Search Publications
The UDF05 Follow-up of the Hubble Ultra Deep Field. III. The Luminosity Function at z ~ 6
Ferguson, Henry C.; Giavalisco, Mauro; Lucas, Ray A. +13 more
In this paper, we present a derivation of the rest-frame 1400 Å luminosity function (LF) at redshift six from a new application of the maximum likelihood method by exploring the five deepest Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) fields, i.e., the Hubble Ultra Deep Field, two UDF05 fields, and two Great Observatories Origins …
Optical Properties of the Ultraluminous X-Ray Source Holmberg IX X-1 and Its Stellar Environment
Motch, C.; Kaaret, P.; Pakull, M. W. +1 more
Holmberg IX X-1 is an archetypal ultraluminous X-ray source (ULX). Here we study the properties of the optical counterpart and of its stellar environment using optical data from SUBARU/Faint Object Camera and Spectrograph, GEMINI/GMOS-N and Hubble Space Telescope (HST)/Advanced Camera for Surveys, as well as simultaneous Chandra X-ray data. The V …
New Evidence for High Activity of the Supermassive Black Hole in our Galaxy
Koyama, K.; Nobukawa, M.; Tsuru, T. G. +1 more
Prominent K-shell emission lines of neutral iron (hereafter Fe I-K lines) and hard-continuum X-rays from molecular clouds (MCs) in the Sagittarius B (Sgr B) region were found in two separate Suzaku observations in 2005 and 2009. The X-ray flux of the Fe I-K lines decreased in correlation with the hard-continuum flux by a factor of 0.4-0.5 in four …
Revisiting the Abundance Gradient in the Maser Host Galaxy NGC 4258
Bresolin, Fabio
New spectroscopic observations of 36 H II regions in NGC 4258 obtained with the Gemini telescope are combined with existing data from the literature to measure the radial oxygen abundance gradient in this galaxy. The [O III]λ4363 auroral line was detected in four of the outermost targets (17-22 kpc from the galaxy center), allowing a determination…
A Study of the X-rayed Outflow of APM 08279+5255 through Photoionization Codes
Chartas, George; Saez, Cristian
We present new results from our study of the X-rayed outflow of the z = 3.91 gravitationally lensed broad absorption line quasar APM 08279+5255. These results are based on spectral fits to all the long exposure observations of APM 08279+5255 using a new quasar-outflow model. This model is based on CLOUDY 3 CLOUDY is a photoionization co…
The Gas Dynamics of NGC 4472 Revealed by XMM-Newton
Hardcastle, M. J.; Sivakoff, G. R.; Sarazin, C. L. +6 more
We present results from a 100 ks XMM-Newton observation of the hot gas in the Virgo cluster elliptical galaxy NGC 4472. We find a surface brightness discontinuity ~21 kpc north of the nucleus, consistent with being a contact discontinuity between two moving fluids. We also detect a >60 kpc long ram-pressure stripped tail. The pressure across th…
The Far-ultraviolet "Continuum" in Protoplanetary Disk Systems. II. Carbon Monoxide Fourth Positive Emission and Absorption
Herczeg, Gregory J.; Valenti, Jeff A.; Harper, Graham M. +21 more
We exploit the high sensitivity and moderate spectral resolution of the Hubble Space Telescope Cosmic Origins Spectrograph to detect far-ultraviolet (UV) spectral features of carbon monoxide (CO) present in the inner regions of protoplanetary disks for the first time. We present spectra of the classical T Tauri stars HN Tau, RECX-11, and V4046 Sgr…
Discovery of Strong Iron Kα Emitting Compton Thick Quasars at z = 2.5 and 2.9
Daddi, E.; Alexander, D. M.; Fiore, F. +3 more
We report the detection of the 6.4 keV iron Kα emission line in two infrared-luminous, massive, star-forming BzK galaxies at z = 2.578 and z = 2.90 in the CDF-S. The Chandra 4 Ms spectra of BzK 4892 and BzK 8608 show a reflection-dominated continuum with strong iron lines, with rest-frame equivalent widths EW ~ 2.3 keV and 1.2 keV, respectively, d…
The Effect of Helium-enhanced Stellar Populations on the Ultraviolet-upturn Phenomenon of Early-type Galaxies
Chung, Chul; Yoon, Suk-Jin; Lee, Young-Wook
Recent observations and modeling of globular clusters (GCs) with multiple populations strongly indicate the presence of super-helium-rich subpopulations in old stellar systems. Motivated by this, we have constructed new population synthesis models with and without helium-enhanced subpopulations to investigate their impact on the UV-upturn phenomen…
What do Spectral Line Profile Asymmetries Tell us About the Solar Atmosphere?
Martínez-Sykora, Juan; De Pontieu, Bart; Hansteen, Viggo +1 more
Recently, analysis of solar spectra obtained with the EUV Imaging Spectrograph (EIS) onboard the Hinode satellite has revealed the ubiquitous presence of asymmetries in transition region (TR) and coronal spectral line profiles. These asymmetries have been observed especially at the footpoints of coronal loops and have been associated with strong u…