European Southern Observatory Very Large Telescope Optical Spectroscopy of Bl Lacertae Objects. Iii. An Extension of the Sample

Sbarufatti, B.; Ciprini, S.; Kotilainen, J. K.; Decarli, Roberto; Treves, A.; Veronesi, A.; Falomo, R.

doi:10.1088/0004-6256/137/1/337

Cited by 31 publications

(23 citation statements)

References 61 publications

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“…Observations with medium aperture telescopes provided redshifts for a number of BL Lac objects (e.g., Falomo et al 1987bFalomo et al , 1987aFalomo 1990;Stickel et al 1993;Veron 1994;Marcha et al 1996;Carangelo et al 2003) but for many of these objects, in particular those with a strong nuclear component, the redshifts remained unknown. With 8 m class telescopes the situation improved as demonstrated among the recent systematic spectroscopic campaigns such as our study of 69 BL Lac objects in the southern sky with ESO−VLT+FORS2, which yielded 23 new redshifts of BL Lac objects basically selected in the Giommi/Padovani list (Padovani & Giommi 1995) before the launch of Fermi (Sbarufatti et al 2005a(Sbarufatti et al , 2005b(Sbarufatti et al , 2006a(Sbarufatti et al , 2006b(Sbarufatti et al , 2009Landoni et al 2013, spectra and redshifts are available in electronic form on our Web site http://www.oapd.inaf.it/zbllac/).…”

Section: Introductionmentioning

confidence: 79%

SPECTROSCOPY OF OPTICALLY SELECTED BL LAC OBJECTS AND THEIR Γ-Ray EMISSION

Sandrinelli

Treves

Falomo

et al. 2013

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We present Very Large Telescope optical spectroscopy of nine BL Lac objects of unknown redshift belonging to the list of optically selected radio-loud BL Lac candidates. We explore their spectroscopic properties and possible link with gamma-ray emission. From the new observations we determine the redshifts of four objects from faint emission lines or from absorption features of their host galaxies. In three cases we find narrow intervening absorptions from which a lower limit to the redshift is inferred. For the remaining two featureless sources, lower limits to the redshift are deduced from the absence of spectral lines. A search for γ counterpart emission shows that six out of the nine candidates are Fermi γ -ray emitters and we find two new detections. Our analysis suggests that most of the BL Lac objects still lacking redshift information are most likely located at high redshifts.

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Section: Introductionmentioning

confidence: 79%

SPECTROSCOPY OF OPTICALLY SELECTED BL LAC OBJECTS AND THEIR Γ-Ray EMISSION

Sandrinelli

Treves

Falomo

et al. 2013

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“…Table 2. List of parameters corresponding to the BL Lac objects in our sample obtained with the approach of Sbarufatti et al (2006Sbarufatti et al ( , 2009see text). Notes.…”

Section: Discussionmentioning

confidence: 99%

BL Lacertae identifications in a ROSAT-selected sample ofFermiunidentified objects

Masetti

Sbarufatti

Parisi

et al. 2013

A&A

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The optical spectroscopic followup of 27 sources belonging to a sample of 30 high-energy objects selected by positionally cross correlating the first Fermi/LAT Catalog and the ROSAT All-Sky Survey Bright Source Catalog is presented here. It has been found or confirmed that 25 of them are BL Lacertae objects (BL Lacs), while the remaining two are Galactic cataclysmic variables (CVs). This strongly suggests that the sources in the first group are responsible for the GeV emission detected with Fermi, while the two CVs most likely represent spurious associations. We thus find an 80% a posteriori probability that the sources selected by matching GeV and X-ray catalogs belong to the BL Lac class. We also show suggestions that the BL Lacs selected with this approach are probably high-synchrotron-peaked sources and in turn good candidates for the detection of ultra-high-energy (TeV) photons from them.

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“…Removing any possible degeneracy in the selection methods requires a certain source classification that can only beachieved by optical spectroscopy (e.g., Masetti et al 2013;Shaw et al 2013a,b;Paggi et al 2014;Massaro et al 2014a). Moreover, several optical spectroscopic campaigns have recently been carried out to obtain redshift estimates for a large sample of BZBs using medium-resolution spectroscopy; some of them are now known as γ-ray emitters associated with Fermi sources (e.g., Sbarufatti et al 2006aSbarufatti et al ,b, 2009Landoni et al 2013;Shaw et al 2013a,b).…”

Section: Introductionmentioning

confidence: 99%

Optical spectroscopic observations ofγ-ray blazar candidates

Massaro

Landoni

D’Abrusco

et al. 2015

A&A

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Context. We recently started a systematic search of low-energy counterparts of the unidentified γ-ray sources (UGSs) listed in the Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL) and the Fermi-LAT 2-Year Source Catalog (2FGL). Aims. The main goal of our investigation is to find active galaxies belonging to the blazar class that lie within the positional uncertainty region of the UGSs and thus could be their potential low-energy counterparts. Methods. To achieve our aims, we first adopted several procedures based on the peculiar observational properties of blazars in the radio and in the IR. Then we carried out a follow-up spectroscopic campaign in the optical band to verify the nature of the candidates selected as potential counterparts of the UGSs. Here we present the results of the observations carried out in 2013 in the northern hemisphere at Kitt Peak National Observatory (KPNO). Optical spectroscopy is crucial to confirm the nature of the sources and can be used to estimate their redshifts; it will also allow us to test the robustness of our methods when the whole campaign is completed. Results. Here we present the optical spectroscopic observations of 39 sources. Within our sample we found that 6 sources are blazars, candidates to be low-energy counterparts of the UGSs listed in the 2FGL. We confirm that an additional 8 sources, previously classified as active galaxies of uncertain type and associated in the 2FGL, are also all BL Lac objects. Moreover, we also present 20 new spectra for known blazars listed in the Multi-frequency Catalogue of Blazars as having an uncertain redshift and/or being classified as BL Lac candidates. Conclusions. We conclude that our methods for selecting γ-ray blazar candidates allows us to discover new blazars and increase the list of potential low-energy counterparts for the Fermi UGSs.

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European Southern Observatory Very Large Telescope Optical Spectroscopy of Bl Lacertae Objects. Iii. An Extension of the Sample

Cited by 31 publications

References 61 publications

SPECTROSCOPY OF OPTICALLY SELECTED BL LAC OBJECTS AND THEIR Γ-Ray EMISSION

SPECTROSCOPY OF OPTICALLY SELECTED BL LAC OBJECTS AND THEIR Γ-Ray EMISSION

BL Lacertae identifications in a ROSAT-selected sample ofFermiunidentified objects

Optical spectroscopic observations ofγ-ray blazar candidates

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