The ensemble variability properties of faint QSOs

Trèvese, D.; Krön, Richard G.; Majewski, S. R.; Bershady, M. A.; Koo, David C.

doi:10.1086/174661

Cited by 103 publications

(132 citation statements)

References 18 publications

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“…As expected, there is a strong correlation between rest frame time baseline and variability detection (Cristiani et al 1990(Cristiani et al , 1996, 1997; Trevese et al 1994;Kawaguchi & Mineshige 1999). Over 60% of the quasars in the longest time baseline bin have GCL > 93, compared to roughly 10% of quasars in the shortest time baseline bin.…”

Section: Variability Detection As Function Of Redshiftsupporting

confidence: 52%

A Synoptic Multiwavelength Analysis of a Large Quasar Sample

2006

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We present variability and multiwavelength photometric information for the 933 known quasars in the QUEST Variability Survey. These quasars are grouped into variable and nonvariable populations based on measured variability confidence levels. In a time-limited synoptic survey, we detect an anticorrelation between redshift and the likelihood of variability. Our comparison of variability likelihood to radio, IR, and X-ray data is consistent with earlier quasar studies. Using already known quasars as a template, we introduce a light-curve morphology algorithm that provides an efficient method for discriminating variable quasars from periodic variable objects in the absence of spectroscopic information. The establishment of statistically robust trends and efficient nonspectroscopic selection algorithms will aid in quasar identification and categorization in upcoming massive synoptic surveys. Finally, we report on three interesting variable quasars, including variability confirmation of the BL Lac candidate PKS 1222+037.

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Section: Variability Detection As Function Of Redshiftsupporting

confidence: 52%

A Synoptic Multiwavelength Analysis of a Large Quasar Sample

2006

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“…It is worth noting that in the GOODS-South field the identification of additional high-redshift AGN is also possible thanks to the variability studies and the wealth of multi-wavelength data available (Trevese et al 1994;Villforth et al 2010), from ultra-deep X-ray imaging by Chandra to the mid-and far-IR (Spitzer, Herschel). In the GOODS-South field we thus exclude 22 AGN at 3.5 ≤ z ≤ 7.5 from the parent sample (∼1%).…”

Section: The Presence Of Agn In the Input Candels Samplementioning

confidence: 99%

The galaxy stellar mass function at 3.5 ≤z≤ 7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields

Grazian

Fontana

Santini

et al. 2015

A&A

269

212

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Context. The form and evolution of the galaxy stellar mass function (GSMF) at high redshifts provide crucial information on star formation history and mass assembly in the young Universe, close or even prior to the epoch of reionization. Aims. We used the unique combination of deep optical/near-infrared/mid-infrared imaging provided by HST, Spitzer, and the VLT in the CANDELS-UDS, GOODS-South, and HUDF fields to determine the GSMF over the redshift range 3.5 ≤ z ≤ 7.5. Methods. We used the HST WFC3/IR near-infrared imaging from CANDELS and HUDF09, reaching H 27−28.5 over a total area of 369 arcmin 2 , in combination with associated deep HST ACS optical data, deep Spitzer IRAC imaging from the SEDS programme, and deep Y and K-band VLT Hawk-I images from the HUGS programme, to select a galaxy sample with high-quality photometric redshifts. These have been calibrated with more than 150 spectroscopic redshifts in the range 3.5 ≤ z ≤ 7.5, resulting in an overall precision of σ z /(1 + z) ∼ 0.037. With this database we have determined the low-mass end of the high-redshift GSMF with unprecedented precision, reaching down to masses as low as M * ∼ 10 9 M at z = 4 and ∼6 × 10 9 M at z = 7. Results. We find that the GSMF at 3.5 ≤ z ≤ 7.5 depends only slightly on the recipes adopted to measure the stellar masses, namely the photometric redshifts, the star formation histories, the nebular contribution, or the presence of AGN in the parent sample. The low-mass end of the GSMF is steeper than has been found at lower redshifts, but appears to be unchanged over the redshift range probed here. Meanwhile the high-mass end of the GSMF appears to evolve primarily in density, although there is also some evidence of evolution in characteristic mass. Our results are very different from previous mass function estimates based on converting UV galaxy luminosity functions into mass functions via tight mass-to-light relations. Integrating our evolving GSMF over mass, we find that the growth of stellar mass density is barely consistent with the time-integral of the star formation rate density over cosmic time at z > 4. Conclusions. These results confirm the unique synergy of the CANDELS+HUDF, HUGS, and SEDS surveys for the discovery and study of moderate/low-mass galaxies at high redshifts, and reaffirm the importance of space-based infrared selection for the unbiased measurement of the evolving GSMF in the young Universe.

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“…The first is related to the incomplete time sampling of the variable sources we wish to detect. Variability surveys usually image the survey field several times over many years (e.g., Trevese et al 1994;Hawkins 2002). Depending on the quality of the data, these surveys have shown that virtually all known AGNs will be found to vary if observed periodically over several years.…”

Section: Variable Nuclei Detected In the Gssmentioning

confidence: 99%

The DEEP Groth Strip Survey. VI. Spectroscopic, Variability, and X‐Ray Detection of Active Galactic Nuclei

Sarajedini

Koo

Phillips

et al. 2006

ASTROPHYS J SUPPL S

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We identify active galactic nuclei (AGNs) in the Groth-Westphal Survey Strip (GSS) using the independent and complementary selection techniques of optical spectroscopy and photometric variability. We discuss the X-ray properties of these AGNs using Chandra/XMM-Newton data for this region. From a sample of 576 galaxies with high-quality spectra we identify 31 galaxies with AGN signatures. Seven of these have broad emission lines (Type 1 AGNs). We also identify 26 galaxies displaying nuclear variability in Hubble Space Telescope Wide Field Planetary Camera 2 (HST WFPC2) images of the GSS separated by $7 yr. The primary overlap of the two selected AGN samples is the set of broad-line AGNs, of which 80% appear as variable. Only a few narrow-line AGNs approach the variability threshold. The broad-line AGNs have an average redshift of hzi ' 1:1, while the other spectroscopic AGNs have redshifts closer to the mean of the general galaxy population (hzi ' 0:7). Eighty percent of the identified broadline AGNs are detected in X-rays, and these are among the most luminous X-ray sources in the GSS. Only one narrowline AGN is X-ray detected. Of the variable nuclei galaxies within the X-ray survey, 27% are X-ray detected. We find that 1:9% AE 0:6% of GSS galaxies to V gal ¼ 24 are broad-line AGNs, 1:4% AE 0:5% are narrow-line AGNs, and 4:5% AE 1:4% contain variable nuclei. The fraction of spectroscopically identified BLAGNs and NLAGNs at z $ 1 reveals a marginally significant increase of 1:3% AE 0:9% when compared to the local population.

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The ensemble variability properties of faint QSOs

Cited by 103 publications

References 18 publications

A Synoptic Multiwavelength Analysis of a Large Quasar Sample

A Synoptic Multiwavelength Analysis of a Large Quasar Sample

The galaxy stellar mass function at 3.5 ≤z≤ 7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields

The DEEP Groth Strip Survey. VI. Spectroscopic, Variability, and X‐Ray Detection of Active Galactic Nuclei

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