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17 Marzo 2009: In a paper published in the March 19, 2009 issue of Science Express, Justyn Maund and Stephen Smartt present data from the Gemini Observatory and Hubble Space Telescope (HST) that confirms the disappearance of the progenitors of two Type II supernovae (SNe). The only other supernova progenitor of this sort known to have definitively disappeared was SN 1987A in the Large Magellanic Cloud, part of our Local Group of Galaxies. Because the identity of the stars found in pre-explosion images has now been confirmed, this work provides the important “nail in the coffin” that the now missing Red Supergiants were the progenitors. The two supernovae, denoted 1993J and 2003gd, both had confirmed pre-existing progenitors identified from archival data which allowed the researchers to compare pre-supernova identification of the progenitor star with post-supernova observations. Maund and Smartt used a technique where images were taken after SN 2003gd had faded away, and …

25 Febrero 2009: Certainly one of the strangest objects in our Milky Way galaxy has been hiding as a variable X-ray source called SAX J1808.4-3658. This X-ray binary has been known to contain an accretion-powered millisecond pulsar located at a distance of 3,500 parsec (~11,500 light-years). It was also the first identified millisecond pulsar system among X-ray binaries. Recent observations with GMOS-S (Gemini Multi-Object Spectrograph – at Gemini South) have revealed a large periodic modulation of its quiescent optical emission. The observations show a light curve with a remarkably regular sinusoidal shape of ~0.4 magnitude in amplitude in r’ band (Figure 1). Conducted by the Canadian-Dutch team led by Zhongxiang Wang (McGill University), the new observations indicate that the light curve modulation is caused by irradiation of the companion star to the pulsar, and not by activity in the accretion disk. The pair is strange because it is comprised of an unusual couple: …

11 Febrero 2009: In the context of the currently favored cosmological Λ-Cold Dark Matter model of the universe, the formation and evolution of galaxies remains a major unsolved problem. In particular, the detailed evolution of the bulge and disk components of spiral galaxies is not well represented in current simulations. The data–model discrepancies do not necessarily reflect a failure in the ΛCDM model, but may indicate physical regimes and processes that are either poorly understood or difficult to implement in large simulations. Given the significant challenges faced by current galaxy formation models, guidance towards a true understanding of disk galaxies must come from an observational perspective such as the one described here using the Gemini Multi-Object Spectrograph. A very useful probe in discerning between formation scenarios is a detailed breakdown of the age, metallicity (Z), and kinematic properties of the stellar population (SP) content comprising bulges of all types. Information about both light- …

22 Enero 2009: Stuart Ryder, Australian Gemini Scientist at the Anglo-Australian Observatory, and colleagues from Europe and South Africa have used the 8-meter Gemini North telescope in Hawai‘i and its laser guide star adaptive optics system to reveal a supernova (SN 2008cs) in a galaxy (IRAS 17138-1017) 250 million light-years away (Figure 1). This is the first supernova to be discovered using laser guide star adaptive optics. Along the way, the researchers also turned up a second, “historical” supernova, SN 2004iq, in the same galaxy. Stellar evolution theory, along with the recent identifications of actual supernova progenitors, indicates that only stars more massive than ~8Msun will end their lives as core-collapse supernovae. Assuming that the ratio of such stars to less massive ones—the initial mass function—is the same everywhere in the universe, then the observed rate of supernovae can be used to gauge the rate of star formation, across a wide range of …

16 Enero 2009: Dr. Timothy Beers of Michigan State University has been appointed to Chair the Gemini Science Committee starting on February 1, 2009. In this capacity Timothy will lead the effort to assure that Gemini's current and future scientific mission fulfills the needs or our user communities. The appointment is for a period of 2 years. Timothy Beers is presently University Distinguished Professor of Astronomy at Michigan State University, and Associate Director of the Physics Frontier Center JINA (Joint Institute for Nuclear Astrophysics). Although his Ph.D. thesis at Harvard University (1983) was on the nature of substructure in clusters of galaxies, for the past 25 years he has worked on surveys and analysis of metal-poor stars in the Milky Way, and on the formation and evolution of galaxies as revealed by their elemental and kinematical signatures. He is a participant in current studies of the Milky Way Galaxy as survey scientist for …

