# 2001B Gemini South Queue Program Abstracts

Abstracts for all successful 2001B queue programs on Gemini South are given below.

GN-2001B-C-1

Title: A Search for Disks around Young Brown Dwarfs and Very-Low-Mass Stars

Abstract: Recent surveys have identified candidate sub-stellar objects down to planetary masses in nearby star-forming regions. In addition, in some cases they have provided indications of disk emission. Reliable determination of the disk frequency in young brown dwarfs is of paramount importance to understanding their origin and diversity. Here we propose to undertake the first systematic study of L-band disk excess in a sample of spectroscopically confirmed objects near and below the sub-stellar boundary, using NIRI on Gemini North

GS-2001B-Q-1

Title: Massive YSOs in NGC 3576

Abstract: We plan to observe candidate massive YSOs in NGC3576 in order to derive the parameters of the embedded stars. Objects with similar characteristics: high luminosity and excess emission in the K-band have been found in other Galactic giant H II regions (M17, W31, W42, W43). Some of these are coincident with ultra-compact H IIregions, indicating the existence of a connection between these two groups. Establishing an evolutionary sequence between the different kinds of observed YSOs is the first step in understanding the physical processes involved in the formation of massive stars. Since the high obscuration and veiling by intense dust emission can preclude the detection of photospheric features, we propose to make observations in the mid-infrared in order to derive the parameters of the embedded stellar cores for a set of objects in NGC 3576 for which we already have near infrared data.

GS-2001B-Q-10

Title: Ten Micron Imaging and Spectroscopy of Orion Nebula Silhouette Disks

Abstract: We propose to take ten-micron images and spectra of four Orion Nebula silhouette disks using OSCIR on Gemini South. Images taken through the 8-13 micron narrow band filters will define the disks' mid-IR spectral energy distribution. The spectra will be taken in the nebular [S IV] line at 10.5 microns to look for extinction effects from the disks.

GS-2001B-Q-11

Title: How Low can the IMF go ? (Mk II)

Abstract: We propose to quantify and study the population of planetary mass objects (PMOs) in the Trapezium Cluster and locate the bottom end of the IMF, via deep JHK imaging with Flamingos 1. This would be followed a year later by multiobject spectroscopy with the same instrument. The survey would be 90% complete to at least J=21 (5 Mjup for A(J) = 1 mag), and could detect less reddened sources down to 1 Mjup (J =~23). The area of 21 square arcminutes is chosen for optimal sensitivity and includes 13/15 known PMOs, whose status has been spectroscopically confirmed with UKIRT. This survey will clearly determine whether there is a lower limit to the Trapezium IMF near 8 Mjup, as suggested by existing UKIRT data (3 magnitudes less sensitive) and two theoretical arguments. The remaining age-mass degeneracy will be broken by spectroscopic temperature measurements and by photometric K band excesses in some cases.

GS-2001B-Q-12

Title: Molecular hydrogen spectroscopy of cooling-flow galaxies

Abstract: We wish to survey a sample of 8 cooling flows for near-IR rovibrational lines of molecular hydrogen. Cooling flows are produced by the cooling of the hot IntraCluster Medium, and eventually this gas cools into a molecular state, where it can radiate in the near-IR. However, the molecular component of the cooling flow and its excitation are still poorly understood, largely due to the paucity of observations. By covering a fairly large range in redshift and cooling flow mass flux, and by using near-IR spectroscopy, we will be able to look for trends in the H2 flux, compare it with the optical and X-ray signatures of atomic and ionic gas, and elucidate the excitation mechanism of the near-IR lines.

GS-2001B-Q-13

Title: G353.2+0.9: A laboratory for theories of star formation.

Abstract: O-type stars, during their very short life, strongly modify the surrounding interstellar medium, starting from the action of their powerful stellar winds and ionizing ratiation, and often finishing with spectacular supernova explosions, which contribute to the chemical enrichment of the interstellar medium, sometimes triggering the formation process of new generations of stars. These hot stars are also responsible for most of the ionization and dynamics of giant HII regions and starbursts, and strongly influence the Initial Mass Function (IMF) of young stellar groups. In spite of their outstanding characteristics, O-type stars are often elusive to careful studies: the beginning of their life happens in dense, highly obscured, molecular clouds, and their evolution is so fast, that by the time they blow away their dusty diapers they are already somewhat evolved, having lost a considerable fraction of their initial mass. More inconveniences come from the fact that the IR, optical and near-UV colors of O-type stars are degenerate, and the far UV is highly affected by extinction. We propose JHKs observations of a selected area in the galactic HII region NGC 6357. Point sources will be imaged down to Ks=18 with S/N = 10, in order to detect not only massive newborn stars but also pre-main sequence (PMS) intermediate and low mass stars. The observations will cover an area of nearly 5 x 5 arcmin centered in the nebula G353.2+0.9 whose radio, IR and optical characteristics are indicative of ongoing massive star formation. The observations will be used to derive photometric near IR magnitudes and colours of stellar sources and to study the morphology of the region. Our aim is to detect IR sources corresponding to newborn massive stars, to analyse the traces of their interaction with the surrounding nebula and its influence in the formation of lower mass stars.

GS-2001B-Q-14

Title: Temperatures and Composition of Halo White Dwarfs

Abstract: The recent direct detection of a substantial population of cool white dwarfs in the Galactic Halo opens a new avenue of exploration that will characterize the oldest stars in the Galaxy. Many of these Halo white dwarfs, several of which may be cooler than WD 0346+246, the prototypical ''ultracool'' white dwarf, are expected to exhibit the effects of H$_2$ collision induced absorption, manifested by substantial suppression of red to infrared flux. The determination of the temperatures and atmospheric compositions of these objects necessarily requires accurate photometry from the optical through the infrared. The infrared, where the broad, continuous, collision-induced absorption is strongest, is critical because it is sensitive to small differences in atmospheric composition. We will obtain accurate photometry in the UBVRIJHK passbands of the 38 stars we discovered in the Halo population. With the models we have developed, we will determine effective temperatures and compositions for all of the stars. We will also be able to construct the bright part of the luminosity function of the Halo white dwarfs for the first time.

