Search Publications
Color and Stellar Population Gradients in Passively Evolving Galaxies at z ~ 2 from HST/WFC3 Deep Imaging in the Hubble Ultra Deep Field
Papovich, Casey; Dickinson, Mark; Ferguson, Henry C. +10 more
We report the detection of color gradients in six massive (stellar mass (M star) > 1010 M ⊙) and passively evolving (specific star formation rate <10-11 yr-1) galaxies at redshift 1.3 < z < 2.5 identified in the Hubble Ultra Deep Field using ultra-deep Hubble Space Telescope (HST) …
The First Observations of Low-redshift Damped Lyα Systems with the Cosmic Origins Spectrograph
Sembach, K. R.; Jenkins, E. B.; Prochaska, J. X. +6 more
We report on the first Cosmic Origins Spectrograph observations of damped Lyα systems (DLAs) and sub-damped Lyα systems (sub-DLAs) discovered in a new survey of the gaseous halos of low-redshift galaxies. From observations of 37 sightlines, we have discovered three DLAs and four sub-DLAs. We measure the neutral gas density ΩH I , and re…
Possible Charge-exchange X-ray Emission in the Cygnus Loop Detected with Suzaku
Katsuda, Satoru; Petre, Robert; Yamaguchi, Hiroya +8 more
X-ray spectroscopic measurements of the Cygnus Loop supernova remnant indicate that metal abundances throughout most of the remnant's rim are depleted to ~0.2 times the solar value. However, recent X-ray studies have revealed in some narrow regions along the outermost rim anomalously "enhanced" abundances (up to ~1 solar). The reason for these ano…
Constraints on Coronal Mass Ejection Evolution from in Situ Observations of Ionic Charge States
Antiochos, Spiro K.; Zurbuchen, Thomas H.; Gruesbeck, Jacob R. +1 more
We present a novel procedure for deriving the physical properties of coronal mass ejections (CMEs) in the corona. Our methodology uses in situ measurements of ionic charge states of C, O, Si, and Fe in the heliosphere and interprets them in the context of a model for the early evolution of interplanetary CME (ICME) plasma, between 2 and 5 R s…
LYRA Observations of Two Oscillation Modes in a Single Flare
Berghmans, D.; Goossens, M.; Zender, J. +2 more
We analyze light curves from the LYRA irradiance experiment on board PROBA2 during the flare of 2010 February 8. We see both long- and short-period oscillations during the flare. The long-period oscillation is interpreted in terms of standing slow sausage modes; the short-period oscillation is thought to be a standing fast sausage mode. The simult…
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…