This week on HST


HST Programs: June 5 - June 12, 2016

Program Number Principal Investigator Program Title
13847 Kailash C. Sahu, Space Telescope Science Institute Determining the Mass of Proxima Centauri through Astrometric Microlensing
14066 Angela Adamo, Stockholm University Hi-PEEC, Hubble imaging Probe of Extreme Environments and Clusters
14076 Boris T. Gaensicke, The University of Warwick An HST legacy ultraviolet spectroscopic survey of the 13pc white dwarf sample
14095 Gabriel Brammer, Space Telescope Science Institute - ESA Calibrating the Dusty Cosmos: Extinction Maps of Nearby Galaxies
14096 Dan Coe, Space Telescope Science Institute - ESA RELICS: Reionization Lensing Cluster Survey
14098 Harald Ebeling, University of Hawaii Beyond MACS: A Snapshot Survey of the Most Massive Clusters of Galaxies at z>0.5
14100 Kevin France, University of Colorado at Boulder A Direct Imaging Experiment to Determine the Origin of H2 Emission from M dwarf Exoplanetary Systems
14104 Jesus Maiz Apellaniz, Centro de Astrobiologia (CAB, CSIC-INTA) The optical-UV extinction law in 30 Doradus
14105 Jonathan David Nichols, University of Leicester Observing Jupiter's FUV auroras near Juno orbit insertion
14122 Lise Christensen, University of Copenhagen, Niels Bohr Institute Unveiling stellar populations in absorption-selected galaxies
14137 Lorrie Straka, Sterrewacht Leiden Damped Lyman-alpha Systems in the Disks of Low-z SDSS Galaxies on Top of QSOs
14143 Vincent Bourrier, Observatoire de Geneve Probing the nature and evolution of the oldest known planetary system through Lyman-alpha observations
14145 Hsiao-Wen Chen, University of Chicago Characterizing Circumgalactic Gas around Passive Galaxies
14163 Mickael Rigault, Humboldt Universitat zu Berlin Honing Type Ia Supernovae as Distance Indicators, Exploiting Environmental Bias for H0 and w.
14164 Ata Sarajedini, University of Florida Exploring the nature and synchronicity of early cluster formation in the Local Group
14171 Guangtun Zhu, The Johns Hopkins University Characterizing the Circumgalactic Medium of Luminous Red Galaxies
14175 Paul Goudfrooij, Space Telescope Science Institute Resolving the Nature of the Stellar Halo of the Sombrero, the Nearest Giant Early-Type Spiral Galaxy
14178 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey: The WISP Deep Fields
14181 S Thomas Megeath, University of Toledo A Snapshot WFC3 IR Survey of Spitzer/Hershel-Identified Protostars in Nearby Molecular Clouds
14199 Patrick Kelly, University of California - Berkeley Refsdal Redux: Precise Measurements of the Reappearance of the First Supernova with Multiple Resolved Images
14204 Antonino Paolo Milone, Australian National University Multiple stellar populations in two young Large Magellanic Cloud clusters: NGC1755 and NGC1866
14210 Russell Julian Smith, Durham Univ. Improved masses for two new low-redshift strong lens galaxies: Do giant ellipticals really have a heavy IMF?
14212 Karl Stapelfeldt, Jet Propulsion Laboratory A Snapshot Imaging Survey of Spitzer-selected Young Stellar Objects in Nearby Star Formation Regions*.t23
14216 Robert P. Kirshner, Harvard University RAISIN2: Tracers of cosmic expansion with SN IA in the IR
14219 John P. Blakeslee, Dominion Astrophysical Observatory Homogeneous Distances and Central Profiles for MASSIVE Survey Galaxies with Supermassive Black Holes
14235 Sangmo Tony Sohn, The Johns Hopkins University Globular Cluster Orbits from HST Proper Motions: Constraining the Formation and Mass of the Milky Way Halo
14241 Daniel Apai, University of Arizona Cloud Atlas: Vertical Cloud Structure and Gravity in Exoplanet and Brown Dwarf Atmospheres
14251 Amy E. Reines, National Optical Astronomy Observatory, AURA The Structures of Dwarf Galaxies Hosting Massive Black Holes
14254 Tommaso L. Treu, University of California - Los Angeles Accurate cosmography from gravitational time delays: 2.3% on H0 from deep WFC3 images of lensed quasars
14257 Dennis Bodewits, University of Maryland Far UV spectroscopic measurements of the deuterium abundance of comets
14327 Saul Perlmutter, University of California - Berkeley See Change: Testing time-varying dark energy with z>1 supernovae and their massive cluster hosts
14333 Robert P. Kirshner, Harvard University SAINTS: Images of SN 1987A
14358 Roberto Assef, Diego Portales University Extremely Luminous Dusty Quasars with Unobscured UV Emission: Dual AGN or Extreme Single AGN Systems?