GS-2001B-Q-15

Title: Type Ia Supernovae in the Epoch of Deceleration

Abstract: We propose to find, and follow, 10-25 Type Ia supernovae in the redshift range 0.9<z<1.2. These supernovae will be used to establish another point on the cosmological world line which will verify our results that Omega_\Lambda > 0, or show that our technique is affected by systematic errors or unaccounted systematic effects. Such systematic effects, such as dust or a simple scale error which is linear in z, will make the distant supernovae too faint with respect to a Omega_Lambda > 0 cosmology. At z>0.9, an (Omega_M, Omega_Lambda)=(0.3,0.7) universe will be in deceleration, causing the supernovae to begin to brighten relative to an empty model. We will search for these SNe at Subaru and CFHT, obtain followup spectra at Keck and the VLT, and follow the optical photometry in U(R), B(I,Z), with HST, the Hawaii time, and with the Gemini-S Acquistion Camera. The most critical aspect of the proposal before you is to get V(J) data with Gemini-N NIRI, to allow us to measure colors of the supernovae near maximum light.

GS-2001B-Q-16

Title: Early stages of star formation in NGC 2068

Abstract: We wish to use the mid-infrared camera OSCIR on Gemini to search for signs of early star formation in the molecular material associated with NGC2068. It is known that HH24-26, to the south of NGC2068, is the site of several Class 0/I young stellar objects, and the NGC2068 region is thought to have a much higher star-forming efficiency than HH24-26. We wish to search for similar objects in NGC2068, in order to compare the population and evolution of young stellar objects between these two regions, which appear to have very different star formation histories.

GS-2001B-Q-17

Title: Studying a Proto-planetary disk at 75 km resolution

Abstract: We have found an unusual object in the star forming Galactic open cluster NGC 2264 that appears to be occulted by its own or a companion's circumstellar disk for approximately one third of its orbit. Time-resolved photometry and optical spectroscopy reveal a pre-main sequence star of approximately 1 solar mass in eclipse for 16 days with clear evidence for gaps in the eclipsing disk. In this and a separate proposal we request NIRI spectroscopy to search for spectral signatures of the possible enshrouded or low luminosity companion, NIRI photometry to measure the signature of the disk, and Acquisition Camera high-speed photometry to map the eclipsing object at 75 km resolution near mid-eclipse.

GS-2001B-Q-18

Title: The star-formation history of field and cluster galaxies at z = 3.09

Abstract: The recent discovery of a z=3.09 proto-cluster (Steidel et al. 1998) offers a powerful opportunity to probe the relative star-formation history of a significant sample of field and cluster galaxies at redshifts that approach the epoch of formation. We propose to obtain J and Ks Flamingos I imaging for three fields located within the z=3.09 structure. J-Ks imaging spans the 4000A break in z=3.09 galaxies and offer a potentially sensitive age indicator. These observations will generate data for 15 spectroscopically-confirmed cluster members (plus an additional 24 members highlighted by a strong narrow-band excess/deficit centred on Lyman-alpha at the cluster redshift) as well as a sample of ~10-12 foreground and background Lyman Break field galaxies. Comparisons of proto--cluster galaxies with data on field galaxies both in the fields we will observe and from archival sources will permit a robust constraint (via stellar population models) of the relative star formation history of high-redshift field and cluster galaxies - at significant look-back times (~10Gyr) this comparison will place strong constraints upon current models of galaxy formation.

GS-2001B-Q-19

Title: Multiplicity and Circumstellar Structure of Deeply Embedded Herbig-Haro Energy Sources

Abstract: We propose to perform a survey of ~100 (33 in 2001B) newborn and deeply embedded sources all of which drive Herbig-Haro flows, using Gemini South and the mid-IR instrument, OSCIR. The sources of Herbig-Haro jets have ages between 10^4 and 10^5 year, and are therefore among the youngest stars known. New studies suggest that jet formation may be triggered by dynamical interactions in binary or multiple young stars (Reipurth 2000). If this is correct our sample should contain a large fraction of multiple sources with many close binaries. We will compare the statistics of binarity and separation distribution with those of much more evolved T Tauri stars to study if disintegration and orbital evolution are important components of these early stages of stellar evolution. Circumstellar material/disks are abundant at such early evolutionary stages, and from the same dataset, we will study the extent, morphology and nature of such material and determine how often circumstellar disks have survived in multiple systems.

GS-2001B-Q-2

Title: The Stellar Density Around Massive Young Stars: A Test of Collisional Models of High Mass Star Formation

Abstract: We propose deep (23.2, 22.3, 22.1 mag. in JHK) observations of the NGC 6334 I core. This core contains two young massive stars surrounded by a cluster of lower mass stars. With the exceptional sensitivity of Gemini, we can detect low mass stars in the vicinity of the two deeply embedded high mass (proto)stars, and obtain the first measurement of the stellar density within 0.02 pc of these massive stars. From this data, we will infer the rate of stellar collisions in a region of very recent massive star formation and test whether massive stars form through the collision and coalescence of lower mass stars.

GS-2001B-Q-20

Title: Study of Low End of the Initiall Mass Function in Large Magellanic Cloud Star Forming Regions: N159

Abstract: Molecular clouds are the site of star formation. In the Magellanic Clouds the molecular clouds show properties wich differ to those of Galactic molecular clouds. Thus, the formation of stars in these low metallicity clouds could be different to that found in our Galaxy. We intend to do deep J,H,Ks observations with FLAMINGOS I of the N159 star forming region in the LMC, region that seems to present different environs: a molecular core associated to a very young HII region (N159 itself) and a quiescent giant molecular cloud (N159-S) associated to the complex but without detectable massive stars. We intend to make a census of young stellar objects in such distinct environments within this metal-poor galaxy. In a next observing run, we plan to observe a molecular cloud associated to N11, an evolved HII region. The identification of the young low and intermediate mass stars in such two star forming regions which show different evolutions, N159 and N11, will allow to study the history of star formation in a starburst region. In particular, we should be able to see if formation of low mass stars started prior to the formation of massive stars and if low mass stars are still forming in the associated molecular cloud. For N159-S region we will probe the low-mass IMF in a quiescent molecular cloud.

