scholarly journals A Gaseous Group with Unusual Remote Star Formation

2011 ◽  
Vol 28 (3) ◽  
pp. 271-279 ◽  
Author(s):  
N. Santiago-Figueroa ◽  
M. E. Putman ◽  
J. Werk ◽  
G. R. Meurer ◽  
E. Ryan-Weber
Keyword(s):  
Star Formation ◽  
Spiral Galaxy ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Spiral Arms ◽  
Gaseous Disk ◽  
Ram Pressure ◽  
The Galaxy ◽  
Galaxy Center ◽  
Region 10

AbstractWe present VLA 21-cm observations of the spiral galaxy ESO 481-G017 to determine the nature of remote star formation traced by an Hii region found 43 kpc and ∼800 km s−1 from the galaxy center (in projection). ESO 481-G017 is found to have a 120 kpc Hi disk with a mass of 1.2 × 1010M⊙ and UV GALEX images reveal spiral arms extending into the gaseous disk. Two dwarf galaxies with Hi masses close to 108M⊙ are detected at distances of ∼200 kpc from ESO 481-G017 and a Hi cloud with a mass of 6 × 107M⊙ is found near the position and velocity of the remote Hii region. The Hii region is somewhat offset from the Hi cloud spatially and there is no link to ESO 481-G017 or the dwarf galaxies. We consider several scenarios for the origin of the cloud and Hii region and find the most likely is a dwarf galaxy that is undergoing ram pressure stripping. The Hi mass of the cloud and Hi luminosity of the Hii region (1038.1 erg s−1) are consistent with dwarf galaxy properties, and the stripping can trigger the star formation as well as push the gas away from the stars.

scholarly journals Dissecting star formation in the “Atoms-for-Peace” galaxy

2018 ◽  
Vol 614 ◽  
pp. A130 ◽  
Author(s):  
K. George ◽  
P Joseph ◽  
P. Côté ◽  
S. K. Ghosh ◽  
J. B. Hutchings ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Initial Conditions ◽  
Dwarf Galaxy ◽  
Main Body ◽  
Star Forming ◽  
Uv Imaging ◽  
Star Forming Regions ◽  
The Galaxy ◽  
Tidal Tails

Context. The tidal tails of post-merger galaxies exhibit ongoing star formation far from their disks. The study of such systems can be useful for our understanding of gas condensation in diverse environments. Aims. The ongoing star formation in the tidal tails of post-merger galaxies can be directly studied from ultraviolet (UV) imaging observations. Methods. The post merger galaxy NGC7252 (“Atoms-for-Peace” galaxy) is observed with the Astrosat UV imaging telescope (UVIT) in broadband NUV and FUV filters to isolate the star-forming regions in the tidal tails and study the spatial variation in star formation rates. Results. Based on ultraviolet imaging observations, we discuss star-forming regions of ages <200 Myr in the tidal tails. We measure star formation rates in these regions and in the main body of the galaxy. The integrated star formation rate (SFR) of NGC7252 (i.e., that in the galaxy and tidal tails combined) without correcting for extinction is found to be 0.81 ± 0.01 M⊙ yr−1. We show that the integrated SFR can change by an order of magnitude if the extinction correction used in SFR derived from other proxies are taken into consideration. The star formation rates in the associated tidal dwarf galaxies (NGC7252E, SFR = 0.02 M⊙ yr−1 and NGC7252NW, SFR = 0.03 M⊙ yr−1) are typical of dwarf galaxies in the local Universe. The spatial resolution of the UV images reveals a gradient in star formation within the tidal dwarf galaxy. The star formation rates show a dependence on the distance from the centre of the galaxy. This can be due to the different initial conditions responsible for the triggering of star formation in the gas reservoir that was expelled during the recent merger in NGC7252.

