Development of the Secon Generation Wide Field and Planetary Camera for Hubble Space Telescope
This paper describes the history of the development of the optical system for WFPC-2.
Hubble Space Telescope Wide Field and Planetary Ca↗
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Asteroid Trails in Hubble Space Telescope WFPC2 Images: First Results
Careful examination of 28,460 selected Wide Field and Planetary Camera 2 (WFPC2) long exposures from 1994, 1995 and early 1996 has revealed trails of 96 distinct moving objects.
asteroids Hubble Space Telescope↗
Saturn's Hydrogen Aurora, WFPC2 Imaging from the Hubble Space Telescope
WFPC2/HST images of Saturn's far-ultraviolet aurora reveal emissions confined to a narrow band of latitudes near Saturn's north and south poles. The aurorae are most prominent in the morning sector with patterns that appear fixed in local time.
far-ultraviolet aurora Hubble Space Telescope WFPC↗
A New Estimate of Hubble's Constant From The Gravitational Lens PKS 1830-211
The Einstein ring gravitational lens PKS 1830-211 consistents of two bright, milliarcsecond-scale radio components separated by 1 arcsec and connected by a fainter ring of radio emission (Rao and Subrahmanyan 1988; Jauncey et al. 1991).
Gravitational Lens PKS 1830-211 Hubble's Constant↗
Far-ultraviolet imaging of the Hubble Deep Field North
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far-ultraviolet Hubble Deep Field North↗
Erratum: The Carnegie Hubble Program: The Leavitt Law at 3.6 micron and 4.5 micron in the Large Magellanic Cloud (2011, APJ, 743, 76)
Due to an error at the publisher, an incorrect version of Table 3 appeared in the published article. The updated version of Table 3 is given.
CARNEGIE↗
Wide-Field Hubble Space Telescope Observations of the Globular Cluster System in NGC 1399*
We present a comprehensive high spatial resolution imaging study of globular clusters (GCs) in NGC 1399, thecentral giant elliptical cD galaxy in the Fornax galaxy cluster, conducted with the Advanced Camera for Surveys(ACS) aboard theHubble Space Telescope(HST).Using a novel technique to construct drizzled point-spreadfunction libraries for HSTACS data, we accurately determine the fidelity of GC structural parameter measurementsfrom detailed artificial star cluster experiments and show the superior robustness of the GC half-light radius,rh,compared with other GC structural parameters, such as King core and tidal radius. The measurement ofrhfor themajor fraction of the NGC 1399 GC system reveals a trend of increasingrhversus galactocentric distance,Rgal,out to about 10 kpc and a flat relation beyond. This trend is very similar for blue and red GCs, which are found tohave a mean size ratio ofrh,redrh,blue0.820.11 at all galactocentric radii from the core regions of the galaxyout to40 kpc. This suggests that the size difference between blue and red GCs is due to internal mechanismsrelated to the evolution of their constituent stellar populations. Modeling the mass density profile of NGC 1399shows that additional external dynamical mechanisms are required to limit the GC size in the galaxy halo regionstorh2 pc. We suggest that this may be realized by an exotic GC orbit distribution function, an extended darkmatter halo, andor tidal stress induced by the increased stochasticity in the dwarf halo substructure at largergalactocentric distances. We compare our results with the GCrhdistribution functions in various galaxies and findthat the fraction of extended GCs withrh5 pc is systematically larger in late-type galaxies compared with GCsystems in early-type galaxies. This is likely due to the dynamically more violent evolution of early-type galaxies.We match our GCrhmeasurements with radial velocity data from the literature and split the resulting sample at themedianrhvalue into compact and extended GCs. We find that compact GCs show a significantly smaller line-of-sight velocity dispersion,cmp22525 km s1, than their extended counterparts,ext31721 km s1.Considering the weaker statistical correlation in the GCrhcolor and the GCrhRgalrelations, the more significantGC sizedynamics relation appears to be astrophysically more relevant and hints at the dominant influence of theGC orbit distribution function on the evolution of GC structural parameters.
Hubble↗
The Home Stretch Almost! Science with the Hubble and James Webb Space Telescope V
JWST has Made tremendous progress in the last few years. JWST Is fully immersed in integration and test, but testing JWST is a formable challenge. JWST's size, complexity, and cryogenic characteristics require a multifaceted test plan to verify mission readiness. Each of these tests are opportunities to uncover issues which must be corrected to be able to move forward. All observatory control, science planning, and science data processing operational systems are on schedule.
