scholarly journals The dwarf galaxy population as revealed by ALFALFA

2018 ◽  
Vol 14 (S344) ◽  
pp. 464-467
Author(s):  
Elizabeth A. K. Adams ◽  
Catherine Ball ◽  
John M. Cannon ◽  
Martha P. Haynes ◽  
Alec Hirschauer ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Optical Counterpart ◽  
Star Forming ◽  
Large Numbers ◽  
Low Surface Brightness ◽  
Low Mass ◽  
Galaxy Population ◽  
Optical Surveys

AbstractThe combination of sensitivity and large sky coverage of the ALFALFA HI survey has enabled the detection of difficult to observe low mass galaxies in large numbers, including dwarf galaxies overlooked in optical surveys. Three different, but connected, studies of dwarf galaxies from the ALFALFA survey are of particular interest: SHIELD (Survey of HI in Extremely Low-mass Dwarfs), candidate gas-rich ultra-faint dwarf galaxies, and the (Almost) Dark population. SHIELD is a systematic multiwavelength study of all dwarf galaxies from ALFALFA with MHI < 107.2M⊙ and clear optical counterparts. Candidate gas-rich ultra-faint dwarf galaxies extend the dwarf galaxy population to even lower masses. These galaxies are identified as isolated HI clouds with no discernible optical counterpart but subsequent observations reveal that some are extremely faint, gas-dominated galaxies. Leo P, discovered first as an HI detection, and then found to be an actively star-forming galaxy, bridges the gap between these candidate galaxies and the SHIELD sample. The (Almost) Dark sample consists of galaxies whose optical counterparts are overlooked in current optical surveys but which are clear detections in ALFALFA. This sample includes field gas-rich ultra-diffuse galaxies. Coma P, with a peak surface brightness of only ∼26.4 mag arcsec−2 in g’, demonstrates the sort of extreme low surface brightness galaxy that can be discovered in an HI survey.

scholarly journals Photometric Structure and Star Formation in Blue Compact Dwarf Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 327-327
Author(s):  
P. Papaderos
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Star Formation History ◽  
Host Galaxy ◽  
Star Forming ◽  
Formation History ◽  
Low Surface Brightness ◽  
Low Mass

The star-formation history and chemodynamical evolution of Blue Compact Dwarf (BCD) galaxies are central issues in dwarf galaxy research. In spite of being old in their vast majority, BCDs resemble in many aspects unevolved low-mass galaxies in the early universe. They are gas-rich (Hi mass fraction of typically > 30%) and metal-deficient (7.1 $\la$ 12+log(O/H) $\la$ 8.3) extragalactic systems, undergoing intense star-forming (SF) activity within an underlying low-surface brightness (LSB) host galaxy.

scholarly journals Very gas-rich extremely metal-poor blue void dwarfs

2018 ◽  
Vol 14 (S344) ◽  
pp. 400-403
Author(s):  
Simon A. Pustilnik ◽  
Yulia A. Perepelitsyna ◽  
Alexei Y. Kniazev ◽  
Evgeniya S. Egorova ◽  
Jayaram N. Chengalur
Keyword(s):  
Surface Brightness ◽  
Stellar Population ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
General Context ◽  
Evolutionary Status ◽  
Low Surface Brightness ◽  
Recent Advancement ◽  
Low Metallicity ◽  
Galaxy Population

AbstractHalf-dozen of extreme representatives of void dwarf galaxy population were found in our study of evolutionary status of a hundred galaxies in the nearby Lynx-Cancer void. They are very gas-rich, extremely low-metallicity [7.0 < 12 + log(O/H) < ∼ 7.3] objects, with blue colours of outer parts. The colours indicate the ages of the oldest visible stellar population of one to a few Gyr. They all are intrinsically faint, mostly Low Surface Brightness dwarfs, with MB range of –9.5m to –14m. Thus, their finding is a subject of the severe observational selection. The recent advancement in search for such objects in other nearby voids resulted in doubled their total number. We summarize all available data on this group of unusual void dwarf galaxies and discuss them in the general context of very low metallicity galaxies and their possible formation and evolutionary scenarios.

