分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shin-Jeong Kim
Se-Heon Oh
Jing Wang
Lister Staveley-Smith
Bärbel S. Koribalski
Minsu Kim
Hye-Jin Park
Shinna Kim
Kristine Spekkens
Tobias Westmeier
O. Ivy Wong
Gerhardt R. Meurer
Peter Kamphuis.
Barbara Catinella
Kristen B. W. McQuinn
Frank Bigiel
Benne W. Holwerda
Jonghwan Rhee
Karen Lee-Waddell
Nathan Deg
摘要： We examine the HI gas kinematics of galaxy pairs in two clusters and a group using Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pilot survey observations. We compare the HI properties of galaxy pair candidates in the Hydra I and Norma clusters, and the NGC 4636 group, with those of non-paired control galaxies selected in the same fields. We perform HI profile decomposition of the sample galaxies using a tool, {\sc baygaud} which allows us to de-blend a line-of-sight velocity profile with an optimal number of Gaussian components. We construct HI super-profiles of the sample galaxies via stacking of their line profiles after aligning the central velocities. We fit a double Gaussian model to the super-profiles and classify them as kinematically narrow and broad components with respect to their velocity dispersions. Additionally, we investigate the gravitational instability of HI gas disks of the sample galaxies using Toomre Q parameters and HI morphological disturbances. We investigate the effect of the cluster environment on the HI properties of galaxy pairs by dividing the cluster environment into three subcluster regions (i.e., outskirts, infalling and central regions). We find that the denser cluster environment (i.e., infalling and central regions) is likely to impact the HI gas properties of galaxies in a way of decreasing the amplitude of the kinematically narrow HI gas ($M_{\rm{narrow}}^{\rm{HI}}$/$M_{\rm{total}}^{\rm{HI}}$), and increasing the Toomre Q values of the infalling and central galaxies. This tendency is likely to be more enhanced for galaxy pairs in the cluster environment.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shun Wang
Jing Wang
Bi-Qing For
Bumhyun Lee
Tristan Reynolds
Xuchen Lin
Lister Staveley-Smith
Li Shao
O. Ivy Wong
Barbara Catinella
Paolo Serra
Lourdes Verdes-Montenegro
Tobias Westmeier
Karen Lee-Waddell
Baerbel S. Koribalski
Chandrashekar Murugeshan
Ahmed Elagali
Dane Kleiner
Jonghwan Rhee
Frank Bigiel
摘要： We study the tidal interaction of galaxies in the Eridanus supergroup, using HI data from the pre-pilot survey of WALLABY (Widefield ASKAP L-band Legacy All-sky Blind surveY). We obtain optical photometric measurements and quantify the strength of tidal perturbation using a tidal parameter $S_{sum}$. For low-mass galaxies of $M_* \lesssim 10^9 M_\odot$, we find a dependence of decreasing HI-to-optical disk size ratio with increasing $S_{sum}$, but no dependence of HI spectral line asymmetry with $S_{sum}$. This is consistent with the behavior expected under tidal stripping. We confirm that the color profile shape and color gradient depend on the stellar mass, but there is additional correlation of low-mass galaxies having their color gradients within $2R_{50}$ increasing with higher $S_{sum}$. For these low-mass galaxies, the dependence of color gradients on $S_{sum}$ is driven by color becoming progressively redder in the inner disk when tidal perturbations are stronger. For high-mass galaxies, there is no dependence of color gradients on $S_{sum}$, and we find a marginal reddening throughout the disks with increasing $S_{sum}$. Our result highlights tidal interaction as an important environmental effect in producing the faint end of the star formation suppressed sequence in galaxy groups.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jing Wang
Dong Yang
Se-Heon Oh
Lister Staveley-Smith
Jie Wang
Q. Daniel Wang
Kelley M. Hess
Luis C. Ho
Ligang Hou
Yingjie Jing
Peter Kamphuis
Fujia Li
Xuchen Lin
Ziming Liu
Li Shao
Shun Wang
Ming Zhu
