This week on HST


HST Programs: January 1 - January 7 2018

Program Number Principal Investigator Program Title
13847 Kailash C. Sahu, Space Telescope Science Institute Determining the Mass of Proxima Centauri through Astrometric Microlensing
14241 Daniel Apai, University of Arizona Cloud Atlas: Vertical Cloud Structure and Gravity in Exoplanet and Brown Dwarf Atmospheres
14243 Deirdre Coffey, University College Dublin True Jet Rotation Probed in NUV Jet Core
14610 Julianne Dalcanton, University of Washington A Legacy Imaging Survey of M33.
14697 Bradley M Peterson, The Ohio State University A Cepheid Distance to NGC 4051
14767 David Kent Sing, University of Exeter The Panchromatic Comparative Exoplanetary Treasury Program
14777 Nahum Arav, Virginia Polytechnic Institute and State University Deciphering Quasar Outflows and Measuring their Contribution to AGN Feedback
15073 Boris T. Gaensicke, The University of Warwick Extreme evolved solar systems (EESS)
15076 Roberta M. Humphreys, University of Minnesota - Twin Cities The Recent Mass Loss History of the Red Hypergiant VY CMa
15113 Abhijit Saha, National Optical Astronomy Observatory, AURA Extending the DA white dwarf spectrophotometric network to the Southern Hemisphere
15133 Peter Erwin, Max-Planck-Institut fur extraterrestrische Physik Solving the Mystery of Galaxy Bulges and Bulge Substructure
15143 Keith S. Noll, NASA Goddard Space Flight Center Slow Rotating Trojans: Tidally Synchronized Binaries?
15153 Dan Watson, University of Rochester The jets and shocks of NGC 1333: a large WFC3 mosaic of [Fe II] and H I line emission
15165 Catherine Espaillat, Boston University Connecting mass accretion and ejection in pre-main sequence stars
15166 Alex V. Filippenko, University of California - Berkeley Continuing a Snapshot Survey of the Sites of Recent, Nearby Supernovae: Cycles 25 & 26
15171 Bryan Jason Holler, Space Telescope Science Institute The rotation period, orbit, and mass of Eris' satellite Dysnomia
15189 David John Wilson, The University of Warwick Post Common Envelope Binaries as probes of M dwarf stellar wind and habitable zone radiation environments
15211 Letizia Stanghellini, National Optical Astronomy Observatory, AURA Carbon in dusty, compact Galactic planetary nebulae: A study of AGB evolution and recycling in the Milky Way
15215 Vardha N. Bennert, Cal Poly Corporation, Sponsored Programs Department A Local Baseline of the Black Hole Mass - Host Galaxy Scaling Relations for Active Galaxies
15233 Will M. Grundy, Lowell Observatory Density of transneptunian object 229762 2007 UK126
15238 Adam L. Kraus, University of Texas at Austin The IMF to Planetary Masses Across the Milky Way
15242 Lucia Marchetti, Open University SNAPshot observations of the largest sample of lensed candidates in the Equatorial and Southern Sky identified with Herschel
15279 Sean Johnson, Princeton University Unveiling Quasar Fueling through a Public Snapshot Survey of Quasar Host Environments
15329 Edo Berger, Harvard University Fine-Tuned Search for Kilonova Emission in a Short Gamma-Ray Burst: Implications for the Progenitors, Advanced LIGO, and r-Process Nucleosynthesis
15348 Andrew James Levan, The University of Warwick The counterparts and environments of magnetars
15350 Walter Peter Maksym, Smithsonian Institution Astrophysical Observatory Resolved BPT Mapping of Nearby AGN
15355 Nao Suzuki, Institute for Physics and Mathematics of the Universe Perfect Blackbody Spectra for JWST and Next Generation UV-Opt-IR Standard Star Network
15405 Karen J. Meech, University of Hawaii Which way home? Finding the origin of our Solar System's first interstellar visitor
15413 Edward M. Cackett, Wayne State University Accretion disk reverberation mapping of the high Eddington rate Seyfert 1 Mrk 110
15424 William B. Sparks, Space Telescope Science Institute An intensive ultraviolet imaging campaign for Europa's plumes
15427 James M. Schombert, University of Oregon Exploring the Nature of Dark Matter Through Near-IR CMD's of LSB Galaxies
15429 Martin A. Cordiner, NASA Goddard Space Flight Center Is C60+ present in the diffuse interstellar medium?
15447 Karen J. Meech, University of Hawaii Which way home? Finding the origin of our Solar System's first interstellar visitor (Part II)cd
15448 Marianne Vestergaard, University of Copenhagen, Niels Bohr Institute Constraining the emergent EUV ionizing emission in the reawakening monster in Mrk 590

