Michael G. Jones, David J. Sand, Burcin Mutlu-Pakdil, Catherine E. Fielder, Denija Crnojevic, Paul Bennet, Kristine Spekkens, Richard Donnerstein, Amandine Doli… 展开作者
Michael G. Jones, David J. Sand, Burcin Mutlu-Pakdil, Catherine E. Fielder, Denija Crnojevic, Paul Bennet, Kristine Spekkens, Richard Donnerstein, Amandine Doliva-Dolinsky, Ananthan Karunakaran, Jay Strader, Dennis Zaritsky
我们报告发现了 Corvus A，这是一个距离约 3.5 Mpc 的低质量、富气星系，它是在 Dark Energy Camera Legacy Imaging Survey 的 DR10 中被识别出的，当时我们正在进行名为 SEmi-Automated Machine LEarning Search for Semi-resolved galaxies (SEAMLESS) 的半自动机器学习半解析星系搜索项目的初始阶段。Jansky Very Large Array 对 Corvus A 的观测在 $523\pm2$ km/s 的径向速度处探测到了 HI 谱线发射。Magellan/Megacam 成像揭示了一个不规则且复杂的恒星群体，包含年轻和年老的恒星。我们在 Neil Gehrels Swift 观测中探测到了紫外发射，这表明近期有恒星形成。然而，在 Steward Observatory 的 Kuiper 望远镜的 H$\alpha$ 成像中没有 HII 区的迹象。基于 Megacam 颜色星等图，我们通过红巨星支尖端标准烛光测量了 Corvus A 的距离为 $3.48\pm0.24$ Mpc。这使得 Corvus A 显得极为孤立，在 $\sim$1 Mpc 范围内没有已知星系。基于该距离，我们估计 Corvus A 的 HI 和恒星质量分别为 $\log M_\mathrm{HI}/\mathrm{M_\odot} = 6.59$ 和 $\log M_\ast/\mathrm{M_\odot} = 6.0$。尽管存在一些旋转迹象，但 Corvus A 的 HI 分布看起来接近正面朝向，类似于 Leo T，因此我们未尝试从其 HI 谱线宽度推断动力学质量。需要更高分辨率的合成成像来确认这一形态，并从其气体运动学中得出可靠的结论。
英文摘要：
We report the discovery of Corvus A, a low-mass, gas-rich galaxy at a distance of approximately 3.5 Mpc, identified in DR10 of the Dark Energy Camera Legacy Imaging Survey during the initial phase of our ongoing SEmi-Automated Machine LEarning Search for Semi-resolved galaxies (SEAMLESS). Jansky Very Large Array observations of Corvus A detect HI line emission at a radial velocity of $523\pm2$ km/s. Magellan/Megacam imaging reveals an irregular and complex stellar population with both young and old stars. We detect UV emission in Neil Gehrels Swift observations, indicative of recent star formation. However, there are no signs of HII regions in H$α$ imaging from Steward Observatory's Kuiper telescope. Based on the Megacam color magnitude diagram we measure the distance to Corvus A via the tip-of-the-red-giant-branch standard candle as $3.48\pm0.24$ Mpc. This makes Corvus A remarkably isolated, with no known galaxy within $\sim$1 Mpc. Based on this distance, we estimate the HI and stellar mass of Corvus A to be $\log M_\mathrm{HI}/\mathrm{M_\odot} = 6.59$ and $\log M_\ast/\mathrm{M_\odot} = 6.0$. Although there are some signs of rotation, the HI distribution of Corvus A appears to be close to face-on, analogous to that of Leo T, and we therefore do not attempt to infer a dynamical mass from its HI line width. Higher resolution synthesis imaging is required to confirm this morphology and to draw robust conclusions from its gas kinematics.
We report HST/ACS observations of two nearby gas-rich dwarf galaxies: DDO 161 and UGCA 319. Their distances determined via the Tip of the Red Giant Branch are 6.03 (-0.21/+0.29) Mpc and 5.75+-0.18 Mpc, respectively. The galaxies form an isolated pair dynamically well separated from the nearest neighbors: KK 176 (7.28+-0.29 Mpc) and NGC 5068 (5.16+-0.21 Mpc). All four galaxies have a bulk spatial peculiar velocity towards the Virgo cluster of ~158+-17 km/s in the Local Group rest frame and ~330 km/s with respect to the cluster center.
