Exploring the active galactic nuclei population with extreme X-ray-to-optical flux ratios (fx/fo &gt; 50)

Ceca, R. Della; Carrera, Francisco J.; Caccianiga, A.; Severgnini, P.; Ballo, L.; Braito, V.; Corral, A.; Moro, A. Del; Mateos, S.; Ruiz, Ángel Liceras; Watson, M. G.

doi:10.1093/mnras/stu2665

Cited by 6 publications

(7 citation statements)

References 86 publications

(109 reference statements)

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“…Many of these objects have X-ray-to-optical flux ratios above 1, and a small fraction of about 5% have F X /F opt ≥ 20 (Della Ceca et al 2015). J103621.39-581520.0 thus seems to be a particularly X-ray active quasar.…”

Section: Discussionmentioning

confidence: 99%

Chandra X-ray observation of the young stellar cluster NGC 3293 in the Carina Nebula Complex

Preibisch

Flaischlen

Gaczkowski

et al. 2017

A&A

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Context. NGC 3293 is a young stellar cluster at the northwestern periphery of the Carina Nebula Complex that has remained poorly explored until now. Aims. We characterize the stellar population of NGC 3293 in order to evaluate key parameters of the cluster population such as the age and the mass function, and to test claims of an abnormal IMF and a deficit of M ≤ 2.5 M stars. Methods. We performed a deep (70 ksec) X-ray observation of NGC 3293 with Chandra and detected 1026 individual X-ray point sources. These X-ray data directly probe the low-mass (M ≤ 2 M ) stellar population by means of the strong X-ray emission of young low-mass stars. We identify counterparts for 74% of the X-ray sources in our deep near-infrared images. Results. Our data clearly show that NGC 3293 hosts a large population of ≈ solar-mass stars, refuting claims of a lack of M ≤ 2.5 M stars. The analysis of the color magnitude diagram suggests an age of ∼ 8 − 10 Myr for the low-mass population of the cluster. There are at least 511 X-ray detected stars with color magnitude positions that are consistent with young stellar members within 7 arcmin of the cluster center. The number ratio of X-ray detected stars in the [1 − 2] M range versus the M ≥ 5 M stars (known from optical spectroscopy) is consistent with the expectation from a normal field initial mass function. Most of the early B-type stars and ≈ 20% of the later B-type stars are detected as X-ray sources. Conclusions. Our data shows that NGC 3293 is one of the most populous stellar clusters in the entire Carina Nebula Complex (very similar to Tr 16 and Tr 15; only Tr 14 is more populous). The cluster probably harbored several O-type stars, whose supernova explosions may have had an important impact on the early evolution of the Carina Nebula Complex.

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Section: Discussionmentioning

confidence: 99%

Chandra X-ray observation of the young stellar cluster NGC 3293 in the Carina Nebula Complex

Preibisch

Flaischlen

Gaczkowski

et al. 2017

A&A

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“…Several studies (e.g. Fiore et al 2003;Mignoli et al 2004;Alexander et al 2002;Del Moro et al 2009;Della Ceca et al 2015) have found that sources with high f x / f O are characterised, on average, by red optical to near-infrared colours (R − K Vega > 5) and column densities in the X-ray of the order of 10 21−23 cm −2 . Moreover, VLT X-Shooter Perna et al 2015) and SINFONI observations of a small subsample of obscured QSOs at z ∼ 1.5, selected on the basis of their observed red colours and high f x / f O ratio, have confirmed the presence of ionised outflowing material in 75% of objects and a dust-reddened type 1 nature.…”

Section: Introductionmentioning

confidence: 99%

SINFONI spectra of heavily obscured AGNs in COSMOS: Evidence of outflows in a MIR/O target atz~ 2.5

