Compact groups have high galaxy densities and low velocity dispersions, and their group members have experienced numerous and frequent interactions during their lifetimes. They provide a unique environment to study the evolution of galaxies. We examined the galaxies types and HI contents in groups to make a study on the galaxy evolution in compact groups. We used the group crossing time as an age indicator for galaxy groups. Our sample is derived from the Hickson Compact Group catalog. We obtained group morphology data from the Hyper-Leda database and the IR classification based on Wide-Field Infrared Survey Explorer (WISE) fluxes from Zucker et al. (2016). By cross-matching the latest released ALFALFA 100% HI source catalog and supplemented by data found in literature, we obtained 40 galaxy groups with HI data available. We confirmed that the weak correlation between HI mass fraction and group crossing time found by Ai & Zhu (2018) in SDSS groups also exists in compact groups. We also found that the group spiral galaxy fraction is correlated with the group crossing time, but the actively star-forming galaxy fraction is not correlated with the group crossing time. These results seem to fit with the hypothesis that the sequential acquisition of neighbors from surrounding larger-scale structures has affected the morphology transition and star formation efficiency in compact groups.
We present the galaxy luminosity functions (LFs) of four Hickson Compact Groups using image data from the Subaru Hyper Suprime-Cam. A distinct dip appeared in the faint-ends of all the LFs at $M_g\sim-12$. A similar dip was observed in the LFs of the galaxy clusters Coma and Centaurus. However, LFs in the Virgo, Hydra, and the field had flatter slopes and no dips. As the relative velocities among galaxies are lower in compact groups than in clusters, the effect of galaxy-galaxy interactions would be more significant in compact groups. The $M_g\sim-12$ dip of compact groups may imply that frequ…
I present observations of the Hickson Compact Group 88 (HCG88) obtained during the commissioning of a new 28-inch telescope at the Wise Observatory. This galaxy group was advertised to be non-interacting, or to be in a very early interaction stage, but this is not the case. The observations reported here were done using a "luminance" filter, essentially a very broad R filter, reaching a low surface brightness level of about 26 mag per square arcsec. Additional observations were obtained in a narrow spectral band approximately centered on the rest-frame H-alpha line from the group. Contrary to …
Many catalogues of isolated compact groups of galaxies (CGs) have been extracted using Hickson's criteria to identify isolated, dense systems of galaxies, with at least three or four galaxies concordant in magnitude and redshift. But is not clear to what extent the catalogues of CGs are complete and reliable, relative to 3D truly isolated, dense groups. Using five different semi-analytical models of galaxy formation (SAMs), we identify isolated dense groups in 3D real space, containing at least three galaxies. We then build mock redshift space galaxy catalogues and run a Hickson-like CG finder…
Compact groups of galaxies are devised as extreme environments where interactions may drive galaxy evolution. In this work, we analysed whether the luminosities of galaxies inhabiting compact groups differ from those of galaxies in loose galaxy groups. We computed the luminosity functions of galaxy populations inhabiting a new sample of 1412 Hickson-like compact groups of galaxies identified in the Sloan Digital Sky Survey Data Release 16. We observed a characteristic absolute magnitude for galaxies in compact groups brighter than that observed in the field or loose galaxy systems. We also obs…
We have found the atomic gas (HI) reservoirs of the blue ultra diffuse galaxy (UDG) candidates identified by Róman and Trujillo in images near Hickson Compact Groups (HCGs). We confirm that all of the objects are indeed UDGs with effective radii R_e > 1.5 kpc. Three of them are likely to be gravitationally bound to the HCG near which they project, one is plausibly gravitationally bound to the nearest HCG, and one is in the background. We measure HI masses and velocity widths for each object directly from the spectra, and use the widths together with the UDG effective radii to estimate dynamica…
We present 21cm HI observations of four Hickson Compact Groups with evidence for a substantial intragroup medium using the Robert C. Byrd Green Bank Telescope (GBT). By mapping H I emission in a region of 25$^{\prime}\times$25$^{\prime}$ (140-650 kpc) surrounding each HCG, these observations provide better estimates of HI masses. In particular, we detected 65% more \HI than that detected in the Karl G. Jansky Very Large Array (VLA) imaging of HCG92. We also identify if the diffuse gas has the same spatial distribution as the high-surface brightness (HSB) HI features detected in the VLA maps of…
