scholarly journals The effect of ram-pressure stripping on dwarf galaxies

2020 ◽  
Vol 494 (1) ◽  
pp. 1114-1127 ◽  
Author(s):  
P Steyrleithner ◽  
G Hensler ◽  
A Boselli
Keyword(s):  
Galaxy Clusters ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Gas Content ◽  
Gas Reservoirs ◽  
Interstellar Gas ◽  
Internal Structures ◽  
Ram Pressure

ABSTRACT Ram-pressure stripping (RPS) is a well observed phenomenon of massive spiral galaxies passing through the hot intracluster medium (ICM) of galaxy clusters. For dwarf galaxies (DGs) within a cluster, the transformation from gaseous to gas-poor systems by RPS is not easily observed and must happen in the outskirts of clusters. In a few objects in close by galaxy clusters and the field, RPS has been observed. Since cluster early-type DGs also show a large variety of internal structures (unexpected central gas reservoirs, blue stellar cores, composite radial stellar profiles), we aim in this study to investigate how ram pressure (RP) affects the interstellar gas content and therefore the star formation (SF) activity. Using a series of numerical simulations, we quantify the dependence of the stripped-off gas on the velocity of the infalling DGs and on the ambient ICM density. We demonstrated that SF can be either suppressed or triggered by RP depending on the ICM density and the DGs mass. Under some conditions, RP can compress the gas, so that it is unexpectedly retained in the central DG region and forms stars. When gas clouds are still bound against stripping but lifted from a thin disc and fall back, their new stars form an ellipsoidal (young) stellar population already with a larger velocity dispersion without the necessity of harassment. Most spectacularly, star clusters can form downstream in stripped-off massive gas clouds in the case of strong RP. We compare our results to observations.

scholarly journals The Fornax Deep Survey (FDS) with VST

2019 ◽  
Vol 625 ◽  
pp. A143 ◽  
Author(s):  
Aku Venhola ◽  
Reynier Peletier ◽  
Eija Laurikainen ◽  
Heikki Salo ◽  
Enrichetta Iodice ◽  
...  
Keyword(s):  
Galaxy Clusters ◽  
Surface Brightness ◽  
Stellar Population ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Virgo Cluster ◽  
Axis Ratio ◽  
Ram Pressure ◽  
Deep Survey ◽  
Fornax Cluster

Context. Dwarf galaxies are the most common type of galaxies in galaxy clusters. Due to their low mass, they are more vulnerable to environmental effects than massive galaxies, and are thus optimal for studying the effects of the environment on galaxy evolution. By comparing the properties of dwarf galaxies with different masses, morphological types, and cluster-centric distances we can obtain information about the physical processes in clusters that play a role in the evolution of these objects and shape their properties. The Fornax Deep Survey Dwarf galaxy Catalog (FDSDC) includes 564 dwarf galaxies in the Fornax cluster and the in-falling Fornax A subgroup. This sample allows us to perform a robust statistical analysis of the structural and stellar population differences in the range of galactic environments within the Fornax cluster. Aims. By comparing our results with works concerning other clusters and the theoretical knowledge of the environmental processes taking place in galaxy clusters, we aim to understand the main mechanisms transforming galaxies in the Fornax cluster. Methods. We have exploited the FDSDC to study how the number density of galaxies, galaxy colors and structure change as a function of the cluster-centric distance, used as a proxy for the galactic environment and in-fall time. We also used deprojection methods to transform the observed shape and density distributions of the galaxies into the intrinsic physical values. These measurements are then compared with predictions of simple theoretical models of the effects of harassment and ram pressure stripping on galaxy structure. We used stellar population models to estimate the stellar masses, metallicities and ages of the dwarf galaxies. We compared the properties of the dwarf galaxies in Fornax with those in the other galaxy clusters with different masses. Results. We present the standard scaling relations for dwarf galaxies, which are the size-luminosity, Sérsic n-magnitude and color-magnitude relations. New in this paper is that we find a different behavior for the bright dwarfs (−18.5 mag < Mr′ <  −16 mag) as compared to the fainter ones (Mr′ >  −16 mag): While considering galaxies in the same magnitude-bins, we find that, while for fainter dwarfs the g′−r′ color is redder for lower surface brightness objects (as expected from fading stellar populations), for brighter dwarfs the color is redder for the higher surface brightness and higher Sérsic n objects. The trend of the bright dwarfs might be explained by those galaxies being affected by harassment and by slower quenching of star formation in their inner parts. As the fraction of early-type dwarfs with respect to late-types increases toward the central parts of the cluster, the color-surface brightness trends are also manifested in the cluster-centric trends, confirming that it is indeed the environment that changes the galaxies. We also estimate the strength of the ram-pressure stripping, tidal disruption, and harassment in the Fornax cluster, and find that our observations are consistent with the theoretically expected ranges of galaxy properties where each of those mechanisms dominate. We furthermore find that the luminosity function, color–magnitude relation, and axis-ratio distribution of the dwarfs in the center of the Fornax cluster are similar to those in the center of the Virgo cluster. This indicates that in spite of the fact that the Virgo is six times more massive, their central dwarf galaxy populations appear similar in the relations studied by us.