Selected highlights

GO 13847: Determining the Mass of Proxima Centauri through Astrometric Microlensing


An AAO image centred on the nearby red dwarf, Proxima Centauri
Gravitational lensing is a consequence of general relativity. Its effects were originally quantified by Einstein himself in the mid-1920s. In the 1930s, Fritz Zwicky suggested that galaxies could serve as lenses, but lower mass objects can also also lens background sources. Bohdan Paczynski pointed out in the mid-1980s that this offered a means of detecting dark, compact objects that might contribute to the dark-matter halo. Paczcynski's suggestion prompted the inception of several large-scale lensing surveys, notably MACHO, OGLE, EROS and DUO. Those wide-field imaging surveys have target high density starfields towards the Magellanic Clouds and the Galactic Bulge, and have succeeded in identifying numerous lensing events. The duration of each event depends on several factors, including the tangential motion of the lens and its mass. Long-term events are generally associated with a massive lens, but duration alone is not sufficient to characterise the lens since a slow-moving source with low mass can mimic a fast-moving high-mass lens. However, microlensing not only leads to flux amplification, but also to small astrometric motions, caused by the appearance and disappearance of features in the lensed light. Those motions serve as a mass discriminant - higher mass lenses produce larger amplitude motions. The present program aims to capitalise on this fact by measuring the positional deflection of a background stars induced by the close passage of Proxima Centauri, the late-type, low-luminosity M dwarf tertiary companion of Alpha Centauri and the nearest star to the Sun. As a nearby star, Proxima has a well-defined proper motion and parallax, and it will pass close (within 1.5 arcsecnds) to two 18th magnitude stars in May 2015 and June 2015, respectively. The expected signals during the encounters (i.e. the deflection of the background stars) are expected to be approximately 0.5 millarcseconds, and therefore within HST's astrometric capabilities.

GO 14164: Exploring the nature and synchronicity of early cluster formation in the Local Group


The cluster NGC 2257 in the Large Magellanic Cloud
Globular clusters are members of the Galactic halo population, which formed during the first extensive period of star formation in the Milky Way. As such, the properties of the 106 to 107 stellar constituents can provide crucial insight into the earliest stages of galaxy formation. Recent observations have shown that many of these systems have multiple stellar populations, with different chemical abundances and ages, indicating a much more complex star formation history than previously thought. Deep imaging with HST has enabled the construction of colour-magnitude diagrams that offer significant insight into the relative ages of Galactic globulars, revealing strong correlations between age and metallicity that are currently difficult to explain. The present program aims to extend observations to the oldest globular cluster systems in the nearby galaxies, primarily the Large Magellanic Cloud. The Advanced Camera for Surveys and Wide-Field Camera 3 will be used to obtain data in the F336W, F606W and F814W filters, corresponding to the U, R and I photometric passbands. Those data will enable a comparison of the earliest epochs of star formation in the Milky Way and LMC.

GO 14212: A Snapshot Imaging Survey of Spitzer-selected Young Stellar Objects in Nearby Star Formation Regions


HST image of the face-on debris disk in the G2 dwarf, HD 107146
Planet formation occurs in circumstellar disks around young stars. Most of the gaseous content of those disks dissipates in less than 10 million years, leaving dusty debris disks that are detectable through reflect light at near-infrared and, to a lesser extent, optical wavelengths. The structure of those disks is affected by massive bodies (i.e. planets and asteroids), which, through dynamical interactions and resonances, can produce rings and asymmetries. Analysis of the rangle of morphological structure in these systems provides insight into the distribution of properties of planetary systems. HST currently provides almost the only means of achieving the high-contrast required for the detection of scattered light from these disks in the presence of the bright parent stars. While many such systems have been observed, only a relatively small number of disks have been imaged successfully at visual or near-infrared wavelengths. The present SNAPSHOT program aims to expand the sample by targetting sources within nearby star-forming regions that have past Spitzer observations that indicate a significant infra-red excess, suggesting the presence of a circumstellar disk.The Advanced Camera for Surveys will be used to obtain images in the V and I-bands (F606W and F814W filter), providing high resolution data that can be analysed for direct evidence of disks or companions.

GO 14333: SAINTS - Images of SN1987A


November 2003 HST image of the SN1987A gaseous ring
SN1987A, in the Large Magellanic Cloud, is (as far as we know) the nearest supernova to the Sun since Kepler's supernova of 1604. While its eruption, in January 1987, predated HST's launch by over 3 years, the remnant has been a regular observational target since the installation of COSTAR at the first servicing mission. Those high resolution observations have revealed the development, and evolution, of extensive, intricate structures as the blast wave from SN1987A encounters the surrounding interstellar medium. In particular, a striking circum-remnant ring has developed, with numerous hot spots stimulated by the fastest moving debris. The present HST program continues to monitor the development of those features, using a series of observations that are co-ordinated with the Chandra X-ray Observatory. Over the past few cycles, the hotspots are fusing as the shock fully enters the ring, and photons from these regions are exciting previously hidden gas outside the ring, illuminating mass lost from the progenitor before the explosion. The inner debris are now well resolved, and clearly aspherical. The present program focuses on imaging with the WFC3-UVIS camera, capturing multicolour data, including H-alpha. Overall, these observations, combined with high resolution imaging with ALMA, provide crucial insight into the earliest stages of formation of a supernova remnant.

Past weeks:
page by Neill Reid, updated 23/12/2014
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