Toward an unbiased sample of X‐ray selected normal galaxies outside the local Universe

Georgakakis, A.

doi:10.1002/asna.200710906

Cited by 4 publications

(4 citation statements)

References 18 publications

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“…In particular, we have considered the possibility that the fraction of AGN could affect the SFR estimate. In fact, since the fraction of AGN is found to be higher in groups as the redshift increases (Georgakakis et al 2007;Georgakakis 2008;Tanaka et al 2012) and the SFR of AGN host galaxies could be enhanced with respect to non-active galaxies of similar stellar mass (Santini et al 2012;Rosario et al 2013), we use PACS data to measure, without biases, their SFR (Popesso et al 2011). This cannot be done using MIPS data or the [O II] doublet.…”

Section: The Sfr-density Relationmentioning

confidence: 99%

Reversal or no reversal: the evolution of the star formation rate–density relation up to z ∼ 1.6

Ziparo¹,

Popesso²,

Finoguenov³

et al. 2013

Monthly Notices of the Royal Astronomical Society

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We investigate the evolution of the star formation rate (SFR)-density relation in the Extended Chandra Deep Field South and the Great Observatories Origin Deep Survey fields up to z ∼ 1.6. In addition to the 'traditional method', in which the environment is defined according to a statistical measurement of the local galaxy density, we use a 'dynamical' approach, where galaxies are classified according to three different environment regimes: group, 'filamentlike' and field. Both methods show no evidence of an SFR-density reversal. Moreover, group galaxies show a mean SFR lower than other environments up to z ∼ 1, while at earlier epochs group and field galaxies exhibit consistent levels of star formation (SF) activity. We find that processes related to a massive dark matter halo must be dominant in the suppression of the SF below z ∼ 1, with respect to purely density-related processes. We confirm this finding by studying the distribution of galaxies in different environments with respect to the so-called main sequence (MS) of star-forming galaxies. Galaxies in both group and 'filament-like' environments preferentially lie below the MS up to z ∼ 1, with group galaxies exhibiting lower levels of star-forming activity at a given mass. At z > 1, the star-forming galaxies in groups reside on the MS. Groups exhibit the highest fraction of quiescent galaxies up

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Section: The Sfr-density Relationmentioning

confidence: 99%

Reversal or no reversal: the evolution of the star formation rate–density relation up to z ∼ 1.6

Ziparo¹,

Popesso²,

Finoguenov³

et al. 2013

Monthly Notices of the Royal Astronomical Society

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“…This fraction is also likely to be an upper limit as some of the galaxy candidates may turn out to be low‐luminosity AGN. Furthermore, Georgakakis (2008) cross‐correlated the 2 XMM p catalogue (Watson et al 2009) with the SDSS spectroscopic data base to select normal galaxies at z ≈ 0.1. Such sources were found to represent 20 per cent of the overall X‐ray population for luminosities .…”

Section: The Colour–magnitude Diagrammentioning

confidence: 99%

A serendipitous XMM survey of the SDSS: the evolution of the colour-magnitude diagram of X-ray AGN from z= 0.8 to 0.1

Georgakakis

Nandra

2011

Monthly Notices of the Royal Astronomical Society

113

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A new serendipitous XMM survey in the area of the Sloan Digital Sky Survey is described (XMM/SDSS), which includes features such as merging of overlapping fields to increase the sensitivity to faint sources, use of a new parametrization of the XMM point spread function for the source detection and photometry and an accurate estimation of the survey sensitivity. About 40 000 X‐ray point sources are detected over a total area of 122 deg2. A subsample of 209 sources detected in the 2–8 keV spectral band with SDSS spectroscopic redshifts in the range of 0.03 < z < 0.2, optical magnitudes r < 17.77 mag and (erg s−1) is selected to explore their distribution on the colour–magnitude diagram. This is compared with the colour–magnitude diagram of X‐ray AGN in the AEGIS field at z≈ 0.8. We find no evidence for evolution of the rest‐frame colours of X‐ray AGN hosts from z= 0.8 to 0.1. This suggests that the dominant accretion mode of the AGN population, which is expected to imprint on the properties of their host galaxies, does not change since z= 0.8. This argues against scenarios that attribute the rapid decline of the accretion power of the Universe with time (1 dex since z= 0.8) to changes in the AGN fuelling/triggering mode.

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“…In addition to the intrinsically low accretion rate, the hard, flat X-ray spectra could be resulted from the other reasons. Observations show that "normal" galaxies are X-ray emitters with a typical X-ray luminosity of 10 38−42 erg s −1 (e,g, Fabbiano 1989;Georgakakis et al 2008;Brandt et al 2001). The X-ray emission in the "normal galaxies" is dominantly emitted from the diffuse hot gas (T ∼ 10 7 K) and evolved stellar point sources with T ∼ 10 6 K (e.g, Fabbiano & Shaply 2002;Read &Ponman 2002, andsee a review in Fabbiano 2006).…”

Section: Contamination In Hard Flat X-ray Spectramentioning

confidence: 99%

Insight Into Active Galactic Nucleus and Host Galaxy Co-Evolution From Hard X-Ray Emission

Wang

Zhou

Wei

2013

ApJ

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We study the AGN-host co-evolution issue here by focusing on the correlation between the hard X-ray emission from central AGNs and the stellar populations of the host galaxies. By focusing on the galaxies with strong Hα line emission (EW(Hα) > 5Å), both X-ray and optical spectral analysis are performed on 67 (partially) obscured AGNs that are selected from the XMM-Newton 2XMMi/SDSS-DR7 catalog originally cross-matched by Pineau et al. The sample allows us to study central AGN activity and host galaxy directly and simultaneously in individual objects. Combining the spectral analysis in both bands reveals that the older the stellar population of the host galaxy, the harder the Xray emission will be, which was missed in our previous study where the ROSAT hardness ratios are used. By excluding the contamination from the host galaxies and from the jet beaming emission, the correlation indicates that the Compton cooling in the accretion disk corona decreases with the mean age of the stellar population. We argue that the correlation is related to the correlation of L/L Edd with the host stellar population. In addition, the [O I]/Hα and [S II]/Hα narrowline ratios are identified to correlate with the spectral slope in hard X-ray, which can be inferred from the currently proposed evolution of the X-ray emission because of the confirmed tight correlations between the two line ratios and stellar population age.

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Toward an unbiased sample of X‐ray selected normal galaxies outside the local Universe

Cited by 4 publications

References 18 publications

Reversal or no reversal: the evolution of the star formation rate–density relation up to z ∼ 1.6

Reversal or no reversal: the evolution of the star formation rate–density relation up to z ∼ 1.6

A serendipitous XMM survey of the SDSS: the evolution of the colour-magnitude diagram of X-ray AGN from z= 0.8 to 0.1

Insight Into Active Galactic Nucleus and Host Galaxy Co-Evolution From Hard X-Ray Emission

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