GS-2001B-Q-21

Title: The hosts and environment of distant radio galaxies

Abstract: We propose to investigate the morphology, stellar population and environment of the radio galaxy PMN J0214-1158 (z=2.336) as a first step in a broader study of high redshift radio galaxies (HZRGs). Redshifts larger than 2 correspond to look-back times of more than 80% of the Hubble time, at approximately the epoch of galaxy formation, and to the peak of the Quasar activity. Recent findings indicate that the formation of supermassive black-holes is strongly linked to the formation of massive galactic bulges. This link can be investigated via the study of the rest-frame optical images of HZRGs, which are Quasars with a hidden nuclear source in the unified scenario. HZRGs are thought to be the progenitors of giant elliptical galaxies as well as the brightest members of distant clusters in formation. We propose to obtain near-infrared images of the above galaxy using FLAMINGOS I in the J, H and K-bands, which will cover the rest-frame near-UV and optical regions of the spectra to: (1) determine the galaxy's morphology; (2) study the continuum and stellar population distribution through color gradients; (3) look for possible companion (cluster) galaxies.

GS-2001B-Q-22

Title: Protoplanetary Disk Evolution in the Orion OB1 Association

Abstract: We propose to search for 10-18 $\mu$m emission from protoplanetary disks in a dispersed sample of stars spanning the age range 1-10 Myr. Our sample, drawn from our successful wide-area survey of low-mass stars in the Orion 1a and 1b associations, is well-suited to studying disk evolution through the likely epoch of (giant) planet formation. Detection of mid-infrared emission, and comparison with near-infrared fluxes from 2MASS, is critical to identifying systems with developing inner disk gaps. We will combine our observations with mass accretion rates estimated from Br(gamma) to determine the structure and evolution of the planet-forming disk regions (< 10 AU) for systems in the significant time interval 1-10 Myr for a much larger sample of stars than presently exists.

GS-2001B-Q-23

Title: The origin of ultra-compact dwarf galaxies

Abstract: We have discovered a new population of compact stellar systems in the Fornax Cluster, which we term ultra-compact dwarfs''. The origin of these objects is currently unknown: they are unlike any known type of galaxy or star cluster. We propose to obtain near-infrared high-resolution images of these very compact objects with Gemini-South. These, combined with our optical imaging, will enable us to measure the ages and metalicities of their stellar populations and thus test different hypotheses for the origin of these objects. In particular we will search for very faint red halos as predicted by the galaxy threshing'' model of their formation by tidal stripping.

GS-2001B-Q-24

Title: Ten-micron imaging and spectroscopy of dust around young solar analogs

Abstract: Excess thermal infrared emission (relative to a photosphere) has been identified with two nearby young Sun-like stars. This emission is most likely from circumstellar dust that is replenished by larger orbiting bodies. The two stars (HD 53143 and HD 128400) were selected as close analogs to the Sun during the Hadean epoch (3.8-4.6 billion years ago), a period of great significance in Earth history. The lunar surface records intense bombardment during this era and dynamical models suggest that residual planetesimals in the outer Solar System were cleared during this time. The late bombardment of Earth may have eroded a primordial atmosphere, imported water, and delayed the origin of life. Analogous impactor populations (e.g. comets) involved in bombardment episodes in nearby, young planetary systems could maintain a detectable mass of dust. Studies of these stars are important to understanding the frequency and evolution of other planetary systems in relation to our own. We propose 10-micron imaging and spectroscopy with Gemini-South/OSCIR to obtain information about the dust distribution, temperature, and grain properties in these unique systems.

GS-2001B-Q-25

Title: Reverberation Mapping of Black Hole X-ray Transients

Abstract: Reverberation mapping has been widely used to explore the broad-line region of AGN, but has only recently been effectively applied to X-ray binaries. This reflects the shorter delay timescales involved, of order seconds, which require demanding time resolutions. We will use the large collecting area of Gemini-South together with the rapid readout of the Acquisition Camera to build on our existing progress in this field. We will perform Quick Response X-ray to optical reverberation mapping on a black hole X-ray transient in outburst with X-ray flux >1 Crab and/or V<14. We will probe the structure of the accretion flow, identifying reprocessing sites (the accretion disc, the heated companion star or both) and exploring the structure of the irradiated disc. These observations will form part of our existing, successful multiwavelength programme, and will be coordinated with our approved RXTE observations.

GS-2001B-Q-26

Title: A Very Unusual, Highly Obscured AGN and Jet-Source in a Spiral Galaxy

Abstract: From an extensive survey of radio sources in Abell clusters, we have identified one powerful (P_20cm ~ 10^24 W/Hz) FR I radio source in a disk/spiral galaxy. The radio source is extended 200 kpc perpendicular to the disk, and we have recently confirmed the existence of a jet on both kpc and 40 kpc scales. This object appears to be the FIRST confirmed identification of a jet-fed, double-lobed FR I radio source within a disk galaxy. In order to investigate the peculiar nature of this object and how it fits into standard models of radio source formation, we propose to obtain high resolution images at J,H,K' with Hokupa'a/QUIRC and a K-band spectrum with FLAMINGOS I. The goals of these observations are to: 1) Separate the bulge/AGN luminosity, 2) map the morphology in the central parts of the galaxy to look for jet/ISM interactions, evidence of a bar/spiral structure and/or star- forming regions, 3) to determine the intrinsic reddening/obscuration and AGN luminosity and to look for an obscured broad-line region, and 4) look for non-thermal NIR emission from radio-jet hotspots and the contribution of non-thermal emission to the NIR continuum to understand the blazer-like radio spectrum. These data will provide a much clearer picture of the physical conditions near the central engine, the intrinsic AGN properties, and help us to understand how this peculiar object fits into the general picture of AGN/radio-source physics.

GS-2001B-Q-27

Title: Number Counts of Extremely Red Galaxies to Extremely Faint Magnitudes

Abstract: Extremely Red Galaxies (ERGs) are resolved objects with R-K>6. They are thought to be either passively evolving systems formed at very high redshifts and observed at 1<z<2, or dust-enshrouded starbursts with vigorous star formation also at 1<z<2. In either case, they play an important role in the story of galaxy formation and evolution. Currently, number counts of ERGs are known to only K<19, and thus likely miss the majority of the ERG population. We propose to constrain ERG number counts to K>20.5 - i.e. >1.5 magnitudes fainter than known presently - by complementing an extremely deep, existing 24-hour VLT R band image with only a modest amount (5.5 hrs) of Gemini K-band imaging (this proposal).

