This week on HST


HST Programs: February 1 - February 7, 2016

Program Number Principal Investigator Program Title
13646 Ryan Foley, University of Illinois at Urbana - Champaign Understanding the Progenitor Systems, Explosion Mechanisms, and Cosmological Utility of Type Ia Supernovae
13702 Sally Oey, University of Michigan Mapping the LyC-Emitting Regions of Local Galaxies
13740 Daniel Stern, Jet Propulsion Laboratory Clusters Around Radio-Loud AGN: Spectroscopy of Infrared-Selected Galaxy Clusters at z>1.4
13757 Saurabh W. Jha, Rutgers the State University of New Jersey The Progenitor System of a Peculiar Thermonuclear White-Dwarf Supernova
13760 Derck L. Massa, Space Science Institute Filling the gap --near UV, optical and near IR extinction
13763 S. Thomas Megeath, University of Toledo WFC3 Spectroscopy of Faint Young Companions to Orion Young Stellar Objects
13765 Bradley M Peterson, The Ohio State University A Cepheid-Based Distance to the Benchmark AGN NGC 4151
13783 George G. Pavlov, The Pennsylvania State University Thermal evolution of old neutron stars
13856 Denija Crnojevic, Texas Tech University Resolving the faint end of the satellite luminosity function for the nearest elliptical Centaurus A
14038 Jennifer Lotz, Space Telescope Science Institute HST Frontier Fields - Observations of Abell 370
14071 Sanchayeeta Borthakur, The Johns Hopkins University How are HI Disks Fed? Probing Condensation at the Disk-Halo Interface
14076 Boris T. Gaensicke, The University of Warwick An HST legacy ultraviolet spectroscopic survey of the 13pc white dwarf sample
14084 Seth Redfield, Wesleyan University Connecting Earth with its Galactic Environment: Probing Our Interstellar Past Along the Historical Solar Trajectory
14089 Paul A. Wilson, CNRS, Institut d'Astrophysique de Paris Far-UV observations of H, C, N and O in exocomets of Beta Pic
14098 Harald Ebeling, University of Hawaii Beyond MACS: A Snapshot Survey of the Most Massive Clusters of Galaxies at z>0.5
14102 Claus Leitherer, Space Telescope Science Institute The II Zw 40 Supernebula: 30 Doradus on Steroids
14110 David Kent Sing, University of Exeter Charaterizing the atmosphere of the enlarged Neptune-mass planet HAT-P-26b
14118 Luigi R. Bedin, Osservatorio Astronomico di Padova The end of the White Dwarf Cooling Sequences of Omega Centauri
14134 Swara Ravindranath, Space Telescope Science Institute Spectral Diagnostics for the Reionization Era: Exploring the Semi-Forbidden CIII] Emission in Low Metallicity Green Pea Galaxies
14141 Guy Worthey, Washington State University NGSL Extension 1. Hot Stars and Evolved Stars
14163 Mickael Rigault, Humboldt Universitat zu Berlin Honing Type Ia Supernovae as Distance Indicators, Exploiting Environmental Bias for H0 and w.
14172 Brendan Bowler, University of Texas at Austin Imaging Accreting Protoplanets in the Young Cluster IC 348
14189 Adam S. Bolton, University of Utah Quantifying Cold Dark Matter Substructure with a Qualitatively New Gravitational Lens Sample
14193 Catherine Espaillat, Boston University Footprints of the Magnetosphere: the Star- Disk Connection in T Tauri Stars
14206 Adam Riess, The Johns Hopkins University A New Threshold of Precision, 30 micro-arcsecond Parallaxes and Beyond
14212 Karl Stapelfeldt, NASA Goddard Space Flight Center 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
14227 Casey Papovich, Texas A & M University The CANDELS Lyman-alpha Emission At Reionization (CLEAR) Experiment
14234 Joshua D. Simon, Carnegie Institution of Washington The Lowest Luminosity Star-Forming Galaxy
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
14259 Denija Crnojevic, Texas Tech University Resolved halo substructures beyond the Local Group: the assembly histories of NGC 253 and NGC 5128
14262 Knud Jahnke, Max-Planck-Institut fur Astronomie, Heidelberg Are the fastest growing black holes at z=2 caused by major galaxy mergers?
14327 Saul Perlmutter, University of California - Berkeley See Change: Testing time-varying dark energy with z>1 supernovae and their massive cluster hosts
14465 Jonathan Charles Tan, University of Florida Peering to the Heart of Massive Star Birth
14474 David Jewitt, University of California - Los Angeles Comet P/2010 V1 fragmentation event

Selected highlights

GO 13763: WFC3 Spectroscopy of Faint Young Companions to Orion Young Stellar Objects


