We present a panoramic survey of the isolated Local Group dwarf irregular galaxy NGC 6822. Our photometry reaches $\sim2-3$ magnitudes deeper than most previous studies and spans the widest area around the dwarf compared to any prior work. We observe no stellar over-densities in the outskirts of NGC 6822 to $V\sim 30$ mag$\,$arcsec$^{-2}$ and a projected radius of $16.5$ kpc. This indicates that NGC 6822 has not experienced any recent interaction with a companion galaxy, despite previous suggestions to the contrary. Similarly, we find no evidence for any dwarf satellites of NGC 6822 to a limiting luminosity $M_V\approx -5$. NGC 6822 contains a disk of HI gas and young stars, oriented at $\sim 60$ degrees to an extended spheroid composed of old stellar populations. We observe no correlation between the distribution of young stars and spheroid members. Our imaging allows us to trace the spheroid to nearly $11$ kpc along its major axis, commensurate with the extent of the NGC 6822 globular cluster system. We find that the spheroid becomes increasingly flattened at larger radii, and its position angle twists by up to $40$ degrees. We use Gaia EDR3 astrometry to measure a proper motion for NGC 6822, and then sample its orbital parameter space. While this galaxy has spent the majority of its life in isolation, we find that it likely passed within the virial radius of the Milky Way $\sim3-4$ Gyr ago. This may explain the apparent flattening and twisting observed in the outskirts of its spheroid.
Recent panoramic observations of the dominant spiral galaxies of the Local Group have revolutionized our view of how these galaxies assemble their mass. However, it remains completely unclear whether the properties of the outer regions of the Local Group large spirals are typical. Here, we present the first panoramic view of a spiral galaxy beyond the Local Group, based on the largest, contiguous, ground-based imaging survey to date resolving the stellar halo of the nearest prime analogue of the Milky Way, NGC 891 (D~10 Mpc). The low surface brightness outskirts of this galaxy are populated by…
Using the MegaCam imager on the Canada-France-Hawaii Telescope, we have resolved individual stars in the outskirts of the nearby large spiral galaxy M81 (NGC 3031) well below the tip of the red giant branch of metal-poor stellar populations over 60 kpc * 58 kpc. In this paper, we report the discovery of new young stellar systems in the outskirts of M81. The most prominent feature is a chain of clumps of young stars distributed along the extended southern HI tidal arm connecting M 81 and NGC 3077. The colour-magnitude diagrams of these stellar systems show plumes of bright main sequence stars a…
We present a panoramic study of the Fornax dwarf spheroidal galaxy, using data obtained as part of the VLT Survey Telescope (VST) ATLAS Survey. The data presented here -- a subset of the full survey -- uniformly cover a region of 25 square degrees centred on the galaxy, in $g$, $r$ and $i$-bands. This large area coverage reveals two key differences to previous studies of Fornax. First, data extending beyond the nominal tidal radius of the dwarf highlight the presence of a second distinct red giant branch population. This bluer red giant branch appears to be coeval with the horizontal branch po…
We studied the nearby edge-on galaxy NGC4656 and its dwarf low surface brightness companion with the enhanced UV brightness, NGC4656UV, belonging to the interacting system NGC4631/56. Regular photometric structure and relatively big size of NGC4656UV allows to consider this dwarf galaxy as a separate group member rather than a tidal dwarf. Spectral long-slit observations were used to obtain the kinematical parameters and gas-phase metallicity of NGC4656UV and NGC4656. Our rough estimate of the total dynamical mass of NGC4656UV allowed us to conclude that this galaxy is the dark-matter dominate…
We report the discovery of three low surface brightness companions to the spiral galaxy NGC 4631, made with small amateur telescopes. Assuming their distances to be 7.4 Mpc, the same as that of NGC 4631, the absolute magnitudes and linear diameters of the dwarfs are ranged within [-12.5, -9.6] mag and [4.7 - 1.3] kpc, respectively. These new three dwarfs, together with the discovered by us diffuse structure called "bridge", look like parts of a tidal filament directed towards NGC 4656 at total extended over 100 kpc.