We report the discovery of Tucana B, an isolated ultra-faint dwarf galaxy at a distance of D=1.4 Mpc. Tucana B was found during a search for ultra-faint satellite companions to the known dwarfs in the outskirts of the Local Group, although its sky position and distance indicate the nearest galaxy to be $\sim$500 kpc distant. Deep ground-based imaging resolves Tucana B into stars, and it displays a sparse red giant branch consistent with an old, metal poor stellar population analogous to that seen in the ultra-faint dwarf galaxies of the Milky Way, albeit at fainter apparent magnitudes. Tucana …
We present observations of the dwarf galaxies GALFA Dw3 and GALFA Dw4 with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). These galaxies were initially discovered as optical counterparts to compact HI clouds in the GALFA survey. Both objects resolve into stellar populations which display an old red giant branch, younger helium burning, and massive main sequence stars. We use the tip of the red giant branch method to determine the distance to each galaxy, finding distances of 7.61$_{-0.29}^{+0.28}$ Mpc and 3.10$_{-0.17}^{+0.16}$ Mpc, respectively. With these distance…
Galaxy triplets are interesting laboratories where we can study the formation and the evolution of small and large systems of galaxies. This study aims to investigate signs of interaction between the members of nine isolated galaxy triplet systems (27 galaxies) selected from the "SDSS-based catalogue of Isolated Triplets" (SIT) with members brighter than 17.0 ($m_r\le$ 17.0) in the $r-$band, and mean projected separation between the members of $r_p \leq$ 0.1 Mpc. In this work, we performed a one-dimensional (1D) fitting of the surface brightness profiles and a two-dimensional (2D) modeling of …
The formation and evolution of elliptical galaxies in low-density environments are less understood than classical elliptical galaxies in high-density environments. Isolated galaxies are defined as galaxies without massive neighbors within scales of galaxy groups. The effect of the environment at several Mpc scales on their properties has been barely explored. Here we study the role of large-scale environment in some physical properties of 573 isolated elliptical galaxies out to z=0.08. We use three environmental estimators of the large-scale structure within a projected radius of 5 Mpc around …
We report the discovery of a new faint dwarf galaxy, GHOSTS I, using HST/ACS data from one of our GHOSTS (Galaxy Halos, Outer disks, Substructure, Thick disk, and Star clusters) fields. Its detected individual stars populate an approximately one magnitude range of its luminosity function (LF). Using synthetic color-magnitude diagrams (CMDs) to compare with the galaxy's CMD, we find that the colors and magnitudes of GHOSTS I's individual stars are most consistent with being young helium-burning and asymptotic giant branch stars at a distance of 12 +/- 2 Mpc. Morphologically, GHOSTS I appears to…
We report the serendipitous identification of a low mass ($M_* \sim 2\times 10^6 \, \mathrm{M}_\odot$), isolated, likely quenched dwarf galaxy in the "foreground" of the COSMOS-CANDELS field. From deep Hubble Space Telescope (HST) imaging we infer a surface brightness fluctuation distance for COSMOS-dw1 of $D_{\mathrm{SBF}} = 22 \pm 3$ Mpc, which is consistent with its radial velocity of $cz = 1222 \pm 64$ km s$^{-1}$ via Keck/LRIS. At this distance, the galaxy is 1.4 Mpc in projection from its nearest massive neighbor. We do not detect significant H$α$ emission (EW(H$α$)$ = -0.4 \pm 0.5$ angs…
The present paper is devoted to the construction of a catalog of isolated galaxy pairs from the Uppsala Galaxy Catalog (UGC), using accurate radial velocities. The UGC lists 12921 galaxies to declination larger than -2 deg 30 min and is complete to an apparent diameter of 1 arcmin. The criteria used to define the isolated galaxy pairs are the following: 1) Velocity criterion: radial velocity difference between the members lower than 500 km/s; 2) Interdistance criterion: projected distance between the members smaller than 1 Mpc; 3) Reciprocity criterion: each member is the closest galaxy to the…
Observations of the highly isolated dwarf spheroidal galaxy KKs 3 = [KK2000] 03 with the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) are presented. We measured the galaxy distance of $2.12\pm0.07$ Mpc using the Tip of Red Giant Branch (TRGB) method. The total blue absolute magnitude of the galaxy is estimated as $M_B = -10.8$ mag. We briefly discuss the star formation history of KKs 3 derived from its colour-magnitude diagram. According to our calculation, the total stellar mass of the galaxy is $2.3\times10^7M_{\odot}$, and most stars (74\%) were formed at an early epoch mo…