GS-2001B-Q-28

Title: Spatially-resolved mid-infrared spectra of the obscuring dust in NGC1068

Abstract: We propose to obtain spatially-resolved spectra of the central few hundred parsecs of the Seyfert II galaxy NGC1068. The unified model of active galaxies contends that Type I and II Seyfert galaxies are fundamentally the same, sharing a common power source obscured anisotropically so that our classification of a Seyfert depends on our viewing angle. The model was a major step forward, but the details of the obscuration remain unclear. We intend to use the profile of the 10 micron silicate dust feature to model the distribution of the obscuring dust, distinguishing between the putative molecular torus, larger scale molecular material and dust in the narrow line region. These observations will not only help us understand the structure of Seyfert galaxies, but also provide us with spectra of dust in conditions very different from any observed in our galaxy.

GS-2001B-Q-29

Title: The impact of the youngest Super Star-Clusters on the insterstellar medium in He 2-10

Abstract: He 2-10 is a galaxy that displays the complete phenomenology of Super Star-Clusters, from their dust-embedded formation to the visible stage. We propose to use OSCIR, both in its imaging and spectroscopic mode to link the very nature and history of the SSCs to their effect on the interstellar medium (ISM). The MIR window AND OSCIR's high spatial resolution are ideal to get this information and to confirm the SSC nature of the strong and compact radio sources with no visible counterparts observed in He 2-10.

GS-2001B-Q-3

Title: Spatial Variations in the PAH Features of the Red Rectangle

Abstract: The Red Rectangle (RR) is a proto-planetary nebula that exhibits the UIR features in its 8-14 micron spectra that are normally associated with the polycyclic aromatic hydrocarbons (PAH). The RR provides an excellent environment to study the development and changes in the PAH spectrum as the physical conditions change radially away from the star. We wish to obtain spatially resolved spectra in the 8-14 micron region, at moderate to high S/N, to study the evolution of the PAH features (band strengths, positions and ratios).

GS-2001B-Q-30

Title: Very Young Super Star Cluster in SBS 0335-052

Abstract: SBS 0335-052, the second most metal-poor galaxy at 1/40th the solar metallicity, is an exceptional starburst galaxy. Even with such a low metallicity, it hosts a powerful infrared source (as powerful as the whole galaxy in the UV-Visible). We postulate that this emission originates in a dust-enshrouded super-star cluster, i.e. the earliest evolutionary phase of such objects. We propose, through high spatial resolution observations and 20 micron photometry with OSCIR, to demonstrate that it is actually the case.

GS-2001B-Q-31

Title: Very Young Stellar Populations in Starburst Galaxies: The Process of Star Formation

Abstract: With OSCIR we propose to produce high spatial resolution mid-IR maps of a sample of four nearby starburst galaxies. A mid-IR image at 18 um will point out to the very young star-forming regions never detected before because of a lack of resolution or due to strong dust extinction. Combined with an image at 8.8 um, we will characterize the nature of these regions. The spatial distribution of the very young star-forming regions seen in these images, compared with the information for the super star clusters already observed with HST/UV, optical, and near-IR data, will give us important clues about the process of star formation in various galaxies.

GS-2001B-Q-32

Title: Study of the Initial Mass Function in Large Magellanic Cloud Star Forming Regions

Abstract: Molecular clouds are the site of star formation. In the Magellanic Clouds the molecular clouds show properties wich differ to those of Galactic molecular clouds. Thus, the formation of stars in these low metallicity clouds could be different to that found in our Galaxy. We intend to do deep J,H,Ks observations with FLAMINGO I of three different star forming regions in the LMC: (1) N159-S: a molecular cloud with no associated H II region. (2) N159: The core of the giant HII region N159, and (3) The molecular cloud associated with N11-B.

We intend to make a census of young stellar objects in three distinct environments within this metal-poor galaxy. The identification of the young low and intermediate mass stars in two star forming regions which show different evolutions, N159 and N11, will allow to study the history of star formation in a starburst region. In particular, we should be able to see if formation of low mass stars started prior to the formation of massive stars and if low mass stars are still forming in the associated molecular cloud. For N159-S region we will probe the low-mass IMF in a quiescent molecular cloud.

GS-2001B-Q-33

Title: Mid-Infrared Probes of Brown Dwarfs

Abstract: Observations of brown dwarfs are currently limited almost entirely to optical and near-IR wavelengths. Here we propose to extend observations of these sub-stellar objects into the mid-infrared, in order to gain access to several spectral features expected, in particular, NH_3, and silicate dust, and possibly also hydrocarbons such as CH_4 and C_2H_6. Both NH_3 and dust should yield features near 10.5um, and both are revealing of the temperature structure and vertical transport rates in the atmosphere. We therefore propose to obtain low-resolution photometry of the brightest 1-3 candidates with OSCIR in imaging mode.

GS-2001B-Q-34

Title: Globular Cluster Systems of Elliptical Galaxies in Low Density Environments

Abstract: We propose to obtain deep K-band images using Flamingos-1 of the globular cluster populations around 3 field ellipticals which have supporting optical photometry from WFPC2. The galaxies span a range of absolute magnitudes and colour distribution functions. One of the galaxies (IC1459) has a classic bimodal colour distribution in V-I, indicative of at least two distinct phases of cluster formation, one (NGC821) has a dominate blue peak and one (NGC584) is intermediate. All three galaxies are members of loose groups and will compliment our Semester 01A NIRI observations of globular cluster systems around elliptical galaxies in dense cluster environments.

We will use optical-IR two-colour diagrams to investigate why these galaxies appear to have undergone such different formation histories and to test the prediction of hierarchical formation models that globular cluster systems around field ellipticals should have younger mean ages than those of cluster ellipticals.

GS-2001B-Q-35

Title: Quick Response to GRBs: the early burst and the late-time decay

Abstract: We propose to perform Quick Response observations of gamma-ray burst afterglows using the Gemini South acquisition camera. The unusual combination of excellent sensitivity and rapid readout will enable unique science goals. For the smallest HETE error boxes (radius < 1'), we propose fast Gemini searches for the counterpart, to explore the unknown early-time afterglow behavior and examine the causes of optical non-detection of many afterglows, including the elusive class of short-hard bursts. In cases where the afterglow is easily found, the rapid readout will allow us to search for short-term variability that could betray continued activity of a compact GRB remnant. In the expected 50% of cases that an associated optical transient is too faint to be found by smaller telescopes, the rapid response by an 8-m class telescope will allow a dramatically deeper search than has so far been performed. Furthermore, Quick Response on Gemini will allow late-time multi-color observations of afterglows, permitting a search for supernova-like features in the light curves on timescales of 2-6 weeks. In conjunction with late-time STIS spectroscopy approved in our HST Cycle 10 proposal, these observations will provide an extraordinarily stringent test of the hypothesis that GRBs are associated the collapse of massive stars.