We present deep Hα imaging of seven Hickson Compact Groups (HCGs) using the 4.1m Southern Astrophysics Research (SOAR) Telescope. The high spatial resolution of the observations allow us to study both the integrated star-formation properties of the main galaxies as well as the 2D distribution of star-forming knots in the faint tidal arms that form during interactions between the individual galaxies. We derive star-formation rates and stellar masses for group members and discuss their position relative to the main sequence of star-forming galaxies. Despite the existence of tidal features within…
The physics regulating star formation (SF) in Hickson Compact Groups (HCG) has thus far been difficult to describe, due to their unique kinematic properties. In this study we expand upon previous works to devise a more physically meaningful SF relation able to better encompass the physics of these unique systems. We combine CO(1--0) data from the Combined Array from Research in Millimeter Astronomy (CARMA) to trace the column density of molecular gas $Σ_\mathrm{gas}$ and deep H$α$ imaging taken on the Southern Astrophysical Research (SOAR) Telescope tracing $Σ_\mathrm{SFR}$ to investigate star…
Galaxies in Hickson Compact Groups (HCGs) are believed to experience morphological transformations from blue, star-forming galaxies to red, early-type galaxies. Galaxies with a high ratio between the luminosities of the warm H2 to the 7.7mu PAH emission ("Molecular Hydrogen Emission Galaxies", MOHEGs) are predominantly in an intermediate phase, the green valley. Their enhanced H2 emission suggests that the molecular gas is affected in the transition. We study the properties of the molecular gas traced by CO in galaxies in HCGs with measured warm H2 emission in order to look for evidence of the…
Understanding the evolution of galaxies from the starforming blue cloud to the quiescent red sequence has been revolutionized by observations taken with Herschel Space Observatory, and the onset of the era of sensitive millimeter interferometers, allowing astronomers to probe both cold dust as well as the cool interstellar medium in a large set of galaxies with unprecedented sensitivity. Recent Herschel observations of of H2-bright Hickson Compact Groups of galaxies (HCGs) has shown that [CII] may be boosted in diffuse shocked gas. CARMA CO(1-0) observations of these [CII]-bright HCGs has show…
Although Compact Groups of galaxies (CGs) have been envisioned as isolated extremely dense structures in the Universe, it is accepted today that many of them could be not as isolated as thought. In this work, we study Hickson-like CGs identified in the Sloan Digital Sky Survey Data Release 16 to analyse these systems and their galaxies when embedded in different cosmological structures. To achieve this goal, we identify several cosmological structures where CGs can reside: Nodes of filaments, Loose Groups, Filaments and cosmic Voids. Our results indicate that 45 per cent of CGs do not reside i…
In this work we present an algorithm to identify compact groups (CGs) that closely follows Hickson's original aim and that improves the completeness of the samples of compact groups obtained from redshift surveys. Instead of identifying CGs in projection first and then checking a velocity concordance criterion, we identify them directly in redshift space using Hickson-like criteria. The methodology was tested on a mock lightcone of galaxies built from the outputs of a recent semi-analytic model of galaxy formation run on top of the Millennium Simulation I after scaling to represent the first-y…
We report the discovery of a very diverse set of five low-surface brightness (LSB) dwarf galaxy candidates in Hickson Compact Group 90 (HCG 90) detected in deep U- and I-band images obtained with VLT/VIMOS. These are the first LSB dwarf galaxy candidates found in a compact group of galaxies. We measure spheroid half-light radii in the range $0.7\!\lesssim\! r_{\rm eff}/{\rm kpc}\! \lesssim\! 1.5$ with luminosities of $-11.65\!\lesssim\! M_U\! \lesssim\! -9.42$ and $-12.79\!\lesssim\! M_I\! \lesssim\! -10.58$ mag, corresponding to a color range of $(U\!-\!I)_0\!\simeq\!1.1\!-\!2.2$ mag and surf…
We present, for the first time, direct evidence that, in a merger of disk galaxies, the preexisting central metallicities will mix as a result of gas being transported in the merger interface region, along the line that joins the two coalescing nuclei. This is shown using detailed 2D kinematics as well as metallicity measurements for the nearby ongoing merger in the center of the compact group HCG 31. We focus on the emission line gas, which is extensive in the system. The two coalescing cores display similar oxygen abundances while in between the two nuclei the metallicity changes smoothly fr…