摘要： We use the single-dish radio telescope FAST to map the HI in the tidally interacting NGC 4631 group with a resolution of 3.24$'$ (7 kpc), reaching a 5-$\sigma$ column density limit of $10^{17.9}$ cm$^{-2}$ assuming a line width of 20 km s$^{-1}$. Taking the existing interferometric HI image from the HALOGAS project of WSRT as reference, we are able to identify and characterize a significant excess of large-scale, low-density, and diffuse HI in the group. This diffuse HI extends for more than 120 kpc across, and accounts for more than one fourth of the total HI detected by FAST in and around the galaxy NGC 4631. In the region of the tidal tails, the diffuse HI has a typical column density above $10^{19.5}$ cm$^{-2}$, and is highly turbulent with a velocity dispersion around 50 km s$^{-1}$. It increases in column density with the dense HI, and tends to be associated with the kinematically ``hotter'' part of the dense HI. Through simple modeling, we find that the majority of the diffuse HI in the tail region is likely to induce cooling out of the hot IGM instead of evaporating or being radiatively ionized. Given these relations of gas in different phases, the diffuse HI may represent a condensing phase of the IGM. Active tidal interactions on-going and in the past may have produced the wide-spreading HI distribution, and triggered the gas accretion to NGC 4631 through the phase of the diffuse HI.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Benne W. Holwerda
Frank Bigiel
Albert Bosma
Helene M. Courtois
Nathan Deg
Helga Dénes
Ahmed Elagali
Bi-Qing For
Baerbel Koribalski
Denis A. Leahy
Karen Lee-Waddell
Ángel R. López-Sánchez
Se-Heon Oh
Tristan N. Reynolds
Jonghwan Rhee
Kristine Spekkens
Jing Wang
Tobias Westmeier
O. Ivy Wong
摘要： Galaxy morphology in atomic hydrogen (HI) and in the ultra-violet (UV) are closely linked. This has motivated their combined use to quantify morphology over the full H i disk for both H i and UV imaging. We apply galaxy morphometrics: Concentration, Asymmetry, Gini, M20 and Multimode-Intensity-Deviation statistics to the first moment-0 maps of the WALLABY survey of galaxies in the Hydra cluster center. Taking advantage of this new HI survey, we apply the same morphometrics over the full HI extent on archival GALEX FUV and NUV data to explore how well HI truncated, extended ultraviolet disk (XUV) and other morphological phenomena can be captured using pipeline WALLABY data products. Extended HI and UV disks can be identified relatively straightforward from their respective concentration. Combined with WALLABY HI, even the shallowest GALEX data is sufficient to identify XUV disks. Our second goal is to isolate galaxies undergoing ram-pressure stripping in the H i morphometric space. We employ four different machine learning techniques, a decision tree, a k-nearest neighbour, a support-vector machine, and a random forest. Up to 80% precision and recall are possible with the Random Forest giving the most robust results.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jing Wang
Dong Yang
Se-Heon Oh
Lister Staveley-Smith
Jie Wang
Q. Daniel Wang
Kelley M. Hess
Luis C. Ho
Ligang Hou
Yingjie Jing
Peter Kamphuis
Fujia Li
Xuchen Lin
Ziming Liu
Li Shao
Shun Wang
Ming Zhu
摘要： We use the single-dish radio telescope FAST to map the HI in the tidally interacting NGC 4631 group with a resolution of 3.24$'$ (7 kpc), reaching a 5-$\sigma$ column density limit of $10^{17.9}$ cm$^{-2}$ assuming a line width of 20 km s$^{-1}$. Taking the existing interferometric HI image from the HALOGAS project of WSRT as reference, we are able to identify and characterize a significant excess of large-scale, low-density, and diffuse HI in the group. This diffuse HI extends for more than 120 kpc across, and accounts for more than one fourth of the total HI detected by FAST in and around the galaxy NGC 4631. In the region of the tidal tails, the diffuse HI has a typical column density above $10^{19.5}$ cm$^{-2}$, and is highly turbulent with a velocity dispersion around 50 km s$^{-1}$. It increases in column density with the dense HI, and tends to be associated with the kinematically ``hotter'' part of the dense HI. Through simple modeling, we find that the majority of the diffuse HI in the tail region is likely to induce cooling out of the hot IGM instead of evaporating or being radiatively ionized. Given these relations of gas in different phases, the diffuse HI may represent a condensing phase of the IGM. Active tidal interactions on-going and in the past may have produced the wide-spreading HI distribution, and triggered the gas accretion to NGC 4631 through the phase of the diffuse HI.
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