The tidal tails of globular clusters have been shown to be sensitive to the external tidal field. We investigate how Galactic globular clusters with observed tails are affected by satellite dwarf galaxies by simulating tails in galaxy models with and without dwarf galaxies. The simulations indicate that tidal tails can be subdivided into into three categories based on how they are affected by dwarf galaxies: 1) dwarf galaxies perturb the progenitor cluster's orbit (NGC 4590, Pal 1, Pal 5), 2) dwarf galaxies perturb the progenitor cluster's orbit and individual tail stars (NGC 362, NGC 1851, NG…
We carried out a survey of low-surface-brightness companions around nine luminous Local Volume galaxies using long exposures with small amateur telescopes. We found 12 low- and very low-surface-brightness objects around the galaxies: NGC 628, NGC 2337, NGC 3368, NGC 3521, NGC 4236, NGC 4258, NGC 4594, NGC 5055, and NGC 6744 situated within 12 Mpc from us. Assuming the dwarf candidates are satellites of the neighbouring massive galaxies, their absolute B magnitudes are in the range of [-8.9, -13.0], linear diameters are [0.6 - 2.7] kpc, and the mean surface brightnesses are [25.1 - 27.5] mag/sq…
In this work a search was carried out for globular clusters belonging to the Sagittarius (Sgr) tidal stream using the analysis of spatial positions, radial velocities relative to the Galactic Standard of Rest (V_{GSR}),proper motions and ratio of "age -- metallicity" ([Fe/H]) for globular clusters and for stars in the tidal stream. As a result, three categories of globular clusters were obtained: A -- most certainly in the stream: Terzan 8, Whiting 1, Arp 2, NGC 6715, Terzan 7, Pal 12; B -- kinematic outliers: Pal 5, NGC 5904, NGC 5024, NGC 5053, NGC 5272, NGC 288; C -- lowest rank candidates:…
We report the discovery of Antlia B, a faint dwarf galaxy at a projected distance of $\sim$72 kpc from NGC 3109 ($M_{V}$$\sim$$-$15 mag), the primary galaxy of the NGC 3109 dwarf association at the edge of the Local Group. The tip of the red giant branch distance to Antlia B is $D$=1.29$\pm$0.10 Mpc, which is consistent with the distance to NGC 3109. A qualitative analysis indicates the new dwarf's stellar population has both an old, metal poor red giant branch ($\gtrsim$10 Gyr, [Fe/H]$\sim$$-$2), and a younger blue population with an age of $\sim$200-400 Myr, analogous to the original Antlia …
Dwarf galaxies are key objects for small-scale cosmological tests like the abundance problems or the planes-of-satellites problem. It is therefore a crucial task to get accurate information for as many nearby dwarf galaxies as possible. Using extremely deep, ground-based $V$ and $i$-band Subaru Suprime Cam photometry with a completeness of $i=27$ mag, we measure the tip of the red giant branch distance for the dwarf galaxy [TT2009] 25. This dwarf resides in the field around the Milky Way-analog NGC 891. By using a Bayesian approach, we measure a distance of $10.28^{+1.17}_{-1.73}$ Mpc, which i…
Characterising the Globular Cluster Systems of Three Local Group Dwarf Galaxies: NGC6822, NGC147 and NGC185
University of Edinburgh（爱丁堡大学）；Independent Researcher（独立研究者）；University of Exeter（埃克塞特大学）；University of Cambridge（剑桥大学）；National Research Council Herzberg Astronomy and Astrophysics（国家研究委员会赫茨伯格天文学与天体物理学研究所）；University of California, Berkeley（加州大学伯克利分校）；University of Leicester（莱斯特大学）
We present deep Hubble Space Telescope imaging of five faint dwarf galaxies associated with the nearby spiral NGC 253 (D$\approx$3.5 Mpc). Three of these are newly discovered ultra-faint dwarf galaxies, while all five were found in the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), a Magellan$+$Megacam survey to identify faint dwarfs and other substructures in resolved stellar light around massive galaxies outside of the Local Group. Our HST data reach $\gtrsim$3 magnitudes below the tip of the red giant branch for each dwarf, allowing us to derive their distances, structural par…
The conjectures of Hawking-Bekenstein of that gravity and temperature are closely related, was the beginning of the formulation of thermodynamic models of gravity. Using one of these models, we show that the thermal bath temperature of NGC1052-DF2 dwarf galaxy is about 6.5 K higher than the temperature of the thermal bath of the local dwarf galaxies. We claim that this temperature difference is responsible by the behavior of the NGC1052-DF2 galaxy to be apparently a galaxy with lack dark matter. This difference arises due to that the host galaxy of NGC1052-DF2, the elliptic galaxy NGC1052 is a…