Megaparsec-Scale Neutral Hydrogen Flows in the Neighborhood of Hickson Compact Group 100
Università degli Studi di Firenze（佛罗伦萨大学）；INAF - Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Xiamen University（厦门大学）；Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS（中国科学院南美天文中心，国家天文台，中国科学院）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）
Hickson Compact Groups (HCGs) are dense configurations of 4 to 10 galaxies, whose HI (neutral gas) morphology appears to follow an evolutionary sequence of three phases, with gas initially confined to galaxies, then significant amounts spread throughout the intra-group medium, and finally with almost no gas remaining in the galaxies themselves. The HI deficiency of HCGs is expected to increase as the HI morphological phase progresses along this sequence, potentially making it a useful proxy for evolutionary phase. We test this hypothesis for the first time with a large sample of 38 HCGs with V…
This study presents the mass distribution for a sample of 18 late-type galaxies in nine Hickson Compact Groups. We used rotation curves from high resolution 2D velocity fields of Fabry-Perot observations and J-band photometry from the 2MASS survey, in order to determine the dark halo and the visible matter distributions. The study compares two halo density profile, an isothermal core-like distribution and a cuspy one. We also compare their visible and dark matter distributions with those of galaxies belonging to cluster and field galaxies coming from two samples: 40 cluster galaxies of Barnes …
We present a photometric catalogue of star cluster candidates in Hickson compact groups (HCGs) 7, 31, 42, 59, and 92, based on observations with the Advanced Camera for Surveys and the Wide Field Camera 3 on the Hubble Space Telescope. The catalogue contains precise cluster positions (right ascension and declination), magnitudes, and colours in the BVI filters. The number of detected sources ranges from 2200 to 5600 per group, from which we construct the high-confidence sample by applying a number of criteria designed to reduce foreground and background contaminants. Furthermore, the high-conf…
According to the standard model of cosmology the visible, baryonic matter of galaxies is embedded in dark matter haloes, thus extending the mass and the size of galaxies by one to two orders of magnitude. Taking into account dynamical friction between the dark matter haloes, the nearby located M81 group of galaxies as well as the Hickson compact groups of galaxies are here investigated with regard to their dynamical behaviour. The results of the employment of the Markov Chain Monte Carlo method and the genetic algorithm show statistically substantial merger rates between galaxies, and long liv…
We present [C II] and [O I] observations from Herschel and CO(1-0) maps from the Combined Array for† Research in Millimeter Astronomy (CARMA) of the Hickson Compact Group HCG 57, focusing on the galaxies HCG 57a and HCG 57d. HCG 57a has been previously shown to contain enhanced quantities of warm molecular hydrogen consistent with shock and/or turbulent heating. Our observations show that HCG 57d has strong [C II] emission compared to L$_{\rm FIR}$ and weak CO(1-0), while in HCG 57a, both the [C II] and CO(1-0) are strong. HCG 57a lies at the upper end of the normal distribution of [C II]/CO a…
X-ray Characterization of Galaxy Groups and Hickson Groups in COSMOS-Web to z~3.8 I. X-ray Luminosity Function Evolution
Aalto University（阿尔托大学）；University of Helsinki（赫尔辛基大学）；Deutsches Zentrum für Astrophysik（德国天体物理中心）；TU Dresden（德累斯顿工业大学）；DESY（德国电子同步辐射实验室）；Durham University（杜伦大学）；Institute for Advanced Studies in Basic Sciences (IASBS)（基础科学高等研究院）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；Aix Marseille Univ（艾克斯-马赛大学）；CNRS（法国国家科学研究中心）；University of Victoria（维多利亚大学）
Eye of the beholder: Observer reference frame bias in Hickson-like compact groups of galaxies
Universidad Nacional de Córdoba (UNC)（科尔多瓦国立大学）；Observatorio Astronómico de Córdoba (OAC)（科尔多瓦天文台）；CONICET（阿根廷国家科学研究委员会）；Instituto de Astronomía Teórica y Experimental (IATE)（理论与实验天文学研究所）
In this work, archive 1.4 and 4.86 GHz radio continuum data from the VLA were re-reduced and, together with the 1.4 GHz maps from the NVSS, investigated for the presence of a detectable, non-thermal continuum radio emission that could be associated with the TDG candidates in HCG 26, 91, and 96. Radio emission highly coincident with the optical and $\rm H_α$ emission maxima of the TDG candidate HCG 91i (estimated physical separation of less than 150 pc) was revealed. Should this emission be intrinsic to this object, it would imply the presence of a magnetic field as strong as 11--16 $μ$G -- com…
