This week on HST

HST Programs: June 22 - June 28, 2015

Program Number Principal Investigator Program Title
13390 Nathan Smith, University of Arizona A Time-Lapse Movie of the Kinematics Across the Carina Nebula with ACS
13641 Peter Capak, California Institute of Technology A Detailed Dynamical And Morphological Study Of 5
13642 Nathalie Degenaar, University of Cambridge The evolutionary link between low-mass X-ray binaries and millisecond radio pulsars
13647 Ryan Foley, University of Illinois at Urbana - Champaign Testing the Standardizability of Type Ia Supernovae with the Cepheid Distance of a Twin Supernova
13650 Kevin France, University of Colorado at Boulder The MUSCLES Treasury Survey: Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems
13665 Bjoern Benneke, California Institute of Technology Exploring the Diversity of Exoplanet Atmospheres in the Super-Earth Regime
13669 Marcella Carollo, Eidgenossiche Technische Hochschule (ETH) The star-formation histories within clumpy disks at z ~ 2.2
13677 Saul Perlmutter, University of California - Berkeley See Change: Testing time-varying dark energy with z>1 supernovae and their massive cluster hosts
13684 Schuyler D. Van Dyk, California Institute of Technology A Wolf-Rayet Progenitor for iPTF13bvn?
13691 Wendy L. Freedman, University of Chicago CHP-II: The Carnegie Hubble Program to Measure Ho to 3% Using Population II
13695 Benne W. Holwerda, Sterrewacht Leiden STarlight Absorption Reduction through a Survey of Multiple Occulting Galaxies (STARSMOG)
13707 Suzanna Randall, European Southern Observatory - Germany Mapping the Extreme Horizontal Branch instability strip in omega Centauri
13720 Stephen E. Zepf, Michigan State University Testing Models of the Black-Hole X-ray Source in the NGC4472 Globular Cluster RZ2109 with COS UV Spectroscopy
13728 Steven Kraemer, Catholic University of America Do QSO2s have Narrow Line Region Outflows? Implications for quasar-mode feedback
13749 David V. Bowen, Princeton University Baryon Structures Around Nearby Galaxies: Using an Edge-On Disk to Assess Inflow/Outflow Models
13767 Michele Trenti, University of Melbourne Bright Galaxies at Hubble's Detection Frontier: The redshift z~9-10 BoRG pure-parallel survey
13776 Michael D. Gregg, University of California - Davis Completing The Next Generation Spectral Library
13779 Sangeeta Malhotra, Arizona State University The Faint Infrared Grism Survey (FIGS)
13816 Misty C. Bentz, Georgia State University Research Foundation High-Resolution Imaging of Active Galaxies with Direct Black Hole Mass Measurements
13821 Andrew C. Fabian, University of Cambridge H-alpha Filaments and Feedback in NGC4696 at the centre of the Centaurus cluster
13852 Rongmon Bordoloi, Massachusetts Institute of Technology How Galaxy Mergers Affect Their Environment: Mapping the Multiphase Circumgalactic Medium of Close Kinematic Pairs
13856 Denija Crnojevic, Texas Tech University Resolving the faint end of the satellite luminosity function for the nearest elliptical Centaurus A

Selected highlights

GO 13650: The MUSCLES Treasury Survey: Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems

SOHO image of an extremely strong solar flare
M dwarfs - at least, the subset of M dwarfs known as flare stars - are renowned for possessing extremely active chromospheres and coronae. Their discovery as highly variable objects happened largely by chance. Willem Luyten had noticed in 1924 that certain M dwarfs showed spectroscopic variability, with the occasional appearance of emission lines, while in the early 1940s van Maanen commented that two late-type dwarfs, Gl 412B (WX UMa) and Gl 285 (YZ CMi), had brightened by over a magnitude on a handful of parallax plates. The crucial observations came in 1948, when E.F Carpenter noticed that the fainter component of a wide binary system had brightened by more than 3 magnitudes in a matter of minutes. In the succeeding 50 years, these stars have been subjected to extensive observations, particularly at optical and X-ray wavelengths, and the underlying physical processes are relatively well understood. However, most attention has focused on the more active flare stars, and we still have a relatively uncertain grasp on the flare frequency among less active stars. This issue has acquired increased importance with the realisation that somewhere between 10 and 50% of M dwarfs host planetary systems. As the most populous stars in the Galaxy, this also makes M dwarfs the premier planet hosts. The habitable zones in those systems lie much closer to the parent star, and planets are correspondingly vulnerable to detrimental effects from enhanced UV radiation, particularly short-wavelength UV-C. This proposal uses the Cosmic Origins Spectrograph and the Space Telescope Imaging Spectrograph to obtain UV and optical spectra (1150-5700 Angstroms) of nearby M dwarfs, providing a broad sampling of the range of activity levels among these low mass dwarfs.

