Showing papers by "Brigitte Rocca-Volmerange published in 2003"

STELIB: A library of stellar spectra at R 2000 ?;??

Abstract: We present STELIB ? , a new spectroscopic stellar library, available at http://webast.ast.obs-mip.fr/stelib. STELIB consists of an homogeneous library of 249 stellar spectra in the visible range (3200 to 9500 A), with an intermediate spectral resolution (<3 A) and sampling (1 A). This library includes stars of various spectral types and luminosity classes, spanning a relatively wide range in metallicity. The spectral resolution, wavelength and spectral type coverage of this library represents a substantial improvement over previous libraries used in population synthesis models. The overall absolute photo- metric uncertainty is 3%.

CO emission and associated H I absorption from a massive gas reservoir surrounding the z = 3 radio galaxy B3 J2330+3927

Abstract: We present results of a comprehensive multi-frequency study of the radio galaxy B3 J2330+3927. The 1. �� 9 wide

CO emission and associated HI absorption from a massive gas reservoir surrounding the z=3 radio galaxy B3 J2330+3927

Abstract: We present results of a comprehensive multi-frequency study of the radio galaxy B3 J2330+3927. The 1.9" wide radio source, consisting of 3 components, is bracketed by 2 objects in our Keck K-band image. Optical and near-IR Keck spectroscopy of these two objects yield z=3.087+-0.004. The brightest (K=18.8) object has a standard type II AGN spectrum, and is the most likely location of the AGN, which implies a one-sided jet radio morphology. Deep 113 GHz observations with the IRAM Plateau de Bure Interferometer reveal CO J=4-3 emission, which peaks at the position of the AGN. The CO line is offset by 500 km/s from the systemic redshift of the AGN, but corresponds very closely to the velocity shift of an associated HI absorber seen in Lya. This strongly suggests that both originate from the same gas reservoir surrounding the AGN host galaxy. Simultaneous 230 GHz interferometer observations find a ~3x lower integrated flux density when compared to single dish 250 GHz observations with MAMBO at the IRAM 30m telescope. This can be interpreted as spatially resolved thermal dust emission at scales of 0.5" to 6". Finally, we present a tau 2 radio galaxies observed to date with the WSRT. We present mass estimates for the atomic, neutral, and ionized hydrogen, and for the dust, ranging from M(HI)=2x10^7 M_Sun derived from the associated HI absorber in Lya up to M(H_2)=7x10^{10} M_Sun derived from the CO emission. This indicates that the host galaxy is surrounded by a massive reservoir of gas and dust. The K-band companion objects may be concentrations within this reservoir, which will eventually merge with the central galaxy hosting the AGN.

STELIB: a library of stellar spectra at R~2000

Abstract: We present STELIB, a new spectroscopic stellar library, available at this http URL . STELIB consists of an homogeneous library of 249 stellar spectra in the visible range (3200 to 9500A), with an intermediate spectral resolution (~3A) and sampling (1A). This library includes stars of various spectral types and luminosity classes, spanning a relatively wide range in metallicity. The spectral resolution, wavelength and spectral type coverage of this library represents a substantial improvement over previous libraries used in population synthesis models. The overall absolute photometric uncertainty is 3%.

A search for distant radio galaxies from SUMSS and NVSS: I. Sample definition, radio and K-band imaging

Abstract: We present the first results from a pilot study to search for distant radio galaxies in the southern hemisphere (delta 15 mJy. We observed 71 sources without bright optical or near-infrared counterparts at 1.385 GHz with the ATCA, providing ~5" resolution images and sub-arcsec positional accuracy. To identify their host galaxies, we obtained near-IR K-band images with IRIS2 at the AAT and SofI at the NTT. We identify 92% of the USS sources down to K~20.5. The SUMSS-NVSS USS sources have a surface density more than 4 times higher than USS sources selected at lower frequencies. This is due to the higher effective selection frequency, and the well-matched resolutions of both surveys constructed using the same source fitting algorithm. The scattering of alpha >-1.3 sources into the USS sample due to spectral index uncertainties can account for only 35% of the observed USS sources. Since our sample appears to contain a similar fraction of very distant (z>3) galaxies, selecting USS sources from SUMSS-NVSS should allow us to identify large numbers of massive galaxies at high redshift.

High Resolution Spectra of Galaxies

Abstract: We present inversion techniques which aim at recovering the composite nature and the kinematics of a stellar population from its high resolution absorption line spectrum. The originality of the combined inversion is its potential to recover both the stellar content and the kinematics simultaneously. These techniques use new synthetic high resolution spectra produced by PEGASE and minimization algorithms. We apply them to mock data representing the bulge and disk population of the inner region of spiral galaxies.

HIGH RESOLUTION SPECTRA OF GALAXIES Models and inversions

Abstract: We present inversion techniques which aim at recovering the composite nature and the kinematics of a stellar population from its high resolution absorption line spectrum. The originality of the combined inversion is its potential to recover both the stellar content and the kinematics sim- ultaneously. These techniques use new synthetic high resolution spectra produced by PEGASE and minimization algorithms. We apply them to mock data representing the bulge and disk population of the inner region of spiral galaxies. The high resolution spectrographs now installed on 10m-class telescopes open new perspectives in the exploration of the formation of galaxies. Absorption line spectra with a good spatial sampling will provide new information on the nature of the stellar components of a galaxy, as well as on their kinematics. This poster presents the first attempt to fit simultaneously the local line-of-sight velocity distribution (LOSVD) and the nature of the stellar population. It is based on efficient non- parametric inversion procedures.