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, A.; Nandra, K.

doi:10.1111/j.1365-2966.2011.18387.x

Cited by 69 publications

(118 citation statements)

References 72 publications

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“…Nandra et al (2007) investigated the positions of X-ray AGN hosts in the optical CMD at z ∼ 1 and found an overdensity of AGN in the luminous galaxies close to and within the green valley. Similar results were found by Coil et al (2009) for a larger sample of X-ray AGN, and the same trend appears to hold at lower redshifts (Hickox et al 2009;Georgakakis & Nandra 2011). However, Silverman et al (2009) and Xue et al (2010) have shown the importance of stellar-mass selection effects in such analyses, indicating that stellar mass, not colour, may be the key parameter that drives the observed trends in the CMD.…”

Section: Colour-magnitude Diagramsupporting

confidence: 81%

Physical properties of AGN host galaxies as a probe of supermassive black hole feeding mechanisms

Gatti¹,

Lamastra²,

Menci³

et al. 2015

A&A

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Using an advanced semi-analytical model (SAM) for galaxy formation, we investigated the statistical effects of assuming two different mechanisms for triggering AGN activity on the properties of AGN host galaxies. We considered a first accretion mode where AGN activity is triggered by disk instabilities (DI) in isolated galaxies, and a second feeding mode where galaxy mergers and fly-by events (interactions, IT) are responsible for producing a sudden destabilization of large quantities of gas, causing the mass inflow onto the central supermassive black hole. The effects of including IT and DI modes in our SAM were studied and compared with observations separately to single out the regimes in which they might be responsible for triggering AGN activity. We obtained the following results: i) the predictions of our model concerning the stellar mass functions of AGN hosts point out that both DI and IT modes are able to account for the observed abundance of AGN host galaxies with M * < ∼ 10 11 M ; for more massive hosts, the DI scenario predicts a much lower space density than the IT model in every redshift bin, lying below the observational estimates for redshift z > 0.8. ii) The analysis of the colour−magnitude diagram of AGN hosts for redshift z < 1.5 can provide a good observational test to effectively distinguish between DI and IT mode, since DIs are expected to yield AGN host galaxy colours skewed towards bluer colours, while in the IT scenario the majority of hosts are expected to reside in the red sequence. iii) While both IT and DI scenarios can account for AGN triggered in main sequence or starburst galaxies, DIs fail in triggering AGN activity in passive galaxies. The lack of DI AGN in passive hosts is rather insensitive to changes in the model describing the DI mass inflow, and it is mainly caused by the criterion for the onset of disk instabilities included in our SAM. iv) The two modes are characterized by a different duration of the AGN phase, with DIs lasting even on time scales of ∼Gyr, much longer than in the IT scenario, where the galaxy interaction sets the duration of the burst phase around ∼10 7 −10 8 yr. v) The scatter of the star formation rate SFR−L bol relation could represent another crucial diagnostics to distinguish between the two AGN triggering modes, since the DI scenario predicts an appreciably lower scatter (especially at lowto-intermediate AGN luminosities) of the relation than the IT scenario. vi) Disk instabilities are unable to account for the observed fraction of AGN in groups for z < ∼ 1 and clusters for z < ∼ 0.7, while the IT scenario matches observational data well.

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Section: Colour-magnitude Diagramsupporting

confidence: 81%

Physical properties of AGN host galaxies as a probe of supermassive black hole feeding mechanisms

Gatti¹,

Lamastra²,

Menci³

et al. 2015

A&A

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“…The sensitivity of the survey is estimated using methods described in Georgakakis et al (2008) and Georgakakis & Nandra (2011). Fig.…”

Section: X-ray Source Cataloguementioning

confidence: 99%

“…In this paper, we cross-correlate the X-ray source positions with the deeper optical photometric catalogue (ugriz bands; AB limiting magnitude r ≈ 24.9 mag) of the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS; Heymans et al 2012;Erben et al 2013). The association of X-ray sources with counterparts was based on the likelihood ratio (LR) method (Sutherland & Saunders 1992;Ciliegi et al 2003;Brusa et al 2007;Laird et al 2009;Luo et al 2010;Xue et al 2010;Georgakakis & Nandra 2011).…”

