Search Publications

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-K_s > 3.92, to a limit K_s~= 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 A_Fe= 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 …

From Globular Clusters to Tidal Dwarfs: Structure Formation in the Tidal Tails of Merging Galaxies

Charlton, Jane C.; Kundu, Arunav; Gallagher, Sarah C. +5 more

Using V and I images obtained with the Wide Field Planetary Camera 2 (WFPC2) of the Hubble Space Telescope, we investigate compact stellar structures within tidal tails. Six regions of tidal debris in the four classic ``Toomre sequence'' mergers: NGC 4038/39 (``Antennae''), NGC 3256, NGC 3921, and NGC 7252 (``Atoms for Peace'') have been studied i…

F stars, metallicity and the ages of red galaxies at z > 1

Dunlop, J. S.; Nolan, L. A.; Jimenez, R. +1 more

We explore whether the rest-frame near-ultraviolet spectral region, observable in high-redshift galaxies via optical spectroscopy, contains sufficient information to allow the degeneracy between age and metallicity to be lifted. We do this by first testing the ability of evolutionary synthesis models to reclaim the correct metallicity when fitted …

The conspicuous absence of X-ray emission from carbon-enriched Wolf-Rayet stars

Hamann, W. -R.; Oskinova, L. M.; Ignace, R. +2 more

The carbon-rich WC5 star WR 114 was not detected during a 15.9 ksec XMM-Newton, observation, implying an upper limit to the X-ray luminosity of L_X <∼ 2.5x 10³⁰ erg s^-1 and to the X-ray to bolometric luminosity ratio of L_X/L_bol <∼ 4*E^-9. This confirms indications from earlier l…