We present newly discovered dwarf galaxy candidates in deep and wide-field images of NGC 1291 obtained with the Korea Microlensing Telescope Network. We identify 15 dwarf galaxy candidates by visual inspection. Using imaging simulations, we demonstrate that the completeness rate of our detection is greater than 70% for the central surface brightness value of $μ_{0,R}\lesssim26$ mag arcsec$^{-2}$ and for magnitudes $M_R\lesssim-10$ mag. The structural and photometric properties of the dwarf galaxy candidates appear to be broadly consistent with those of ordinary dwarf galaxies in nearby groups …
Outskirts of large galaxies contain important information about the galaxy formation and assembly process, and resolved star count studies can probe the extremely low surface brightness of the outer halos. We use images obtained with the VISTA telescope to construct spatially resolved J vs Z-J colour-magnitude diagrams (CMDs) of NGC 253, a nearly edge-on disk galaxy in the Sculptor group. The very deep photometry, down to J ~ 23.5, and the wide area covered allows us to trace the red giant branch (RGB) and asymptotic giant branch (AGB) stars that belong to the outer disk and the halo of NGC 25…
The abundance of satellite dwarf galaxies has long been considered a crucial test for the current model of cosmology leading to the well-known missing satellite problem. Recent advances in both simulations and observations have allowed to study dwarf galaxies around host galaxies in more detail. We have surveyed a 72 deg2 area of the nearby Sculptor group using the Dark Energy Camera - also encompassing the two low-mass Local Volume galaxies NGC24 and NGC45 residing behind the group - to search for hitherto undetected dwarf galaxies. Apart from the previously known dwarf galaxies we have found…
We present our discovery and analysis of dwarf galaxies in the NGC 3585 galaxy group by the KMTNet Supernova Program. Using deep stack images reaching $\simeq$ 28 mag arcsec$^{-2}$ in $BVI$, we discovered 46 dwarf galaxy candidates distributed in a 7 square degree field. The dwarf galaxy candidates exhibit central surface brightness as faint as $μ_{0,V} = 26.2$ mag arcsec$^{-2}$, with effective radii larger than 150 pc and total absolute magnitudes brighter than $M_V \approx -10$ mag, if at the distance of NGC 3585. The dwarf galaxy surface number density decreases with projected distance from…
The isolated elliptical (IE) NGC 7796 is accompanied by an interesting early-type dwarf galaxy, named NGC7796-DW1. It exhibits a tidal tail, very boxy isophotes, and multiple nuclei or regions (A, B, and C) that are bluer than the bulk population of the galaxy, indicating a younger age. These properties are suggestive of a dwarf-dwarf merger remnant. We use the Multi-Unit Spectroscopic Explorer (MUSE) at the VLT to investigate NGC 7796-DW1. We extract characteristic spectra to which we apply the STARLIGHT population synthesis software to obtain ages and metallicities of the various population …
We present the deepest optical photometry for any dwarf elliptical (dE) galaxy based on Hubble Space Telescope ACS observations of the Local Group dE galaxies NGC 147 and NGC 185. The resulting F606W and F814W color-magnitude diagrams are the first to reach below the main sequence turnoff in a dE galaxy, allowing us to determine full star formation histories in these systems. The ACS fields are located ~1.5 effective radii from the galaxy center to avoid photometric crowding. While our ACS pointings in both dEs show unambiguous evidence for old and intermediate age stars, the mean age in NGC 1…
The ultra-diffuse dwarf galaxy NGC 1052-DF2 (DF2) has ten (eleven) measured globular clusters (GCs) with a line-of-sight velocity dispersion of $σ=7.8^{+5.2}_{-2.2}\,$km/s ($σ=10.6^{+3.9}_{-2.3}\,$km/s). Our conventional statistical analysis of the original ten GCs gives $σ=8.0^{+4.3}_{-3.0}\,$km/s. The overall distribution of velocities agrees well with a Gaussian of this width. Due to the non-linear Poisson equation in MOND, a dwarf galaxy has weaker self-gravity when in close proximity to a massive host. This external field effect is investigated using a new analytic formulation and fully s…