Understanding the dynamics of galaxy triplet systems is one of the significant ways of obtaining insight into the dynamics of large galaxy clusters. Toward that aim, we present a detailed study of all isolated triplet systems (total of 315) taken from the `SDSS-based catalogue of Isolated Triplets' (SIT). In addition, we compared our results with those obtained for a sample of triplets from the Local Supercluster (LS), SDSS-triplets, Tully's catalogue, Wide (W) and Compact (K)-triplets. In addition, we performed the correlation between the dynamical parameters and the Large Scale Structure (LS…
We have selected a sample of extremely isolated galaxies (EIGs) from the local Universe ($\mbox{z} < 0.024$), using a simple isolation criterion: having no known neighbours closer than $300\,{\rm km\,s}^{-1}$ ($3\,h^{-1}\,\mbox{Mpc}$) in the three-dimensional redshift space $(α,δ,\mbox{z})$. The sample is unique both in its level of isolation and in the fact that it utilizes HI redshifts from the Arecibo Legacy Fast ALFA survey (ALFALFA). We analysed the EIG sample using cosmological simulations and found that it contains extremely isolated galaxies with normal mass haloes which have evolved g…
The physical origin of the large-scale conformity in the colours and specific star formation rates of isolated low mass central galaxies and their neighbours on scales in excess of 1 Mpc is still under debate. One possible scenario is that gas is heated over large scales by feedback from active galactic nuclei (AGN), leading to coherent modulation of cooling and star formation between well-separated galaxies. In this Letter, the metal line absorption catalogue of Zhu & Menard (2013) is used to probe gas out to large projected radii around a sample of a million galaxies with stellar masses ~10^…
A Sample of Nearby Isolated Dwarf Galaxies: A First Look at the Mass Function of Field Dwarfs
Princeton University（普林斯顿大学）；Fermi National Accelerator Laboratory（费米国家加速器实验室）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理研究所）；Department of Astronomy and Astrophysics, University of Chicago（芝加哥大学天文学与天体物理学系）；School of Physics and Astronomy, Tel Aviv University（特拉维夫大学物理与天文学院）
The present paper is devoted to the construction of a catalog of isolated galaxy pairs extracted from the HyperLEDA extragalactic database. The radial velocities of the galaxies in the pairs are in the range $[3000,16000]$ km.s$^{-1}$. In order to get an unbiased pair catalog as complete as possible, we have limited the absolute magnitude of the galaxies to $M \leq-18.5$). The criteria used to define the isolated galaxy pairs are the following: 1) Velocity criterion: radial velocity difference between the pair members $ΔV<500$ km.s$^{-1}$; 2) Interdistance criterion: projected distance between…
We investigate the lowest-mass quiescent galaxies known to exist in isolated environments ($\mathrm{M^* = 10^{9.0-9.5} \ M_\odot}$; 1.5 Mpc from a more massive galaxy). This population may represent the lowest stellar mass galaxies in which internal feedback quenches galaxy-wide star formation. We present Keck/ESI long-slit spectroscopy for 27 isolated galaxies in this regime: 20 quiescent galaxies and 7 star-forming galaxies. We measure emission line strengths as a function of radius and place galaxies on the Baldwin Phillips Terlevich (BPT) diagram. Remarkably, 16 of 20 quiescent galaxies in…
We investigate the global neutral hydrogen (HI) content of isolated galaxies selected from the SDSS spectroscopic survey with optical evidence of Active Galactic Nuclei (AGN). Our sample includes galaxies with unresolved HI observations from the ALFALFA 70% data release combined with deeper HI observations of low-mass galaxies with 7.0 < log(M*) < 9.5. We examine the HI masses of this sample using the distance from the star-forming sequence on the OIII\Hb and NII\Ha Baldwin Phillips Terlevich (BPT) diagram as a measurement of AGN activity. In agreement with previous studies, we find that, for …
Milky Way galaxy-analogs and isolated galaxies with bars: environmental density in the Local Volume
Main Astronomical Observatory of the National Academy of Sciences of Ukraine（乌克兰国家科学院主要天文台）；Institute of Astronomy of V. N. Karazin Kharkiv National University（哈尔科夫国立大学瓦西里·卡拉津天体物理研究所）