GS-2001B-Q-36

Title: The Morphology of Low-luminosity High-z Galaxies Magnified by the Massive Cluster Lens Abell AC114 (z=0.312)

Abstract: We propose to image, with high angular resolution, the central area of the galaxy cluster AC114 down to K'=23.5 and J=24.0 mag (SNR=5) with the aim of: 1) Examining the morphology of 23 gravitationally amplified galaxies with 0.7<z<3.5 recently confirmed spectroscopically with VLT by Campusano et al, (2001), located on the central 2'x2' area; 2) Examine the morphology and parity of the 5-image system discovered by Campusano et al.(2001); 3) Search for new arclets in the cluster core and calculation of their photometric and lensing redshifts; and 4) Search for z>5 sources.

AC114 has deep HST images, a well constrained mass model, and its core can produce amplifications up to ~2 mag. This research will contribute to the build up of a sample of high-z galaxies, less biased towards high-luminosity objects.

GS-2001B-Q-37

Title: OSCIR imaging of the LINER in the heavily interacting Virgo Galaxy NGC4438

Abstract: The galaxy which exhibits the most environmental damage in the Virgo cluster is LINER NGC~4438, with a suspected 2000~km~s^{-1} FWHM component in Halpha. HST imaging revealed bipolar outflows in Halpha and [N II], a case of bipolar nuclear bubble 400~pc in size, at most 10^6~yr old. What is the central engine that provided the 10^{55}~ergs required to inflate the bubble? Is the phenonemon linked to NGC~4438's presumed recent interaction with NGC~4435, a projected 20~kpc away?

As an essential step towards answering these questions, the high angular resolution and sensitivity offered by OSCIR imaging will allow investigating the presence of a nuclear point source at 10um, a systematic feature of AGN, but rare in starbursts. The nuclear 10um flux will then be compared to the column of dust implied by visual extinction estimates, and will put constraints on the central engine's luminosity.

GS-2001B-Q-38

Title: Dust in Halo and Magellanic Cloud PNe

Abstract: What is the relation between ZAMS mass and final white-dwarf mass in 0.8-7~Msun stars? Why is the [OIII] PN luminosity function (LF) a good extragalactic distance indicator, independent of Hubble type? Is there a metallicity dependence in the kind of dust grains found in PNe, or even a low metallicity cut-off for the production of dust? Does the dredge-up efficiency of AGB stars vary with metallicity? Such questions may be answered by 8-13~um spectroscopy of Halo, Magenallic Cloud and Galactic Bulge PNe, accessible only to 8m telescopes. The presence of warm dust grains will select the youngest objects, still optically thick to ionising radiation and evolving at constant luminosity on post-AGB tracks, while the dust composition will provide information on carbon enrichment at low metallicity. As an essential step towards these goals, this semester we propose to complete the sample of galactic halo PNe, and initiate unprecedented 8-13um observations of Magellanic Cloud PNe.

GS-2001B-Q-39

Title: Nuclear Starbursts in Seyfert 1 Galaxies

Abstract: We propose to obtain medium-dispersion (R ~ 1300) NIR long-slit spectra of a carefully selected sample of 5 Seyfert~1 galaxies (and one comparison Seyfert~2 galaxy) to search for stellar absorption lines from circumnuclear starbursts. By comparing Si and CO stellar absorption lines at 1.59, 1.62 and 2.3 um to those of giant stars and supergiants, and from spectral synthesis, we will determine the velocity dispersion of the stars and thus the dynamical mass.

We will estimate the luminosity of the stellar component and measure the light-to-mass ratio in the nuclear region, and thus determine if young starbursts are present in Seyfert nuclei.

The goals of this project are: (1) determine how common the starbursts are in type~1 Seyferts (from studies of type~2 Seyferts, one expects ~50% to have starbursts), and (2) determine if the presence, luminosity, or age of the detected starbursts has any relationship with the level of activity of the AGN. The results from this project may help to understand the possible connection between starburst galaxies, Seyfert~1, and Seyfert~2 galaxies.

GS-2001B-Q-4

Title: The Extended Star Formation Histories of the Sculptor Group Dwarf Galaxies ESO540-032 and ESO294-010

Abstract: We propose to use FLAMINGOS I to image in the J and K bands the dwarf elliptical (dE) galaxies ESO540-032 and ESO294-010. These dwarfs are members of the Sculptor group, the nearest galaxy aggregate beyond the Local Group. A recent VLT study (in the V and I bands; Jerjen & Rejkuba, 2001) has revealed the presence of a number of stars above the tip of the red giant branch in ESO540-032, an indication of the presence of an intermediate-age (2 < age < 10 Gyr) population. Moreover, evidence for a young stellar population in ESO294-010 exists in the form of a prominent HII region in this dE galaxy (Jerjen et al. 1998). Near IR-band photometry is required to explore the extended star formation histories of these dwarfs and to determine bolometric magnitudes for upper-AGB stars, from which improved estimates of their ages can be derived. Our results will be directly comparable to existing information for Local Group dEs, such as the dwarf spheroidal companions to the Galaxy and to M31. In this way we will add to the understanding of the factors, including environment, that govern the star formation history in these allegedly simple galaxies.

GS-2001B-Q-40

Title: Mid-IR Spectra of Ultradense HII Regions

Abstract: We will use Gemini South to obtain spectra of the newly discovered ''ultradense HII regions'' in the starburst galaxy He~2-10 in the 8um to 14um thermal IR window. These luminous but compact HII regions are likley to harbor the youngest massive star clusters yet observed, and their properties inferred from radio observations imply that we may be witnessing the birth of the globular cluster-like super star clusters'. The discovery of ultradense HII regions in He~2-10 allows us to make systematic observations of the earliest stages of massive super star cluster formation for the {\it first time}. Because these ultra-young clusters are still embedded in their birth material, they can {\it only} be studied at mid-IR to radio wavelengths. Spectroscopic observations with OSCIR on Gemini will allow us measure the fine structure emission lines of [ArIII], [SIV], and [NeII] in addition to establishing the presence of absence of the PAH features at 8.6 and 11.3$\mu$m and checking for silicate absorption. These results will be critical for understanding the origin of massive super star clusters and thus also to the birth of of globular clusters, thereby illuminating the types of physical conditions in the early universe required to create them so prodigiously.

