars. There are some reasons to expect differences, but no one has been able to demonstrate a difference to date,” explains Etienne Artigau, an astronomer on the team who is also at the University of Montreal. This work will be published in The Astrophysical Journal Supplement Series, and a preprint is now available.
We present the results of a near-infrared (NIR) spectroscopic follow-up survey of 182 M4–L7 low-mass stars and brown dwarfs (BDs) from the BANYAN All-Sky Survey (BASS) for candidate members of nearby, young moving groups (YMGs). We confirm signs of low-gravity for 42 new BD discoveries with estimated masses between 8–75MJup and identify previously unrecognized signs of low gravity for 24 known BDs. This allows us to refine the fraction of low-gravity dwarfs in the high-probability BASS sample to 82%. We use this unique sample of 66 young BDs, supplemented with 22 young BDs from the literature, to construct new empirical NIR absolute magnitude and color sequences for low-gravity BDs. We show that low-resolution NIR spectroscopy alone cannot differentiate between the ages of YMGs younger than 120 Myr, and that the BTSettl atmosphere models do not reproduce well the dust clouds in field or low-gravity L-type dwarfs. We obtain a spectroscopic confirmation of low-gravity for 2MASS J14252798–3650229, which is a new 27MJup, L4 γ bona fide member of AB Doradus. We identify in this work a total of 19 new low-gravity candidate members of YMGs with estimated masses below 13MJup, seven of which have kinematically estimated distances within 40 pc. These objects will be valuable benchmarks for a detailed atmospheric characterization of planetary-mass objects with the next generation of instruments such as the James Webb Space Telescope. We find 16 strong candidate members of the Tucana-Horologium association with estimated masses between 12.5–14MJup, a regime where our study was particularly sensitive. This would indicate that for this association there is at least one isolated object in this mass range for every 17:5+6:6-5:0 main-sequence stellar member, a number significantly higher than expected based on standard log-normal initial mass function, however in the absence of radial velocity and parallax measurements for all of them, it is likely that this over-density is caused by a number of young interlopers from other moving groups. Finally, as a byproduct of this project, we identify 12 new L0–L5 field BDs, seven of which display peculiar spectroscopic properties.
THE FOLLOWING ITEM WAS ISSUED BY THE NATIONAL OPTICAL ASTRONOMY OBSERVATORY IN TUCSON, ARIZONA.
The new image of NGC 2346 showing unprecedented resolution of the molecular hydrogen gas. The image is about 1 arc minute on a side: north is up, east is to the left. In contrast, the size of the full moon is 30 arc minutes. Image from GeMS/GSAOI Multi-Conjugat Adaptive Optics System.
Computer simulation showing how the nebula is expected to evolve over a period of about 9,000 years. Presently the nebula is just starting this process. The thumbnail above shows the process in nine, 1,000 year, steps. There is also version of the movie that uses increments of 200 years.
Dr. Katy Garmany
NOAO Deputy Press Officer
Dr. Letizia Stanghellini
NOAO scientists, using the Gemini Observatory 8-meter telescope in Chile, have obtained the highest resolution image ever obtained for the planetary nebula NGC 2346. Shaped like a butterfly, or an hourglass, but known scientifically as a bipolar planetary nebula, this object is at a distance of 2,300 light-years from our Sun in the constellation Monoceros.
The new observations of this gaseous nebula, shown in the first figure, resolve details comparable in size to our own solar system. The team detected previously unresolved knots and filaments of molecular hydrogen gas -- details that no other telescope on the ground or in space, not even the Hubble Space Telescope, has been able to resolve.
Molecular hydrogen in the bipolar lobes of NGC 2346 was detected almost 30 years ago, although previous observations suggested only a smooth torus. This filamentary structure observed by the team matches the mechanism they have proposed in which a hot bubble of gas surrounding the central star breaks out and fragments the shell of surrounding gas. The gaseous knots probably represent a common phenomenon that occurs whenever two fluids (or gases) of different densities come in contact, and the lighter fluid is pushing on the heavier fluid. This is easily seen by anyone who has ever watched colored oil in a glass of water.
The authors have constructed computer models to understand how the gases are expected to interact: the accompanying movie shows how the gas will evolve in time. As first author Arturo Manchado said, “In this movie we show the model results in time steps up to 9,000 years. The blue color corresponds with the emission of the molecular hydrogen gas. The model shows an initial toroid of cool gas at the equator. Once the swept-up shell is highly fragmented, the toroid is no longer visible and only the large clumps will be seen.”