Perna

Brusa

Salvato

et al. 2015

A&A

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Aims. We present new data for four candidate obscured Compton-Thick (CT) quasars at z ∼ 1-2.5 observed with the SINFONI VLT spectrograph in adaptive optics (AO) mode. These sources were selected from a 24 µm Spitzer MIPS survey of the COSMOS field, on the basis of red mid-infrared to optical and optical to near-infrared colours, with the intention of identifying active galactic nuclei (AGNs) in dust enshrouded environments, where most of the black hole mass is assembled. Methods. Near-infrared spectra were analysed to check for emission line features and to search for broad components in the [OIII]-Hβ and Hα-[NII] regions. We also employed X-ray spectral analysis, radio and MIR diagnostics, and SED fitting to study the nature of the sources. Results. We successfully identified three objects for which we had only a photometric redshift estimate. Based on their emission line diagnostics and on ancillary multi-wavelength constraints, we find that all four targets harbour obscured AGNs. Broad profiles, which could be attributed to the effects of outflows, are revealed in only one target, MIRO20581. In particular, we clearly resolved a fast (∼1600 km s −1 ) and extended (∼5 kpc) outflow in the [OIII]5007 emission line. This feature, the commonly used indicator for ionised outflowing gas, was only sampled and detected for this target; hence, we cannot exclude the presence of outflows in the other sources. Overall, the constraints we obtain from our targets and from other comparative samples from the literature suggest that these optically faint luminous infrared galaxies, hosting obscured AGNs, may represent a brief evolutionary phase between the post-merger starburst and the unobscured quasar phases.

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“…Among seven EXO50s studied in Della Ceca et al (2015), three are classified as EDOGs (f24/fR > 2000). Their absorption column densities NH are measured to be > 0.4, 3.61 +1.03 −0.92 , and > 0.1 × 10 22 cm −2 .…”

Section: Mid-infrared Emission and Obscuration Of Agnmentioning

confidence: 99%

“…Optically faint sources also tend to be bright in mid-infrared relative to the optical bands if detected in the mid-infrared band. 24 µm to R-band flux ratios (F24/FR) of some sources exceed 1000 (Lanzuisi et al 2009, Brusa et al 2010, Della Ceca et al 2015, which is a criterion of dust-obscured galaxies (Dey et al 2008). Among 43 objects with F24/FR > 2000 in the sample of Lanzuisi et al (2009), at least 23 are X-ray bright optically faint for example.…”

Section: Introductionmentioning

confidence: 99%

“…Della Ceca et al (2015) utilized the second XMM-Newton serendipitous source catalogue and optical imaging data to find seven extreme optical-to-X-ray ratio objects (FX/FR > 50) with an X-ray flux greater than 1.5×10 −13 erg cm −2 s −1 . Three and two of the seven sources are classified as type 2 quasar, and BL Lac objects, respectively.…”

Section: Introductionmentioning

confidence: 99%

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X-ray-bright optically faint active galactic nuclei in the Subaru Hyper Suprime-Cam wide survey

Terashima

Suganuma

Akiyama

et al. 2017

Publications of the Astronomical Society of Japan

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We construct a sample of X-ray bright optically faint active galactic nuclei by combining Subaru Hyper Suprime-Cam, XMM-Newton, and infrared source catalogs. 53 X-ray sources satisfying i band magnitude fainter than 23.5 mag and X-ray counts with EPIC-PN detector larger than 70 are selected from 9.1 deg 2 , and their spectral energy distributions (SEDs) and X-ray spectra are analyzed.44 objects with an X-ray to i-band flux ratio F X /F i > 10 are classified as extreme X-ray-to-optical flux sources. SEDs of 48 among 53 are represented by templates of type 2 AGNs or starforming galaxies and show signature of stellar emission from host galaxies in the optical in the source rest frame. Infrared/optical SEDs indicate significant contribution of emission from dust to infrared fluxes and that the central AGN is dust obscured. Photometric redshifts determined from the SEDs are in the range of 0.6-2.5. X-ray spectra are fitted by an absorbed power law model, and the intrinsic absorption column densities are modest (best-fit log N H = 20.5 − 23.5 cm −2 in most cases). The absorption corrected X-ray luminosities are in the range of 6 × 10 42 − 2 × 10 45 erg s −1 . 20 objects are classified as type 2 quasars based on X-ray luminsosity and N H . The optical faintness is explained by a combination of redshifts (mostly z > 1.0), strong dust extinction, and in part a large ratio of dust/gas.

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Exploring the active galactic nuclei population with extreme X-ray-to-optical flux ratios (fx/fo > 50)

Cited by 6 publications

References 86 publications

Chandra X-ray observation of the young stellar cluster NGC 3293 in the Carina Nebula Complex

Chandra X-ray observation of the young stellar cluster NGC 3293 in the Carina Nebula Complex

SINFONI spectra of heavily obscured AGNs in COSMOS: Evidence of outflows in a MIR/O target atz~ 2.5

X-ray-bright optically faint active galactic nuclei in the Subaru Hyper Suprime-Cam wide survey

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