We present the SALT spectroscopy of a globular cluster in the center of the nearby isolated dSph galaxy KKs3 situated at a distance of 2.12 Mpc. Its heliocentric radial velocity is 316+-7 km/s that corresponds to V_{LG} = 112 km/s in the Local Group (LG) reference frame. We use its distance and velocity along with the data on other 35 field galaxies in the proximity of the LG to trace the local Hubble flow. Some basic properties of the local field galaxies: their morphology, absolute magnitudes, average surface brightnesses, specific star formation rates, and hydrogen mass-to-stellar mass rati…
School of Earth and Space Exploration, Arizona State University（亚利桑那州立大学地球与空间探索学院）；Center for Astrophysics | Harvard & Smithsonian（哈佛-史密森天体物理中心）；Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）
Observations with the Hubble Space Telescope unexpectedly revealed that the dwarf galaxy ESO 006-001 is a near neighbor to the Local Group at a distance of 2.70 +- 0.11 Mpc. The stellar population in the galaxy is well resolved into individual stars to a limit of M I ~ -0.5 mag. The dominant population is older than 12 Gyr yet displays a significant range in metallicity of -2 < [Fe/H] < -1, as evidenced by a Red Giant Branch with substantial width. Superimposed on the dominant population are stars on the Main Sequence with ages less than 100 Myr and Helium burning Blue Loop stars with ages of …
We have obtained deep images of the highly isolated (d = 1 Mpc) Aquarius dwarf irregular galaxy (DDO 210) with the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS). The resulting color-magnitude diagram (CMD) reaches more than a magnitude below the oldest main-sequence turnoff, allowing us to derive the star formation history (SFH) over the entire lifetime of the galaxy with a timing precision of ~10% of the lookback time. Using a maximum likelihood fit to the CMD we find that only ~10% of all star formation in Aquarius took place more than 10 Gyr ago (lookback time equivalent to…
KDG 162: A Nearby Isolated Star-forming Dwarf Galaxy
Space Telescope Science Institute（太空望远镜科学研究所）；Special Astrophysical Observatory, Russian Academy of Sciences（俄罗斯科学院特殊天体物理观测台）；University of Washington（华盛顿大学）；University of California Berkeley（加州大学伯克利分校）；University of Hawaii（夏威夷大学）；Johns Hopkins University（约翰斯·霍普金斯大学）；Raytheon（雷神公司）；University of Arizona（亚利桑那大学）；University of Maryland（马里兰大学）
We present the discovery of rotation in quenched, low-mass early-type galaxies that are isolated. This finding challenges the claim that (all) rotating dwarf early-type galaxies in clusters were once spiral galaxies that have since been harassed and transformed into early-type galaxies. Our search of the Sloan Digital Sky Survey data within the Local volume ($z<0.02$) has yielded a sample of 46 galaxies with a stellar mass $M_\star \lesssim 5\times10^9$ M$_\odot$ (median $M_\star \sim 9.29 \times 10^8$ M$_\odot$), a low H$α$ equivalent width EW$_{{\rm H}α}< 2$ Å, and no massive neighbour ($M_{…
In this paper, we describe a new method to select globular cluster (GC) candidates, including galaxy subtraction with unsharp masking, template fitting techniques and the inclusion of Gaia's proper motions. We report the use of the 12-band photometric system of S-PLUS to determine radial velocities and stellar populations of GCs around nearby galaxies. Specifically, we assess the effectiveness of identifying GCs around nearby and massive galaxies (D $< 20$ Mpc and $σ> 200$ km/s) in a multi-band survey such as S-PLUS by using spectroscopically confirmed GCs and literature GC candidate lists aro…
We present a photometric study of the field lenticular galaxy NGC 4546 using Gemini/GMOS imaging in g'r'i'z'. We perform a 2D image decomposition of the surface brightness distribution of the galaxy using GALFIT, finding that four components adequately describe it. The subtraction of this model from our images and the construction of a colour map allow us to examine in great detail the asymmetric dust structures around the galactic centre. In addition, we perform a detailed analysis of the globular cluster (GC) system of NGC 4546. Using a Gaussian Mixture Model algorithm in the colour-colour p…