JWST Hubble↗
Demographics of Sloan digital sky survey galaxies along the Hubble sequence
We present the statistical properties of a volume-limited sample of 7429 nearby (z = 0.033-0.044) galaxies from the Sloan Digital Sky Survey Data Release 7. Our database includes morphology distribution as well as the structural and spectroscopic properties of each morphology type based on the recent remeasurements of spectral line strengths by Oh and collaborators. Our database does not include galaxies that are apparently smaller and flatter because morphology classification of them turned out to be difficult. Our statistics confirmed the up-to-date knowledge of galaxy populations, e.g., correlations between morphology and line strengths as well as the derived ages. We hope that this database will be useful as a reference.
79 ASTRONOMY AND ASTROPHYSICS↗
THE VELOCITY ANISOTROPY OF DISTANT MILKY WAY HALO STARS FROM HUBBLE SPACE TELESCOPE PROPER MOTIONS
Based on long baseline (5-7 years) multi-epoch HST/ACS photometry, used previously to measure the proper motion of M31, we present the proper motions (PMs) of 13 main-sequence Milky Way halo stars. The sample lies at an average distance of r {approx_equal} 24 kpc from the Galactic center, with a root-mean-square spread of 6 kpc. At this distance, the median PM accuracy is 5 km s{sup -1}. We devise a maximum likelihood routine to determine the tangential velocity ellipsoid of the stellar halo. The velocity second moments in the directions of the Galactic (l, b) system are {sup 1/2}= 123{sup +29}{sub -23} km s{sup -1}, and {sup 1/2}= 83{sup +24}{sub -16} km s{sup -1}. We combine these results with the known line-of-sight second moment, {sup 1/2}= 105{+-}5 km s{sup -1}, at this (r) to study the velocity anisotropy of the halo. We find approximate isotropy between the radial and tangential velocity distributions, with anisotropy parameter {beta}= 0.0{sup +0.2}{sub -0.4}. Our results suggest that the stellar halo velocity anisotropy out to r {approx} 30 kpc is less radially biased than solar neighborhood measurements. This is opposite to what is expected from violent relaxation, and may indicate the presence of a shell-type structure at r {approx} 24 kpc. With additional multi-epoch HST data, the method presented here has the ability to measure the transverse kinematics of the halo for more stars, and to larger distances. This can yield new improved constraints on the stellar halo formation mechanism, and the mass of the Milky Way.
79 ASTRONOMY AND ASTROPHYSICS↗
THE MEGAMASER COSMOLOGY PROJECT. IV. A DIRECT MEASUREMENT OF THE HUBBLE CONSTANT FROM UGC 3789
In Papers I and II from the Megamaser Cosmology Project, we reported initial observations of H{sub 2}O masers in an accretion disk of a supermassive black hole at the center of the galaxy UGC 3789, which gave an angular-diameter distance to the galaxy and an estimate of H{sub 0} with 16% uncertainty. We have since conducted more very long baseline interferometric observations of the spatial-velocity structure of these H{sub 2}O masers, as well as continued monitoring of its spectrum to better measure maser accelerations. These more extensive observations, combined with improved modeling of the masers in the accretion disk of the central supermassive black hole, confirm our previous results, but with significantly improved accuracy. We find H{sub 0} = 68.9 {+-} 7.1 km s{sup -1} Mpc{sup -1}; this estimate of H{sub 0} is independent of other methods and is accurate to {+-}10%, including sources of systematic error. This places UGC 3789 at an angular-diameter distance of 49.6 {+-} 5.1 Mpc, with a central supermassive black hole of (1.16 {+-} 0.12) Multiplication-Sign 10{sup 7} M{sub Sun }.