GS-2001B-Q-41

Title: The nature of unidentified X-ray sources in CMa star formation region

Abstract: X-ray observations have shown a strong correlation between high energy emission and star formation, providing means to elucidate the size, age and mass distribution of a young stellar population. We have used ROSAT images to study the moderately distant (~1Kpc) molecular cloud Canis Majoris (CMa). Most of the detected sources have optical counterparts, showing properties compatible with low- and intermediate-mass pre-main sequence stars in nearby star forming regions: point-like sources are T Tauri and Herbig Ae/Be stars, while diffuse emission can be caused by unresolved young stellar object clusters. The few remaining X-ray sources do not have counterpart in any spectral domain making them a very interesting sample. They could be deeply embedded young stars or isolated neutron stars. We propose to verify the nature of these objects using deep direct VRI imaging. The detection or not of the optical counterpart would provide imediate results, as they would indicate the presence of interesting objects (young or evolved) in the unexplored Canis Majoris star formation region.

GS-2001B-Q-42

Title: The circumstellar matter distribution around massive young stellar objects

Abstract: We propose to use the high resolution of Gemini-S at 20 microns to map the circumstellar matter distribution around massive young stellar objects The distribution of circumstellar material is shaped by the interplay between infall and outflow in massive star formation. Rotation and/or magnetic fields lead to a flattening of the infalling envelope whilst the outflows clear cavities along the polar axes. Our radio imaging has shown that two of our targets drive predominatly equatorial winds which could be collimated into a bipolar flow by a dense torus. The proposed observations will allow us to test various infall/outflow models. The results will be analysed using a 2D radiative transfer code, thereby bringing in additional constraints from other wavelengths. We will also determine the mass of material in the disk which will allow an assessment of the evolutionary status of these objects.

GS-2001B-Q-43

Title: Dusty dwarfs

Abstract: We have found good evidence that photospheric dust is a major opacity in cool dwarf stars. Its effects can be easily seen at optical and infrared wavelengths in objects with spectral types later than M6.5V. Theoretically this means that at longer wavelengths dusty M dwarfs and brown dwarfs are expected to show a dust excess. We propose to search for this using OSCIR to obtain the 8-14 micron data for M and L dwarfs. These data will be a vital calibration on the most suitable dust grain parameters to use for modelling M dwarfs and brown dwarfs. Furthermore these spectra are important in the long-standing quest to reliably determine effective temperatures and luminosities for low-mass stars.

GS-2001B-Q-44

Title: Multiplicity and Circumstellar Structure of Deeply Embedded Herbig-Haro Energy Sources

Abstract: We propose to perform a survey of ~100 (33 in 2001B) newborn and deeply embedded sources all of which drive Herbig-Haro flows, using Gemini South and the mid-IR instrument, OSCIR. The sources of Herbig-Haro jets have ages between 10^4 and 10^5 year, and are therefore among the youngest stars known. New studies suggest that jet formation may be triggered by dynamical interactions in binary or multiple young stars (Reipurth 2000). If this is correct our sample should contain a large fraction of multiple sources with many close binaries. We will compare the statistics of binarity and separation distribution with those of much more evolved T Tauri stars to study if disintegration and orbital evolution are important components of these early stages of stellar evolution. Circumstellar material/disks are abundant at such early evolutionary stages, and from the same dataset, we will study the extent, morphology and nature of such material and determine how often circumstellar disks have survived in multiple systems.

GS-2001B-Q-45

Title: Testing Dusty torus models in AGN

Abstract: Recently published ISO 10micron spectroscopy of a few Seyfert (Sy) 2 nuclei shows shallow silicate absorption features at 9.7micron, lacking unidentified IR band (PAH) features that may have contaminated previous measurements. This seems to indicate that the 10micron emission of Sys is not optically thick. We propose to obtain Gemini/OSCIR spectra (8-14micron), of a sample of AGNs. The OSCIR data will allow to separate out between PAH emission from the underlying galaxy and dust silicate absorption at much higher angular and spectral resolution than previously possible. We propose here to test the hypothesis that the mid-IR emission is not in general optically thick in Sy 2s. If this is the case, the dusty torus models must be redesigned and the mid-IR emission is likely to provide a good estimate of the bolometric flux emitted from an AGN. By constraining the wavelength at which the bulk of the energy is emitted in AGNs, we will motivate and guide future deep field surveys which have the capability of probing the growth rates of massive black holes throughout the universe.

GS-2001B-Q-46

Title: The Nature of Narrow-Line, FIR-Luminous, X-ray Galaxies

Abstract: We propose to make OSCIR observations of 4 ROSAT/ISO sources which have been identified as Narrow-Line X-ray galaxies, a population which is a strong candidate for explaining a significant fraction of the X-ray Background. 7(/14) of this class of galaxies have been detected by ISO at 60-200 microns, compared to only 1/6 of a QSO control sample, suggesting that these galaxies contain more 30<T<900K dust than broad-line QSOs. In turn, this may suggest an isotropic rather than a toroidal distribution of nuclear dust in AGN. These NL galaxies have been accepted for high resolution X-ray imaging by Chandra ACIS. We wish to use OSCIR to determine if a sample of ISO NL galaxies are detected at 10microns. In the case of positive detection, we will establish if the sources are point-like or diffuse and hence provide a new test of the unified AGN model.