scholarly journals The Z Velocity Dispersion of Outer H I Disks

1996 ◽  
Vol 169 ◽  
pp. 489-495
Author(s):  
John M. Dickey
Keyword(s):  
Velocity Distribution ◽  
Velocity Dispersion ◽  
Spiral Galaxies ◽  
Thermal State ◽  
Stellar Disk ◽  
Interstellar Gas ◽  
Heating And Cooling ◽  
Outer Disk ◽  
Atomic Gas

The velocity dispersion of the interstellar gas measured perpendicular to the disk in face-on spiral galaxies shows a remarkable consistency. Typically the width of the velocity distribution decreases monotonically with increasing galactic radius through the luminous, stellar disk; but in the outer disk where there is gas but no stars the velocity dispersion is συ ≃ 7 km s−1 with a scatter of 2 km s–1 at most from one position to another and from one galaxy to another. Trying to understand this number raises questions about the thermal state of the H I in outer, gaseous disks. The most important issue is to understand the dominant heating and cooling processes for the atomic gas.

scholarly journals Explaining the enhanced star formation rate of Jellyfish galaxies in galaxy clusters

2019 ◽  
Vol 486 (1) ◽  
pp. L26-L30 ◽  
Author(s):  
Mohammadtaher Safarzadeh ◽  
Abraham Loeb
Keyword(s):  
Star Formation ◽  
Galaxy Clusters ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Control Sample ◽  
External Pressure ◽  
Gas Content ◽  
Ram Pressure ◽  
Inclination Angles ◽  
Formation Efficiency

ABSTRACT We study the recently observed JellyFish galaxies (JFGs), which are found to have their gas content ram pressure stripped away in galaxy clusters. These galaxies are observed to have an enhanced star formation rate of about 0.2 dex compared with a control sample of the same stellar mass in their discs. We model the increase in the star formation efficiency as a function of intracluster medium pressure and parametrize the cold gas content of the galaxies as a function of cluster-centric distance. We show that regarding the external pressure as a positive feedback results in agreement with the observed distribution of enhanced star formation in the JFGs if clouds are shielded from evaporation by magnetic fields. Our results predict that satellites with halo mass $\lt 10^{11}{\rm \, M_\odot }$ moving with Mach numbers $\mathcal {M}\approx 2$, and inclination angles below 60 deg, are more likely to be detected as JFGs.

scholarly journals Ultra-Compact Dwarf Galaxies – More Massive than Allowed?

2007 ◽  
Vol 3 (S246) ◽  
pp. 427-428 ◽  
Author(s):  
Michael Hilker ◽  
S. Mieske ◽  
H. Baumgardt ◽  
J. Dabringhausen
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Dwarf Galaxies ◽  
Population Models ◽  
High Mass ◽  
Early Type ◽  
Dynamical Mass ◽  
Dispersion Diagram

AbstractDynamical mass estimates of ultra-compact dwarfs galaxies and massive globular clusters in the Fornax and Virgo clusters and around the giant elliptical Cen A have revealed some surprising results: 1) above ~106M⊙ the mass-to-light (M/L) ratio increases with the objects' mass; 2) some UCDs/massive GCs show high M/L values (4 to 6) that are not compatible with standard stellar population models; and 3) in the luminosity-velocity dispersion diagram, UCDs deviate from the well-defined relation of “normal” GCs, being more in line with the Faber-Jackson relation of early-type galaxies. In this contribution, we present the observational evidences for high mass-to-light ratios of UCDs and discuss possible explanations for them.