We have conducted a new spectroscopic survey to characterize the nature of nuclear activity in Hickson Compact Groups (HCGs) galaxies and establish its frequency. We have obtained new intermediate resolution optical spectroscopy for 200 member-galaxies and corrected for underlying stellar population contamination using galaxy templates. Spectra for 11 additional galaxies have been acquired from the ESO and 6dF public archives and emission line ratios have been taken from the literature for 59 galaxies more. Here we present the results of our classification of the nuclear activity for 270 membe…
We present a Herschel far-IR and sub-mm study of a sample of 120 galaxies in 28 Hickson Compact Groups. Fitting their UV to sub-mm spectral energy distributions with the model of da Cunha et al. (2008), we accurately estimate the dust masses, luminosities and temperatures of the individual galaxies. We find that nearly half of the late-type galaxies in dynamically "old" groups, those with more than 25% of early-type members and redder UV-optical colours, have also significantly lower dust-to-stellar mass ratios compared to those of actively star-forming galaxies of the same mass found both in …
The handful of low-mass, late-type galaxies that comprise Hickson Compact Group 31 is in the midst of complex, ongoing gravitational interactions, evocative of the process of hierarchical structure formation at higher redshifts. With sensitive, multicolor Hubble Space Telescope imaging, we characterize the large population of <10 Myr old star clusters that suffuse the system. From the colors and luminosities of the young star clusters, we find that the galaxies in HCG 31 follow the same universal scaling relations as actively star-forming galaxies in the local Universe despite the unusual comp…
We use the outputs of a semi-analytical model of galaxy formation run on the Millennium Simulation to investigate the prevalence of 3D compact groups (CGs) of galaxies from $z = 11$ to 0. Our publicly available code identifies CGs using the 3D galaxy number density, the mass ratio of secondary+tertiary to the primary member, mass density in a surrounding shell, the relative velocities of candidate CG members, and a minimum CG membership of three. We adopt "default" values for the first three criteria, representing the observed population of Hickson CGs at $z = 0$. The percentage of non-dwarf g…
We present $Chandra$ X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances $34 - 89$ Mpc. We perform detailed X-ray point source detection and photometry, and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities ($L_X$) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices ($Γ$), hardness ratios, and $L_X$, in the full ($0.5-8.0$ keV), soft ($0.5-2.0$ keV) and hard ($2.0-8.0$ keV) bands. We use opti…
We have explored the properties of a peculiar object detected in deep optical imaging and located at the tip of an HI tail emerging from Hickson Compact Group 16. Using multiband photometry from infrared to ultraviolet, we were able to constrain its stellar age to 58$^{+22}_{-9}$ Myr with a rather high metallicity of [Fe/H] = $-$0.16$^{+0.43}_{-0.41}$ for its stellar mass of M$_\star$ = 4.2$\times$10$^6$ M$_\odot$, a typical signature of tidal dwarf galaxies. The structural properties of this object are similar to those of diffuse galaxies, with a round and featureless morphology, a large effe…
We use the LOFAR Two-metre Sky Survey (LoTSS) Data Release I to identify the groups of galaxies (and individual galaxies) from the Hickson Compact Groups and Magnitude Limited Compact Groups samples that emit at the frequency of 150\,MHz, characterise their radio emission (extended or limited to the galaxies), and compare new results to earlier observations and theoretical predictions. The detection of 73 systems (and 7 more -- probably) out of 120, of which as many as 17 show the presence of extended radio structures, confirms the previous hypothesis of the common character of the magnetic fi…
Galaxies in Hickson Compact Group 91 (HCG 91) were observed with the WiFeS integral field spectrograph as part of our ongoing campaign targeting the ionized gas physics and kinematics inside star forming members of compact groups. Here, we report the discovery of HII regions with abundance and kinematic offsets in the otherwise unremarkable star forming spiral HCG 91c. The optical emission line analysis of this galaxy reveals that at least three HII regions harbor an oxygen abundance ~0.15 dex lower than expected from their immediate surroundings and from the abundance gradient present in the …