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. And now known to harbour a planetary system. 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 14777: Deciphering Quasar Outflows and Measuring their Contribution to AGN Feedback


An artist's impression of outflows from a massive black hole
Quasars and active galactic nuclei (AGN) are generally held to be powered by the accretion of material onto a central supermassive black hole. That accretion gives rise to strong, high energy electromagnetic emission and generates material outflow that provides a feedback mechanism that may have helped shape the formation and assembly of galaxies in the early universe. Hubble has undertaken extensive observations of these systems over its lifetime, particularly focusing on spectroscopy at ultraviolet wavelengths, probing the motions and ionisation levels of the outflowing gaseous material. The present program breaks new ground by using the Cosmic Origins Spectrograph to survey several high energy quasars at extreme ultraviolet wavelengths, between 500 and 1050 Angstroms. With the quasars at redshifts between 0.4 and 1.5, these observations probe rest-frame wavelengths extending well below 500 Angstroms. The measurements cover a regime that is rich with features of highly ionised elements, providing insight into the structure of the outflows close to the central black holes.

GO 15143: Slow Rotating Trojans: Tidally Synchronized Binaries?


Artist's impresson of the Patroclus/Menoetius system
The Solar System includes a number of regions occupied by numerous small solid bodies, notably the main asteroid belt, between the orbits of Mars and Jupiter, and the Edgeworth-Kuiper Belt, beyond the orbit of Neptune. More than 96,000 bodies have been catalogued in the former region, including the larger (few hundred km diameter) minor planets like Ceres, Pallas, Juno and Vesta. The main belt asteroids fall into three main categories: carbonaeous (C-type), silicate (S-type) and metal-rich (M-type). A subset of these asteroids have been captured by Jupiter into orbits that lead or trail Jupiter itself by ~ 60 degrees. These are the Trojan asteroids. The first, Achilles, was detected in 1908 by Max Wolf; there are now close to 4,000 known members, with the largest around 150 km in size; there may be as many as 600,000 larger than 1 km in diameter. One of the most interesting systems is 617 Patroclus, one of the largest at 140 km diameter, and one of 18 known binary Trojans with a similar-sized companion, Menoetius, at a separation of ~680 km. The system is tidally locked, leading to a noticeable slow rotation rate compared with other asteroids. The present program will use Hubble's Wide-Field Camera 3 to target six Trojan asteroids that are also known to have slow rotation rates, searching for potential companions. Once orbits are determined, binary asteroids provide a means of determing the mass, density and hence the composition of these objects.

GO 15328: The IMF to planetary masses across the Milky Way


The massive, dust-reddened open star cluster, Westerlund 2
The Initial Mass Function (IMF) is a fundamental parameter for star formation, defining how a gaseous molecular cloud collapses and transforms itself into star-like objects spanning a four-five decade range in masses. There have long been theoretical argments suggesting that the IMF should vary under different environmental conditions - clouds of different densities, chemical composition or radiation environment. The observational IMF has stubbornly resisted such changes. Westerlund 2 is a massive, young star cluster that lies somewhere between 4 and 7 kpc from the Sun in the constellation Carina in the general direction of the Galactic Centre. The cluster was discovered just over 50 years ago by Bengt Westerlund, but has only been subject to detailed scrutiny in more recent years since interstellar material along the line of sight leads to foreground absorption of around 14 magnitudes at optical wavelengths. Detailed investigations became possible as near-infrare astronomy came of age in the 1990s. These show that Westerlund 2 has an age of 1-2 Myrs, comparable with the Orion Nebula Cluster but significantly more massive. The cluster includes a dozen or so O stars within an extremely compact region. As a result, it presents an opportunity to examine how the star formation, and the IMF, might be influenced by such an extreme environment. The present proposal is using the WFC3-IR camera to map the cluster using the DASH technique, with a particularfocus on probing the low mas regime. Observations will be taken with the J and h abnds (F110W and F160W), together with medium-band imaging (F139M) centred on a water band. This will clearlty descriminate low-mass cluster members from foreground and (reddened) background stars. obtain deep, multi-band

Past weeks:
page by Neill Reid, updated 31/8/2017
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