GO 13665: Exploring the Diversity of Exoplanet Atmospheres in the Super-Earth Regime

Artist's impression of the GJ 1214 system
The first exoplanet, 51 Peg b, was discovered through radial velocity measurements in 1995. 51 Pegb was followed by a trickle, and then a flood of other discoveries, as astronomers realised that there were other solar systems radically different from our own, where "hot jupiters" led to short-period, high-amplitude velocity variations. Then, in 1999, came the inevitable discovery that one of those hot jupiters. HD 209458b, was in an orbit aligned with our line of sight to the star, resulting in transits. Since that date, the number of known transiting exoplanet systems has grown to more than 100 from ground-based observations, most detected through wide-field photometric surveys, while the high-sensitivity data provided by Kepler has added a further 1000+ confirmed systems and ~2000 additional candidates. With the added numbers, observations have pushed detections to lower and lower masses, and it is now clear that the most common type of planet is the "super-Earth" - planets with masses that are several (3-6) times that of Earth and radii 2-4 times larger than Earth. One of the earliest examples is the planet circling the M dwarf, GJ 1214. Such planets have no obvious analogue in the Solar System, and the measured masses and diameters might reflect a range of interior structurees: large rocky bodies with relatively thin atmospheres; dense cores surrounded by a steam atmosphere; or "mini-Neptunes", with rock or ice cores surrounded by extended hydrogen or helium atmospheres. The present program aims to probe the diversity of these systems by using the G141 grism on Wide-Field Camera 3 to obtain time-resolved scanning observations of five transiting systems. The goal is to obtain data that will clearky distinguish between large scaleheight, hydrogen-dominated atmospheres and a more compact, steam-dominated systems.

GO 13691: CHP-II: The Carnegie Hubble Program to Measure Ho to 3% Using Population II

RR Lyrae's light curve at visible wavelengths
The classical cosmic distance scale rests on a series of distance indicators that step outwards from the Milky Way, establishing reliable measurements to ever more distant galaxies. Cepheids have long been the prime calibrators in this process, but other pulsating variables, notably Mira AGB long-period variables and RR Lyrae variables, also make significant contributions, while stellar population characteristics, such as the location of the tip of the red giant branch (TRGB), also play a role. RR Lyrae variables are evolved, near-solar-mass stars that are passing through the instability strip where it crosses the horizontal branch. With periods of 0.5 to 1.5 days, they have long served as distance indicators for old stellar populations (Baade's Population II). They have been known in the Galactic field and in Galactic globular clusters for over 150 years, and they are also present in the older stellar populations of the dwarf spheroidal Galactic satellites. Cluster (or dsph) RR Lyraes are particularly interesting, since their metallicities and ages can be deduced from analysis of the colour-magnitude diagrams for those systems. They are significantly less luminous than Cepheids, nonetheless, near-infrared photometric monitoring has demonstrated that these stars delineate a period-luminosity relation at those wavelengths that has the potential to establish distances to better than 1.5% accuracy. Distances to stellar populations can also be derived from measuring the location of the TRGB, marking the point in intermediate- and low-mass star evolution where core temperatures are raised to the point thatn helium ignites in the triple-alpha reaction, and the star evolves rapidly onto the horizontal branch. The present programs combines deep optical/far-red/near-IR imaging of moderately distant galaxies that have hosted Type Ia supernovae and of nearby galaxies with RR Lyraes with WFC3-IR observations of 4 individual Galactic variables with trigonometric parallaxes to cosmntruct a distance ladder that is independent of the Cepheid calibration. The oevrall goal is to define H0 to 3% accuracy.

GO 13767: Bright Galaxies at Hubble's Detection Frontier: The redshift z~9-10 BoRG pure-parallel survey

The ACS optical/far-red image of the Hubble Ultra Deep Field
Galaxy evolution in the early Universe is a discipline of astronomy that has been transformed by observations with the Hubble Space Telescope. The original Hubble Deep Field, the product of 10 days observation in December 1995 of a single pointing of Wide Field Planetary Camera 2, demonstrated conclusively that galaxy formation was a far from passive process. The images revealed numerous blue disturbed and irregular systems, characteristic of star formation in galaxy collisions and mergers. Building on this initial progam, the Hubble Deep Field South (HDFS) provided matching data for a second southern field, allowing a first assessment of likely effects due to field to field cosmic variance, and the Hubble Ultra-Deep Field (UDF) probed to even fainter magitude with the Advanced Camera for Surveys (ACS). The highest redshift objects found in the UDF have redshifts approaching z~7. Pushing to larger distances, and greater ages, demands observatons at near-infrared wavelengths, as the characteristics signatures of star formation are driven further redward in the spectrum. Wide Field Camera 3, installed in Servicing Mission 4, is well suited to these observations, and a number of programs are in place in Cycle 17 that address these issues. Indeed, WFC3 is employed in pure parallel mode by several programs. These take advantage of other science programs, usually with COS, that involve 2-5 orbit pointings on sources at high galactic latitude. The WFC3 pointing is unplanned, since it depends on the orientation adopted for the prime observations, but 2-5 orbits of IR imaging can reach galaxies at redshifts exceeding z=7 (potentially even z~8) in high latitude fields. The present program builds on similar programs in Cycles 17 and 19, and aims to detect the brightest galaxies at z~9, within 600 Myrs of the Big Bang.

Past weeks:
page by Neill Reid, updated 11/11/2014
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