We analyze the relationship between maximum cluster mass, M_max, and surface densities of total gas (Sigma_gas), molecular gas (Sigma_H2) and star formation rate (Sigma_SFR) in the flocculent galaxy M33, using published gas data and a catalog of more than 600 young star clusters in its disk. By comparing the radial distributions of gas and most massive cluster masses, we find that M_max is proportional to Sigma_gas^4.7, M_max is proportional Sigma_H2^1.3, and M_max is proportional to Sigma_SFR^1.0. We rule out that these correlations result from the size of sample; hence, the change of the max…
The nearby S0 galaxy IC 5181 is studied to address the origin of the ionized gas component that orbits the galaxy on polar orbit. We perform detailed photometric and spectroscopic observations measuring the surface brightness distribution of the stars (I-band), ionized gas of IC 5181 (H-alpha narrow band), the ionized-gas and stellar kinematics along both the major and minor axis, and the corresponding line strengths of the Lick indices. We conclude that the galaxy hosts a geometrically and kinematically decoupled component of ionized gas. It is elongated along the galaxy minor axis and in ort…
We use $N$-body/smoothed particle hydrodynamics simulations of encounters between an early-type galaxy (ETG) and a late-type galaxy (LTG) to study the effects of hot halo gas on the evolution for a case with the mass ratio of the ETG to LTG of 2:1 and the closest approach distance of $\sim$100 kpc. We find that the dynamics of the cold disk gas in the tidal bridge and the amount of the newly formed stars depend strongly on the existence of a gas halo. In the run of interacting galaxies not having a hot gas halo, the gas and stars accreted into the ETG do not include newly formed stars. However…
We present high spatial resolution imaging of the CO(1-0) line from the Karl G. Jansky Very Large Array (VLA) of COSMOS27289, a massive, compact star forming galaxy at z=2.234. This galaxy was selected to be structurally similar to z~2 passive galaxies. Our previous observations showed that it is very gas-poor with respect to typical star-forming galaxies at these redshifts, consistent with a rapid transition to quiescence as the molecular gas is depleted. The new data show that both the molecular gas fraction f_H2 = M_H2/M_star and the molecular gas depletion time t_dep = M_H2/SFR are lower i…
Theoretically, inflowing filaments of gas are one of the main causes of growth for a galaxy. Nonetheless, observationally, probing ongoing gas accretion is challenging. As part of the Gas Stripping Phenomena in galaxies with MUSE (GASP) program, we present the analysis of a spiral galaxy at z=0.04648 whose characteristics indeed are consistent with a scenario in which gas accretion plays a major role. The most salient indirect parts of evidence that support this picture are: 1) The galaxy is isolated, its position rules out the mechanisms expected in dense environments. 2) It shows a pronounce…
Galaxy interactions can have an important effect in a galaxy's evolution. Cosmological models predict a large number of small satellites around galaxies. It is important to study the effect that these small satellites can have on the host. The present work explores the effect of small N-body spherical satellites with total mass ratios in the range approx 1:1000-1:100 in inducing gas flows to the central regions of a disc galaxy with late-type morphology resembling the Milky Way. Two model galaxies are considered: barred and non-barred models; the latter one is motivated in order to isolate and…
We investigate the connection between star formation and molecular gas properties in galaxy mergers at low redshift (z$\leq$0.06). The study we present is based on IRAM 30-m CO(1-0) observations of 11 galaxies with a close companion selected from the Sloan Digital Sky Survey (SDSS). The pairs have mass ratios $\leq$4, projected separations r$_{\mathrm{p}} \leq$30 kpc and velocity separations $Δ$V$\leq$300 km s$^{-1}$, and have been selected to exhibit enhanced specific star formation rates (sSFR). We calculate molecular gas (H$_{2}$) masses, assigning to each galaxy a physically motivated conv…
Observations suggest a slower stellar rotation relative to gas rotation in the outer part of the Milky Way Galaxy. This difference could be attributed to an interaction with the interstellar magnetic field. In a simple model, fields of order 10 micro Gauss are then required, consistently with the observed values. This coincidence suggests a tool for estimating magnetic fields in spiral galaxies. A North-South asymmetry in the rotation of gas in the Galaxy could be of magnetic origin too.