GS-2001B-Q-47

Title: A Search for Disks around Nearby Young Stars

Abstract: We propose a search for previously undetectable circumstellar disks around nearby young stars. We have identified 23 young southern hemisphere stars, including the two nearest T Tauri stars to Earth (both space motion companions to $\beta$ Pictoris), which range in spectral type from F2 to M0. Because these stars span a critical range in disk evolution -- 15-40 Myr and a range in mass, they provide a controlled natural laboratory for exploring the diversity in disk evolution. We will obtain high signal-to-noise ratio 10 and 18$\mu$m photometry to search for infrared excess around these stars. Infrared excess signals the re-processing of starlight by a disk and characterizes the amount of dust present. Previous surveys, including IRAS, had insufficient sensitivity to detect $\beta$ Pic-like disks around late type stars, which comprise the majority of nearby stars. Now, OSCIR on Gemini South can provide sixteen times greater sensitivity than IRAS and serve as an excellent means for a disk search.

GS-2001B-Q-48

Title: Mid-infrared spectra of Parkes Quasars

Abstract: The mid-infrared (MIR) wavelength region is crucial to understanding the dominant emission processes in radio-loud quasars. The MIR spectra of Parkes Quasars is expected to be dominated by either non-thermal synchrotron emission (which is seen at optical wavelengths), or thermal emission from hot dust. For these observations, we are requesting time with OSCIR to obtain MIR spectra of five (5) radio-loud quasars and BL Lacs, as part of our on-going study of the Parkes Half-Jansky Flat-spectrum Sample. We wish to use these spectra to determine the nature of the MIR continuum, primarily by examining the spectral slope and comparing with non-thermal and thermal predictions, and also by examining emission lines, should these be visible above the continuum.

GS-2001B-Q-49

Title: Bolometric luminosities of post-AGB stars in the LMC

Abstract: The MSX satellite has discovered 1809 mid-infrared point sources in the LMC. These objects are mostly stars surrounded by dust envelopes of ejected matter (winds, shells). Examination of a subset of 504 of the MSX sources reveals red supergiants, WR stars, AGB stars with strong dusty stellar winds, post-AGB (PAGB) stars and planetary nebulae. In particular, this is the first time that a post-AGB star evolutionary sequence has been found. However, because of the low K luminosities of these stars, one might question their authenticity. Here we aim to get mid-infrared photometry to 20 microns to derive bolometric luminosities to prove that the PAGB star candidates are as luminous as expected for genuine PAGB stars.

GS-2001B-Q-5

Title: The Star-Forming History of Nearby Isolated Dwarf Spheroidal Galaxies

Abstract: The dwarf spheroidal galaxies that have been most extensively studied to date are those that are in the outer halo of the Milky-Way. However, the evolution of these galaxies has likely been influenced by interactions with the Milky-Way. In order to understand the evolution of dwarf spheroidal galaxies in general and make meaningful comparisons with models it is necessary to study this type of galaxy in isolated environments as well. We propose to use Flamingos I to obtain deep J and Ks images of three nearby isolated dwarf spheroidal galaxies. One of our targets, Tucana, is on the periphery of the Local Group, while the other systems (ESO540-030 and Scl-dE1) are located in the Sculptor group, with distances of 0.5 - 0.7 Mpc from other large galaxies. The data will be used to probe the star-forming histories of these systems based on the luminosity function of AGB stars. Moreover, these data will serve as the basis for follow-up spectroscopic observations with the same instrument when the multi-slit mode becomes available to probe the chemical composition of these galaxies.

GS-2001B-Q-50

Title: OSCIR Spectroscopy of Comet C/2000 WM1 (LINEAR)

Abstract: Comets are the frozen reservoirs of the primitive materials from the early solar nebula whose chemical composition and chemical evolution can be studied during perihelion passage when solar irradiation enhances the production rate of volatile gases and the release of dust from the nucleus while exposing refractory material to UV flux. We propose to obtain high signal-to-noise (S/N) 10um OSCIR spectroscopy (R ~ 122) and imaging observations of the long-period comet C/2000 WM1 (LINEAR) near perihelion passage (2002~Jan~22.7~UT, r_h ~ 0.55 AU) to determine the silicate mineral and organic composition of the coma dust. These data, combined with our extensive analytical modeling efforts, will enable us to develop a fundamental understanding of connections between silicate mineralogy in comets and the origins and evolution of our protoplanetary disk. Such data is requisite to fully interpret spectra of comets and protoplanetary disk environments to be studied with the NASA STARDUST and SIRTF missions.

GS-2001B-Q-51

Title: Ultra-Short-Period X-Ray Binaries in Globular Clusters

Abstract: Different models of X-ray binary (XRB) formation and evolution predict substantially different numbers of ultra-short period XRBs in globular cluster XRB populations. The relative abundances of ultra-short period XRBs (orbital periods less than 50 min) also has significant implications on our understanding of globular cluster evolution and the theory of tidal capture. For these reasons it is extremely important to accurately determine the orbital periods of globular cluster XRBs. We propose to use the Acquisition Camera on Gemini South to determine the orbital periods of two ultra-short period XRB candidates, X0512-401 in NGC 1851 and X1832-330 in NGC 6652.

GS-2001B-Q-52

Title: The Nature of Optical Flaring in Quiescent Black Holes and Neutron Stars

Abstract: Observations of quiescent black hole and neutron star binary systems show that even in their faintest states they remain highly variable objects. We will use the Acquisition Camera on Gemini-South to study these variations. The variability indicates that instabilities are present in the quiescent accretion flow; timescales and amplitudes illuminate the nature of the instabilities, test models for the accretion flows, and explore the fundamental differences between accretion onto black holes and neutron stars. Such studies have been hampered, however, by the faintness of these objects. With Gemini, we will be able to study a much larger and more representative sample of these objects and probe shorter variability timescales than has previously been possible.

GS-2001B-Q-53

Title: A Near-IR Study of the Properties of Lyman Break Galaxies

Abstract: Recently there have been numerous detections of z>= 3 galaxies using the Lyman break technique [7] allowing for direct observations of galaxies in a young state. Understanding the properties of these young galaxies, when the universe was ~10% of its current age, is crucial in our efforts to better understand galaxy formation and evolution. We propose to conduct a comprehensive study of these Lyman break galaxies (LBGs) using near-IR spectroscopy to study their rest-frame optical emission lines H(beta), [OII]  3727, and [OIII] 4959, 5007. Observations of these emission lines will allow us to determine the source of excitations (AGN vs. star formation), star formation rates, and chemical abundances of LBGs in two QSO fields. Ultimately, we will combine the information obtained from these spectra with existing HST NICMOS and WFPC-2 observations and galaxy formation models to determine the nature of LBGs. The multi-slit capability of FLAMINGOS and the availability of large aperture telescopes make it now efficient to carry out a comprehensive study of these LBGs.

