21-cm absorption from galaxies at<i>z</i>~ 0.3

Gupta, N.; Srianand, R.; Noterdaeme, P.; Petitjean, P.; Muzahid, Sowgat

doi:10.1051/0004-6361/201321609

Cited by 34 publications

(42 citation statements)

References 59 publications

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“…Because the impact parameter is small, we can, however, expect this extinction to be similar to that in the star-forming region as evidenced in e.g. Gupta et al (2013).…”

Section: Dependence On Dustmentioning

confidence: 92%

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

Noterdaeme

Petitjean

Pâris

et al. 2014

A&A

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107

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We present a study of ∼100 high redshift (z ∼ 2−4) extremely strong damped Lyman-α systems (ESDLA, with N(H i) ≥ 0.5 × 10 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(H i) 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 α emission with L ESDLA (Ly α) (0.6 ± 0.2) × 10 42 erg s −1 in the core of ESDLAs (corresponding to about 0.1 L at z ∼ 2−3), obtained through stacking the fibre spectra (of radius 1 corresponding to ∼8 kpc at z ∼ 2.5). Statistical errors on the Ly α luminosity are of the order of 0.1 × 10 42 erg s −1 but we caution that the measured Ly α 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 0.2 × 10 42 erg s −1 . The properties of the Ly α line (luminosity distribution, velocity width and velocity offset compared to systemic redshift) are very similar to that of the population of Lyman-α emitting galaxies (LAEs) with L LAE (Ly α) ≥ 10 41 erg s −1 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 = 2.5 kpc, i.e., significantly smaller than the radius corresponding to the BOSS fibre aperture, making fibre losses likely negligible. Finally, the average measured Ly α luminosity indicates a star-formation rate consistent with the Schmidt-Kennicutt law, SFR (M yr −1 ) ≈ 0.6/ f esc , where f esc < 1 is the Ly α 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 ≈ 2.5 kpc. Finally, we note that possible overestimation of the Ly α emission would result in both smaller r gas and r gal . Our results support a close association between LAEs and stro...

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“…Because the impact parameter is small, we can, however, expect this extinction to be similar to that in the star-forming region as evidenced in e.g. Gupta et al (2013).…”

Section: Dependence On Dustmentioning

confidence: 92%

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

Noterdaeme

Petitjean

Pâris

et al. 2014

A&A

Self Cite

107

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“…Gupta et al (2013) reported a weak correlation between impact parameter and τ dV , with a Spearman rank coefficient of r = −0.3. Adding our two new systems and two systems from the literature that Gupta et al (2013) did not consider (J074110.85+311154.7 and KAC2002), we find a slightly higher value of r = −0.39, with an associated significance level of 0.81.…”

Section: Low Redshift Galaxy-quasar Pairsmentioning

confidence: 99%

“…We somewhat arbitrarily adopted a redshift limit of z < 0.5 to include the two systems recently presented in Gupta et al (2013), and the system at z = 0.43 identified by Kanekar, Athreya & Chengalur (2002). Gupta et al (2013) reported a weak correlation between impact parameter and τ dV , with a Spearman rank coefficient of r = −0.3. Adding our two new systems and two systems from the literature that Gupta et al (2013) did not consider (J074110.85+311154.7 and KAC2002), we find a slightly higher value of r = −0.39, with an associated significance level of 0.81.…”

Section: Low Redshift Galaxy-quasar Pairsmentioning

confidence: 99%

New H i 21-cm absorbers at low and intermediate redshifts

Liske¹,

Péroux²,

Murphy³

et al. 2015

Mon. Not. R. Astron. Soc.

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We present the results of a survey for intervening H I 21-cm absorbers at intermediate and low redshift (0 < z < 1.2). For our total sample of 24 systems, we obtained high quality data for 17 systems, the other seven being severely affected by radio frequency interference (RFI). Five of our targets are low redshift (z < 0.17) optical galaxies with small impact parameters (< 20 kpc) toward radio-bright background sources. Two of these were detected in 21-cm absorption, showing narrow, high optical depth absorption profiles, the narrowest having a velocity dispersion of only 1.5 km s −1 , which puts an upper limit on the kinetic temperature of T k < 270 K. Combining our observations with results from the literature, we measure a weak anti-correlation between impact parameter and integral optical depth in local (z < 0.5) 21-cm absorbers. Of eleven Ca II and Mg II systems searched, two were detected in 21-cm absorption, and six were affected by RFI to a level that precludes a detection. For these two systems at z ∼ 0.6 we measure spin temperatures of T s = (65 ± 17) K and T s > 180 K. A subset of our systems were also searched for OH absorption, but no detections were made.

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“…The points are binned via the Kaplan-Meier estimator, giving the maximum-likelihood estimate based upon the parent population (Feigelson & Nelson 1985), from which we see no overwhelming bias in the survey sensitivity between the Mgii absorbers and DLAs. Darling et al (2004); Curran et al (2005Curran et al ( , 2007aCurran et al ( ,b,c, 2010; York et al (2007); Gupta et al (2009aGupta et al ( ,b, 2012Gupta et al ( , 2013 …”

Section: Line Strengths Of the Intervening H I 21-cm Absorbersmentioning

confidence: 99%

The potential of tracing the star formation history with H I 21-cm in intervening absorption systems

Curran

2017

A&A

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Unlike the neutral gas density, which remains largely constant over redshifts of 0 < ∼ z < ∼ 5, the star formation density, ψ * , exhibits a strong redshift dependence, increasing from the present day before peaking at a redshift of z ≈ 2.5. Thus, there is a stark contrast between the star formation rate and the abundance of raw material available to fuel it. However, using the ratio of the strength of the H i 21-cm absorption to the total neutral gas column density to quantify the spin temperature, T spin , of the gas, it has recently been shown that 1/T spin may trace ψ * . This would be expected on the grounds that the cloud of gas must be sufficiently cool to collapse under its own gravity. This, however, relies on very limited data and so here we explore the potential of applying the above method to absorbers for which individual column densities are not available (primarily Mg ii absorption systems). By using the mean value as a proxy to the column density of the gas at a given redshift, we do, again, find that 1/T spin (degenerate with the absorber-emitter size ratio) traces ψ * . If confirmed by higher redshift data, this could offer a powerful tool for future surveys for cool gas throughout the Universe with the Square Kilometre Array.

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21-cm absorption from galaxies atz~ 0.3

Cited by 34 publications

References 59 publications

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

New H i 21-cm absorbers at low and intermediate redshifts

The potential of tracing the star formation history with H I 21-cm in intervening absorption systems

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