Using Hubble Space Telescope imaging of the resolved stellar population of KK~242 = NGC6503-d1 = PGC~4689184, we measure the distance to the galaxy to be $6.46\pm0.32$ Mpc and find that KK~242 is a satellite of the low-mass spiral galaxy NGC~6503 located on the edge of the Local Void. Observations with the Karl G. Jansky Very Large Array show signs of a very faint HI-signal at the position of KK~242 within a velocity range of $V_{hel} = -80\pm10$ km\,s$^{-1}$. This velocity range is severely contaminated by HI emission from the Milky Way and from NGC6503. The dwarf galaxy is classified as the …
We introduce the Solitary Local Dwarfs Survey (Solo), a wide field photometric study targeting every isolated dwarf galaxy within 3 Mpc of the Milky Way. Solo is based on (u)gi multi-band imaging from CFHT/MegaCam for northern targets, and Magellan/Megacam for southern targets. All galaxies fainter than Mv = -18 situated beyond the nominal virial radius of the Milky Way and M31 (>300 kpc) are included in this volume-limited sample, for a total of 42 targets. In addition to reviewing the survey goals and strategy, we present results for the Sagittarius Dwarf Irregular Galaxy (Sag DIG), one of t…
Distance determinations of extremely-low-surface-brightness galaxies are expensive in terms of spectroscopic time. Because of this, their distances are often inferred by associating such galaxies with larger structures such as groups or clusters, leading to a systematic bias by selecting objects in high density environments. Here we report the discovery of a red ultra-diffuse galaxy (S82-DG-1: $r_{\mathrm{eff}}$ = 1.6 kpc; $<μ_{g}>$ = 25.7 mag arcsec$^{-2}$; $g-i$ = 0.78 mag) located in a nearby cosmic void. We used multi-band luminosity functions of its globular clusters to obtain the distanc…
A Quenched and Relatively Isolated Dwarf Galaxy in the Local Volume
Rutgers University（罗格斯大学）；Space Telescope Science Institute（太空望远镜科学研究所）；University of Utah（犹他大学）；Raytheon（雷神公司）；Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）
We undertook a search for new dwarf galaxies in the vicinity of relatively isolated nearby galaxies with distances $D < 12$ Mpc and stellar masses in the $2\times10^{11}-3\times10^8~M_{\odot}$ interval, using the data from the DESI Legacy Imaging Surveys. Around the 46 considered Local Volume galaxies, $67$ new candidates for satellites of these galaxies were found. About half of them are classified as spheroidal dwarfs of low surface brightness. The new galaxies are included in the Local Volume database (LVGDB), which now contains 1421 objects, being 63% more than the Updated Nearby Galaxy Ca…
We apply a spectral stacking technique to Westerbork Synthesis Radio Telescope observations to measure the neutral atomic hydrogen content (HI) of nearby galaxies in and around galaxy groups at $z < 0.11$. Our sample includes 577 optically-selected galaxies (120 isolated galaxies and 457 satellites) covering stellar masses between 10$^{10}$ and 10$^{11.5}$ M$_{\odot}$, cross-matched with Yang's group catalogue, with angular and redshift positions from the Sloan Digital Sky Survey. We find that the satellites in the centres of groups have lower HI masses at fixed stellar mass and morphology (ch…
The role of the environment on galaxy evolution is still not fully understood. In order to quantify and set limits on the role of nurture one must identify and study a sample of isolated galaxies. The AMIGA project "Analysis of the Interstellar Medium of Isolated GAlaxies" is doing a multi-wavelength study of a large sample of isolated galaxies in order to examine their interstellar medium and star formation activity. We processed data for 950 galaxies from the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973) and evaluated their isolation using an automated star-galaxy classification p…
We report deep imaging observations with DOLoRes@TNG of an ultra-faint dwarf satellite candidate of the Triangulum galaxy (M33) found by visual inspection of the public imaging data release of the DESI Legacy Imaging Surveys. Pisces VII/Triangulum (Tri) III is found at a projected distance of 72 kpc from M33, and using the tip of the red giant branch method we estimate a distance of D=1.0 +0.3,-0.2 Mpc, meaning the galaxy could either be an isolated ultra-faint or the second known satellite of M33. We estimate an absolute magnitude of M_V=-6.1+/-0.2 if Pisces VII/Tri II is at the distance of M…
