ROSAT PSPC spectra of X-ray-selected narrow-emission-line galaxies

Romero-Colmenero, E.; Branduardi‐Raymont, G.; Carrera, Francisco J.; Jones, Laura; Mason, K. O.; McHardy, I. M.; Mittaz, J. P. D.

doi:10.1093/mnras/282.1.94

Cited by 32 publications

(39 citation statements)

References 11 publications

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“…3). Such a trend had been found in ROSAT surveys (Romero-Colmenero et al 1996;Almaini et al 1996). The weighted average hardness ratios for these objects are HR 1 = −0.48±0.11 and HR 2 = −0.37 ± 0.04.…”

Section: The Extragalactic X-ray Sourcessupporting

confidence: 70%

The XMM-Newton serendipitous survey

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Watson

et al. 2002

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Abstract. We present the first results on the identifications of a medium sensitivity survey (X-ray flux limit 2 × 10 −14 erg cm −2 s −1 in the 0.5-4.5 keV band) at high galactic latitude (|b| > 20 • ) carried out with the XMM-Newton X-ray observatory within the AXIS observing programme. This study is being conducted as part of the XMMNewton Survey Science Centre activities towards the identification of the sources in the X-ray serendipitous sky survey. The sample contains 29 X-ray sources in a solid angle of 0.26 deg 2 (source density 113 ± 21 sources deg −2 ), out of which 27 (93%) have been identified. The majority of the sources are broad-line AGN (19), followed by narrow emission line X-ray emitting galaxies (6, all of which turn out to be AGN), 1 nearby non-emission line galaxy (NGC 4291) and 1 active coronal star. Among the identified sources we find 2 broad-absorption line QSOs (z ∼ 1.8 and z ∼ 1.9), which constitute ∼10% of the AGN population at this flux level, similar to optically selected samples. Identifications of a further 10 X-ray sources fainter than our survey limit are also presented.

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Section: The Extragalactic X-ray Sourcessupporting

confidence: 70%

The XMM-Newton serendipitous survey

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Watson

et al. 2002

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“…As such, their general properties closely resemble those of other samples of x-ray luminous, narrow emission-line galaxies (e.g., Boyle et al 1995a,b;Carballo et al 1995; Griffit.lis et al 1996;Romero-Colmenero et al 1996).…”

Section: Lcrs-ros Atsrc Sample Characteristicssupporting

confidence: 60%

ROSAT public PSPC observations in the Las Campanas Redshift Survey

1997

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The Las Campanas Redshift Survey, an optically selected survey which contains 26 418 galaxy redshifts, has been correlated with "The First ROSAT Source Catalogue of Pointed Observations with the PSPC," which contains 50408 sources from 2876 ROSAT pointed observations. Ten matches were found. The optical spectra of most of the ten matches show weak narrow emission lines. Due to their high x-ray luminosities, their high x-ray-to-optical flux ratios, and the evidence of rapid x-ray variability in the two brightest matches, we interpret the majority of these objects to be narrow-line Seyfert galaxies or "hidden" active galactic nuclei. Of the ten matches, only one galaxy shows the characteristics of a bona fide starburst.Key words: catalogs -surveys -galaxies: active -galaxies: starburst -x-rays: galaxies A A A subject classification: 157; 158 1. IntroductionGreat strides have been made in recent years in resolving the soft (0.5 -2 keV) extragalactic x-ray background (XRB) into discrete sources (for a review, see Hasinger 1996). These sources include stars, galaxies, quasars and other active galactic nuclei (AGNs), and groups and clusters of galaxies. Most recent surveys of the soft XRB have focused on finding the optical counterparts of x-ray sources from flux-limited x-ray catalogues. In this paper, however, we reverse the process: we take an optically selected galaxy redshift survey -the Las Campanas Redshift Survey (LCRS; Shectinan et al. 1996) -and search for x-ray sources within it, taking for our x-ray sample "The First ROSAT Source Catalogue of Point,ed Observat,ions with t.he PSPC" (ROSATSRC; Zimmermann 1994). That our approach is complement,ary t,o the standard strategy is evident,, since it is based upon a magnitude-limited optical galaxy survey which therefore contains much fainter x-ray sources (down to -3 x erg s-l cm-2) than most presenbday x-ray surveys. With such an approach, we can learn about the x-ray properties of a typical, optically selected catalogue of galaxies. 2. The LCRS and the R.OSATSRCThe LCRS is an optically selected galaxy redshift survey which extends to a redshift of 0.2 and which is composed of a total of 6 alternating 105 x 80' slices in t,lie North and Sout,li Galactic Caps. Accurate R-band photometry and sky positions for program objects have been extracted from CCD drift scans obtained on the Las Campanas Swope l-m telescope; spectroscopy has been performed at the Las Campanas Du Pont 2.5-m telescope, originally via a 50-fiber Multi-Object, Spectrograph (MOS), and later via a 112-fiber MOS. For observing efficiency, all the fibers are used, but each MOS field is observed only once. Hence, the LCRS is a collection of 50-fiber fields (with nominal apparent magnitude limits of 16 < m R < 17.3) and 112-fiber fields (with nominal apparent magnitude limits of 15 < mR < 17.7). Recently completed, the LCRS contains 26418 galaxy redshifts; in this paper, we consider only those 25327 LCRS galaxy redshifts which lie in the 6 published slices (Shectman et al. 1996).Our x-ray sample, ROSAT...