We report the results of a survey of the region within 40 arcmin of NGC 891, a nearby nearly perfectly edge-on spiral galaxy. Candidate "non-stars" with diameters greater than 15 arcsec were selected from the GSC 2.3.2 catalog and cross-comparison of observations in several bands using archived \galex, DSS2, WISE, and 2MASS images identified contaminating stars, artifacts and background galaxies, all of which were excluded. The resulting 71 galaxies, many of which were previously uncataloged, comprise a size limited survey of the region. A majority of the galaxies are in the background of NGC …
We exploit data from the Pan-Andromeda Archaeological Survey (PAndAS) to study the extended structures of M31's dwarf elliptical companions, NGC147 and NGC185. Our wide-field, homogeneous photometry allows to construct deep colour-magnitude diagrams (CMDs) which reach down to $\sim3$ mag below the red giant branch (RGB) tip. We trace the stellar components of the galaxies to surface brightness of $μ_g \sim 32$ mag arcsec$^{-2}$ and show they have much larger extents ($\sim5$ kpc radii) than previously recognised. While NGC185 retains a regular shape in its peripheral regions, NGC147 exhibits p…
It has been claimed in the recent literature that a non-trivial relation between the mass of the most-massive star, mmax, in a star cluster and its embedded star cluster mass (the mmax-Mecl relation) is falsified by observations of the most-massive stars and the Halpha luminosity of young star clusters in the starburst dwarf galaxy NGC 4214. Here it is shown by comparing the NGC 4214 results with observations from the Milky Way that NGC 4214 agrees very well with the predictions of the the mmax-Mecl relation and the integrated galactic stellar initial mass function (IGIMF) theory and that this…
We report the discovery of a UV-bright tidal dwarf galaxy candidate in the NGC 4631/4656 galaxy group, which we designate NGC 4656UV. Using survey and archival data spanning from 1.4 GHz to the ultraviolet we investigate the gas kinematics and stellar properties of this system. The HI morphologies of NGC 4656UV and its parent galaxy NGC 4656 are extremely disturbed, with significant amounts of counterrotating and extraplanar gas. From UV-FIR photometry, computed using a new method to correct for surface gradients on faint objects, we find that NGC 4656UV has no significant dust opacity and a b…
Dwarf spheroidal galaxies are among the most numerous galaxy population in the Universe, but their main formation and evolution channels are still not well understood. The three dwarf spheroidal satellites (NGC147, NGC185, and NGC205) of the Andromeda galaxy are characterised by very different interstellar medium (ISM) properties, which might suggest them being at different galaxy evolutionary stages. While the dust content of NGC205 has been studied in detail by De Looze et al. (2012), we present new Herschel dust continuum observations of NGC147 and NGC185. The non-detection of NGC147 in Her…
We report observations of five dwarf galaxies in the vicinity of the luminous S0 galaxy NGC 3115 performed with the Advanced Camera for Surveys on the Hubble Space Telescope. Their distances determined via the Tip of the Red Giant Branch are: 10.05 Mpc (UGCA 193), 9.95 Mpc (KKSG 17), 10.13 Mpc (2MASX-J0957-0915), 10.42 Mpc (2dFGRS-TGN218Z179) and 11.01 Mpc (KKSG 19). With their typical distance error of about 0.75 Mpc all the five dwarfs are consistent to be true satellites of the host galaxy NGC 3115 (10.2$\pm$0.2 Mpc). Using the DESI Legacy Imaging Surveys we also found 5 new probable dwarf …
We present radial velocities (from Gemini/GMOS) of the second sample of ultra-compact dwarfs (UCDs) and bright globular clusters (GCs) in the Antlia cluster. Twenty-three objects are located around the giant elliptical NGC 3268, and one is close to the fainter lenticular NGC 3273. Together with previously found UCDs around NGC 3258 a total of 35 UCDs and bright GCs has been now identified in the Antlia cluster. Their colours and magnitudes are compared with those of the nuclei of dE,N galaxies already confirmed as Antlia members. For a subsample that lie on ACS images and are brighter than M_V…
