Optical identification of ROSAT-FSC sources

Mickaelian, A. M.; Hovhannisyan, L. R.; Engels, D.; Hagen, H. J.; Voges, W.

doi:10.1051/0004-6361:20053967

Cited by 39 publications

(36 citation statements)

References 23 publications

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“…However, the size of the emission region (3 ) is very small in comparison with R 500 value for the cluster (40 ). In addition, according to Mickaelian et al (2006) this emission belongs to a star. Therefore, we did not assign this X-ray source to ZwCl 2259+0746.…”

Section: Final Matching and Confirmationmentioning

confidence: 99%

Correcting for peculiar velocities of Type Ia supernovae in clusters of galaxies

Léget¹,

Pruzhinskaya²,

Ciulli³

et al. 2018

A&A

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Context. Type Ia Supernovae (SNe Ia) are widely used to measure the expansion of the Universe. To perform such measurements the luminosity and cosmological redshift (z) of the SNe Ia have to be determined. The uncertainty on z includes an unknown peculiar velocity, which can be very large for SNe Ia in the virialized cores of massive clusters. Aims. We determine which SNe Ia exploded in galaxy clusters. We then study how the correction for peculiar velocities of host galaxies inside the clusters improves the Hubble residuals. Methods. Using 145 SNe Ia from the Nearby Supernova Factory we found 11 candidates for membership in clusters. To estimate the redshift of a cluster we applied the bi-weight technique. Then, we use the galaxy cluster redshift instead of the host galaxy redshift to construct the Hubble diagram. Results. For SNe Ia inside galaxy clusters the dispersion around the Hubble diagram when peculiar velocities are taken into account is smaller in comparison with a case without peculiar velocity correction, with a wRMS =0.130 ± 0.038 mag instead of wRMS =0.137 ± 0.036 mag. The significance of this improvement is 3.58 σ. If we remove the very nearby Virgo cluster member SN2006X (z < 0.01) from the analysis, the significance decreases to 1.34 σ. The peculiar velocity correction is found to be highest for the SNe Ia hosted by blue spiral galaxies, with high local specific star formation rate and smaller stellar mass, seemingly counter to what might be expected given the heavy concentration of old, massive elliptical galaxies in clusters. Conclusions. As expected, the Hubble residuals of SNe Ia associated with massive galaxy clusters improve when the cluster redshift is taken as the cosmological redshift of the SN. This fact has to be taken into account in future cosmological analyses in order to achieve higher accuracy for cosmological redshift measurements. Here we provide an approach to do so.

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Section: Final Matching and Confirmationmentioning

confidence: 99%

Correcting for peculiar velocities of Type Ia supernovae in clusters of galaxies

Léget¹,

Pruzhinskaya²,

Ciulli³

et al. 2018

A&A

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“…The NED lists 127a as QSO, but without reference. See also Mickaelian et al (2006). The SDSS-III spectrum classifies 127a as broadline QSO at z = 0.2336.…”

Section: Sdss Spectramentioning

confidence: 99%

“…A supposed variability of the northern component is uncertain because of faintness and blending. Identification as K star from Mickaelian et al (2006). 229b is probably a AGN due to its blue colour, and therefore a good counterpart candidate.…”

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confidence: 99%

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Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes

Greiner

Richter

2015

A&A

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Context. The optical identification of large number of X-ray sources such as those from the ROSAT All-Sky Survey is challenging with conventional spectroscopic follow-up observations. Aims. We investigate two ROSAT All-Sky Survey fields of size 10 • × 10 • each, one at galactic latitude b = 83 • (26 Com), the other at b = −5 • (γ Sge), in order to optically identify the majority of sources. Methods. We used optical variability, among other more standard methods, as a means of identifying a large number of ROSAT All-Sky Survey sources. All objects fainter than about 12 mag and brighter than about 17 mag, in or near the error circle of the ROSAT positions, were tested for optical variability on hundreds of archival plates of the Sonneberg field patrol.Results. The present paper contains probable optical identifications of altogether 256 of the 370 ROSAT sources analysed. In particular, we found 126 active galactic nuclei (some of them may be misclassified cataclysmic variables, CVs), 17 likely clusters of galaxies, 16 eruptive double stars (mostly CVs), 43 chromospherically active stars, 65 stars brighter than about 13 mag, 7 UV Cet stars, 3 semiregular resp. slow irregular variable stars of late spectral type, 2 DA white dwarfs, 1 Am star, 1 supernova remnant and 1 planetary nebula. As expected, nearly all active galactic nuclei are found in the high-galactic latitude field, while the majority of CVs is located at low galactic latitudes. We identify in total 72 new variable objects. Conclusions. X-ray emission is, expectedly, tightly correlated with optical variability, and thus our new method for optically identifying X-ray sources is demonstrated to be feasible. Given the large number of optical plates used, this method was most likely not more efficient than e.g. optical spectroscopy. However, it required no telescope time, only access to archival data.

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“…By merging Hamburg-ROSAT (HRC, Zickgraf et al 2003) and Byurakan-Hamburg-ROSAT (BHRC, Mickaelian et al 2006) catalogs made up on the basis of optical identifications of ROSAT BSC (Voges et al 1999) and ROSAT FSC (Voges et al 2000) sources by means of Hamburg Quasar Survey (HQS, Hagen et al 1995) (Massaro et al 2009). There are 2908 objects in the SDSS DR10 (Ahn et al 2013) giving possibility of their classification, particularly the activity types for AGN.…”

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confidence: 99%

Activity types for X-ray candidate AGN from SDSS

Paronyan¹,

Harutyunyan²,

Mickaelian³

2013

Proc. IAU

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Abstract. The Joint Catalogue of Hamburg ROSAT Sources (HRC/BHRC) is the result of merging of HRC and BHRC catalogs built on the basis of optical identifications of ROSAT BSC and ROSAT FSC. Altogether, 8132 sources are present. Based on this catalogue, we have compiled a sample of ROSAT AGN, including candidate ones. In this paper we classify candidate AGN (those that previously had not been spectroscopically classified) by their activity type. The sample contains 955 objects with count rate of photons CR > 0.04 ct/s in the area with galactic latitudes |b| > 30 and declinations δ > 0, however only 217 objects have SDSS DR10 spectra. The classification led to the following results: 95 AGN, 71 absorption-line galaxies, 42 stars, and 9 unclassified objects.

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Optical identification of ROSAT-FSC sources

Cited by 39 publications

References 23 publications

Correcting for peculiar velocities of Type Ia supernovae in clusters of galaxies

Correcting for peculiar velocities of Type Ia supernovae in clusters of galaxies

Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes

Activity types for X-ray candidate AGN from SDSS

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