5 Enero 2009: The newest addition to the Gemini Legacy imaging program is a laser-guide-star enabled near-infrared image of the well-known planetary nebula NGC 7027 (Figure 1). NGC 7027 lies at a distance of about 3,000 light-years from Earth and is located in the direction of the constellation Cygnus. The nebula itself is approximately 14,000 astronomical units from end-to-end, about 140 times larger than our Solar System. NGC 7027 is a planetary nebula, so-named because early observers with small telescopes thought that these targets resembled fuzzy ‘planets’ in the sky. We now know that objects like NGC 7027 are not planets, but the name has stuck throughout the years. We also know that objects like NGC 7027 give us a tantalizing peek into the future of our own Sun. Toward the end of their lives, when they get close to exhausting all of the nuclear fuel they are born with, stars like the …

23 Diciembre 2008: The Subaru and Gemini Observatories are pleased to announce a jointly sponsored science meeting that will be held at Kyoto University, Kyoto Japan, between May 18-21, 2009. An estimated two-hundred and fifty participants, approximately half coming from each community, will meet to present research conducted at the two observatories and to explore possible collaborations. The two main goals of the conference are to promote a mutual understanding of both communities and to highlight the international nature of modern astronomy. Other goals are to: Better understand the Subaru and Gemini instruments and science programs Foster scientific collaborations Define key areas of 'niche science' for both observatories Initiate scientific collaboration for, and with respect to, the International Year of Astronomy in 2009 The Scientific and Local Organizing Committees have recently been appointed. The SOC is led by two co-chairs Masashi Chiba (Tohoku University) and Timothy C. Beers (Michigan State University). The LOC …

15 Diciembre 2008: A recent optical spectroscopic study led by Guillermo Bosch (Universidad de La Plata), Elena and Roberto Terlevich (INAOE, Tonantzintla) used the spectro-imager GMOS-South to reveal that a surprisingly high fraction (>50%) of the stars in the cluster NGC 2070 are binary. This massive cluster is responsible for ionizing the gas in the spectacular 30 Doradus nebula located in the Large Magellanic Cloud. The fraction of binaries is an important factor influencing the initial mass function (IMF), the cluster’s age, and dynamical mass determination. Although a large amount of work has been done on 30 Doradus and its ionizing cluster, little is known of it binary fraction. Bosch and his colleagues obtained optical spectroscopy with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South of 52 early-type stars on six epochs. Radial velocities derived for each night were very stable, with variation less than 1.0 km/sec. Twenty-five out of the 52 stars …

10 Diciembre 2008: Nathan Smith (University of California – Berkeley), Ken Hinkle (NOAO) and Nils Ride (Lund Observatory) have used the near infrared spectrograph PHOENIX on Gemini South to study the geometry and kinematics of the active circumstellar envelopes in the supergiant stars Betelgeuse and VY Canis Majoris. These two stars are shedding huge amounts of mass in their “last gasps” and could explode as supernovae any time now. Stars with initial mass of 20-40 solar mass are important, because their complex post-main sequence evolution is determined by their poorly understood mass loss. Massive stars shed copious amount of mass before exploding as supernovae; as instability of the interior and outer layers increases, such episodes of mass loss may be extremely intense in the late phases. Sampling the observable circumstellar envelopes around nearby massive stars can help to predict what type of supernovae we might expect in the event that they explode. Many …

3 Diciembre 2008: An international team led by Brazilian astronomer Denise Gonçalves used the Gemini Multi-Object Spectrograph (GMOS) on Gemini North to discover the most distant known symbiotic star. The star is part of a dwarf starburst galaxy in the Local Group called IC10 and is located about 750 kiloparsecs (about 2.5 million light-years) away. A symbiotic star is a variable binary star in which one star has expanded its outer envelope, in the late stages of its evolution, and is shedding mass quickly on another hot star (often a white dwarf). Some time in the future, the pair will end catastrophically with the white dwarf detonating as a Type Ia supernova as more material is dumped on it by the red giant. Symbiotic stars are critical in understanding Type Ia supernovae and the evolution of binary star systems. However, relatively few systems of this sort are known so finding them outside of …