It is still unknown how magnetic field-generation mechanisms could operate in low-mass dwarf galaxies. Here, we present a detailed study of a nearby pure-disk dwarf galaxy NGC 2976. Unlike previously observed dwarf objects, this galaxy possesses a clearly defined disk. For the purpose of our studies, we performed deep multi-frequency polarimetric observations of NGC 2976 with the VLA and Effelsberg radio telescopes. Additionally, we supplement them with re-imaged data from the WSRT-SINGS survey. The magnetic field morphology discovered in NGC 2976 consists of a southern polarized ridge. This s…
Discoveries of low mass galaxy pairs and groups are increasing. Studies indicate that dwarf galaxy pairs are gas rich in the field and exhibit elevated star formation rates, suggestive of interactions. Lacking are dynamical models of observed dwarf galaxy pairs to disentangle the physical processes regulating their baryon cycles. We present new optical data and the first detailed theoretical model of an observed tidal encounter between two isolated low mass galaxies, NGC 4490 & NGC 4485. This system is an isolated analog of the Magellanic Clouds and is surrounded by a ~50 kpc extended HI envel…
Context. Ultra-compact dwarfs (UCDs) are stellar systems displaying colours and metallicities between those of globular clusters (GCs) and early-type dwarf galaxies, as well as sizes of Reff <= 100 pc and luminosities in the range -13.5 < MV < -11 mag. Although their origin is still subject of debate, the most popular scenarios suggest that they are massive star clusters or the nuclei of tidally stripped dwarf galaxies. Aims. NGC 5044 is the central massive elliptical galaxy of the NGC 5044 group. Its GC/UCD system is completely unexplored. Methods. In Gemini+GMOS deep images of several fields…
We present an observational study of the interacting pair of dwarf galaxies, MCG+07-20-052, in the vicinity of Milky Way mass spiral galaxy NGC 2998. MCG+07-20-052 is located at a sky-projected distance of 105 kpc from NGC 2998 and the two have a relative line-of-sight velocity of 60 kms. We observed tidal tail-like extensions on both members (D1 and D2) of the interacting pair MCG+07-20-052. The interacting dwarf galaxies, D1 and D2, have B-band absolute magnitudes of $-$17.17 and $-$17.14 mag, respectively, and D2 is significantly bluer than D1. We obtained HI 21 cm line data of the NGC 2998…
Spectra that cover wavelengths from 0.6 to 1.1um are used to examine the behavior of emission and absorption features in a contiguous 22 x 300 arcsec region centered on the nearby dwarf galaxy NGC 55. Based on the relative strengths of various emission features measured over spatial scales of many tens of parsecs, it is concluded that the ionization states and sulphur abundances in most of the star-forming regions near the center of NGC 55 are similar. A large star-forming region is identified in the north west part of the disk at a projected distance of ~1 kpc from the galaxy center that has …
We have followed up two ultra-diffuse galaxies (UDGs), detected adjacent to stellar streams, with Hubble Space Telescope (HST) imaging and HI mapping with the Jansky Very Large Array (VLA) in order to investigate the possibility that they might have a tidal origin. With the HST F814W and F555W images we measure the globular cluster (GC) counts for NGC 2708-Dw1 and NGC 5631-Dw1 as $2^{+1}_{-1}$ and $5^{+1}_{-2}$, respectively. NGC 2708-Dw1 is undetected in HI down to a 3$σ$ limit of $\log (M_\mathrm{HI}/\mathrm{M_\odot}) = 7.3$, and there is no apparent HI associated with the nearby stellar str…
NGC 6822 is the closest isolated dwarf irregular galaxy to the Milky Way. Its proximity and stellar mass ($10^8 M_\odot$, large for a dwarf galaxy) allow for a detailed study of its kinematic properties. The red giant branch (RGB) stars at the galaxy's center are particularly interesting because they are aligned on an axis perpendicular to the galaxy's more extended HI disk. We detected a velocity gradient among the RGB population using spectra from Keck DEIMOS. This rotation is aligned with the HI disk, but the sense of rotation is about the major axis of the central RGB population. We measur…
We report the discovery of Scl-MM-Dw2, a new dwarf galaxy at a projected separation of $\sim$50 kpc from NGC 253, as part of the PISCeS (Panoramic Imaging Survey of Centaurus and Sculptor) project. We measure a tip of the red giant branch distance of $3.12\pm0.30$ Mpc, suggesting that Scl-MM-Dw2 is likely a satellite of NGC 253. We qualitatively compare the distribution of red giant branch (RGB) stars in the color-magnitude diagram with theoretical isochrones and find that it is consistent with an old, $\sim$12 Gyr, and metal poor, $-2.3<$[Fe/H]$<-1.1$, stellar population. We also detect a sma…
