J/A+A/566/A24ivo://CDS.VizieR/J/A+A/566/A24doi:10.26093/cds/vizier.35660024CDSNoterdaeme P.Petitjean P.Paris I.Cai Z.Finley H.Ge J.,Pieri M.M.York D.G.2015-09-22T14:17:03Z2014-09-17T11:41:23ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frquasarsredshiftedWe present a study of ~100 high redshift (z ~2-4) extremely strong damped Lyman-{alpha} systems (ESDLA, with N(HI)>=0.5x10^22^cm^-2^) detected in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) Data Release 11. We study the neutral hydrogen, metal, and dust content of this elusive population of absorbers and confirm our previous finding that the high column density end of the N(HI) frequency distribution has a relatively shallow slope with power-law index -3.6, similar to what is seen from 21-cm maps in nearby galaxies. The stacked absorption spectrum indicates a typical metallicity ~1/20th solar, similar to the mean metallicity of the overall DLA population. The relatively small velocity extent of the low-ionisation lines suggests that ESDLAs do not arise from large-scale flows of neutral gas. The high column densities involved are in turn more similar to what is seen in DLAs associated with gamma-ray burst afterglows (GRB-DLAs), which are known to occur close to star-forming regions. This indicates that ESDLAs arise from a line of sight passing at very small impact parameters from the host galaxy, as observed in nearby galaxies. This is also supported by simple theoretical considerations and recent high-z hydrodynamical simulations. We strongly substantiate this picture by the first statistical detection of Ly{alpha} emission with <L_ESDLA_(Ly{alpha})>=~(0.6+/-0.2)x10^42^erg/s in the core of ESDLAs (corresponding to about 0.1L^*^ at z~2-3), obtained through stacking the fibre spectra (of radius 1" corresponding to ~8kpc at z~2.5). Statistical errors on the Ly{alpha} luminosity are of the order of 0.1x10^42^erg/s but we caution that the measured Ly{alpha} luminosity may be overestimated by ~35% due to sky light residuals and/or FUV emission from the quasar host and that we have neglected flux-calibration uncertainties. We estimate a more conservative uncertainty of 0.2x10^42^erg/s. The properties of the Ly{alpha} line (luminosity distribution, velocity width and velocity offset compared to systemic redshift) are very similar to that of the population of Lyman-{alpha} emitting galaxies (LAEs) with L_LAE_(Ly{alpha})>=10^41^erg/s detected in long-slit spectroscopy or narrow-band imaging surveys. By matching the incidence of ESDLAs with that of the LAEs population, we estimate the high column density gas radius to be about r_gas_=2.5kpc, i.e., significantly smaller than the radius corresponding to the BOSS fibre aperture, making fibre losses likely negligible. Finally, the average measured Ly{alpha} luminosity indicates a star-formation rate consistent with the Schmidt-Kennicutt law, SFR (M_{sun}_/yr)=~0.6/f_esc_, where f_esc_<1 is the Ly{alpha} escape fraction. Assuming the typical escape fraction of LAEs, f_esc_~0.3, the Schmidt-Kennicutt law implies a galaxy radius of about r_gal_=~2.5kpc. Finally, we note that possible overestimation of the Ly{alpha} emission would result in both smaller r_gas_ and r_gal_. Our results support a close association between LAEs and strong DLA host galaxies.2014A&A...566A..24Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/566/A24CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/547/L1 : SDSS-III DR9 DLA catalogue (Noterdaeme+, 2012)http://www.sdss.org : SDSS Home Pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/566/A24https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/566/A24http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/566/A24https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/566/A24https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/566/A24http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/566/A24GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/566/A24/table2 (Intervening extremely strong damped Lymna-{alpha} systems (ESDLA) sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/566/A24/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/566/A24/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/566/A24/table2?GETtext/xml+votable180.050000true4.432833313.12773330.0055555555555555566/666 2212 2235 4134 4166 4490 4510 4598 4610 4634 4703 4795 4870 5129 5148 5171 5351 5427 5772 5802 5841 5897 6208 6356 6508 6736 8209 8434 8531 8568 8623 8715 8780 8999 9139 9230 9275 9306 9331 9474 9738 9765 9946 10347 10461 10516 10567 10593 10831 10871 10884 11268 11396 12757 17693 17766 17826 17971 18116 18134 18389 18795 18797 18994 19258 19376 19389 19405 19412 19459 19574 19582 19910 20154 20163 21849 21876 22486 26077 26165 26305 26389 26480 26554 26981 27006 27016 27054 27361 27639 27666 27717 27792 27820 27881 27960 28173 28278 28324 28421 28596 31656 32397 32498https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/566/A24?format=asciiOpticaldefaultJ/A+A/566/A24/table2Intervening extremely strong damped Lymna-{alpha} systems (ESDLA) sampleStack?[y/n] Used in stack?meta.codecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintQSOQSO name (JHHMMSS.ss+DDMMSS.ss)meta.id;meta.maincharMPFSDSS MJD-plate-fibermeta.notecharzQSOQSO redshiftsrc.redshift;pos.heliocentricfloatC/NContinuum-to-noise ratiostat.snrfloatzabsAbsoption redshiftsrc.redshiftfloatlogN(HI)HI column densitylog(cm**-2)phys.columnDensityfloatsig.dark1{sigma} noise level in the DLA trough (luminosity at DLA rest-frame {sigma}_dark_ in 10^42^erg/s/{AA})1e+36W.nm**-1instr.det.noisefloatSloanDisplay the SDSS data for this quasarmeta.ref.urlchar_RAPosition from QSO name (right ascension part)degpos.eq.ra;meta.main_DEPosition from QSO name (declination part)degpos.eq.dec;meta.main