NGC 2346 is a star caught in the final phases of its lifecycle. It began life as a double star system, each companion about twice as massive as the Sun and both revolving around their common center of gravity. The more massive of the two stars burned through its fuel faster than its lower mass companion, expanded as a red giant, and has now shed its outer layers to become a white dwarf star, with a present mass between 0.3 and 0.7 solar mass. The bipolar nebula, or butterfly shape of this planetary, has probably been sculpted by the star pair, although this is still under study. With an orbital period of 16 days, the two stars are closer together than the Sun and Mercury. Material spilling from the more massive star over the lifetime of the pair makes it difficult to calculate the initial mass of the star.
The observations were taken with the new near infrared Adaptive Optics Imager system on the Gemini telescope during the initial testing phase of this instrument. Adaptive optics is a novel technique that allows for real time correction of distortions to an astronomical image caused by the Earth’s atmosphere.
“High Resolution Imaging of NGC 2346 with GSAOI/GeMS: Disentangling the Planetary Nebula Molecular Structure to Understand Its Origin and Evolution,” Arturo Manchado, Letizia Stanghellini, Eva Villaver, Guillermo Garcia-Segura, Richard A. Shaw & D. A. Garcia-Hernandez, 2015, Astrophysical Journal [http://apj.aas.org, preprint: http://arxiv.org/abs/1506.03712].
NOAO is operated by Association of Universities for Research in Astronomy Inc. (AURA) under a cooperative agreement with the National Science Foundation.
Gemini Observatory near-infrared image of the globular cluster Liller 1 obtained with the GeMS adaptive optics system on the Gemini South telescope in Chile.
Credit: Gemini Observatory/AURA
Summary: Using the advanced adaptive optics system GeMS, on the Gemini South telescope, astronomers have imaged a beautiful stellar jewel-box – a tightly packed cluster of stars that is one of the few places in our galaxy where astronomers think stars can actually collide.
Scientists have imaged a cluster of stars, heavily obscured by material in our galaxy, where stars are so densely packed that it is likely a rare environment where stars can collide. “It’s a bit like a stellar billiards table; where the probability of collisions depends on the size of the table and on the number of billiard balls on it,” said Francesco R. Ferraro of the University of Bologna (Italy), one of the team members who used the Gemini Observatory to make the observations.
The cluster of stars, known as Liller 1, is a difficult target to study due to its distance and also because it is located close to the center of the Milky Way (about 3,200 light-years away from it), where the obscuration by dust is very high. The unprecedented ultra-sharp view of the cluster reveals a vast city of stars estimated by the team to contain a total mass of at least 1.5 million suns, very similar to the most massive globular clusters in our galaxy: Omega Centauri and Terzan 5.
“Although our galaxy has upwards of 200 billion stars, there is so much vacancy between stars that there are very few places where suns actually collide,” said Douglas Geisler, Principal Investigator of the original observing proposal, from University of Concepcion (Chile). “The congested overcrowded central regions of globular clusters are one of these places. Our observations confirmed that, among globular clusters, Liller 1 is one of the best environments in our galaxy for stellar collisions.”
Geisler’s team specializes in the study of globular clusters near the center of the Milky Way, while Ferraro’s team is adept at the reduction of infrared data on globular clusters. Both groups worked together to obtain the beautiful and detailed observations of Liller 1 with Gemini.
Liller 1 is a tight sphere of stars known as a globular cluster. Globular clusters orbit in a large halo around the center, or nucleus, of our galaxy and many of the closer globular clusters are spectacular showpieces, even in small telescopes or binoculars. “This isn’t one of these showpieces, it is so obscured by material in the central bulge of our galaxy that is almost completely invisible in visual light,” observed Sara Saracino, lead author on the paper, from the University of Bologna. Indeed, Liller 1 is located at almost 30,000 light years from Earth, in one of the most inaccessible regions of our galaxy, where thick clouds of dust prevent the optical light from emerging. “Only infrared radiation can travel across these clouds and bring us direct information on its stars,” commented Emanuele Dalessandro of University of Bologna.
The observations of the tightly packed cluster used Gemini Observatory’s powerful adaptive optics system at the Gemini South telescope in Chile.