We report the discovery of a new faint dwarf galaxy, which we dub Scl-MM-Dw1, at a projected distance of $\sim$65 kpc from the spiral galaxy NGC 253. The discovery results from the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), a program with the Magellan/Megacam imager to study faint substructure in resolved stellar light around massive galaxies outside of the Local Group. We measure a tip of the red giant branch distance to Scl-MM-Dw1 of $D$=3.9$\pm$0.5 Mpc, consistent with that of NGC 253, making their association likely. The new dwarf's stellar population is complex, with an …
VST-SMASH: VST Survey of Mass Assembly and Structural Hierarchy II. Exploring dwarf galaxies in the vicinity of NGC 5068 and of the two galaxies NGC 5084 and NGC 5087 at the edges of the Virgo Supercluster
INAF – Osservatorio Astronomico di Capodimonte（那不勒斯天文台）；INAF – Osservatorio Astrofisico di Arcetri（阿切特里天文台）；Sterrenkundig Observatorium, Universiteit Gent（根特大学天文台）；Department of Astronomy, Indiana University（印第安纳大学天文学系）；INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚空间科学与天文台）；Department of Physics “E. Pancini”, University of Naples Federico II（那不勒斯费德里科二世大学物理系）；School of Mechanical, Electrical and Information Engineering, Shandong University（山东大学机电与信息工程学院）；Space physics and astronomy research unit, University of Oulu（奥卢大学空间物理与天文学研究部）；INAF – Osservatorio Astronomico di Trieste（的里雅斯特天文台）
We present $BVI$ surface photometry of 31 dwarf galaxy candidates discovered in a deep image stack from the KMTNet Supernova Program of $\sim$ 30 square degrees centered on the nearby NGC 2784 galaxy group. Our final images have a 3$σ$ surface brightness detection limit of $μ_V\approx 28.5$ mag arcsec$^{-2}$. The faintest central surface brightness that we measure is $μ_{0,V} = 26.1$ mag arcsec$^{-2}$. If these candidates are at the distance of NGC 2784, then they have absolute magnitudes greater than $M_V = -9.5$ mag and effective radii larger than 170 pc. Their radial number density decrease…
Here we study 16 planetary nebulae (PNe) in the dwarf irregular galaxy NGC 205 by using GMOS@Gemini spectra to derive their physical and chemical parameters. The chemical patterns and evolutionary tracks for 14 of our PNe suggest that there are no type I PNe among them. These PNe have an average oxygen abundance of 12+log(O/H)=8.08$\pm$0.28, progenitor masses of 2-2.5M$_{\odot}$ and thus were born ~1.0-1.7Gyr ago. Our results are in good agreement with previous PN studies in NGC 205. The present 12+log(O/H) is combined with our previous works and with the literature to study the PN metallicity…
We have measured absolute proper motions for the three populations intercepted in the direction of the Galactic globular cluster NGC 6681: the cluster itself, the Sagittarius dwarf spheroidal galaxy and the field. For this we used Hubble Space Telescope ACS/WFC and WFC3/UVIS optical imaging data separated by a temporal baseline of 5.464 years. Five background galaxies were used to determine the zero point of the absolute-motion reference frame. The resulting absolute proper motion of NGC 6681 is ($μ_α\cosδ, μ_δ$)=($1.58\pm0.18, -4.57\pm0.16$) \masyr. This is the first estimate ever made for th…
The halos of disk galaxies form a crucial connection between the galaxy disk and the intergalactic medium. Massive stars, HII regions, or dwarf galaxies located in the halos of galaxies are potential tracers of recent accretion and/or outflows of gas, and are additional contributors to the photon field and the gas phase metallicity. We investigate the nature and origin of a star-forming dwarf galaxy candidate located in the halo of the edge-on Virgo galaxy NGC 4634 with a projected distance of 1.4 kpc and a H$α$ star formation rate of $\sim 4.7 \times 10^{-3} \text{M}_\odot \text{yr}^{-1}$ in …
