Search Publications
Missions
Journals
Publication Years
Hubble Space Telescope Astrometry of m4 and the Galactic Constant V0/R0
Anderson, Jay; Bedin, Luigi R.; Piotto, Giampaolo +1 more
From multiepoch WFPC2/HST observations we present astrometric measurements of stars in the Galactic globular cluster M4 (NGC 6121) and in the foreground and background. The presence of an extragalactic point source allows us to determine the absolute proper motion of the cluster and, through use of the field stars in this region only 18° from the …
Deep Hubble Space Telescope Imaging of Sextans A. III. The Star Formation History
Dolphin, Andrew E.; Skillman, Evan D.; Saha, A. +6 more
We present a measurement of the star formation history of Sextans A, based on WFPC2 photometry that is 50% complete to V=27.5 (MV~+1.9) and I=27.0. The star formation history and chemical enrichment history have been measured through modeling of the color-magnitude diagram (CMD). We find evidence for increased reddening in the youngest …
Gemini observations of Wolf-Rayet stars in the Local Group starburst galaxy IC 10
Smartt, S. J.; Crowther, P. A.; Royer, P. +2 more
We present Gemini-N GMOS and CFHT MOS spectroscopy of Wolf-Rayet candidates in the Local Group dwarf galaxy IC 10 that were previously identified by Massey et al. and Royer et al. From the present spectroscopic survey, the WC/WN ratio for IC 10 remains unusually high, given its low metallicity, although none of the WC9 stars suspected from narrow-…
The nature, evolution, clustering and X-ray properties of extremely red galaxies in the Chandra Deep Field South/Great Observatories Origins Deep Survey field
Almaini, Omar; Dunlop, James; Roche, Nathan D.
We identify a very deep sample of 198 extremely red objects (EROs) in the Chandra Deep Field South, selected on the basis of I775-Ks > 3.92, to a limit Ks~= 22 using the public European Southern Observatory (ESO)/Great Observatories Origins Deep Survey (GOODS) survey.
The ERO number counts flatten from a sl…Iron and nickel line properties in the X-ray-reflecting region of the Circinus galaxy
Bianchi, Stefano; Matt, Giorgio; Molendi, Silvano
We discuss the iron and nickel properties in the nuclear X-ray-reflecting region of the Circinus galaxy, studied with XMM-Newton. The main results are as follows. (i) From the depth of the Fe Kα edge, a value of AFe= 1.7 in number with respect to the cosmic value (as for Anders & Grevesse) is measured, if the (not directly visible) …
The pre-main sequence spectroscopic binary AK Scorpii revisited
Andersen, J.; Alencar, S. H. P.; Batalha, C. +4 more
We present an analysis of 32 high-resolution echelle spectra of the pre-main sequence spectroscopic binary AK Sco obtained during 1998 and 2000, as well as a total of 72 photoelectric radial-velocity observations from the period 1986-1994. These data allow considerable improvement of the period and other orbital parameters of AK Sco. Our analysis …
Chandra and XMM-Newton Observations of the First Quasars: X-Rays from the Age of Cosmic Enlightenment
Brandt, W. N.; Strauss, Michael A.; Vignali, C. +6 more
We report on Chandra and XMM-Newton observations of a sample of 13 quasars at z~4.7-5.4 mostly taken from the Sloan Digital Sky Survey (SDSS). The present sample complements previous X-ray studies of z>=4 quasars, in which the majority of the objects are optically more luminous and at lower redshifts. All but two of our quasars have been detect…
The Araucaria Project: Dependence of Mean K, J, and I Absolute Magnitudes of Red Clump Stars on Metallicity and Age
Udalski, A.; Gieren, W.; Pietrzyński, G.
As a part of our ongoing Araucaria Project on the improvement of stellar distance indicators we present deep near-infrared JK imaging of several fields in four Local Group galaxies: LMC, SMC, and the Carina and Fornax dwarf galaxies. These data were obtained under excellent seeing conditions at the European Southern Observatory Very Large Telescop…
On the Assembly History of Early-Type Galaxies in the Hubble Deep Field-North
van Dokkum, Pieter G.; Ellis, Richard S.
We present deep Keck spectroscopy for a sample of I814<22.5 field early-type galaxies selected morphologically in the redshift range 0.56<=z<=1.02 in the Hubble Deep Field-North (HDF-N). Using velocity dispersions determined from the Keck spectra in conjunction with structural parameters measured from the deep WFPC2 images, we …
Molecular Gas and Dust at z=2.6 in SMM J14011+0252: A Strongly Lensed Ultraluminous Galaxy, Not a Huge Massive Disk
Downes, D.; Solomon, P. M.
We used the IRAM interferometer to detect CO (3-2), CO (7-6), and 1.3 mm dust continuum emission from the submillimeter galaxy SMM J14011+0252 at z=2.6. Contrary to a recent claim that the CO was extended over 6.6" (57 kpc), the new data yield a size of 2''×<=0.5" for the CO and the dust. Although previous results placed the CO peak …