A technical jewel named GeMS (derived from “Gemini Multi-conjugate adaptive optics System”), in combination with the powerful infrared camera Gemini South Adaptive Optics Imager (GSAOI), was able to penetrate the dense fog surrounding Liller 1 and to provide astronomers with this unprecedented view of its stars. This has been made possible thanks to the combination of two specific characteristics of GeMS: first, the capability of operating at near-infrared wavelengths (especially in the K pass-band); second, an innovative and revolutionary way to remove the distortions (blurriness) that the Earth’s turbulent atmosphere inflicts on astronomical images. To compensate for the degradation effects of the Earth’s atmosphere, the GeMS system uses three natural guide stars, a constellation of five laser guide stars, and multiple deformable mirrors. The correction is so fine that astronomers are provided with images of unprecedented sharpness. In the best K-band exposures of Liller 1, stellar images have an angular resolution of only 75 milliarcseconds, just slightly larger than the theoretical limit of Gemini’s 8-meter mirror (known as the diffraction limit). This means that GeMS performed with almost perfect corrections of atmospheric distortions.
The international research team published the results in The Astrophysical Journal (article 152, volume 806, issue 2, June 15, 2015). The astro-ph version of the article can be found here.
The observations for this project also included several other globular clusters. The results achieved on their first target, Liller 1, have been so important that they have increased their collaboration and are currently working on the other clusters which promise to deliver even more exciting science.
Background: Stellar Collisions
Stellar collisions are important because they can provide the key to understand the origin of exotic objects that cannot be interpreted in terms of the passive evolution of single stars. Nearly head-on collisions in which the stars actually merge, mixing their nuclear fuel and re-stoking the fire of the nuclear fusion are suggested to be the origin of (at least part) of the so-called Blue Straggler Stars. But collisions can also involve binary systems, with the effect of shrinking the initial size of the system and thus promoting the two components to interact and producing a variety of objects like Low mass X-ray binaries, Millisecond pulsars etc. In particular Millisecond pulsars are old neutron stars reaccelerated to millisecond rotation period by mass accretion from a companion in a binary system. Indeed Liller 1 is suspected to have a large population of such exotic objects. Although no millisecond pulsar has been directly observed up to now, a large hidden population has been suggested because of the detection of an intense γ-ray emission (the most intense detected so far from a globular cluster). The Gemini observations indeed confirm that this is possible.
“Indeed our observations confirm Liller 1 as one of the best “laboratories” where the impact of star cluster dynamics on stellar evolution can be studied: it opens the window to a sort of stellar sociology study, aimed at measuring the impact of the reciprocal influence of stars when they are forced to live in conditions of extreme crowding and stress.” concludes Ferraro.
Additional information can be found at http://www.cosmic-lab.eu/Cosmic-Lab/Liller1.html
Figure 1. Image of HD 115600 showing a bright debris ring viewed nearly edge-on and located just beyond a Pluto-like distance to the star. One or more unseen solar system-like planets are causing the disk center (diamond) to be offset from the star's position (cross).
Using the Gemini Planet Imager (GPI) at the Gemini South telescope in Chile, astronomers have discovered a young, emerging planetary system that shares remarkable similarities to our own Solar System in its infancy.
GPI images reveal the disk as a bright ring of dust around a star only slightly more massive than the Sun. It is located about 360 light-years away, in a region similar to that in which the Sun was formed. The disk is not perfectly centered on the star, likely sculpted by one or more Solar System-like planets. Even more remarkable, the disk is almost exactly the same distance from its host star as, and may have a composition similar to, our Solar System’s Kuiper Belt. The Kuiper Belt is a region of micron-sized dust to moon-sized objects like Pluto left over from the formation of our Solar System more than 4 billion years ago.
“It’s like looking at the outer Solar System when it was a toddler,” said principal investigator Thayne Currie, an astronomer at the Subaru Observatory in Hawai‘i.
The discovery was made possible by GPI’s cutting edge adaptive optics system and coronagraph, which greatly reduced the star’s glare obscuring the light from the disk. “In just one of our many 50-second exposures we could see what previous instruments failed to see in more than 50 minutes,” Currie said. The star, going by the designation HD 115600, was the first object the research team looked at. “Over the next few years, I’m optimistic that GPI will reveal many more debris disks and young planets. Who knows what strange, new worlds we will find,” Currie added.
The University of Cambridge, UK, has a press release of this discovery as well.
The paper is accepted for publication in The Astrophysical Journal and can be found here.