An image of the orion Nebula superimposed on the 13CO map of Orion A (from this link ).
The Orion association is the largest nearby star-forming complex, providing a key laboratory for unlocking the secrets of star formation. As such, it has been subject to intense scrutiny at all wavelengths from both ground and space. Surveys at near-infrared and mid-infrared wavelenths, notably by Spitzer, have identified an extensive number of embedded sources, young stellar objects (YSOs) that are still accreting from the surrounding molecular gas. A follow-up HST proposal focused on more than 250 sources within the Orion A molecular cloud, the complex that includes the Orion Nebula Cluster. Initially,NICMOS was used to survey a subset of the protostars; following SM4, the WFC3-IR camera was applied to the task. The observations provided an excellent complement to Spitzer since, while HST cannot offer either the same areal coverage or sensitivity at mid-infrared wavelegths, HST gives a resolution close to 0.1 arcsecond, an order of magnitude higher than the Spitzer images. That program resulted in the detection of several very faint companions, with luminosities consistent with planetary mass (5 MJ) objects. The present program is using the G141 grism on WFC3-IR to obtain spectra and determine the true nature of these objects.

GO 13783: Thermal evolution of old neutron stars


Artist's impression of a neutron star
Neutron stars are extremely compact (~10 km diameter) massive (~1.4 to 2 solar mass) remnants of high mass (> 7 solar mass) stars. Formed during the gravitational core-collapse of Type Ib, Ic and II supernovae, they have initial temperatures exceeding 1011 Kelvon, but cool very rapidly with time. Their existence was originally proposed by Zwicky and Baade in the 1930s, but they remained unobserved until the late-1960s, when Hewish and Bell identified a pulsing radio source in the Crab nebula as a neutron star. (Hewish and Okoye had previously identified "an unusual source of high radio brightness temperature" within the crab.) Neutron stars have strong magnetic fields and rapid rotation, leading to radiation beaming along the magnetic poles; the observed pulses result from the beams sweeping across the terrestrial line of sight. Numerous pulsars are currently known, but direct observations of the neutron star's "photosphere" are much rarer. At their birth, neutron stars are extremely hot, and the initial thermal evolution can be traced by monitoring the base level X-ray flux (ie photospheric, not beamed, radiation). That method is only available for neutron stars younger than a few Myrs; older systems have cooled to the extent that the peak flux is at UV wavelengths, but those systems are also extremely faint. To date only one system has been detected at far-UV wavelengths by HST. The present program aims to use the ACS Solar Blind Camera to obtain far-UV imaging of three pulsars with ages between 17 Myrs and ~6 Gyrs, with the aim of further constraining the cooling timescales.

GO 14110: Characterizing the atmosphere of the enlarged Neptune-mass planet HAT-P-26b


Artist's impression an exo-Neptune
HAT-P-26b is a Neptune-mass planet orbiting a fairly anonymous 11th magnitude K dwarf, GSC 0320-01027, with a period of 4.23 days. The planet transits the parent star, and those transits were discovered in 2010 by the HATNet (Hungarian Automated Transit Netowrk) project - a network of small telescopes distributed in various sites around the globe, enabling near-continuous observations (weather permitting) of exoplanet transits. The planet has a mass only 6% that of Jupiter, comparable with that of Neptune. HAT-P-26b is almost twice as big as Neptune, however, with 56% the radius of Jupiter. This indicates that the planet has a low mean density, possibly due to the outer atmospheric layers being inflated due to its close proximity to the parent star. The present program aims to use the WFC3 G141 grism to measure the transmission spectrum of the planet during transit, searching for absorption features due to water, methane, sodium and potassium, as well as probing possible contributions from Rayleigh scattering that might illuminate the properties and composition of the outer atmosphere.

GO 14118: The end of the White Dwarf Cooling Sequences of Omega Centauri


ACS imaging of the central regions of Omega Cen
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. Hubble has conducted a significant number of observing programs targeting these systems, with the majority designed to obtain moderately deep, multicolour imaging data of a range of clusters. Those programs probe evolved stars, on the red giant and horizontal branch, and generally extend only a few magnitudes below the main-sequence turnoff. Noetheless, the exqusite photometric precision offered by HST's camera has revealed that the majority of these systems have multiple stellar populations, rather than conforming to traditional single-burst formation models. A few clusters have been studied in detail - specifically, the two nearest clusters, NGC 6397, an extremely metal-poor cluster, and M4, a moderately metal-rich systems; Omega Centauri, one of the most massive clusters, perhaps even the remnant core of a dwarf galaxy; and 47 Tucanae, one of the higher metallicity systems, lying in the foreground of the Small Magellanic Cloud. Deep imaging of all four clusters has succeeded in clear detecion of the white dwarf cooling sequence in those clusters, and those data have been used to derive age estimates. The present program builds on past observations in aiming to probe the multiple white dwarf cooling sequences in Omega Cen. The WFC3/UVIS and ACS/WFC cameras will be used to obtain multi-colour imaging of the cluster. Those observations should enable measurement over the full extent of the white dwarf cooling sequences, offering the potential of resolving the nature and origin(s) of the distinct stellar populations.

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