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A Deep Chandra ACIS Study of NGC 4151. III. The Line Emission and Spectral Analysis of the Ionization Cone
Elvis, Martin; Zezas, Andreas; Schinnerer, Eva +6 more
This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy of the Seyfert 1 galaxy NGC 4151, devoted to study its complex circumnuclear X-ray emission. Emission features in the soft X-ray spectrum of the bright extended emission (L 0.3-2 keV ~ 1040 erg s-1) at r > 130 pc (2'…
The Variable Quiescent X-Ray Emission of the Transient Neutron Star XTE J1701-462
Homan, Jeroen; Cackett, Edward M.; Fridriksson, Joel K. +6 more
We present the results of continued monitoring of the quiescent neutron star low-mass X-ray binary XTE J1701-462 with Chandra and Swift. A new Chandra observation from 2010 October extends our tracking of the neutron star surface temperature from ≃ 800 days to ≃ 1160 days since the end of an exceptionally luminous 19 month outburst. This observati…
Morphological Evolution of Galaxies from Ultra-deep Hubble Space Telescope Wide Field Camera 3 Imaging: The Hubble Sequence at z ~ 2
van Dokkum, Pieter G.; Franx, Marijn; Illingworth, Garth D. +4 more
We use ultra-deep Hubble Space Telescope Wide Field Camera 3/infrared imaging of the Hubble Ultra Deep Field to investigate the rest-frame optical morphologies of a mass-selected sample of galaxies at z ~ 2. We find a large variety of galaxy morphologies, ranging from large, blue, disk-like galaxies to compact, red, early-type galaxies. We derive …
Emission Measure Distribution and Heating of Two Active Region Cores
Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A.
Using data from the Extreme-ultraviolet Imaging Spectrometer aboard Hinode, we have studied the coronal plasma in the core of two active regions. Concentrating on the area between opposite polarity moss, we found emission measure distributions having an approximate power-law form EMvpropT 2.4 from log T = 5.5 up to a peak at log T = 6.5…
Lyα Emitting Galaxies as Early Stages in Galaxy Formation
Cowie, Lennox L.; Barger, Amy J.; Hu, Esther M.
We present optical spectroscopy of two samples of Galaxy Evolution Explorer grism selected Lyα emitters (LAEs): one at z = 0.195-0.44 and the other at z = 0.65-1.25. We have also observed a comparison sample of galaxies in the same redshift intervals with the same UV magnitude distributions but with no detected Lyα. We use the optical spectroscopy…
The Wolf-Rayet Content of M33
Massey, Philip; Neugent, Kathryn F.
Wolf-Rayet (WR) stars are evolved massive stars, and the relative number of WC-type and WN-type WRs should vary with metallicity, providing a sensitive test of stellar evolutionary theory. The observed WC/WN ratio is much higher than that predicted by theory in some galaxies but this could be due to observational incompleteness for WN types, which…
A Hubble Space Telescope Study of Lyman Limit Systems: Census and Evolution
Lehner, Nicolas; Howk, J. Christopher; Ribaudo, Joseph
We present a survey for optically thick Lyman limit absorbers at z < 2.6 using archival Hubble Space Telescope observations with the Faint Object Spectrograph and Space Telescope Imaging Spectrograph. We identify 206 Lyman limit systems (LLSs), increasing the number of cataloged LLSs at z < 2.6 by a factor of ~10. We compile a statistical sa…
Observational Constraints on Red and Blue Helium Burning Sequences
McQuinn, Kristen B. W.; Dolphin, Andrew E.; Skillman, Evan D. +4 more
We derive the optical luminosity, colors, and ratios of the blue and red helium burning (HeB) stellar populations from archival Hubble Space Telescope observations of nineteen starburst dwarf galaxies and compare them with theoretical isochrones from Padova stellar evolution models across metallicities from Z = 0.001 to 0.009. We find that the obs…
Lifting the Veil on Obscured Accretion: Active Galactic Nuclei Number Counts and Survey Strategies for Imaging Hard X-Ray Missions
Rigby, J. R.; Treister, E.; Ballantyne, D. R. +2 more
Finding and characterizing the population of active galactic nuclei (AGNs) that produces the X-ray background (XRB) is necessary to connect the history of accretion to observations of galaxy evolution at longer wavelengths. The year 2012 will see the deployment of the first hard X-ray imaging telescope which, through deep extragalactic surveys, wi…
Images of the Extended Outer Regions of the Debris Ring around HR 4796 A
Kuzuhara, M.; Tamura, M.; Ishii, M. +48 more
We present high-contrast images of HR 4796 A taken with Subaru/HiCIAO in the H band, resolving the debris disk in scattered light. The application of specialized angular differential imaging methods allows us to trace the inner edge of the disk with high precision and reveals a pair of "streamers" extending radially outward from the ansae. Using a…