The Hamburg Objective-Prism Surveys for Bright Quasars

Wisotzki, L.; Bade, N.; Engels, D.; Groote, D.; Hagen, H. J.; Köhler, Thorsten; Reimers, D.

doi:10.1007/978-94-011-5722-3_66

Cited by 141 publications

(193 citation statements)

References 1 publication

Supporting

Mentioning

186

Contrasting

Unclassified

Order By: Relevance

“…The SDSS quasars were selected on the basis of multiple color-color diagrams (Richards et al 2001); nonetheless, as with the PG sample, UV excess is the dominant characteristic. The incompleteness of the PG quasar selection (U −B < −0.46 and B < 16.16) has long been known (Goldschmidt et al 1992;Wisotzki et al 2000;Mickaelian et al 2001;Jester et al 2005). Comparisons of PG quasars to other quasar surveys indicate a completeness of ∼50%-100% (Wisotzki et al 2000;Mickaelian et al 2001;Jester et al 2005).…”

Section: Cosmic Evolution Of the Comoving Sfir Luminosity Density Andmentioning

confidence: 99%

COSMIC EVOLUTION OF STAR FORMATION IN TYPE-1 QUASAR HOSTS SINCEz= 1

Shi

Rieke

Ogle

et al. 2009

ApJ

View full text Add to dashboard Cite

We present Spitzer Infrared Spectrograph observations of a complete sample of 57 Sloan Digital Sky Survey type-1 quasars at z ∼ 1. Aromatic features at 6.2 and/or 7.7 μm are detected in about half of the sample and show profiles similar to those seen in normal galaxies at both low and high redshift, indicating a star formation origin for the features. Based on the ratio of aromatic to star formation infrared (SFIR) luminosities for normal star-forming galaxies at z ∼ 1, we have constructed the SFIR luminosity function (LF) of z ∼ 1 quasars. As we found earlier for low-redshift Palomar-Green (PG) quasars, these z ∼ 1 quasars show a flatter SFIR LF than do z ∼ 1 field galaxies, implying the quasar host galaxy population has on average a higher star formation rate (SFR) than the field galaxies do. As measured from their SFIR LF, individual quasar hosts have on average LIRG-level SFRs, which mainly arise in the circumnuclear regions. By comparing with similar measurements of low-redshift PG quasars, we find that the comoving SFIR luminosity density in quasar hosts shows a much larger increase with redshift than that in field galaxies. The behavior is consistent with pure density evolution since the average SFR and the average SFR/BH accretion rate in quasar hosts show little evolution with redshift. For individual quasars, we have found a correlation between the aromatic-based SFR and the luminosity of the nuclear radiation, consistent with predictions of some theoretical models. We propose that type-1 quasars reside in a distinct galaxy population that shows elliptical morphology but that harbors a significant fraction of intermediate-age stars and is experiencing intense circumnuclear star formation.

show abstract

Section: Cosmic Evolution Of the Comoving Sfir Luminosity Density Andmentioning

confidence: 99%

COSMIC EVOLUTION OF STAR FORMATION IN TYPE-1 QUASAR HOSTS SINCEz= 1

Shi

Rieke

Ogle

et al. 2009

ApJ

View full text Add to dashboard Cite

show abstract

“…8 We are engaged in a large-scale project to find additional extremely metal-poor stars exploiting the database of the Hamburg / ESO Survey (HES). The HES is an objective prism survey primarily targeting bright quasars (Wisotzki et al 2000). However, it is also possible to efficiently select a variety of interesting stellar objects in the HES (Christlieb 2000;Christlieb et al 2001aChristlieb et al , 2001b, among them EMP stars (Christlieb 2003).…”