GS-2001B-Q-54

Title: High-Resolution Mid-IR Imaging of Southern Proto-Planetary Nebula Candidates

Abstract: We propose to obtain high-resolution mid-infrared images of southern proto-planetary nebula (PPN) candidates to investigate the structure of the dust emission in the innermost regions of these PPN dust shells. Due to sub-arcsecond scale of the PPN shells and the diffraction-limited nature of mid-infrared imaging, obtaining fully-resolved spatial information on the dust distribution was extremely difficult with the existing mid-size infrared telescopes. Now, with Gemini-South/OSCIR, we can obtain mid-infrared images of southern PPN candidates at sub-arcsecond resolution for the first time. Our proposed observations of southern PPN shells will reveal the shell structure and will test the inherent axisymmetry suggested from previous mid-infrared PPN imaging surveys done with mostly northern PPNs. We will also use the images to constrain model parameters in our 2-D dust radiative transfer modeling. The derived quantities such as the pole-to-equator mass loss ratio would quantify the axisymmetric characteristics of PPN shells and put tighter constraints on theoretical models of axisymmetric planetary nebula formation.

GS-2001B-Q-55

Title: Gemini JHK imaging of z~6 candidates in the HDF-S: Pregalactic objects forming around young weak AGN

Abstract: We propose 5 hours of Gemini-S JHK imaging with FLAMENGOS of two candidate galaxies at 5.5< z < 7. These were found in our multi-color survey with the CTIO-4m + MOSAICII in a 0.5deg x 0.5deg field around the HDF-South, using medium-band filters at 0.8--1.0um (AB < 23.5 mag) that suppress most of the strongest and most variable night sky-lines. Theoretical predictions of the surface density of galaxies at 5.5 < z < 7 is highly uncertain, and could be several tens \sqdeg to AB=23.5 mag following standard CDM models. At this flux level, our z > 5.5 candidates are expected to be a mixture of weak AGN and luminous (L < Lstar), young galaxies. Our hypothesis is that they are similar to the several young galaxies with weak AGN we discovered with HST at z=2.4, but of higher luminosity and higher redshift. A careful FLAMENGOS JHK imaging study will yield: (1) Confirmation of their photometric redshifts; (2) Estimates of Lya fluxes and SFR's; (3) A first glimpse of the young galaxy population at z > 6; (4) Clues how young galaxies may be forming around weak AGN; and (5) From the results of our CTIO MOSAIC survey, begin to constrain the reionization epoch of the universe, which is predicted to occur at z~6-8, and may be observable as the rather sudden decline in the LF of luminous objects in the redshift range z~6-7, of which we will begin to study the first ones. The exact redshift value z_ion is currently one of the last remaining great unknowns in cosmology.

GS-2001B-Q-6

Title: Extremely Red Galaxies in the Early Universe

Abstract: The high redshift universe is full of extremely red galaxies. What are they? There are two rival theories: either they are dusty starbursts or young elliptical galaxies.

We propose to use Flamingos-1 to obtain rest-frame optical spectra of two of these extremely red galaxies. These spectra will allow us to discriminate between the two models. If these galaxies are ellipticals, they will be the youngest and most distant ever seen: their properties will help show us how and when massive elliptical galaxies formed. If they are starbursts, this is further evidence that most star formation in the early universe is hidden by dust.

GS-2001B-Q-7

Title: Quick Response to GRBs: the early burst and the late-time decay

Abstract: We propose to perform Quick Response observations of gamma-ray burst afterglows using the Gemini South acquisition camera. The unusual combination of excellent sensitivity and rapid readout will enable unique science goals. For the smallest HETE error boxes (radius $< 1'$), we propose fast Gemini searches for the counterpart, to explore the unknown early-time afterglow behavior and examine the causes of optical non-detection of many afterglows. In cases where the afterglow is easily found, the rapid readout will allow us to search for short-term variability that could betray continued activity of a compact GRB remnant. In the expected $\sim 50\%$ of cases that an associated optical transient (OT) is too faint to be found by smaller telescopes, the rapid response by an 8-m class telescope will allow a dramatically deeper search than has so far been performed. Furthermore, Quick Response on Gemini will allow late-time multi-color observations of afterglows, permitting a search for supernova-like features in the light curves on timescales of 2-6 weeks. In conjunction with late-time STIS spectroscopy approved in our HST Cycle 11 proposal, these observations will provide an extraordinarily stringent test of the hypothesis that GRBs are associated with the collapse of massive stars.

GS-2001B-Q-8

Title: Search for Small-Scale Structure in Gamma-ray Burst Afterglows

Abstract: We propose to obtain high S/N optical photometry with rapid time sampling of bright (R < 21) gamma-ray burst afterglows in order to detect predicted small-scale fluctuations about the mean decay. Such deviations must be present at some level (1) due to inhomogeneities in the circumburst medium, and (2) if the afterglow is `refreshed'' by collisions among separate shells of ejecta (refreshed shocks). Detection of small-scale fluctuations and their interpretation within the context of the first mechanism would probe the immediate environment of the GRB progenitor, e.g., revealing a clumpy star-forming region or ISM turbulence. Detection of refreshed shocks would, for the first time, link the optical afterglow directly to the gamma-ray burst and affirm the internal-external shock model for GRBs. This is an ideal program to help develop the advertised Quick-Response observing mode using the Acquisition Camera on Gemini South by obtaining unique time-domain data on GRB afterglows.

GS-2001B-Q-9

Title: Ten Micron Imaging of the Beta Pictoris Dust Disk

Abstract: We propose to take a deep N-band image of the Beta Pic dust disk using OSCIR on Gemini South. This will be the first thermal-IR image of Beta Pic taken with an 8-meter class telescope. The 0.35" angular resolution will reveal new details of the morphology of the disk glimpsed in previous IR images made with smaller telescopes, permitting detailed measurements of the radial profile within 1" of the star, where there appears to be a relatively dust-free zone perhaps caused by planet formation, and possibly revealing bright spots in the inner disk that would indicate clumping of material. High resolution imaging of this important object will improve our understanding of the physical conditions in young planetary systems and in the early history of our solar system.

Last update July 9, 2001; Phil Puxley