J/A+A/570/A126 XShooter spectrum of 4 BL Lacs (Landoni+, 2014)
Spectroscopy of BL Lac objects of extraordinary luminosity.
Landoni M, Falomo R., Treves A., Sbarufatti B.
<Astron. Astrophys. 570, A126 (2014)>
=2014A&A...570A.126L 2014A&A...570A.126L
ADC_Keywords: BL Lac objects ; Spectroscopy
Keywords: BL Lacs spectroscopy - instrumentation: spectrographs -
cosmology: observations
Abstract:
We aim to determine the redshift (or stringent lower limits) of a
number of bright BL Lacs objects.
We secured optical and near-infrared medium resolution spectra of four
bright BL Lac objects of unknown redshift using the spectrograph
X-Shooter at the ESO-VLT.
In spite of the high quality of the spectra and the extended spectral
range of the observations, we have not detected intrisic spectral
features for these sources. However, we are able to provide strigent
lower limits to their redshift. In particular, for the two TeV sources
PG 1553+113 and H 1722+119, we infer z>0.30 and z>0.35 respectively.
We also detect an intervening CaII absorption doublet in the spectrum
of MH 2136-428 that is ascribed to the the halo of a nearby giant
elliptical galaxy at a projected distance of ∼100kpc.
Under the hypothesis that all BL Lacs are hosted by a luminous bulge
dominated galaxies, the presently spectroscopic observations of bright
BL Lacs indicate that these objects are likely sources with extremely
beamed nuclear emission. We present simulations to show under which
circumstances it is possible to probe this hypothesis from the
detection of very weak absorptions using the next generation of
extremely large optical telescopes.
Description:
We provide spectra obtained for the sources PG1553+113, H1722+119,
MH2136-428 and PKS2254-204 collected with VLT/XSHOOTER, adopting slit
width of 1.5". Spectra were collected under fair seeing condition,
almost clear sky. Resolution is about 3000 for nearUV and near IR and
5500 for visible region of the spectrum.
Objects:
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RA (ICRS) DE Designation(s) (files)
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15 55 43.04 +11 11 24.4 PG1553+113 = QSO B1553+113 (pg1553.dat)
17 25 04.34 +11 52 15.5 H1722+119 = QSO B1722+119 (h1722.dat)
21 39 24.13 -42 35 20.1 MH2136-428 = QSO B2136-428 (mh2136.dat)
22 56 41.21 -20 11 40.5 PKS2254-204 = QSO B2254-204 (pks2254.dat)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
pks2254.dat 19 41831 XShooter spectrum of PKS 2254-204
h1722.dat 19 41918 XShooter spectrum of H 1722+119
mh2136.dat 19 42170 XShooter spectrum of MH 2136-428
pg1553.dat 19 40644 XShooter spectrum of PG 1553+113
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Byte-by-byte Description of file(#): h1722.dat mh2136.dat pg1553.dat pks2254.dat
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Bytes Format Units Label Explanations
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1- 8 F8.2 0.1nm lambda [3100/15000] Wavelength (Å)
10- 19 E10.4 --- S Flux density (erg/cm2/s/Å)
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Acknowledgements:
Marco Landoni, marco.landoni(at)brera.inaf.it
(End) Patricia Vannier [CDS] 30-Jul-2014