We study the resolved radio-continuum spectral energy distribution of the dwarf irregular galaxy, NGC 1569, on a beam-by-beam basis to isolate and study its spatially resolved radio emission characteristics. Utilizing high quality NRAO Karl G. Jansky Very Large Array (VLA) observations that densely sample the 1--34\,GHz frequency range, we adopt a Bayesian fitting procedure, where we use H$α$ emission that has not been corrected for extinction as a prior, to produce maps of how the separated thermal emission, non-thermal emission and non-thermal spectral index vary across NGC\,1569's main disk…
In the last years, a new generation of large-scale imaging surveys have probed wide field regions around some nearby galaxies at unprecedented low surface brightness regime (~28.0-29.0 mag arcsec^-2). This offers a chance of discovering very faint dwarf satellites by means of visual inspection of these public deep images. We report the first results of a systematic survey of faint dwarf spheroidal galaxies in the vicinity of the bright late-type spiral NGC 253 galaxy by means of a visual inspection of the images taken by the Dark Energy Survey. Three new dwarf galaxies have been discovered in …
We report the discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep imaging with Subaru/Hyper Suprime-Cam. MADCASH J074238+652501-dw lies $\sim$35 kpc in projection from NGC 2403, a dwarf spiral galaxy at $D$$\approx$3.2 Mpc. This new dwarf has $M_{g} = -7.4\pm0.4$ and a half-light radius of $168\pm70$ pc, at the calculated distance of $3.39\pm0.41$ Mpc. The color-magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low luminosity dw…
We report the discovery of NGC 253-dw2, a dwarf spheroidal (dSph) galaxy candidate undergoing tidal disruption around a nearby spiral galaxy, NGC 253 in the Sculptor group: the first such event identified beyond the Local Group. The dwarf was found using small-aperture amateur telescopes, and followed up with Suprime-Cam on the 8 m Subaru Telescope in order to resolve its brightest stars. Using g- and R_c-band photometry, we detect a red giant branch consistent with an old, metal-poor stellar population at a distance of ~ 3.5 Mpc. From the distribution of likely member stars, we infer a highly…
Deep observations of the dwarf elliptical (dE) galaxy NGC 1396 (M$_V = -16.60$, Mass $\sim 4\times10^8$ M$_\odot$), located in the Fornax cluster, have been performed with the VLT/ MUSE spectrograph in the wavelength region from $4750-9350$ Å. In this paper we present a stellar population analysis studying chemical abundances, the star formation history (SFH) and the stellar initial mass function (IMF) as a function of galacto-centric distance. Different, independent ways to analyse the stellar populations result in a luminosity-weighted age of $\sim$ 6 Gyr and a metallicity [Fe/H]$\sim$ $-0.4…
We report the photometric properties of 16 dwarf galaxies, 15 of which are newly identified, in the Western halo of the nearby giant elliptical galaxy NGC5128. All candidates are found at projected distances $\sim\!100\!-\!225$kpc from their giant host, with luminosities $-10.82\!\leq\!M_V/{\rm mag}\!\leq\!-7.42$ and effective radii $4''\!\leq\!r_{\rm eff}\!\leq\!17''$ (or $75\!\leq\!r_{\rm eff}/{\rm pc}\!\leq\!300$ at the distance of NGC5128). We compare to other low-mass dwarf galaxies in the local universe and find them to populate the faint/compact extension of the size-luminosity relation…
It was recently proposed that the globular cluster system of the very low surface-brightness galaxy NGC1052-DF2 is dynamically very cold, leading to the conclusion that this dwarf galaxy has little or no dark matter. Here, we show that a robust statistical measure of the velocity dispersion of the tracer globular clusters implies a mundane velocity dispersion and a poorly constrained mass-to-light ratio. Models that include the possibility that some of the tracers are field contaminants do not yield a more constraining inference. We derive only a weak constraint on the mass-to-light ratio of t…
We have obtained 53 images with the $g$ filter and 19 images with the $i$ filter, each with 600-second exposures of the super metal rich open cluster NGC 6253 with the Gemini-South telescope to create deep images of the cluster to observe the cluster white dwarfs for the first time. We will analyze the white dwarf luminosity function to measure the cluster's white dwarf age, search for any anomalous features (as has been seen in the similarly metal rich cluster NGC 6791), and constrain the initial-final mass relation at high metallicities. We present an update on these observations and our pro…