28 Octubre 2008: A group of astronomers using a battery of 8-meter telescopes, including both Gemini North and South, have discovered a small pair of gravitationally bound Kuiper Belt objects with an enormous separation (Figure 1). The extreme binary, 2001 QW322, orbits at 43 astronomical units or about 6.5billion kilometers from the Sun. The two bodies are separated by about 125,000 kilometers (one third the distance from the Earth to the Moon) which is very large for these two tiny bodies. As a comparison, this is approximately equivalent to a pair of baseballs gravitationally "connected" and orbiting each other at a distance of 200 kilometers! 2001 QW322 was discovered in August 2001 with the Canada-France-Hawai‘i Telescope. Since then, (from 2002-2007), the pair has been monitored closely using 8-meter-class telescopes (Gemini North,Gemini South and the European Southern Observatory’s Very Large Telescope) to obtain high precision photometric observations of the faint double system (mg = …

7 Octubre 2008: Supernova 2006jc occurred when its massive progenitor star ended its life in spectacular fashion. The star exploded following a Luminous Blue Variable (LBV)-like outburst two years before (Pastorello et al.2007, Nature, 447, 829). An international team led by Seppo Mattila (Queen’s University, Belfast and University of Turku) observed the supernova and followed its evolution between days 86-493 after the explosion with an array of telescopes including the Gemini North telescope (using the Near Infrared Imager NIRI), the United Kingdom Infrared Telescope (UKIRT) and the Spitzer Space Telescope. This exceptional event has contributed significantly to our understanding of how core-collapse supernovae (SNe) and their progenitors can add to the dust content of the universe. Mattila et al. imaged SN 2006jc in the near infrared between days 86 and 493 with the UKIRT and Gemini North telescopes (Figure 1). Mid-IR observations were obtained with the Spitzer Space Telescope before the explosion and …

14 Agosto 2008: Optical spectroscopy from the Gemini telescopes has revealed a relatively uncommon type of asteroid in the main-belt for the first time. The discovery was made by a joint Brazil and US project led by Thais Mothé-Diniz of the Observatório Nacional in Rio de Janeiro and David Nesvorný of the Southwest Research Institute (Boulder, Colorado). The team used both GMOS North and South to obtain optical spectra of asteroids with estimated ages of < 1 Myr which they then compared to laboratory spectra of meteorites that have fallen to Earth. They found that spectra of asteroids in the newly discovered Datura family have a deep absorption feature near 0.8 microns which classifies them as ‘Q-type’ asteroids. This spectral feature is produced by silicate material, in particular olivine and pyroxene. Most interestingly, the spectra of Q-type objects are well-matched to the most common type of meteorite found on Earth called an ordinary …

14 Agosto 2008: During the second half of July 2008, the Gemini North telescope facility on Mauna Kea underwent a major 20-day scheduled shutdown. The shutdown allowed engineers and technicians to address a number of deferred upgrades and maintenance projects, (see a list of projects here), that are only possible during an extended period of electromechanical work. Included was the successful re-coating of the 8-meter primary mirror with protected silver. "As a scheduled shutdown, we are able to take care of maintenance and upgrades that are not possible when we are on the sky each night," said Brian Walls of Gemini's Systems Engineering team. "And while the new silver coating gets most of the attention, the concurrent work done on the telescope is critical since the entire telescope system needs to function at the same high level..." About four years ago the Gemini North telescope's primary mirror received its first protected silver coating …

31 Julio 2008: Based on laser guide star adaptive optics (LGS-AO) -fed integral field spectroscopy with the Near-Infrared Spectrograph (NIFS) at Gemini North, Anil C. Seth of the Harvard-Smithsonian Center for Astrophysics and his collaborators demonstrate that the massive nuclear stellar cluster at the core of the spiral galaxy NGC 4244 is strongly rotating. Most late-type spiral galaxies and early-type galaxies have prominent nuclear star clusters (NSCs), i.e. a significant conglomerate of stars about the same size (~ 5 parsecs) as normal globular clusters. Furthermore, the masses of NSCs are coupled to the mass of their host galaxy, following the similar mass vs. velocity dispersion relation known for massive black holes. This suggests that the formation of NSCs and black holes are linked to the formation of their host galaxy. However, unlike that of black holes, the assembly history of NSCs can be inferred from studies of their kinematics and stellar content. NGC …

