Prevalence of neutral gas in centres of merging galaxies

Dutta, Rajeshwari; Srianand, R.; Gupta, N.

doi:10.1093/mnras/sty1872

Cited by 31 publications

(28 citation statements)

References 125 publications

(166 reference statements)

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“…Earlier, a redshifted absorption with a similarly large velocity of 636 km s −1 relative to the AGN, was detected towards PKS 0428+20 at z = 0.219, by Vermeulen et al (2003). Recently, Dutta et al (2018) have also reported large velocity inflows in merging systems at z 0.2. Such large gas inflows could be explained in scenarios of galaxy mergers, wherein gas components get channelled to the central regions due to removal of angular momentum (e.g., Jogee 2006;Di Matteo et al 2008).…”

Section: Resultsmentioning

confidence: 88%

uGMRT detections of H i 21-cm absorption associated with intermediate redshift galaxies

Aditya

2018

Monthly Notices of the Royal Astronomical Society

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I report detections of four new Hi 21-cm absorbers associated with sources at intermediate redshifts, 0.7 < z < 1.0. The sources are part of a sample of 11 radio-loud galaxies, all at 0.7 < z < 1.0, that were searched for associated Hi 21-cm absorption using uGMRT. Previously, just four such absorbers were known in the literature at these redshifts; the current observations have increased the total to eight. The results indicate that the detection fraction at intermediate redshifts could be as high as that at lower redshifts, ≈ 30%, on contrary to a much lower detection fraction observed in samples at z > 1. Three detections show strong blueshifted features, indicating cold gas outflows. These three sources also tentatively show excess [O ii] line luminosity compared to a bulk of the remaining sample, possibly suggesting that the hosts of these AGNs harbour different environments, either due to interaction with the radio jets or due to excess star formation in the host galaxy. Further, a cold Hi mass outflow rate of ≈ 78 M ⊙ yr −1 , assuming T s = 1000 K, is estimated for the detection towards SDSS J014652.79-015721.2, at z = 0.95904, which is the highest till date in comparison to similar estimates available in the literature.

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Section: Resultsmentioning

confidence: 88%

uGMRT detections of H i 21-cm absorption associated with intermediate redshift galaxies

Aditya

2018

Monthly Notices of the Royal Astronomical Society

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“…Remarkably, the optical depth estimated for the source J1209−2032 is one of the highest known for GPS and CSS sources. In a HI absorption study of galaxies with z > 0.2, Dutta et al (2018) reported that 40% of sources with column densities of HI > 10 21 cm −2 , and 100% of sources with HI > 10 22 cm −2 are associated with mergers. Also, the HI detection rate is high (∼80%) in merging systems.…”

Section: Discussionmentioning

confidence: 99%

“…Also, the HI detection rate is high (∼80%) in merging systems. Dutta et al (2018) used SDSS images of galaxies to identify signatures of galaxy mergers. However, no evidence of a merger is found in the SDSS optical image of J1209−2032 (Sect.…”

Section: Discussionmentioning

confidence: 99%

uGMRT HI 21-cm absorption observations of two extremely inverted spectrum sources

Mhaskey

Paul

Gupta

et al. 2020

A&A

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We report the detection of HI 21-cm absorption in a member of the rare and recently discovered class of compact radio sources: extremely inverted spectrum extragalactic radio sources (EISERS). The EISERS conceivably form a special subclass of the inverted spectrum radio galaxies since the spectral index of the optically thick part of the spectrum for these sources crosses the synchrotron self-absorption limit of α = +2.5 (S(ν) ∝ να). We searched for HI absorption in two EISERS using the recently upgraded Giant Metrewave Radio Telescope (uGMRT) and detected an absorption feature in one of them. The strong associated HI absorption detected against the source J1209−2032 (z = 0.4040) implies an optical depth of 0.178 ± 0.02, corresponding to an HI column density of 34.8 ± 2.9 × 1020 cm−2, for an assumed HI spin temperature of 100 K and covering factor of 1. This is among the highest known optical depth and HI column densities found for compact radio sources of peaked spectrum type and supports the free-free absorption model for the steeply inverted radio spectrum of this source. For the other source, J1549+5038 (z = 2.171), no HI absorption was detected in our observations.

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“…Remarkably, the optical depth estimated for the source J1209−2032 is one of the highest known for GPS/CSS sources. In a HI absorption study of galaxies with z > 0.2, Dutta et al (2018) report that 40% of sources with column density, HI > 10 21 cm −2 and 100% of sources with HI > 10 22 cm −2 are associated with mergers. Also, the HI detection rate is high (∼80%) in merging systems.…”

Section: Discussionmentioning

confidence: 99%

uGMRT HI 21-cm absorption observations of two extremely inverted spectrum sources

Mhaskey,

Paul,

Gupta

et al. 2020

Preprint

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We report the detection of HI 21-cm absorption in a member of the rare and recently discovered class of compact radio sources, "Extremely Inverted Spectrum Extragalactic Radio Sources (EISERS)" . EISERS conceivably form a special sub-class of the inverted spectrum radio galaxies since the spectral index of the optically thick part of the spectrum for these sources crosses the synchrotron self absorption limit of α = +2.5 (S(ν) ∝ ν α ). We have searched for HI absorption in two EISERS using the recently upgraded Giant Metrewave Radio Telescope (uGMRT) and detected an absorption feature in one of them. The strong associated HI absorption detected against the source J1209−2032 (z=0.4040) implies an optical depth of 0.178±0.02 corresponding to an HI column density of 34.8±2.9 ×10 20 cm −2 , for an assumed HI spin temperature of 100 K and covering factor of 1. This is among the highest known optical depth and HI column densities found for compact radio sources of GPC/CSS type and supports the free-free absorption model for the steeply inverted radio spectrum of this source. For the other source, J1549+5038 (z = 2.171), no HI absorption was detected in our observations.

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Prevalence of neutral gas in centres of merging galaxies

Cited by 31 publications

References 125 publications

uGMRT detections of H i 21-cm absorption associated with intermediate redshift galaxies

uGMRT detections of H i 21-cm absorption associated with intermediate redshift galaxies

uGMRT HI 21-cm absorption observations of two extremely inverted spectrum sources

uGMRT HI 21-cm absorption observations of two extremely inverted spectrum sources

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