Search Publications
Star Formation Rates in Resolved Galaxies: Calibrations with Near- and Far-infrared Data for NGC 5055 and NGC 6946
Helou, G.; Roussel, H.; Calzetti, Daniela +21 more
We use the near-infrared Brγ hydrogen recombination line as a reference star formation rate (SFR) indicator to test the validity and establish the calibration of the Herschel/PACS 70 µm emission as a SFR tracer for sub-galactic regions in external galaxies. Brγ offers the double advantage of directly tracing ionizing photons and of being rel…
Dynamics of Large Fragments in the Tail of Active Asteroid P/2010 A2
Jewitt, David; Agarwal, Jessica; Weaver, Harold
We examine the motions of large fragments at the head of the dust tail of the active asteroid P/2010 A2. In previous work, we showed that these fragments were ejected from the primary nucleus in early 2009, either following a hypervelocity impact or by rotationally induced breakup. Here, we follow their positions through a series of Hubble Space T…
Investigating the Potential Dilution of the Metal Content of Hot Gas in Early-type Galaxies by Accreted Cold Gas
Irwin, Jimmy A.; Su, Yuanyuan
The measured emission-weighted metal abundance of the hot gas in early-type galaxies has been known to be lower than theoretical expectations for 20 years. In addition, both X-ray luminosity and metal abundance vary significantly among galaxies of similar optical luminosities. This suggests some missing factors in the galaxy evolution process, esp…
The Optical Colors of Giant Elliptical Galaxies and their Metal-Rich Globular Clusters Indicate a Bottom-Heavy Initial Mass Function
Kruijssen, J. M. Diederik; Goudfrooij, Paul
We report a systematic and statistically significant offset between the optical (g - z or B - I) colors of seven massive elliptical galaxies and the mean colors of their associated massive metal-rich globular clusters (GCs) in the sense that the parent galaxies are redder by ~0.12-0.20 mag at a given galactocentric distance. However, spectroscopic…
Helioseismology of Pre-emerging Active Regions. I. Overview, Data, and Target Selection Criteria
Leka, K. D.; Barnes, G.; Birch, A. C. +4 more
This first paper in a series describes the design of a study testing whether pre-appearance signatures of solar magnetic active regions were detectable using various tools of local helioseismology. The ultimate goal is to understand flux-emergence mechanisms by setting observational constraints on pre-appearance subsurface changes, for comparison …
The Ages of High-mass X-Ray Binaries in NGC 2403 and NGC 300
Williams, Benjamin F.; Dolphin, Andrew; Eracleous, Michael +2 more
We have examined resolved stellar photometry from HST imaging surrounding 18 high-mass X-ray binary (HMXB) candidates in NGC 300 and NGC 2403 as determined from combined Chandra/HST analysis. We have fit the color-magnitude distribution of the surrounding stars with stellar evolution models. All but one region in NGC 300 and two in NGC 2403 contai…
Green Galaxies in the COSMOS Field
Kong, Xu; Pan, Zhizheng; Fan, Lulu
We present research on the morphologies, spectra, and environments of ≈2350 "green valley" galaxies at 0.2 < z < 1.0 in the COSMOS field. The bimodality of dust-corrected NUV-r + color is used to define "green valley"; it removes dusty star-forming galaxies from galaxies that are truly transitioning between the blue cloud and the …
The Discrepant Kinematics of ORLs and CELs in NGC 7009 as a Function of Ionization Structure
Richer, Michael G.; Georgiev, Leonid; Arrieta, Anabel +1 more
We present spatially and velocity-resolved echelle spectroscopy for NGC 7009 obtained with the UVES spectrograph at the European Southern Observatory's Very Large Telescope. Our objective is to analyze the kinematics of emission lines excited by recombination and collisions with electrons to determine whether similarities or differences could be u…
A Deep Search for Faint Galaxies Associated with Very Low-redshift C IV Absorbers: A Case with Cold-accretion Characteristics
Tripp, Todd M.; Prochaska, J. Xavier; Davé, Romeel +4 more
Studies of QSO absorber-galaxy connections are often hindered by inadequate information on whether faint/dwarf galaxies are located near the QSO sight lines. To investigate the contribution of faint galaxies to QSO absorber populations, we are conducting a deep galaxy redshift survey near low-z C IV absorbers. Here we report a blindly detected C I…
Herschel Reveals Massive Cold Clumps in NGC 7538
Bernard, J. -P.; Martin, P. G.; Hill, T. +30 more
We present the first overview of the Herschel observations of the nearby high-mass star-forming region NGC 7538, taken as part of the Herschel imaging study of OB young stellar objects (HOBYS) Key Programme. These PACS and SPIRE maps cover an approximate area of one square degree at five submillimeter and far-infrared wavebands. We have identified…