scholarly journals Abundance of dwarf galaxies around low-mass spiral galaxies in the Local Volume

2020 ◽  
Vol 644 ◽  
pp. A91
Author(s):  
Oliver Müller ◽  
Helmut Jerjen
Keyword(s):  
Surface Brightness ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Current Model ◽  
Host Galaxies ◽  
Local Volume ◽  
Satellite Problem ◽  
Low Mass ◽  
Crucial Test

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 simulations and observations have allowed the study of dwarf galaxies around host galaxies in more detail. Using the Dark Energy Camera we surveyed a 72 deg2 area of the nearby Sculptor group, also encompassing the two low-mass Local Volume galaxies NGC 24 and NGC 45 residing behind the group, to search for as yet undetected dwarf galaxies. Apart from the previously known dwarf galaxies we found only two new candidates down to a 3σ surface brightness detection limit of 27.4 r mag arcsec−2. Both systems are in projection close to NGC 24. However, one of these candidates could be an ultra-diffuse galaxy associated with a background galaxy. We compared the number of known dwarf galaxy candidates around NGC 24, NGC 45, and five other well-studied low-mass spiral galaxies (NGC 1156, NGC 2403, NGC 5023, M 33, and the LMC) with predictions from cosmological simulations, and found that for the stellar-to-halo mass models considered, the observed satellite numbers tend to be on the lower end of the expected range. This could mean either that there is an overprediction of luminous subhalos in ΛCDM or that we are missing some of the satellite members due to observational biases.

scholarly journals Gas-rich LSB Galaxies – Progenitors of Blue Compact Dwarfs?

1999 ◽  
Vol 171 ◽  
pp. 253-260 ◽  
Author(s):  
John J. Salzer ◽  
Stuart A. Norton
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Mass Density ◽  
Central Mass ◽  
Galaxy Distribution ◽  
Low Surface Brightness ◽  
Central Regions ◽  
Lsb Galaxies

AbstractWe analyze deep CCD images of nearby Blue Compact Dwarf (BCD) galaxies in an attempt to understand the nature of the progenitors which are hosting the current burst of star formation. In particular, we ask whether BCDs are hosted by normal or low-surface-brightness dI galaxies. We conclude that BCDs are in fact hosted by gas-rich galaxies which populate the extreme high-central-mass-density end of the dwarf galaxy distribution. Such galaxies are predisposed to having numerous strong bursts of star formation in their central regions. In this picture, BCDs can only occur in the minority of dwarf galaxies, rather than being a common phase experienced by all gas-rich dwarfs.

scholarly journals Wolf-Rayet Populations in Dwarf Galaxies

1991 ◽  
Vol 143 ◽  
pp. 601-612
Author(s):  
Lindsey F. Smith
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
High Surface ◽  
Hii Regions ◽  
Necessary Condition ◽  
Large Numbers ◽  
The Galaxy ◽  
Nearby Galaxies ◽  
High Metallicity

The Wolf-Rayet (WR) feature at 4650 A is observed in about 10% of the dwarf galaxies with high surface brightness knots. The intensity of the feature implies the presence of tens to thousands of WR stars. Hbeta fluxes imply correspondingly large numbers of O stars. The easily observed intensity ratio WRbump/Hbeta is a measure of the WR/O star numbers.The metallicity of dwarf galaxies ranges from Z = Zo/30 to Zo/2, or O/H” = log(O/H)+12 = 7.4 to 8.6. WRbump/Hbeta correlates with O/H′ and O/H″ > 7.9 appears to be a necessary condition for the presence of the WR feature. Giant HII regions in ordinary galaxies extend to higher than solar metallicities and, in extreme cases, WR/O ≈ 1 are implied.The subtypes present in giant HII regions in nearby galaxies appear to be exclusively late type WN and, occasionally, early type WC. Spectra of most BCD galaxies are compatible with a similar population. However, some high metallicity giant HII regions in large galaxies appear to have stronger NIII4640 relative to HeII4686 than occurs in WN subtypes in the Galaxy and the Magellanic Clouds.The data needed for more detailed analysis of dwarf galaxy observations is collected.

