scholarly journals Rotating Halos and Heavy Disks: The Case of NGC 2915

2004 ◽  
Vol 220 ◽  
pp. 293-298
Author(s):  
Frédéric S. Masset ◽  
Martin Bureau
Keyword(s):  
Surface Brightness ◽  
Spiral Structure ◽  
Dwarf Galaxy ◽  
Neutral Hydrogen ◽  
Dark Halo ◽  
Pattern Frequency ◽  
Spin Parameter ◽  
Low Surface Brightness ◽  
Hydrodynamical Simulations ◽  
Blue Compact Dwarf Galaxy

NGC 2915 is a blue compact dwarf galaxy embedded in an extended, low surface brightness HI disk with a bar and two-armed spiral structure. Common mechanisms are unable to explain those patterns and disk dark matter or a rotating triaxial dark halo were proposed as alternatives. Hydrodynamical simulations were run for each case and compared to observations using customized column density and kinematic constraints. the spiral structure can be accounted for by an unseen bar or triaxial halo, but the large bar mass or halo pattern frequency required make it unlikely that the spiral is driven by an external perturber. in particular, the spin parameter lambda is much higher than predicted by current CDM structure formation scenarios. Massive disk models show that when the gas surface density is scaled up by a factor of about 10, the disk develops a spiral structure matching the observed one in perturbed density as well as velocity. This suggests that the disk of NGC 2915 contains much more mass than is visible, tightly linked to the neutral hydrogen. A classic (quasi-)spherical halo is nevertheless still required, as increasing the disk mass further to fit the circular velocity curve would make the disk violently unstable

Rotating Halos and Heavy Disks: the Case of NGC 2915

2004 ◽  
Vol 217 ◽  
pp. 172-173
Author(s):  
Frédéric S. Masset ◽  
Martin Bureau
Keyword(s):  
Surface Brightness ◽  
Spiral Structure ◽  
Dwarf Galaxy ◽  
Neutral Hydrogen ◽  
Dark Halo ◽  
Pattern Frequency ◽  
Spin Parameter ◽  
Low Surface Brightness ◽  
Hydrodynamical Simulations ◽  
Blue Compact Dwarf Galaxy

NGC 2915 is a blue compact dwarf galaxy embedded in an extended, low surface brightness HI disk with a bar and two-armed spiral structure. Common mechanisms are unable to explain those patterns and disk dark matter or a rotating triaxial dark halo were proposed as alternatives. Hydrodynamical simulations were run for each case and compared to observations using customized column density and kinematic constraints. The spiral structure can be accounted for by an unseen bar or triaxial halo, but the large bar mass or halo pattern frequency required make it unlikely that the spiral is driven by an external perturber. In particular, the spin parameter lambda is much higher than predicted by current CDM structure formation scenarios. Massive disk models show that when the gas surface density is scaled up by a factor of about 10, the disk develops a spiral structure matching the observed one in perturbed density as well as velocity. This suggests that the disk of NGC 2915 contains much more mass than is visible tightly linked to the neutral hydrogen. A classic (quasi-)spherical halo is nevertheless still required, as increasing the disk mass further to fit the circular velocity curve would make the disk violently unstable

scholarly journals Nearby Blue Compact Dwarf Galaxy NGC 6789

1999 ◽  
Vol 192 ◽  
pp. 253-258
Author(s):  
I. Drozdovsky ◽  
N. Tikhonov
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxy ◽  
High Surface ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Metal Abundance ◽  
The Mean ◽  
Red Giant ◽  
Halo Population ◽  
Blue Compact Dwarf Galaxy

We present the results of a detailed BVRI and Hα study of the isolated nearby blue compact dwarf (BCD) galaxy NGC 6789. Judging from the literature the observed galaxy has not yet been resolved into stars up to now. On CCD frames obtained with 6m BTA telescope and 2.5m Nordic telescope the galaxy is well resolved. Its colour-magnitude diagram confirms the two component (core-halo) galaxy morphology, which consists of two stellar populations distinct in structure and colour: an inner high surface-brightness young population within 150 pc from the center of the galaxy, and a relatively low surface-brightness intermediate-age population extending out to at least 600 pc. The distance to the galaxy, estimated from the tip of the red giant branch (TRGB) is 2.1 Mpc which places NGC 6789 close to the Local Group. From the mean colour of the RGB, the mean metal abundance of the halo population is estimated as [Fe/H] ≃ −1 dex.

scholarly journals The blue compact dwarf galaxy I Zw 18: A comparative study of its low-surface-brightness component

