Search Publications
A HIPPARCOS Census of the Nearby OB Associations
Brown, A. G. A.; de Bruijne, J. H. J.; de Zeeuw, P. T. +2 more
A comprehensive census of the stellar content of the OB associations within 1 kpc from the Sun is presented, based on Hipparcos positions, proper motions, and parallaxes. It is a key part of a long-term project to study the formation, structure, and evolution of nearby young stellar groups and related star-forming regions. OB associations are unbo…
The NextGen Model Atmosphere Grid for 3000<=Teff<=10,000 K
Baron, E.; Hauschildt, Peter H.; Allard, France
We present our NextGen Model Atmosphere grid for low-mass stars for effective temperatures larger than 3000 K. These LTE models are calculated with the same basic model assumptions and input physics as the VLMS part of the NextGen grid so that the complete grid can be used, e.g., for consistent stellar evolution calculations and for internally con…
Dust Absorption and the Ultraviolet Luminosity Density at z ~ 3 as Calibrated by Local Starburst Galaxies
Heckman, Timothy M.; Meurer, Gerhardt R.; Calzetti, Daniela
We refine a technique to measure the absorption-corrected ultraviolet (UV) luminosity of starburst galaxies using rest-frame UV quantities alone and apply it to Lyman-limit U dropouts at z~3 found in the Hubble Deep Field (HDF). The method is based on an observed correlation between the ratio of far-infrared (FIR) to UV fluxes with spectral slope …
Measuring and modelling the redshift evolution of clustering: the Hubble Deep Field North
Matarrese, S.; Fontana, A.; Cristiani, S. +4 more
The evolution of galaxy clustering from z=0 to z~=4.5 is analysed using the angular correlation function and the photometric redshift distribution of galaxies brighter than IAB<=28.5 in the Hubble Deep Field North. The reliability of the photometric redshift estimates is discussed on the basis of the available spectroscopic redshifts…
The Luminosity Function of Young Star Clusters in ``the Antennae'' Galaxies (NGC 4038-4039)
Leitherer, Claus; Whitmore, Bradley C.; Fall, S. Michael +3 more
The Wide Field Planetary Camera 2 of the Hubble Space Telescope has been used to obtain high-resolution images of NGC 4038/4039 that go roughly 3 mag deeper in V than previous observations made during cycle 2. These new images allow us to measure the luminosity functions (LFs) of clusters and stars over a range of 8 mag (-14<M_V<-6). To firs…
Far-Infrared and Submillimeter Emission from Galactic and Extragalactic Photodissociation Regions
Wolfire, Mark G.; Kaufman, Michael J.; Hollenbach, David J. +1 more
Photodissociation region (PDR) models are computed over a wide range of physical conditions, from those appropriate to giant molecular clouds illuminated by the interstellar radiation field to the conditions experienced by circumstellar disks very close to hot massive stars. These models use the most up-to-date values of atomic and molecular data,…
Continuous tracking of coronal outflows: Two kinds of coronal mass ejections
Howard, R. A.; Sheeley, N. R.; Wang, Y. -M. +1 more
We have developed a new technique for tracking white-light coronal intensity features and have used this technique to construct continuous height/time maps of coronal ejecta as they move outward through the 2-30Rs field of view of the Large-Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) spacecra…
A Spectroscopic Catalog of 10 Distant Rich Clusters of Galaxies
Smail, Ian; Ellis, Richard S.; Dressler, Alan +4 more
We present spectroscopic observations of galaxies in the fields of 10 distant clusters for which we have previously presented deep imaging with WFPC2 on board the Hubble Space Telescope. The clusters span the redshift range z=0.37-0.56 and are the subject of a detailed ground- and space-based study to investigate the evolution of galaxies as a fun…
Heavy-Element Abundances in Blue Compact Galaxies
Thuan, Trinh X.; Izotov, Yuri I.
We present high-quality ground-based spectroscopic observations of 54 supergiant H II regions in 50 low-metallicity blue compact galaxies with oxygen abundances 12+logO/H between 7.1 and 8.3. We use the data to determine abundances for the elements N, O, Ne, S, Ar, and Fe. We also analyze Hubble Space Telescope (HST) Faint Object Spectrograph arch…
The afterglow, redshift and extreme energetics of the γ-ray burst of 23 January 1999
Kelson, D. D.; Malkan, M. A.; Harrison, F. A. +26 more
Long-lived emission, known as afterglow, has now been detected from about a dozen γ-ray bursts. Distance determinations place the bursts at cosmological distances, with redshifts, z, ranging from ~1 to 3. The energy required to produce these bright γ-ray flashes is enormous: up to ~10 53erg, or 10 per cent of the rest-mass energy of a n…