We present recent {\it Chandra} X-ray observations of the RXJ0821.0+0752 galaxy cluster in addition to ALMA observations of the CO(1-0) and CO(3-2) line emission tracing the molecular gas in its central galaxy. All of the CO line emission, originating from a $10^{10}\,M_{\odot}$ molecular gas reservoir, is located several kpc away from the nucleus of the central galaxy. The cold gas is concentrated into two main clumps surrounded by a diffuse envelope. They form a wide filament coincident with a plume of bright X-ray emission emanating from the cluster core. This plume encompasses a putative X…
Cold Fronts and shocks are hallmarks of the complex intra-cluster medium (ICM) in galaxy clusters. They are thought to occur due to gas motions within the ICM and are often attributed to galaxy mergers within the cluster. Using hydro-cosmological simulations of clusters of galaxies, we show that collisions of inflowing gas streams, seen to penetrate to the very centre of about half the clusters, offer an additional mechanism for the formation of shocks and cold fronts in cluster cores. Unlike episodic merger events, a gas stream inflow persists over a period of several Gyrs and it could genera…
Through an ongoing MUSE program dedicated to study gas removal processes in galaxies (GAs Stripping Phenomena in galaxies with MUSE, GASP), we have obtained deep and wide integral field spectroscopy of the galaxy JO171. This galaxy resembles the Hoag's galaxy, one of the most spectacular examples of ring galaxies, characterized by a completely detached ring of young stars surrounding a central old spheroid. At odds with the isolated Hoag's galaxy, JO171 is part of a dense environment, the cluster Abell 3667, which is causing gas stripping along tentacles. Moreover, its ring counter-rotates wit…
Evidence is mounting that a significant fraction of the early-type galaxy population contains substantial reservoirs of cold interstellar gas and dust. We investigate the gas and dust in NGC 5485, an early-type galaxy with a prominent minor-axis dust lane. Using new Herschel PACS and SPIRE imaging data, we detect 3.8 x 10^6 Msun of cool interstellar dust in NGC 5485, which is in stark contrast with the non-detection of the galaxy in sensitive HI and CO observations from the ATLAS3D consortium. The resulting gas-to-dust ratio upper limit is Mgas/Md < 14.5, almost an order of magnitude lower tha…
We derive the circular velocity curves of the gaseous and stellar discs of UGC 4056, a giant barred galaxy with an active galactic nucleus (AGN). We analyse UGC 4056 using the 2D spectroscopy obtained within the framework of the Mapping Nearby Galaxies at APO (MaNGA) survey. Using images and the colour index g-r from the Sloan Digital Sky Survey (SDSS), we determined the tilt of the galaxy, which allows us to conclude that the galaxy rotates clockwise with trailing spiral arms. We found that the gas motion at the central part of the UGC 4056 shows peculiar features. The rotation velocity of th…
The probability distribution of the velocity of gas molecules in a closed container is described by the kinetic theory of gases. When molecules collide or impact the walls of a container, they exchange energy and momentum in accordance with Newton's laws of motion. Between collisions, the trajectory of individual molecules is a straight line, neglecting gravity. During the formation of a galaxy, the stars are constrained to a region of space and exchange energy and momentum in a manner similar to molecules. In this paper, an exact model of an ideal gas is derived and analyzed to determine the …
Absorption-selected galaxies offer an effective way to study low-mass galaxies at high redshift. However, the physical properties of the underlying galaxy population remains uncertain. In particular, the multiphase circum-galactic medium is thought to hold key information on gas flows into and out of galaxies that are vital for galaxy evolution models. Here we present ALMA observations of CO molecular gas in host galaxies of H_2-bearing absorbers. In our sample of six absorbers we detect molecular gas-rich galaxies in five absorber fields although we did not target high-metallicity (>50 per ce…
In early type galaxies, externally accreted gas is thought to be the main source of gas replenishment at late times. We use MUSE integral field spectroscopy data to study the active S0 galaxy NGC 5077, known to have disturbed dynamics, indicative of a past external interaction. We confirm the presence of a stellar kinematically distinct core with a diameter of 2.8 kpc, counter-rotating with respect to the main stellar body of the galaxy. We find that the counter-rotating core consists of an old stellar population, not significantly different from the rest of the galaxy. The ionised gas is stro…
The remarkable 1994 discovery of the Sagittarius dwarf galaxy (Sgr) revealed that, together with the Magellanic Clouds (MCs), there are at least three major dwarf galaxies, each with a total mass of order 10^10 - 10^11 solar masses, falling onto the Galaxy in the present epoch. Beyond a Galactic radius of 300 kpc, dwarfs tend to retain their gas. At roughly 50 kpc, the MCs have experienced substantial gas stripping as evidenced by the Magellanic Stream which extends from them. Since Sgr experienced star formation long after it fell into the Galaxy, it is interesting to explore just how and whe…