2002 ◽  
Vol 393 (2) ◽  
pp. 461-483 ◽  
Author(s):  
P. Papaderos ◽  
Y. I. Izotov ◽  
T. X. Thuan ◽  
K. G. Noeske ◽  
K. J. Fricke ◽  
...  
Keyword(s):  
Comparative Study ◽  
Surface Brightness ◽  
Dwarf Galaxy ◽  
Low Surface Brightness ◽  
Blue Compact Dwarf Galaxy

Kinematics and Neutral Hydrogen Properties of the Giant Low Surface Brightness Galaxy UGC 2936

1999 ◽  
Vol 118 (2) ◽  
pp. 765-776 ◽  
Author(s):  
T. E. Pickering ◽  
J. H. van Gorkom ◽  
C. D. Impey ◽  
A. C. Quillen
Keyword(s):  
Surface Brightness ◽  
Neutral Hydrogen ◽  
Low Surface Brightness

scholarly journals Delayed Stellar Mass Assembly in the Low Surface Brightness Dwarf Galaxy KDG 215

2018 ◽  
Vol 864 (1) ◽  
pp. L14 ◽  
Author(s):  
John M. Cannon ◽  
Zili Shen ◽  
Kristen B. W. McQuinn ◽  
Joshua Bartz ◽  
Lilly Bralts-Kelly ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxy ◽  
Stellar Mass ◽  
Low Surface Brightness ◽  
Mass Assembly

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.

The Hi Neighborhoods Around STARBIRDS

2018 ◽  
Vol 14 (S344) ◽  
pp. 280-282
Author(s):  
Megan C. Johnson ◽  
Kristen B. W. McQuinn ◽  
John Cannon ◽  
Charlotte Martinkus ◽  
Evan Skillman ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Neutral Hydrogen ◽  
Tidal Interactions ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Green Bank Telescope ◽  
Intense Star Formation

AbstractStarbursts are finite periods of intense star formation (SF) that can dramatically impact the evolutionary state of a galaxy. Recent results suggest that starbursts in dwarf galaxies last longer and are distributed over more of the galaxy than previously thought, with star formation efficiencies (SFEs) comparable to spiral galaxies, much higher than those typical of non-bursting dwarfs. This difference might be explainable if the starburst mode is externally triggered by gravitational interactions with other nearby systems. We present new, sensitive neutral hydrogen observations of 18 starburst dwarf galaxies, which are part of the STARburst IRregular Dwarf Survey (STARBIRDS) and each were mapped with the Green Bank Telescope (GBT) and/or Parkes Telescope in order to study the low surface brightness gas distributions, a common tracer for tidal interactions.

scholarly journals VLA HI Imaging of the Low Surface Brightness Dwarf Galaxy DDO 47

1999 ◽  
Vol 171 ◽  
pp. 224-227 ◽  
Author(s):  
F. Walter ◽  
E. Brinks
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxy ◽  
Dynamical Analysis ◽  
Stellar Winds ◽  
Mass Model ◽  
Dynamical Mass ◽  
Systemic Velocity ◽  
Low Surface Brightness ◽  
Simple Mass ◽  
Hi Shells

AbstractWe present high resolution VLA-observations of the nearby Low Surface Brightness Dwarf Galaxy DDO 47. This object shows many hole-like structures in its neutral interstellar medium. The majority of the detected H I-shells are found to be expanding. Their origin is therefore believed to be due to stellar winds of the most massive stars and their subsequent supernova (SN type II) explosions within regions of recent star formation (SF). Current SF in DDO 47 is predominantly present on the rims of the HI-shells suggesting propagating SF. At a projected distance of 20 kpc (adopting a distance to DDO 47 of 4 Mpc), a companion galaxy was detected at almost the same systemic velocity (DDO 47 B). A search for an optical identification suggests that CGCG 087-033 is the optical counterpart of the companion. A preliminary dynamical analysis based on DDO 47’s rotation curve yields that it is dark matter dominated (about 80% of its dynamical mass is in some non-visible form). A simple mass model suggests that DDO 47 is one of the ‘thickest’ dwarf galaxies studied so far.

scholarly journals The Low Surface Brightness Galaxy HIPASS1126-72

1999 ◽  
Vol 171 ◽  
pp. 204-206
Author(s):  
Virginia Kilborn ◽  
Erwin de Blok ◽  
Lister Staveley-Smith ◽  
Rachel Webster
Keyword(s):  
Surface Brightness ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Low Surface Brightness ◽  
The Galaxy

AbstractThe low surface brightness galaxy HIPASS1126-72 was detected in the HI Parkes All Sky Survey (HIPASS). The galaxy was previously listed in the Southern Galaxy Catalogue under the name SGC1124.87221. This galaxy represents a class of galaxies that we will readily detect in the HIPASS survey, which have low surface brightness in the optical, but are easily detectable in neutral hydrogen.

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