European Southern Observatory

About: European Southern Observatory is a facility organization based out in Garching bei München, Germany. It is known for research contribution in the topics: Galaxy & Stars. The organization has 3594 authors who have published 16157 publications receiving 823095 citations. The organization is also known as: The European Southern Observatory，ESO & ESO.

HiZELS: a high-redshift survey of Hα emitters – I. The cosmic star formation rate and clustering at z= 2.23

Abstract: We present results from a near-infrared narrow-band survey of emission-line galaxies at z = 2.23, using the Wide Field Camera on the United Kingdom Infrared Telescope. The H2S1 narrow-band filter ( �c = 2.121µm) we employ selects the Hemission line redshifted to z = 2.23, and is thus suitable for selecting 'typical' star forming g alaxies and active galactic nuclei at this epoch. The pilot study was undertaken in the well studied Cosmological Evolution Survey field (COSMOS) and is already the largest near-infrar ed narrow-band survey at this depth, with a line flux limit of FH� � 10 −16 erg s −1 cm −2 over 0.60 square degrees, probing �220× 10 3 Mpc 3 (co-moving) down to a limiting star formation rate of �30M⊙ yr −1 (3�). In this paper we present the results from our pilot survey and evaluate the Hluminosity function and estimate the clustering properties of Hemitters at z = 2.23 from 55 detected galaxies. The integrated luminosity function is used to est imate the volume averaged star formation rate at z = 2.23: �SFR = 0.17 +0.16 −0.09M⊙ yr −1 Mpc −3 for LH� > 10 42 erg s −1 . For the first time, we use the Hstar-formation tracer to reliably constrainSFR out to z = 2.23 demonstrating the rapid increase inSFR out to this redshift as well as confirming the flattening inSFR betweenz � 1-2. In addition to the luminosity distribution, we analyse t he clustering properties of these galaxies. Using the 2-point angular correlation function, !(�), we estimate a real space correlation length of r0 = 4.2 +0.4 −0.2 h −1 Mpc. In comparison to models of clustering which take into account bias evolution, we estimate that these galaxies are hosted by dark matter halos of mass Mhalo � 10 12 M⊙ consistent with the progenitors of the Milky

Optical spectroscopy of a complete sample of southern 2-Jy radio sources

Abstract: We present optical spectra for a complete sample of radio galaxies and quasars comprising all sources from the Wall & Peacock 2.7-GHz sample with redshifts z<0.7 and declinations δ<+10°; this sample is complete down to a flux density of 2 Jy. Although not all of the 2-Jy sources have spectroscopic redshifts, we argue that most of the unidentified objects are at high redshifts and that our z<0.7 sample is largely complete. The optical data will be analysed in a future paper

Star formation in AGN hosts in GOODS-N

Abstract: Sensitive Herschel far-infrared observations can break degeneracies that were inherent to previous studies of star formation in high-z AGN hosts. Combining PACS 100 and 160 μm observations of the GOODS-N field with 2 Ms Chandra data, we detect ∼20% of X-ray AGN individually at >3σ. The host far-infrared luminosity of AGN with L2−10 keV ≈ 10 43 erg s −1 increases with redshift by an order of magnitude from z = 0 to z ∼ 1. In contrast, there is little dependence of far-infrared luminosity on AGN luminosity, for L2−10 keV 1. We do not find a dependence of far-infrared luminosity on X-ray obscuring column, for our sample which is dominated by L2−10 keV < 10 44 erg s −1 AGN. In conjunction with properties of local and luminous high-z AGN, we interpret these results as reflecting the interplay between two paths of AGN/host coevolution. A correlation of AGN luminosity and host star formation is traced locally over a wide range of luminosities and also extends to luminous high-z AGN. This correlation reflects an evolutionary connection, likely via merging. For lower AGN luminosities, star formation is similar to that in non-active massive galaxies and shows little dependence on AGN luminosity. The level of this secular, non-merger driven star formation increasingly dominates over the correlation at increasing redshift.

The dust content of galaxies from z = 0 to z = 9

Abstract: We study the dust content of galaxies from $z=0$ to $z=9$ in semi-analytic models of galaxy formation that include new recipes to track the production and destruction of dust. We include condensation of dust in stellar ejecta, the growth of dust in the interstellar medium (ISM), the destruction of dust by supernovae and in the hot halo, and dusty winds and inflows. The rate of dust growth in the ISM depends on the metallicity and density of molecular clouds. Our fiducial model reproduces the relation between dust mass and stellar mass from $z=0$ to $z=7$, the number density of galaxies with dust masses less than $10^{8.3}\,\rm{M}_\odot$, and the cosmic density of dust at $z=0$. The model accounts for the double power-law trend between dust-to-gas (DTG) ratio and gas-phase metallicity of local galaxies and the relation between DTG ratio and stellar mass. The dominant mode of dust formation is dust growth in the ISM, except for galaxies with $M_*<10^7\,\rm{M}_\odot$, where condensation of dust in supernova ejecta dominates. The dust-to-metal ratio of galaxies depends on the gas-phase metallicity, unlike what is typically assumed in cosmological simulations. Model variants including higher condensation efficiencies, a fixed timescale for dust growth in the ISM, or no growth at all reproduce some of the observed constraints, but fail to simultaneously reproduce the shape of dust scaling relations and the dust mass of high-redshift galaxies.

H emission in pre-main sequence stars. I. An atlas of line profiles

Abstract: We present an atlas of very high resolution ( R ~ 50000) H α line profiles of 63 pre-main sequence stars, divided among 43 T Tauri stars, 18 Herbig Ae/Be stars, and 2 FU Orionis objects. H α emission is the most common and prominent spectroscopic feature of pre-main sequence stars, and although it is optically very thick it is still the most frequently modelled emission line in young stars. In T Tauri stars the principal models involve magnetically driven winds, and more recently the role of infalling magnetospheric material has been explored. For Herbig Ae/Be stars a variety of models have been proposed, current emphasis is directed towards obscuration by clumpy circumstellar disk structures. In order to provide constraints on such models, we have made a statistical analysis of the 63 high resolution profiles. We here ignore the considerable variability of the H α emission, which is discussed in detail in a second paper. Most of our observed lines show complex profiles due to an interplay between emission and absorption features, and we suggest a two-dimensional classification scheme to describe these line profiles, based on the relative height of a secondary peak to the primary peak, as well as whether the absorption is blue- or red-shifted. Among T Tauri stars, 25% have symmetric profiles, 49% have blueshifted absorption dips, and 5% have P Cygni profiles; the remaining 21% show a variety of redshifted absorptions. For Herbig Ae/Be stars symmetric lines are quite rare (11%), indeed almost all of these stars have deep and prominent central absorptions. We have measured the extent of the line wings for all of our stars at the I max /40 level, and find that almost all have very extended wings, with typical extents of ± 350 km/s, but in high spectra the wings can be traced to lower intensities, and velocities as high as ± 900 km/s have been observed. Pronounced asymmetries of these extended wings are found for many stars, suggesting the possibility that the highest velocity material could be non-uniformly distributed. The equivalent widths of the H α emission in our sample of stars span two orders of magnitude, with a distribution that increases with decreasing equivalent width.