scholarly journals Study of the Milky Way's hot coronal gas with its dwarf galaxies

2015 ◽  
Vol 11 (S317) ◽  
pp. 340-341
Author(s):  
Stefano Pasetto ◽  
Mark Cropper ◽  
Yutaka Fujita ◽  
Cesare Chiosi ◽  
Eva K. Grebel
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Analytical Framework ◽  
Host Galaxy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Tidal Forces ◽  
Diffuse Halo ◽  
Analytical Criterion

AbstractA large amount (5 × 1010 M⊙) of hot gas is thought to exist in an extended (≈ 200 kpc) hot diffuse halo around the Milky Way. We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation of this gravitationally bound systems in this external environment. Ram pressure, Kelvin-Helmholtz and Rayleigh- Taylor instabilities, and tidal forces are accounted for separately in an analytical framework and compared in their role in influencing the star forming regions. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment, useful in observational applications as well as theoretical interpretations of numerical results. We consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams (CMDs) of the orbiting system, thus investigating the detectability limits and relevance of these different effects for future observational projects. The theoretical framework developed has direct applications to the cases of our MW system as well as dwarf galaxies in galaxy clusters or any primordial gas-rich star cluster of stars orbiting within its host galaxy.

scholarly journals Environmental effects on stellar populations of star clusters and dwarf galaxies

2015 ◽  
Vol 12 (S316) ◽  
pp. 171-172
Author(s):  
Stefano Pasetto ◽  
Mark Cropper ◽  
Yutaka Fujita ◽  
Cesare Chiosi ◽  
Eva K. Grebel
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Star Clusters ◽  
Analytical Framework ◽  
Host Galaxy ◽  
Rich Cluster ◽  
Star Forming ◽  
Star Forming Regions ◽  
Tidal Forces

AbstractWe investigate the competitive role of the different dissipative phenomena acting on the onset of star formation of gravitationally bound systems in an external environment. Ram pressure, Kelvin-Helmholtz and Rayleigh-Taylor instabilities, and tidal forces are accounted for separately in an analytical framework and compared in their role in influencing the star forming regions. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment. We consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams (CMDs) of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance. The developed theoretical framework has direct applications to the cases of massive star clusters, dwarf galaxies in galaxy clusters and dwarf galaxies orbiting our Milky Way system, as well as any primordial gas-rich cluster of stars orbiting within its host galaxy.

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 Blowin' in the wind: both ‘negative’ and ‘positive’ feedback in an outflowing quasar at z∼1.6

2014 ◽  
Vol 10 (S309) ◽  
pp. 239-242
Author(s):  
Giovanni Cresci
Keyword(s):  
Star Formation ◽  
Positive Feedback ◽  
Near Infrared ◽  
Host Galaxy ◽  
Narrow Component ◽  
Massive Galaxies ◽  
Star Forming ◽  
Star Forming Regions ◽  
Integral Field Spectroscopy ◽  
Outflow Rate

AbstractQuasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation, preventing massive galaxies to over-grow and producing the red colors of ellipticals. On the other hand, some models are also requiring ‘positive’ AGN feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively-driven winds are available. We present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z=1.59 QSO, in which we clearly resolve a fast (1500 km/s) and extended (up to 13 kpc from the black hole) outflow in the [OIII] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of Hα emission and the rest frame U band flux show that the outflow position lies in the center of an empty cavity surrounded by star forming regions on its edge. The outflow is therefore removing the gas from the host galaxy (‘negative feedback’), but also triggering star formation by outflow induced pressure at the edges (‘positive feedback’). XID2028 represents the first example of a host galaxy showing both types of feedback simultaneously at work.

scholarly journals Supernova progenitor mass constraints through spatial correlations with host galaxy star formation

2013 ◽  
Vol 9 (S296) ◽  
pp. 121-125
Author(s):  
Joseph P Anderson
Keyword(s):  
Star Formation ◽  
Host Galaxy ◽  
Surprising Result ◽  
Spatial Correlations ◽  
Host Galaxies ◽  
Star Forming ◽  
Circumstellar Material ◽  
Star Forming Regions ◽  
Type Ia ◽  
Degree Of Association