Recent advancements in the imaging of low-surface-brightness objects revealed numerous ultra-diffuse galaxies in the local Universe. These peculiar objects are unusually extended and faint: their effective radii are comparable to the Milky Way, but their surface brightnesses are lower than that of dwarf galaxies. Their ambiguous properties motivate two potential formation scenarios: the "failed" Milky Way and the dwarf galaxy scenario. In this paper, for the first time, we employ X-ray observations to test these formation scenarios on a sample of isolated, low-surface-brightness galaxies. Sinc…
We report on a study of the galaxy environments of low redshift physical quasars pairs. We selected 20 pairs having projected separation $<$ 0.5 Mpc and difference of systemic velocity $<$ 800 km s$^{-1}$. Using Sloan Digital Sky Survey images we evaluated the galaxy overdensity around these quasars in pairs and then compare it with that of a sample of isolated quasars with same redshift and luminosity. It is found that on average there is a systematic larger overdensity of galaxies around quasars in pairs with respect to that of isolated quasars. This may represent a significant link between …
We investigate the properties of the galaxy environment of a sample of 14 low redshift (z $<$ 0.85) quasar physical pairs extracted from SDSS DR10 archives. The pairs have a systemic radial velocity difference $ΔV_\parallel \leqslant$ 600 $km \ s^{-1}$ (based on [OIII]5007 Å\ line) and projected distance $ R_\bot \leqslant$ 600 kpc. The physical association of the pairs is statistically confirmed at a level of $\sim$ 90 %. For most of the images of these quasars we are able to resolve their host galaxies that turn out to be on average similar to those of quasars not in pairs. We also found tha…
It is of broad interest for galaxy formation theory to carry out a full inventory of the numbers and properties of dwarf galaxies in the Local Volume, both satellites and isolated ones. Ultra-deep imaging in wide areas of the sky with small amateur telescopes can help to complete the census of these hitherto unknown low surface brightness galaxies, which cannot be detected by the current resolved stellar population and HI surveys. We report the discovery of Donatiello I, a dwarf spheroidal galaxy located one degree from the star Mirach (Beta And) in a deep image taken with an amateur telescope…
As part of a large Hubble Space Telescope investigation aiming at reaching the faintest stars in the Galactic globular cluster NGC 6752, an ACS/WFC field was the subject of deep optical observations reaching magnitudes as faint as V~30. In this field we report the discovery of Bedin I a dwarf spheroidal galaxy too faint and too close to the core of NGC 6752 for detection in earlier surveys. As it is of broad interest to complete the census of galaxies in the local Universe, in this Letter we provide the position of this new object along with preliminary assessments of its main param eters. Ass…
The Survey of HI in Extremely Low-mass Dwarf galaxies (SHIELD) is an on-going multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very low-mass galaxies. The galaxies were selected from the first ~10% of the HI ALFALFA survey based on their inferred low HI mass and low baryonic mass, and all systems have recent star formation. Thus, the SHIELD sample probes the faint end of the galaxy luminosity function for star-forming galaxies. Here, we measure the distances to the 12 SHIELD galaxies to be between 5-12 Mpc by applying the tip of the red giant method …
Observations are presented of the isolated dwarf irregular galaxy And IV made with the Hubble Space Telescope Advanced Camera for Surveys and the Giant Metrewave Radio Telescope in the 21 cm HI line. We determine the galaxy distance of $7.17\pm0.31$ Mpc using the Tip of Red Giant Branch method. The galaxy has a total blue absolute magnitude of -12.81 mag, linear Holmberg diameter of 1.88 kpc and an HI-disk extending to 8.4 times the optical Holmberg radius. The HI mass-to-blue luminosity ratio for And IV amounts $12.9~M_{\odot}/L_{\odot}$. From the GMRT data we derive the rotation curve for th…
Galaxies and groups of galaxies exist in dark-matter halos filled with diffuse gas. The diffuse gas represents up to 80\% of the mass in baryonic matter within the halos(1,2), but is difficult to detect because of its low density (particle number densities of $\lesssim10^{-4}$\,cm$^{-3}$) and high temperature (mostly greater than $10^{6}$\,K). Here we analyze the impact of diffuse gas associated with nearby galaxies using the dispersion measures (DMs) of extragalactic fast radio bursts (FRBs). FRB DMs provide direct measurements of the total ionized-gas contents along their sightlines. Out of …