79 ASTRONOMY AND ASTROPHYSICS↗
On the origin of the Hubble sequence: I. Insights on galaxy color migration from cosmological simulations
An analysis of more than 3000 galaxies resolved at better than 114 h{sup –1} pc at z = 0.62 in a 'LAOZI' cosmological adaptive mesh refinement hydrodynamic simulation is performed and insights are gained on star formation quenching and color migration. The vast majority of red galaxies are found to be within three virial radii of a larger galaxy at the onset of quenching, when the specific star formation rate experiences the sharpest decline to fall below ∼10{sup –2}-10{sup –1} Gyr{sup –1} (depending on the redshift). Thus, we shall call this mechanism 'environment quenching', which encompasses satellite quenching. Two physical processes are largely responsible: Ram pressure stripping first disconnects the galaxy from the cold gas supply on large scales, followed by a longer period of cold gas starvation taking place in a high velocity-dispersion environment, in which during the early part of the process, the existing dense cold gas in the central region (≤10 kpc) is consumed by in situ star formation. On average, quenching is found to be more efficient (i.e., a larger fraction of galaxies being quenched) but not faster (i.e., the duration being weakly dependent on the environment) in a denser environment. Throughout this quenching period and the ensuing one in the red sequence, galaxies follow nearly vertical tracks in the color-stellar mass diagram. In contrast, individual galaxies of all masses grow most of their stellar masses in the blue cloud, prior to the onset of quenching, and progressively more massive blue galaxies with already relatively older mean stellar ages continue to enter the red sequence. Consequently, correlations among observables of red galaxies—such as the age-mass relation— are largely inherited from their blue progenitors at the onset of quenching. While the color makeup of the entire galaxy population strongly depends on the environment, which is a direct result of environment quenching, physical properties of blue galaxies as a subpopulation show little dependence on the environment. A variety of predictions from the simulation are shown to be in accordance with extant observations.
79 ASTRONOMY AND ASTROPHYSICS↗
The emergent 1.1-1.7 μm spectrum of the exoplanet COROT-2B as measured using the Hubble space telescope
We have used Hubble/WFC3 and the G141 grism to measure the secondary eclipse of the transiting, very hot Jupiter CoRoT-2b in the 1.1-1.7 μm spectral region. We find an eclipse depth averaged over this band equal to 395{sub −45}{sup +69} parts per million, equivalent to a blackbody temperature of 1788 ± 18 K. We study and characterize several WFC3 instrumental effects, especially the 'hook' phenomenon described by Deming et al. We use data from several transiting exoplanet systems to find a quantitative relation between the amplitude of the hook and the exposure level of a given pixel. Although the uncertainties in this relation are too large to allow us to develop an empirical correction for our data, our study provides a useful guide for optimizing exposure levels in future WFC3 observations. We derive the planet's spectrum using a differential method. The planet-to-star contrast increases to longer wavelength within the WFC3 bandpass, but without water absorption or emission to a 3σ limit of 85 ppm. The slope of the WFC3 spectrum is significantly less than the slope of the best-fit blackbody. We compare all existing eclipse data for this planet to a blackbody spectrum, and to spectra from both solar abundance and carbon-rich (C/O = 1) models. A blackbody spectrum is an acceptable fit to the full data set. Extra continuous opacity due to clouds or haze, and flattened temperature profiles, are strong candidates to produce quasi-blackbody spectra, and to account for the amplitude of the optical eclipses. Our results show ambiguous evidence for a temperature inversion in this planet.
79 ASTRONOMY AND ASTROPHYSICS↗
Hubble space telescope/advanced camera for surveys confirmation of the dark substructure in A520
We present a weak-lensing study of the cluster A520 based on Advanced Camera for Surveys (ACS) data. The excellent data quality provides a mean source density of ∼109 arcmin{sup –2}, which improves both resolution and significance of the mass reconstruction compared to a previous study based on Wide Field Planetary Camera 2 (WFPC2) images. We take care in removing instrumental effects such as the charge trailing due to radiation damage of the detector and the position-dependent point-spread function. This new ACS analysis confirms the previous claims that a substantial amount of dark mass is present between two luminous subclusters where we observe very little light. The centroid of the dark peak in the current ACS analysis is offset to the southwest by ∼1' with respect to the centroid from the WFPC2 analysis. Interestingly, this new centroid is in better agreement with the location where the X-ray emission is strongest, and the mass-to-light ratio estimated with this centroid is much higher (813 ± 78 M {sub ☉}/L {sub R☉}) than the previous value; the aperture mass with the WFPC2 centroid provides a consistent mass. Although we cannot provide a definite explanation for the dark peak, we discuss a revised scenario, wherein dark matter with a more conventional range (σ{sub DM}/m {sub DM} < 1 cm{sup 2} g{sup –1}) of self-interacting cross-section can lead to the detection of this dark substructure. If supported by detailed numerical simulations, this hypothesis opens up the possibility that the A520 system can be used to establish a lower limit of the self-interacting cross-section of dark matter.
79 ASTRONOMY AND ASTROPHYSICS↗