An XMM-<i>Newton</i>study of hyper-luminous infrared galaxies

Ruiz, Ángel Liceras; Carrera, Francisco J.; Panessa, F.

doi:10.1051/0004-6361:20066708

“…The potential AGN bias is therefore negligible, and we consider the F02 sample suitable for drawing general conclusions about the HLIRG population. Only five sources of this sample have been observed by XMM-Newton, and just two of these five HLIRG were detected (Ruiz et al 2007). In order to study the relation between the X-ray and MIR emission for this kind of sources, we included four additional HLIRG in our sample.…”

Section: The Samplementioning

confidence: 94%

“…In Ruiz et al (2007) we tried to disentangle the AGN and SB emission of HLIRG following a different approach. Since the 2−10 keV X-ray emission above ∼10 42 erg s −1 is the "smoking gun" of AGN activity (Mushotzky 2004), we studied the X-ray spectra of a sample of fourteen HLIRG observed by XMM-Newton.…”

Section: Introductionmentioning

confidence: 99%

Analysis ofSpitzer-IRS spectra of hyperluminous infrared galaxies

Ruiz¹,

Risaliti²,

Nardini³

et al. 2013

A&A

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Context. Hyperluminous infrared galaxies (HLIRG) are the most luminous persistent objects in the Universe. They exhibit extremely high star formation rates, and most of them seem to harbour an active galactic nucleus (AGN). They are unique laboratories for investigating the most extreme star formation and its connection to super-massive black hole growth. Aims. The relative AGN and starburst (SB) contributions to the total output in these objects is still debated. Our aim is to disentangle the AGN and SB emission of a sample of thirteen HLIRG. Methods. We studied the MIR low-resolution spectra of a sample of thirteen HLIRG obtained with the Infrared Spectrograph on board Spitzer. The 5−8 µm range is an optimal window for detecting AGN activity even in a heavily obscured environment. We performed an SB/AGN decomposition of the continuum using templates, which has been successfully applied for ULIRG in previous works. Results. The MIR spectra of all sources is largely dominated by AGN emission. By converting the 6 µm luminosity into IR luminosity, we found that ∼80% of the sample shows an IR output dominated by the AGN emission. However, the SB activity is significant in all sources (mean SB contribution ∼30%), showing star formation rates ∼300−3000 M yr −1 . With X-ray and MIR data we estimated the dust covering factor (CF) of these HLIRG, finding that a significant fraction presents a CF consistent with unity. Along with the high X-ray absorption shown by these sources, this suggests that large amounts of dust and gas enshroud the nucleus of these HLIRG, as also observed in ULIRG. Conclusions. Our results agree with previous studies of the IR SED of HLIRG using radiative transfer models, and we find strong evidence that all HLIRG harbour an AGN. Moreover, this work provides further support for the idea that AGN and SB are both crucial to understanding the properties of HLIRG. Our study of the CF supports the hypothesis that HLIRG can be divided into two different populations.

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“…All type II and one NL-SB galaxy are Compton-thick (CT) candidates. See Ruiz et al (2007) for a further discussion on this sample.…”

Section: The Hlirg Samplementioning

confidence: 99%

“…We have then three sources with a SB-dominated SED (IRAS F12509+3122, IRAS 14026+4341 and IRAS F14218+3845), one AGN-dominated source with an important SB contribution (IRAS 18216+6418), and three objects which seem to be extremely luminous quasars with no particular differences from the local ones, judging from their SED and X-ray spectra (Ruiz et al 2007).…”

Section: Class a Hlirgmentioning

confidence: 99%

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Spectral energy distribution of hyperluminous infrared galaxies

Ruiz

¹

,

Miniutti

²

,

Panessa

³

et al. 2010

A&A

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Aims. The relationship between star formation and super-massive black hole growth is central to our understanding of galaxy formation and evolution. Hyperluminous infrared galaxies (HLIRG) are unique laboratories to investigate the connection between starburst (SB) and active galactic nuclei (AGN), because they exhibit extreme star-formation rates, and most of them show evidence of harbouring powerful AGN. Methods. Our previous X-ray study of a sample of HLIRG shows that the X-ray emission of most of these sources is dominated by AGN activity. To improve our estimate of the relative contribution of the AGN and SB emission to its total bolometric output, we have built multi-wavelength (from radio to X-rays) spectral energy distributions (SED) for these HLIRG and fitted standard empirical AGN and SB templates to these SED. Results. In broad terms, most sources are well fitted with this method, and we found AGN and SB contributions similar to those obtained by previous studies of HLIRG. We have classified the HLIRG SED into two groups, class A and class B. Class A HLIRG show a flat SED from the optical to the infrared energy range. Three out of seven class A sources can be modelled with a pure luminosity-dependent quasar template, while the rest of them require a type 1 AGN template and a SB template. The SB component is dominant in three out of four class A objects. Class B HLIRG show SED with a prominent and broad IR bump. These sources cannot easily be modelled with a combination of pure AGN and pure SB, they require templates of composite objects, suggesting that > ∼ 50% of their emission comes from stellar formation processes. Conclusions. We propose that our sample is actually composed of three different populations: very luminous quasars (class A objects with negligible SB contribution), young galaxies going through their maximal star-formation period (class A objects with significant SB emission) and the high luminosity tail of the ultraluminous infrared galaxies population distribution (class B sources).

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Spectral Energy Distribution of Hyper-Luminous Infrared Galaxies

Ruiz

¹

,

Carrera

²

,

Panessa

³

et al. 2010

Astrophysics and Space Science Proceedings

Self Cite

1

0

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Aims. The relationship between star formation and super-massive black hole growth is central to our understanding of galaxy formation and evolution. Hyperluminous infrared galaxies (HLIRG) are unique laboratories to investigate the connection between starburst (SB) and active galactic nuclei (AGN), because they exhibit extreme star-formation rates, and most of them show evidence of harbouring powerful AGN. Methods. Our previous X-ray study of a sample of HLIRG shows that the X-ray emission of most of these sources is dominated by AGN activity. To improve our estimate of the relative contribution of the AGN and SB emission to its total bolometric output, we have built multi-wavelength (from radio to X-rays) spectral energy distributions (SED) for these HLIRG and fitted standard empirical AGN and SB templates to these SED. Results. In broad terms, most sources are well fitted with this method, and we found AGN and SB contributions similar to those obtained by previous studies of HLIRG. We have classified the HLIRG SED into two groups, class A and class B. Class A HLIRG show a flat SED from the optical to the infrared energy range. Three out of seven class A sources can be modelled with a pure luminosity-dependent quasar template, while the rest of them require a type 1 AGN template and a SB template. The SB component is dominant in three out of four class A objects. Class B HLIRG show SED with a prominent and broad IR bump. These sources cannot easily be modelled with a combination of pure AGN and pure SB, they require templates of composite objects, suggesting that > ∼ 50% of their emission comes from stellar formation processes. Conclusions. We propose that our sample is actually composed of three different populations: very luminous quasars (class A objects with negligible SB contribution), young galaxies going through their maximal star-formation period (class A objects with significant SB emission) and the high luminosity tail of the ultraluminous infrared galaxies population distribution (class B sources).

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An XMM-Newtonstudy of hyper-luminous infrared galaxies

Cited by 21 publications

References 83 publications

Analysis ofSpitzer-IRS spectra of hyperluminous infrared galaxies

Analysis ofSpitzer-IRS spectra of hyperluminous infrared galaxies

Spectral energy distribution of hyperluminous infrared galaxies

Spectral Energy Distribution of Hyper-Luminous Infrared Galaxies

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