In the context of the GAs Stripping Phenomena in galaxies with Muse (GASP) survey, we present the characterization of JO204, a jellyfish galaxy in A957, a relatively low-mass cluster with $M=4.4 \times10^{14}M_\odot$. This galaxy shows a tail of ionized gas that extends up to 30 kpc from the main body in the opposite direction of the cluster center. No gas emission is detected in the galaxy outer disk, suggesting that gas stripping is proceeding outside-in. The stellar component is distributed as a regular disk galaxy; the stellar kinematics shows a symmetric rotation curve with a maximum radi…
We present the serendipitous discovery of an extended cold gas structure projected close to the brightest cluster galaxy (BCG) of the z=0.045 cluster Abell 3716, from archival integral field spectroscopy. The gas is revealed through narrow Na D line absorption, seen against the stellar light of the BCG, which can be traced for $\sim$25 kpc, with a width of 2-4 kpc. The gas is offset to higher velocity than the BCG (by $\sim$100 km/s), showing that it is infalling rather than outflowing; the intrinsic linewidth is $\sim$80 km/s (FWHM). Very weak H$α$ line emission is detected from the structure…
To understand the role that AGN feedback plays in galaxy evolution we need in-depth studies of the multi-phase structure and energetics of galaxy-wide outflows. In this work we present new, deep ($\sim$50 hr) NOEMA CO(1-0) line observations of the molecular gas in the powerful outflow driven by the AGN in the ultra-luminous infrared galaxy IRAS F08572+3915. We spatially resolve the outflow, finding that its most likely configuration is a wide-angle bicone aligned with the kinematic major axis of the rotation disk. The molecular gas in the wind reaches velocities up to approximately $\pm$1200 k…
GAs Stripping Phenomena in galaxies with MUSE (GASP) is a program aimed at studying gas removal processes in nearby galaxies in different environments. We present the study of four galaxies that are part of the same group (z= 0.06359) and highlight the multitude of mechanisms affecting the spatially resolved properties of the group members. One galaxy is passive and shows a regular stellar kinematics. The analysis of its star formation history indicates that the quenching process lasted for a few Gyr and that the star formation declined throughout the disk in a similar way, consistent with str…
We present results of sub-arcsec ALMA observations of CO(2-1) and CO(5-4) toward a massive main sequence galaxy at z = 1.45 in the SXDS/UDS field, aiming at examining the internal distribution and properties of molecular gas in the galaxy. Our target galaxy consists of the bulge and disk, and has a UV clump in the HST images. The CO emission lines are clearly detected and the CO(5-4)/CO(2-1) flux ratio (R_52) is ~1, similar to that of the Milky Way. Assuming a metallicity dependent CO-toH_2 conversion factor and a CO(2-1)/CO(1-0) flux ratio of 2 (the Milky Way value), the molecular gas mass an…
We report the first characterization of an extended outflow of high ionized gas in the Circinus Galaxy by means of the coronal line [FeVII] $λ$6087 Å. This emission is located within the ionization cone already detected in the [OIII] $λ$5007 Å line and is found to extend up to a distance of 700 pc from the AGN. The gas distribution appears clumpy, with several knots of emission. Its kinematics is complex, with split profiles and line centroids shifted from the systemic velocity. The physical conditions of the gas show that the extended coronal emission is likely the remnants of shells inflated…
A systematic study of AGN feedback in a disk galaxy using MACER. III. High Gas Fractions in AGN Hosts
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；University of Chinese Academy of Sciences（中国科学院大学）；Fudan University（复旦大学）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学天体物理与天文卡弗里研究所）；Peking University（北京大学）
Diffuse ionized gas (DIG) in galaxies can be found in early-type galaxies, in bulges of late-type galaxies, in the interarm regions of galaxy disks, and outside the plane of such disks. The emission-line spectrum of the DIG can be confused with that of a weakly active galactic nucleus. It can also bias the inference of chemical abundances and star formation rates in star forming galaxies. We discuss how one can detect and feasibly correct for the DIG contribution in galaxy spectra.
Numerical models of disc galaxy formation predict the existence of extended, hot ( T~10^6 K) gas haloes around present day spirals. The X-ray luminosity of these haloes is predicted to increase strongly with galaxy mass. However, searches for their X-ray emission have not been successful so far. We calculate the all sky O VII column density distributions for the haloes of three Milky Way like disc galaxies, resulting from cosmological high-resolution, N-body/gasdynamical simulations. We perform calculations both including the disc gas and without it, so the disc contribution to the column dens…
