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Gemini e-Newscast #24 -- March 12, 2010

Mar 12, 2010



Dust hides the mass of merging galaxies

While velocity dispersion measurements of elliptical galaxies in the optical (using the calcium triplet) and near-infrared (using the CO bandhead) yield consistent results, near-IR measurements of merging luminous infrared galaxies suggest that these systems are relatively low mass, being offset from the fundamental plane. Considering both optical and near-IR observations of ellipticals and merging systems, Barry Rothberg and Jacqueline Fischer of the Naval Research Laboratory (US) account for this discrepancy. In the IR-luminous systems, they find evidence for younger stellar populations in a central disk, so the CO velocity dispersion does not accurately trace the full mass. The calcium triplet yields a better mass estimate because dust obscures these younger stars in the optical. Thus, IR-luminous merging systems could be the progenitors of even higher-mass ellipticals. Observations with the Gemini Near-Infrared Spectrometer (GNIRS) were a key component of this work, which also uses data from the Keck and Hubble Space Telescopes. See for more informationat the Gemini website, or find complete results in the Astrophysical Journal 2010, Volume 712, page 318 (

Mass exodus from a galaxy - continued

The Durham University has issued a press release featuring the work of David M. Alexander and colleagues using the Near-Infrared Integral Field Spectrometer (NIFS) on Gemini North to measure galactic-scale outflow in a redshift z=2.07 quasar. Read the brief story at (noted in e-newscast #22), or see the full publication in Monthly Notices of the Royal Astronomical Society 2010, Volume 402, page 2211 (

Earthquake in Chile

The facilities of Gemini South were not damaged during the recent 8.8 magnitude earthquake in Chile and subsequent aftershocks. The Gemini South telescope was back on the sky within half an hour of the main tremor, and subsequent operations have been normal. We do extend our sympathy and concern for those throughout Chile who have suffered, including members of our staff. AURA, Gemini employees, and friends have been contributing generously to relief efforts. See for more information.

Laser ready for Gemini South (and vice-versa)

The high-power laser for the Gemini Multi-Conjugate Adaptive Optics System (GeMS) has passed pre-ship acceptance tests in Colorado. Gemini South is ready to receive the laser in the instrument laboratory on Cerro Pachon, but transport will be briefly delayed while humanitarian aid cargo has priority for arrival in Chile following the February 27 earthquake.