Mapping HI 21-cm in the Klemola 31 group at z = 0.029: emission and absorption towards PKS2020-370

E. K. Maina; Abhisek Mohapatra; G. I. G. Jozsa; N. Gupta; F. Combes; P. Deka; J. D. Wagenveld; R. Srianand; S. A. Balashev; Hsiao-Wen Chen; J. -K. Krogager; E. Momjian; P. Noterdaeme; P. Petitjean

doi:10.1093/mnras/stac1752

arXiv · 2206.09940

Mapping HI 21-cm in the Klemola 31 group at z = 0.029: emission and absorption towards PKS2020-370

E. K. Maina·Abhisek Mohapatra·G. I. G. Jozsa·N. Gupta·F. Combes·P. Deka·J. D. Wagenveld·R. Srianand·S. A. Balashev·Hsiao-Wen Chen·J. -K. Krogager·E. Momjian·P. Noterdaeme·P. Petitjean

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Abstract

We present MeerKAT Absorption Line Survey (MALS) observations of the HI gas in the Klemola31 galaxy group ($z=0.029$), located along the line of sight to the radio-loud quasar PKS2020-370 ($z=1.048$). Four galaxies of the group are detected in HI emission, and HI absorption is also detected in front of PKS2020-370 in Klemola31A. The emission and absorption are somewhat compensating on the line of sight of the quasar, and the derived column density of the absorption appears under-estimated, with respect to the neighbouring emission. A symmetric tilted-ring model of Klemola31A, assuming the absorbing gas in regular rotation in the plane, yields a rather high spin temperature of 530K. An alternative interpretation is that the absorbing gas is extra-planar, which will also account for its non-circular motion. The NaI/CaII ratio also suggests that the absorbing gas is unrelated to cold HI disk. Two of the galaxies in the Klemola group are interacting with a small companion, and reveal typical tidal tails, and velocity perturbations. Only one of the galaxies, ESO400-13, reveals a strong HI deficiency, and a characteristic ram-pressure stripping, with a total asymmetry in the distribution of its gas. Since a small galaxy group as Klemola31 is not expected to host a dense intra-group gas, this galaxy must be crossing the group at a very high velocity, mostly in the sky plane.

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E. K. Maina, Abhisek Mohapatra, G. I. G. Jozsa, N. Gupta, F. Combes, P. Deka, J. D. Wagenveld, R. Srianand, S. A. Balashev, Hsiao-Wen Chen, J. -K. Krogager, E. Momjian, P. Noterdaeme, P. Petitjean. 2022-06-20. Mapping HI 21-cm in the Klemola 31 group at z = 0.029: emission and absorption towards PKS2020-370. https://doi.org/10.1093/mnras%2Fstac1752

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