scholarly journals Evolution of Dwarf Galaxies in High Pressure Environments

1999 ◽  
Vol 186 ◽  
pp. 483-483
Author(s):  
I. Murakami ◽  
A. Babul
Keyword(s):  
High Pressure ◽  
Star Formation ◽  
Mass Shell ◽  
Dwarf Galaxies ◽  
External Medium ◽  
External Pressure ◽  
Thermal Pressure ◽  
Ram Pressure ◽  
The Galaxy ◽  
Transient Feature

We use 2D hydrodynamical calculations to examine the effect of the external medium on evolution of supernova-driven outflows from dwarf galaxies. Babul & Rees (1992) have suggested a high external pressure may be able to prevent the outflows from escaping beyond the galaxy and that this material, as it cools and falls back into the galaxy, would serve as fuel for a second epoch of star formation. When thermal pressure is dominant, such evolution of the outflows is seen in our simulations and the gas falls back into the galaxy. Babul & Rees, however, did not take into account the possibility that in high pressure environments such as clusters, galaxies are moving and therefore, subject to ram pressure. In our simulations, we find that ram pressure causes the mass shell associated with the outflow to fragment into clumps. These clumps remain in the vicinity of the galaxy for a few tens of million years before being swept away. The distribution of the clouds gives the galaxy in our simulations a characteristic “head-tail” appearance. If the clouds experience star formation during this epoch, we would expect that the light distribution would also show this “head-tail” feature. The tail-like structure is a transient feature that will eventually disappear. We speculate that galaxies observed by Dickinson (1996) in the z = 1.15 cluster around 3C324 are such galaxies.

scholarly journals Zoom-in cosmological hydrodynamical simulation of a star-forming barred, spiral galaxy at redshift z = 2

2019 ◽  
Vol 488 (4) ◽  
pp. 4674-4689 ◽  
Author(s):  
Fiorenzo Vincenzo ◽  
Chiaki Kobayashi ◽  
Tiantian Yuan
Keyword(s):  
Star Formation ◽  
Angular Velocity ◽  
Spiral Galaxy ◽  
Stellar Populations ◽  
Spiral Arms ◽  
Star Forming ◽  
Thin Disc ◽  
The Galaxy ◽  
Barred Spiral Galaxy ◽  
Zoom In

ABSTRACTWe present gas and stellar kinematics of a high-resolution zoom-in cosmological chemodynamical simulation, which fortuitously captures the formation and evolution of a star-forming barred spiral galaxy, from redshift z ∼ 3 to z ∼ 2 at the peak of the cosmic star formation rate. The galaxy disc grows by accreting gas and substructures from the environment. The spiral pattern becomes fully organized when the gas settles from a thick (with vertical dispersion σv > 50 km s−1) to a thin (σv ∼ 25 km s−1) disc component in less than 1 Gyr. Our simulated disc galaxy also has a central X-shaped bar, the seed of which formed by the assembly of dense gas-rich clumps by z ∼ 3. The star formation activity in the galaxy mainly happens in the bulge and in several clumps along the spiral arms at all redshifts, with the clumps increasing in number and size as the simulation approaches z = 2. We find that stellar populations with decreasing age are concentrated towards lower galactic latitudes, being more supported by rotation, and having also lower velocity dispersion; furthermore, the stellar populations on the thin disc are the youngest and have the highest average metallicities. The pattern of the spiral arms rotates like a solid body with a constant angular velocity as a function of radius, which is much lower than the angular velocity of the stars and gas on the thin disc; moreover, the angular velocity of the spiral arms steadily increases as a function of time, always keeping its radial profile constant. The origin of our spiral arms is also discussed.

scholarly journals When the Largest Spiral is Formed

2012 ◽  
Vol 8 (S292) ◽  
pp. 328-328
Author(s):  
Rafael T. Eufrasio ◽  
Duília F. de Mello ◽  
Fernanda Urrutia-Viscarra ◽  
Claudia Mendes de Oliveira ◽  
Eli Dwek
Keyword(s):  
Spatial Distribution ◽  
Star Formation ◽  
Spatial Correlation ◽  
Spiral Galaxy ◽  
Stellar Population ◽  
Spiral Galaxies ◽  
Dwarf Galaxy ◽  
Archival Data ◽  
Physical Size ◽  
The Galaxy