Section: Introductionmentioning

confidence: 99%

Abundances In Very Metal‐Poor Dwarf Stars

Cohen

Christlieb

McWilliam

et al. 2004

ApJ

180

277

View full text Add to dashboard Cite

We discuss the detailed composition of 28 extremely metal-poor (EMP) dwarfs, 22 of which are from the Hamburg / ESO Survey (HES), based on Keck echelle spectra. Our sample has a median [Fe/H] of À2.7 dex, extends to À3.5 dex, and is somewhat less metal-poor than was expected from [Fe/H](HK, HES) determined from low-resolution spectra. Our analysis supports the existence of a sharp decline in the distribution of halo stars with metallicity below ½Fe=H ¼ À3:0 dex. So far no additional turnoff stars with ½Fe=H < À3:5 have been identified in our follow-up efforts. For the best-observed elements between Mg and Ni, we find that the abundance ratios appear to have reached a plateau, i.e., [X/Fe] is approximately constant as a function of [Fe/H], except for Cr, Mn, and Co, which show trends of abundance ratios varying with [Fe/H]. These abundance ratios at low metallicity correspond approximately to the yield expected from Type II supernovae (SNe) with a narrow range in mass and explosion parameters; high-mass Type II SN progenitors are required. The dispersion of [X/Fe] about this plateau level is surprisingly small and is still dominated by measurement errors rather than intrinsic scatter. These results place strong constraints on the characteristics of the contributing SNe. The dispersion in neutron-capture elements and the abundance trends for Cr, Mn, and Co are consistent with previous studies of evolved EMP stars. We find halo-like enhancements for the -elements Mg, Ca, and Ti, but solar Si / Fe ratios for these dwarfs. This contrasts with studies of EMP giant stars, which show Si enhancements similar to other -elements. Sc/ Fe is another case where the results from EMP dwarfs and from EMP giants disagree; our Sc/ Fe ratios are enhanced compared to the solar value by $0.2 dex. Although this conflicts with the solar Sc/ Fe values seen in EMP giants, we note that -like Sc/ Fe ratios have been claimed for dwarfs at higher metallicity. Two dwarfs in the sample are carbon stars, while two others have significant C enhancements, all with 12 C/ 13 C $7 and with C/ N between 10 and 150. Three of these C-rich stars have large enhancements of the heavy neutron capture elements, including lead, which implies a strong s-process contribution, presumably from binary mass transfer; the fourth shows no excess of Sr or Ba.

show abstract

“…Over the past two decades, the quest to find the most metal-poor stars to study the chemical evolution of the Galaxy led to a significant number of stars with metallicities down to [Fe/H] ∼ −4.0 (see Beers & Christlieb 2005 for a more detailed review). Those stars were initially selected as candidates from a large survey, such as the HK survey (Beers et al 1992) and the Hamburg/ESO survey (Wisotzki et al 1996). A large survey is required to provide numerous low-resolution spectra to search for weak-lined stellar candidates indicating metal deficiency.…”

Section: The Metallicity Distribution Function Of the Galactic Halomentioning

confidence: 99%

Exploring the Universe with Metal-Poor Stars

Frebel

2012

The First Galaxies

View full text Add to dashboard Cite

The early chemical evolution of the Galaxy and the Universe is vital to our understanding of a host of astrophysical phenomena. Since the most metal-poor Galactic stars (with metallicities down to [Fe/H] ∼ −5.5) are relics from the highredshift Universe, they probe the chemical and dynamical conditions of the Milky Way and the origin and evolution of the elements through nucleosynthesis. They also provide constraints on the nature of the first stars, their associated supernovae and initial mass function, and early star and galaxy formation. The Milky Way's dwarf satellites contain a large fraction (∼ 30%) of the known most metal-poor stars that have chemical abundances that closely resemble those of equivalent halo stars. This suggests that chemical evolution may be universal, at least at early times, and that it is driven by massive, energetic SNe. Some of these surviving, ultra-faint systems may show the signature of just one such Pop III star; they may even be surviving first galaxies. Early analogs of the surviving dwarfs may thus have played an important role in the assembly of the old Galactic halo whose formation can now be studied with stellar chemistry. Following the cosmic evolution of small halos in simulations of structure formation enables tracing the cosmological origin of the most metalpoor stars in the halo and dwarf galaxies. Together with future observations and additional modeling, many of these issues, including the reionization history of the Milky Way, may be constrained this way. The chapter concludes with an outlook about upcoming observational challenges and ways forward is to use metal-poor stars to constrain theoretical studies.

show abstract

The Hamburg Objective-Prism Surveys for Bright Quasars

Cited by 141 publications

References 1 publication

COSMIC EVOLUTION OF STAR FORMATION IN TYPE-1 QUASAR HOSTS SINCEz= 1

COSMIC EVOLUTION OF STAR FORMATION IN TYPE-1 QUASAR HOSTS SINCEz= 1

Abundances In Very Metal‐Poor Dwarf Stars

Exploring the Universe with Metal-Poor Stars

Contact Info

Product

Resources

About