Section: X-ray Source Cataloguementioning

confidence: 99%

X-ray constraints on the fraction of obscured active galactic nuclei at high accretion luminosities

Georgakakis

Salvato

Liu

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The wide-area XMM-XXL X-ray survey is used to explore the fraction of obscured active galactic nuclei (AGNs) at high accretion luminosities, L X (2−10 keV) 10 44 erg s −1 , and out to redshift z ≈ 1.5. The sample covers an area of about 14 deg 2 and provides constraints on the space density of powerful AGNs over a wide range of neutral hydrogen column densities extending beyond the Compton-thick limit, N H ≈ 10 24 cm −2 . The fraction of obscured Compton-thin (N H = 10 22 −10 24 cm −2 ) AGNs is estimated to be ≈0.35 for luminosities L X (2−10 keV) > 10 44 erg s −1 , independent of redshift. For less luminous sources, the fraction of obscured Compton-thin AGNs increases from 0.45 ± 0.10 at z = 0.25 to 0.75 ± 0.05 at z = 1.25. Studies that select AGNs in the infrared via template fits to the observed spectral energy distribution of extragalactic sources estimate space densities at high accretion luminosities consistent with the XMM-XXL constraints. There is no evidence for a large population of AGNs (e.g. heavily obscured) identified in the infrared and missed at X-ray wavelengths. We further explore the mid-infrared colours of XMM-XXL AGNs as a function of accretion luminosity, column density and redshift. The fraction of XMM-XXL sources that lie within the mid-infrared colour wedges defined in the literature to select AGNs is primarily a function of redshift. This fraction increases from about 20-30 per cent at z = 0.25 to about 50-70 per cent at z = 1.5.

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“…The starting sample was extracted from the XMM-Newton/ SDSS-DR7 cross-correlation presented in Georgakakis & Nandra (2011), including more than 40 000 X-ray sources. We first selected the sources detected in the X-ray hard band (2−8 keV), a band less affected by obscuration than is the soft one (0.5−2 keV).…”

Section: X-ray Selectionmentioning

confidence: 99%

The XMM spectral catalog of SDSS optically selected Seyfert 2 galaxies

Koulouridis

Georgantopoulos

Loukaidou

et al. 2016

A&A

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We present an X-ray spectroscopic study of optically selected (SDSS) Seyfert 2 (Sy2) galaxies. The goal is to study the obscuration of Sy2 galaxies beyond the local universe, using good quality X-ray spectra in combination with high S/N optical spectra for their robust classification. We analyzed all available XMM-Newton archival observations of narrow emission line galaxies that meet the above criteria in the redshift range 0.05 < z < 0.35. We initially selected narrow line AGN using the SDSS optical spectra and the BPT classification diagram. We further modeled and removed the stellar continuum, and we analyzed the residual emission line spectrum to exclude any possible intermediate-type Seyferts. Our final catalog comprises 31 Sy2 galaxies with median redshift z ∼ 0.1. X-ray spectroscopy is performed using the available X-ray spectra from the 3XMM and the XMMFITCAT catalogs. Implementing various indicators of obscuration, we find seven (∼23%) Compton-thick AGN. The X-ray spectroscopic Compton-thick classification agrees with other commonly used diagnostics, such as the X-ray to mid-IR luminosity ratio and the X-ray to [OIII]λ5007 luminosity ratio. Most importantly, we find four (∼13%) unobscured Sy2 galaxies, at odds with the simplest unification model. Their accretion rates are significantly lower than the rest of our Sy2 sample, in agreement with previous studies that predict the absence of the broad line region below a certain Eddington ratio threshold.

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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

Cited by 69 publications

References 72 publications

Physical properties of AGN host galaxies as a probe of supermassive black hole feeding mechanisms

Physical properties of AGN host galaxies as a probe of supermassive black hole feeding mechanisms

X-ray constraints on the fraction of obscured active galactic nuclei at high accretion luminosities

The XMM spectral catalog of SDSS optically selected Seyfert 2 galaxies

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