AbstractWe present progenitor mass constraints on supernovae (SNe), from correlations with star-forming regions within host galaxies. Through a pixel statistics method used together with H-alpha imaging of host galaxies, we present a progenitor mass sequence running from supernovae type Ia (SNIa) arising from the lowest, through SNII, SNIb, and finally SNIc arising from the highest mass progenitors, implied from an increasing association of their explosion sites with star formation (SF). We also present constraints on the various core-collapse (CC) sub-types, finding the perhaps surprising result that SNIIn show the lowest degree of association with SF of any CC type, implying relatively low-mass progenitors. Finally, we compare the SNIIn environment distribution to that of SNIa, posing the provocative question that additional SNIIn may be linked to the SNIa phenomenon where the latter's spectra are hidden beneath that of circumstellar material (CSM) interaction.

scholarly journals The host galaxy of GRB 980425/SN1998bw: a collisional ring galaxy

2019 ◽  
Vol 485 (4) ◽  
pp. 5411-5422 ◽  
Author(s):  
M Arabsalmani ◽  
S Roychowdhury ◽  
T K Starkenburg ◽  
L Christensen ◽  
E Le Floc’h ◽  
...  
Keyword(s):  
Star Formation ◽  
Gamma Ray ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Host Galaxy ◽  
Gamma Ray Burst ◽  
Star Forming ◽  
Star Forming Regions ◽  
Very Large Telescope ◽  
Companion Galaxy

ABSTRACT We report Giant Metrewave Radio Telescope (GMRT), Very Large Telescope (VLT), and Spitzer Space Telescope observations of ESO 184−G82, the host galaxy of GRB 980425/SN 1998bw, that yield evidence of a companion dwarf galaxy at a projected distance of 13 kpc. The companion, hereafter GALJ193510-524947, is a gas-rich, star-forming galaxy with a star formation rate of $\rm 0.004\, M_{\odot }\, yr^{-1}$, a gas mass of $10^{7.1\pm 0.1} \, \mathrm{M}_{\odot}$, and a stellar mass of $10^{7.0\pm 0.3} \, \mathrm{M}_{\odot}$. The interaction between ESO 184−G82 and GALJ193510-524947 is evident from the extended gaseous structure between the two galaxies in the GMRT H i 21 cm map. We find a ring of high column density H i gas, passing through the actively star-forming regions of ESO 184−G82 and the GRB location. This ring lends support to the picture in which ESO 184−G82 is interacting with GALJ193510-524947. The massive stars in GALJ193510-524947 have similar ages to those in star-forming regions in ESO 184−G82, also suggesting that the interaction may have triggered star formation in both galaxies. The gas and star formation properties of ESO 184−G82 favour a head-on collision with GALJ193510-524947 rather than a classical tidal interaction. We perform state-of-the-art simulations of dwarf–dwarf mergers and confirm that the observed properties of ESO 184−G82 can be reproduced by collision with a small companion galaxy. This is a very clear case of interaction in a gamma-ray burst host galaxy and of interaction-driven star formation giving rise to a gamma-ray burst in a dense environment.

scholarly journals Radio jets from AGNs in dwarf galaxies in the COSMOS survey: mechanical feedback out to redshift ∼3.4

2019 ◽  
Vol 488 (1) ◽  
pp. 685-695 ◽  
Author(s):  
M Mezcua ◽  
H Suh ◽  
F Civano
Keyword(s):  
Star Formation ◽  
Radio Emission ◽  
Dwarf Galaxies ◽  
Spectral Energy Distribution ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Strong Impact ◽  
Star Forming ◽  
Radio Jets ◽  
Mechanical Feedback

Abstract Dwarf galaxies are thought to host the remnants of the early Universe seed black holes (BHs) and to be dominated by supernova feedback. However, recent studies suggest that BH feedback could also strongly impact their growth. We report the discovery of 35 dwarf galaxies hosting radio active galactic nucleus (AGN) out to redshift ∼3.4, which constitutes the highest redshift sample of AGNs in dwarf galaxies. The galaxies are drawn from the VLA-COSMOS 3 GHz Large Project and all are star forming. After removing the contribution from star formation to the radio emission, we find a range of AGN radio luminosities of $L^\mathrm{AGN}_\mathrm{1.4\, GHz} \sim 10^{37}$–1040 erg s−1. The bolometric luminosities derived from the fit of their spectral energy distribution are ≳1042 erg s−1, in agreement with the presence of AGNs in these dwarf galaxies. The 3 GHz radio emission of most of the sources is compact and the jet powers range from Qjet ∼ 1042 to 1044 erg s−1. These values, as well as the finding of jet efficiencies ≥10  per cent in more than 50 per cent of the sample, indicate that dwarf galaxies can host radio jets as powerful as those of massive radio galaxies whose jet mechanical feedback can strongly affect the formation of stars in the host galaxy. We conclude that AGN feedback can also have a very strong impact on dwarf galaxies, either triggering or hampering star formation and possibly the material available for BH growth. This implies that those low-mass AGNs hosted in dwarf galaxies might not be the untouched relics of the early seed BHs, which has important implications for seed BH formation models.