AbstractWe used UV-to-IR archival data to investigate the nature of the giant spiral galaxy, NGC 6872, 65 Mpc away. It belongs to the southern Pavo group and is interacting with a small lenticular galaxy, IC4970. GALEX UV images show a very large part of the galaxy not seen before, making it one of the largest spiral galaxies known, with a physical size greater than 150 kpc. The SED of 17 regions (10 kpc of diameter) across the two arms show a remarkable spatial distribution, as if they were mirror images with respect to their stellar population. However, the last 40 kpc of the northeastern arm are much bluer than any other region of the southwestern one. There is a strong spatial correlation between the NUV luminosity and the distance to the nucleus. The UV data supports the scenario of an interaction at 130 Myr which triggered star formation all over the disk of NGC 6872. The tip of the northeastern arm resembles a tidal dwarf galaxy in the process of formation.

scholarly journals Spiral morphology in an intensely star-forming disk galaxy more than 12 billion years ago

Science ◽  
2021 ◽  
pp. eabe9680
Author(s):  
Takafumi Tsukui ◽  
Satoru Iguchi
Keyword(s):  
Big Bang ◽  
Compact Structure ◽  
Spiral Arms ◽  
Star Forming ◽  
Gas Kinematics ◽  
Internal Structures ◽  
The Galaxy ◽  
Galaxy Center ◽  
The Big Bang ◽  
Tidal Tails

Spiral galaxies have distinct internal structures including a stellar bulge, disk and spiral arms. It is unknown when in cosmic history these structures formed. We analyze observations of BRI 1335–0417, an intensely star-forming galaxy in the distant Universe, at redshift 4.41. The [C ii] gas kinematics show a steep velocity rise near the galaxy center and have a two-armed spiral morphology, which extends from about 2 to 5 kiloparsecs in radius. We interpret these features as due to a central compact structure, such as a bulge; a rotating gas disk; and either spiral arms or tidal tails. These features had formed within 1.4 billion years after the Big Bang, long before the peak of cosmic star formation.

scholarly journals NIHAO – XXV. Convergence in the cusp-core transformation of cold dark matter haloes at high star formation thresholds

2020 ◽  
Vol 499 (2) ◽  
pp. 2648-2661
Author(s):  
Aaron A Dutton ◽  
Tobias Buck ◽  
Andrea V Macciò ◽  
Keri L Dixon ◽  
Marvin Blank ◽  
...  
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Good Description ◽  
Good Match ◽  
Virial Mass ◽  
Density Threshold

ABSTRACT We use cosmological hydrodynamical galaxy formation simulations from the NIHAO project to investigate the response of cold dark matter (CDM) haloes to baryonic processes. Previous work has shown that the halo response is primarily a function of the ratio between galaxy stellar mass and total virial mass, and the density threshold above which gas is eligible to form stars, n[cm−3]. At low n all simulations in the literature agree that dwarf galaxy haloes are cuspy, but at high n ≳ 100 there is no consensus. We trace halo contraction in dwarf galaxies with n ≳ 100 reported in some previous simulations to insufficient spatial resolution. Provided the adopted star formation threshold is appropriate for the resolution of the simulation, we show that the halo response is remarkably stable for n ≳ 5, up to the highest star formation threshold that we test, n = 500. This free parameter can be calibrated using the observed clustering of young stars. Simulations with low thresholds n ≤ 1 predict clustering that is too weak, while simulations with high star formation thresholds n ≳ 5, are consistent with the observed clustering. Finally, we test the CDM predictions against the circular velocities of nearby dwarf galaxies. Low thresholds predict velocities that are too high, while simulations with n ∼ 10 provide a good match to the observations. We thus conclude that the CDM model provides a good description of the structure of galaxies on kpc scales provided the effects of baryons are properly captured.