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“…Previous results based on ROS AT data (see Almaini et al 1996;Romero-Colmenero et al 1996) do find a flatter average spectral slope for NELGs (∼1.5) than for BLAGN (∼2). Our data shows that the spectral differences between these two classes of sources are due mostly (if not totally) to differing amounts of absorption rather than to differences in the underlying power law spectra.…”

Section: Photon Index Intrinsic Dispersionmentioning

confidence: 72%

X-ray spectra of XMM-Newton serendipitous medium flux sources

Mateos

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Carrera

et al. 2005

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Abstract. We report on the results of a detailed analysis of the X-ray spectral properties of a large sample of sources detected serendipitously with the XMM-Newton observatory in 25 selected fields, for which optical identification is in progress. The survey covers a total solid angle of ∼3.5 deg 2 and contains 1137 sources with ∼10 −15 < S 0.5−10 < 10 −12 erg cm −2 s −1 with good enough spectral quality as to perform a detailed X-ray spectral analysis of each individual object. We find evidence for hardening of the average X-ray spectra of the sources towards fainter fluxes, and we interpret this as indicating a higher degree of photoelectric absorption amongst the fainter population. Absorption is detected at 95% confidence in 20% of the sources, but it could certainly be present in many other sources below our detection capabilities. For Broad Line AGNs (BLAGNs), we detect absorption in ∼10% of the sources with column densities in the range 10 21 −10 22 cm −2 . The fraction of absorbed Narrow Emission Line galaxies (NELGs, most with intrinsic X-ray luminosities >10 43 erg s −1 , and therefore classified as type 2 AGNs) is significantly higher (40%), with a hint of moderately higher columns. After correcting for absorption, we do not find evidence for a redshift evolution of the underlying power law index of BLAGNs, which stays roughly constant at Γ ∼ 1.9, with intrinsic dispersion of 0.4. A small fraction (∼7%) of BLAGNs and NELGs require the presence of a soft excess, that we model as a black body with temperature ranging from 0.1 to 0.3 keV. Comparing our results on absorption to popular X-ray background synthesis models, we find absorption in only ∼40% of the sources expected. This is due to a deficiency of heavily absorbed sources (with N H ∼ 10 22 −10 24 cm −2 ) in our sample in comparison with the models. We therefore conclude that the synthesis models require some revision in their specific parameters.

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ROSAT PSPC spectra of X-ray-selected narrow-emission-line galaxies

Cited by 32 publications

References 11 publications

The XMM-Newton serendipitous survey

The XMM-Newton serendipitous survey

ROSAT public PSPC observations in the Las Campanas Redshift Survey

X-ray spectra of XMM-Newton serendipitous medium flux sources

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