scholarly journals A search for LSB dwarf galaxies in various environments

2004 ◽  
Vol 220 ◽  
pp. 341-342
Author(s):  
Sarah Roberts ◽  
Jonathan Davies ◽  
Sabina Sabatini
Keyword(s):  
Dark Matter ◽  
Hierarchical Clustering ◽  
Surface Brightness ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Low Surface Brightness ◽  
Galaxy Populations

The varying dwarf galaxy populations in different environments pose a problem for Cold Dark Matter (CDM) hierarchical clustering models. in this paper we present results from a survey conducted in different environments to search for low surface brightness (LSB) dwarf galaxies.

scholarly journals Galactic Winds in Low-Mass Galaxies

2018 ◽  
Vol 14 (S344) ◽  
pp. 301-304
Author(s):  
Kristen B. W. McQuinn ◽  
Liese van Zee ◽  
Evan D. Skillman
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Critical Role ◽  
Ionized Gas ◽  
Stellar Feedback ◽  
Galactic Winds ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Show Evidence ◽  
Low Mass

AbstractMass-loss via stellar-feedback driven outflows is predicted to play a critical role in the baryon cycle of low-mass galaxies. However, observational constraints on warm winds are limited as outflows are transient, intrinsically low-surface brightness events and, thus, difficult to detect. Here, we search for outflows in a sample of eleven nearby starburst dwarf galaxies which are strong candidates for outflows. Despite deep H? imaging on galaxies, only a fraction of the sample show evidence of winds. The spatial extent of all detected ionized gas is limited and would still be considered part of the ISM by simulations. These new observations indicate that the physical extent of warm phase outflows is modest and most of the mass will be recycled to the galaxy. The sample is part of the panchromatic STARBurst IRegular Dwarf Survey (STARBIRDS) designed to characterize the starburst phenomenon and its impact on the evolution of low-mass galaxies.

scholarly journals The Halos and Environments of Nearby Galaxies (HERON) Survey

2016 ◽  
Vol 11 (S321) ◽  
pp. 186-189 ◽  
Author(s):  
R. Michael Rich ◽  
Noah Brosch ◽  
James Bullock ◽  
Andreas Burkert ◽  
Michelle Collins ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
General Survey ◽  
Tidal Disruption ◽  
Local Volume ◽  
Low Surface Brightness ◽  
Nearby Galaxies

AbstractWe have used dedicated 0.7m telescopes in California and Israel to image the halos of ~ 200 galaxies in the Local Volume to 29 mag/sq arcsec, the sample mainly drawn from the 2MASS Large Galaxy Atlas (LGA). We supplement the LGA sample with dwarf galaxies and more distant giant ellipticals. Low surface brightness halos exceeding 50 kpc in diameter are found only in galaxies more luminous than L*, and classic interaction signatures are relatively infrequent. Halo diameter is correlated with total galaxy luminosity. Extended low surface brightness halos are present even in galaxies as faint as MV = - 18. Edge-on galaxies with boxy bulges tend to lack extended spheroidal halos, while those with large classical bulges exhibit extended round halos, supporting the notions that boxy or barlike bulges originate from disks. Most face-on spiral galaxies present features that appear to be irregular extensions of spiral arms, although rare cases show smooth boundaries with no sign of star formation. Although we serendipitously discovered a dwarf galaxy undergoing tidal disruption in the halo of NGC 4449, we found no comparable examples in our general survey. A search for similar examples in the Local Volume identified hcc087, a tidally disrupting dwarf galaxy in the Hercules Cluster, but we do not confirm an anomalously large half-light radius reported for the dwarf VCC 1661.

Sign in / Sign up

Export Citation Format

Share Document