scholarly journals Pushing back the limits: detailed properties of dwarf galaxies in a ΛCDM universe

2018 ◽  
Vol 616 ◽  
pp. A96 ◽  
Author(s):  
Yves Revaz ◽  
Pascale Jablonka
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Mass Scale ◽  
Dwarf Spheroidal Galaxies ◽  
The Galaxy ◽  
Dynamical Simulations ◽  
Ursa Minor ◽  
Stellar Properties ◽  
Star Formation Histories

We present the results of a set of high-resolution chemo-dynamical simulations of dwarf galaxies in a ΛCDM cosmology. Out of an original (3.4 Mpc/h)3 cosmological box, a sample of 27 systems are re-simulated from z = 70 to z = 0 using a zoom-in technique. Gas and stellar properties are confronted to the observations in the greatest details: in addition to the galaxy global properties, we investigated the model galaxy velocity dispersion profiles, half-light radii, star formation histories, stellar metallicity distributions, and [Mg/Fe] abundance ratios. The formation and sustainability of the metallicity gradients and kinematically distinct stellar populations are also tackled. We show how the properties of six Local Group dwarf galaxies, NGC 6622, Andromeda II, Sculptor, Sextans, Ursa Minor and Draco are reproduced, and how they pertain to three main galaxy build-up modes. Our results indicate that the interaction with a massive central galaxy could be needed for a handful of Local Group dwarf spheroidal galaxies only, the vast majority of the systems and their variety of star formation histories arising naturally from a ΛCDM framework. We find that models fitting well the local Group dwarf galaxies are embedded in dark haloes of mass between 5 × 108 to a few 109 M⊙, without any missing satellite problem. We confirm the failure of the abundance matching approach at the mass scale of dwarf galaxies. Some of the observed faint however gas-rich galaxies with residual star formation, such as Leo T and Leo P, remain challenging. They point out the need of a better understanding of the UV-background heating.

scholarly journals Pinning down the ram-pressure-induced halt of star formation in the Virgo cluster spiral galaxy NGC 4388

2010 ◽  
Vol 514 ◽  
pp. A33 ◽  
Author(s):  
C. Pappalardo ◽  
A. Lançon ◽  
B. Vollmer ◽  
P. Ocvirk ◽  
S. Boissier ◽  
...  
Keyword(s):  
Star Formation ◽  
Spiral Galaxy ◽  
Virgo Cluster ◽  
Ram Pressure

scholarly journals SDSS J114818.18-013823.7: Forming Compact Dwarf Galaxy through the Dwarf-Dwarf Merger

2021 ◽  
Vol 7 (2) ◽  
pp. 49-57
Author(s):  
D. N. Chhatkuli ◽  
S. Paudel ◽  
A. K. Gautam ◽  
B. Aryal
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Absolute Magnitude ◽  
Spectroscopic Properties ◽  
Normal Galaxies ◽  
Star Formation Activity ◽  
The Galaxy

We studied the spectroscopic properties of the low redshift (z = 0.0130) interacting dwarf galaxy SDSS J114818.18-013823.7. It is a compact galaxy of half-light radius 521 parsec. It’s r-band absolute magnitude is -16.71 mag. Using a publicly available optical spectrum from the Sloan Sky Survey data archive, we calculated star-formation rate, emission line metallicity, and dust extinction of the galaxy. Star formation rate (SFR) due to Hα is found to be 0.118 Mʘ year-1 after extinction correction. The emission-line metallicity, 12+log(O/H), is 8.13 dex. Placing these values in the scaling relation of normal galaxies, we find that SDSS J114818.18-013823.7 is a significant outlier from both size-magnitude relation and SFR-B-band absolute relation. Although SDSS J114818.18-013823.7 possess enhance rate of star-formation, the current star-formation activity can persist several Giga years in the future at the current place and it remains compact.

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.

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