8 Julio 2008: In mid June 2008, the 500th refereed Gemini paper was accepted for publication in The Astrophysical Journal, one of the main refereed astronomical journals. The last time we reported on Gemini papers statistics was on September 27th 2007 for the 400th Gemini paper. The 500th paper is titled “First Stellar Velocity Dispersion Measurements of a Luminous Quasar Host with Gemini North Laser Guide Star Adaptive Optics”, 2008, The Astrophysical Journal, by Linda C. Watson and 7 co-authors. Linda C. Watson is a Ph.D. student at the Department of Astronomy of the Ohio State University. The authors team consists of researchers from the United States, Canada and Germany. The paper presents new results on the kinematics of stars orbiting at the heart of the quasar host galaxy PG 1426+015 (z = 0.086). The velocities were derived from high spatial resolution near infrared spectra obtained with the integral field unit spectrograph NIFS. …

5 Julio 2008: The Supernova Legacy Survey (SNLS) had ambitious goals from the start - to produce a definitive sample of distant supernovae for cosmology. The aim was not only to find an order-of-magnitude more distant supernovae than previous surveys, but study them with higher precision. Such a dataset has the potential to distinguish between theories for the mysterious Dark Energy that appears to be causing the expansion of the Universe to accelerate. The 5-year survey began in 2003 and the final supernova spectrum was recently taken at Gemini North (Fig. 1). The survey has been a great success, generating over 400 spectroscopically confirmed Type Ia supernovae. This has been achieved by the international SNLS team using a combination of survey images from CFHT, (obtained from the "Deep" part of the CFHT Legacy Survey), and spectroscopic follow-up using the worlds largest ground-based telescopes including Gemini North and South, VLT, Keck and Magellan. The …

1 Julio 2008: Probing the Host Galaxy of a Luminous Quasar with Gemini Laser Adaptive Optics A team led by Linda C. Watson, Ph. D. student at the Department of Astronomy, Ohio State University, has made the first bulge stellar velocity dispersion measurement of a luminous quasar host with the Gemini North Laser Guide Star adaptive optics system. The target quasar was PG1426+015, about 1.36 billion light-years away (Figure 1). This result is also the basis for the 500th refereed paper based on Gemini observations. They employed the spectro-imaging spectrograph NIFS fed by the Gemini facility adaptive optics system Altair to obtain high signal-to-noise ratio measurements of near-infrared Si I and Mg I lines and also several CO bandheads in the quasar host galaxy spectrum of PG 1426+15 (Figure 2). Using these measurements, the team found a stellar velocity dispersion of 217 +/- 15 kilometers/second in the region of the galaxy between 0.1'' …

16 Mayo 2008: A team of astronomers has used infrared spectral images of Saturn’s moon, Titan, acquired with the Gemini North Frederick C. Gillett Telescope, to dispute an earlier claimed detection of widespread morning methane drizzle. Titan, the second largest moon in the solar system, has long fascinated astronomers because it is the only moon in the solar system with a thick atmosphere. Adding to the fascination, its cold atmosphere (94 K or -180º C near the surface) has a number of interesting similarities to our Earth’s atmosphere. For example, its complex temperature profile (temperature vs. altitude) has the same overall structure as Earth’s and the atmospheric surface pressures are nearly the same. Also like the earth’s atmosphere, nitrogen is the dominant chemical species. After nitrogen, methane is the most abundant chemical species in Titan’s atmosphere. It has sometimes been said that methane plays the same role in Titan’s atmosphere as water does …

6 Mayo 2008: Taking advantage of the spatial resolution and sensitivity offered by T-ReCS on Gemini South, an international team led by Tanio Diaz-Santos (CSIC, Spain) has completed a survey of nearby Luminous Infrared Galaxies (LIRGs) at 8-microns. The survey showed that to first order the star-formation-rate (SFR) of a galaxy can be determined from its 8-micron emission. This is particularly important for these sources since LIRGs produce the majority of their extended IR luminosity in deeply obscured star-forming regions. This makes traditional star-formation rate (SFR) indicators, for example the UV continuum or the H-alpha line emission, unsuitable for use with LIRGs due to the heavy extinction caused by the dust associated with the star formation sites. However, at longer wavelengths the extinction due to the dust begins to decrease and features like the Paschen-alpha line or even the mid-infrared (MIR) dust continuum emission itself serve as reliable tracers of the star-formation rate …