Abell 1367: a high fraction of late-type galaxies displaying H i morphological and kinematic perturbations

Abstract

To investigate the effects the cluster environment has on Late-Type Galaxies (LTGs) we studied HI perturbation signatures for all Abell 1367 LTGs with HI detections. We used new VLA H i observations combined with AGES single dish blind survey data. Our study indicates that the asymmetry between the high-and low-velocity wings of the characteristic double-horn integrated H i spectrum as measured by the asymmetry parameter, A flux , can be a useful diagnostic for ongoing and/or recent HI stripping. 26% of A1367 LTGs have an A flux ratio, more asymmetrical than 3 times the 1σ spread in the A flux ratio distribution of an undisturbed sample of isolated galaxies (2%) and samples from other denser environments (10% to 20%). Over half of the A 1367 LTGs, which are members of groups or pairs, have an A flux ratio larger than twice the 1 σ spread found in the isolated sample. This suggests inter-group/pair interactions could be making a significant contribution to the LTGs displaying such A flux ratios. The study also demonstrates that the definition of the H i offset from the optical centre of LTGs is resolution dependent, suggesting that unresolved AGES H i offsets that are significantly larger than the pointing uncertainties (> 2 σ) reflect interactions which have asymmetrically displaced significant masses of lower density H i, while having minimal impact on the location of the highest density HI in resolved maps. The distribution of A flux from a comparable sample of Virgo galaxies provides a clear indication that the frequency of H i profile perturbations is lower than in A 1367.

H i asymmetries in LVHIS, VIVA, and HALOGAS galaxies

“…• We find no correlations between H i asymmetries and either stellar or H i mass. The lack of correlation with H i mass is in disagreement with the results of Scott et al (2018) for Virgo cluster galaxies. Scott et al (2018) found a larger asymmetric fraction (42%) of galaxies with H i masses log(M HI /M ) ≤ 8.48 compared with 16% with log(M HI /M ) > 8.48 (117 and 90 galaxies, respectively) and is potentially due to the small sample size used in this work (136 galaxies).…”

“…Probing morphological and kinematic asymmetries requires observations with similar physical scales, as decreasing resolution can smooth out flux and velocities or produce offsets in the H i defined centre of the galaxy (e.g. Scott et al 2018). Nearby galaxies with higher physical scale resolution can be smoothed to match the lower resolutions of more distant galaxies, which will increase the sample size for direct comparison of morphological and kinematic asymmetries and enable the comparison of galaxies at a greater range of distances.…”

“…Applying the 2σ cut to the isolated samples of Haynes et al (1998) and Matthews et al (1998) gives fractions of 9% and 17%, respectively. Recent studies of single dish spectra of Virgo and Abell 1367 cluster galaxies considered A flux > 2σ or 3σ as likely produced by external, environmental influences and found asymmetric fractions of ∼ 16-26% (Scott et al 2018) and 27% for close galaxy pairs (Bok et al 2019) using the AMIGA sample 3σ significance threshold. Watts et al (2020) classified xGASS (Catinella et al 2018) galaxies as satellites or centrals and measured A flux , finding that satellites show a higher frequency of asymmetries than centrals, which supports the previous findings of asymmetries being more common in higher density environments.…”

xGASS: Robust quantification of asymmetries in global H i spectra and their relationship to environmental processes

“…Although there are already published values for the integrated flux and velocity width of each spectrum in the xGASS catalogue we have made our own measurements of these parameters using our fits as they provide a less subjective measure of the limits of each spectrum and allow us to measure velocity widths at the 20% level, compared to the published xGASS values measured at the 50% level (ω 50 ), to be consistent with previous global Hi asymmetry studies (e.g. Espada et al 2011;Scott et al 2018;Bok et al 2019). We measure a median relative difference of -4.2% and -4.3% in integrated flux and velocity width compared to the existing xGASS measurements, but this can be attributed to differences in the measurement techniques and identification of spectrum peaks.…”

Dark matter and H i in ultra-diffuse galaxy UGC 2162

“…The value of an A flux deviating by 1 σ from the mean of that distribution is then 1.13. A study by Scott et al (2018) indicated that A flux is quite sensitive to recent ( 0.7 Gyr) interactions which impact H i disks. For UGC 2162 A flux = 1.07 ± 0.13, measured from the GBT H i spectrum, which is within the 1 σ value from the isolated sample.…”