Gamma-ray burst models

2007 ◽  
Vol 365 (1854) ◽  
pp. 1277-1280 ◽  
Author(s):  
Andrew King
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Neutron Star ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Close Binaries ◽  
Host Galaxy ◽  
Star Forming ◽  
Star Forming Regions ◽  
Long Duration

I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts.

scholarly journals Satellite dwarf galaxies: stripped but not quenched

2019 ◽  
Vol 624 ◽  
pp. A11 ◽  
Author(s):  
Loic Hausammann ◽  
Yves Revaz ◽  
Pascale Jablonka
Keyword(s):  
Milky Way ◽  
Dwarf Galaxies ◽  
Direct Consequence ◽  
Host Galaxy ◽  
Star Forming ◽  
Tidal Forces ◽  
Ram Pressure ◽  
Halo Gas ◽  
The Impact ◽  
Cold Gas

In the Local Group, quenched gas-poor dwarfs galaxies are most often found close to the Milky Way and Andromeda, while star forming gas-rich ones are located at greater distances. This so-called morphology-density relation is often interpreted as the consequence of the ram pressure stripping of the satellites during their interaction with the Milky Way hot halo gas. While this process has been often investigated, self-consistent high resolution simulations were still missing. In this study, we have analysed the impact of both the ram pressure and tidal forces induced by a host galaxy on dwarf models as realistic as possible emerging from cosmological simulations. These models were re-simulated using both a wind tunnel and a moving box technique. The secular mass growth of the central host galaxy, as well as the gas density and temperature profiles of its hot halo have been taken into account. We show that while ram pressure is very efficient at stripping the hot and diffuse gas of the dwarf galaxies, it can remove their cold gas (T <  103 K) only in very specific conditions. Depending on the infall time of the satellites relatively to the build-up stage of the massive host, star formation can thus be prolonged instead of being quenched. This is the direct consequence of the clumpy nature of the cold gas and the thermal pressure the hot gas exerts onto it. We discuss the possibility that the variety in satellite populations among Milky Way-like galaxies reflects their accretion histories.

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 VLT/MUSE and ATCA Observations of the Host Galaxy of the Short GRB 080905A at z = 0.122

2021 ◽  
Vol 923 (1) ◽  
pp. 38
Author(s):  
A. M. Nicuesa Guelbenzu ◽  
S. Klose ◽  
P. Schady ◽  
K. Belczynski ◽  
D. H. Hartmann ◽  
...  
Keyword(s):  
Star Formation ◽  
Line Emission ◽  
Large Magellanic Cloud ◽  
Radio Continuum ◽  
Host Galaxy ◽  
Strong Line ◽  
Host Galaxies ◽  
Star Forming ◽  
Star Forming Regions ◽  
Field Unit

Abstract Short-GRB progenitors could come in various flavors, depending on the nature of the merging compact stellar objects (including a stellar-mass black hole or not) or depending on their ages (millions or billions of years). At a redshift of z = 0.122, the nearly face-on spiral host of the short GRB 080905A is one of the closest short-GRB host galaxies identified so far. This made it a preferred target to explore spatially resolved star formation and to investigate the afterglow position in the context of its star formation structures. We used VLT/MUSE integral-field unit observations, supplemented by ATCA 5.5/9.0 GHz radio-continuum measurements and publicly available HST data, to study the star formation activity in the GRB 080905A host galaxy. The MUSE observations reveal that the entire host is characterized by strong line emission. Using the Hα line flux, we measure for the entire galaxy an SFR of about 1.6 M ⊙ yr−1, consistent with its non-detection by ATCA. Several individual star-forming regions are scattered across the host. The most luminous region has a Hα luminosity that is nearly four times as high as the luminosity of the Tarantula nebula in the Large Magellanic Cloud. Even though star-forming activity can be traced as close to about 3 kpc (in projection) distance to the GRB explosion site, stellar population synthesis calculations show that none of the Hα-bright star-forming regions is a likely birthplace of the short-GRB progenitor.

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