scholarly journals Stellar population properties of ETGs in compact groups of galaxies

2020 ◽  
Vol 493 (3) ◽  
pp. 3238-3254
Author(s):  
Tatiana C Moura ◽  
Reinaldo R de Carvalho ◽  
Sandro B Rembold ◽  
Marina Trevisan ◽  
Andre L B Ribeiro ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Stellar Population ◽  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Gas Content ◽  
Dynamical Analysis ◽  
Compact Groups ◽  
Low Mass Stars ◽  
Groups Of Galaxies ◽  
Low Mass

ABSTRACT We present results on the study of the stellar population in early-type galaxies (ETGs) belonging to 151 compact groups (CGs). We also selected a field sample composed of 846 ETGs to investigate environmental effects on galaxy evolution. We find that the dependences of mean stellar ages, [Z/H] and [α/Fe] on central stellar velocity dispersion are similar, regardless where the ETG resides, CGs or field. When compared to the sample of centrals and satellites from the literature, we find that ETGs in CGs behave similarly to centrals, especially those embedded in low-mass haloes ($M_{\mathrm{ h}} \lt 10^ {12.5}\, \mathrm{M}_{\odot }$). Except for the low-mass limit, where field galaxies present a star-forming signature, not seen in CGs, the ionization agent of the gas in CG and field galaxies seem to be similar due to hot, evolved low-mass stars. However, field ETGs present an excess of H α emission relative to ETGs in CGs. Additionally, we performed a dynamical analysis, which shows that CGs present a bimodality in the group velocity dispersion distribution – a high- and low-σ mode. Our results indicate that high-σ groups have a smaller fraction of spirals, shorter crossing times, and a more luminous population of galaxies than the low-σ groups. It is important to emphasize that our findings point to a small environmental impact on galaxies located in CGs. The only evidence we find is the change in gas content, suggesting environmentally driven gas loss.

scholarly journals Effects of environment on the properties of cluster galaxies via ram pressure stripping

2009 ◽  
Vol 5 (H15) ◽  
pp. 294-294
Author(s):  
T. E. Tecce ◽  
S. A. Cora ◽  
P. B. Tissera ◽  
M. G. Abadi
Keyword(s):  
Star Formation ◽  
Galaxy Clusters ◽  
Galaxy Formation ◽  
Gas Content ◽  
Analytic Model ◽  
Cluster Galaxies ◽  
Ram Pressure ◽  
Cold Gas

AbstractWe study the effect of ram pressure stripping (RPS) on the colours, cold gas content and star formation of galaxies in clusters, using a combination of N-Body/SPH simulations of galaxy clusters and a semi-analytic model of galaxy formation that includes the effect of RPS.

scholarly journals Rejuvenation of spiral bulges

2007 ◽  
Vol 3 (S245) ◽  
pp. 289-292
Author(s):  
Daniel Thomas ◽  
Roger L. Davies
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Spiral Galaxies ◽  
Stellar Populations ◽  
Elliptical Galaxies ◽  
Element Abundances ◽  
Secular Evolution ◽  
The Past ◽  
Show Evidence ◽  
Inside Out

AbstractWe seek to understand whether the stellar populations of galactic bulges show evidence of secular evolution triggered by the presence of the disc. To this end we re-analyse the sample of Proctor & Sansom (2002), deriving stellar population ages and element abundances from absorption line indices as functions of central velocity dispersion and Hubble type. In agreement with other studies in the literature, we find that bulges have relatively low luminosity weighted ages, the lowest age derived being 1.3 Gyr. Hence bulges are not generally old, but actually rejuvenated systems. We discuss evidence that this might be true also for the bulge of the Milky Way. The smallest bulges are the youngest with the lowest α/Fe ratios indicating the presence of significant star formation events involving 10 − 30 per cent of their total mass in the past 1 − 2 Gyr. No significant correlations of the stellar population parameters with Hubble Type are found. We show that the above relationships with σ coincide perfectly with those of early-type galaxies. At a given velocity dispersion, bulges and elliptical galaxies are indistinguishable as far as their stellar populations are concerned. These results favour an inside-out formation scenario and indicate that the discs in spiral galaxies of Hubble types Sbc and earlier cannot have a significant influence on the evolution of the stellar populations in the bulge component. The phenomenon of pseudobulge formation must be restricted to spirals of types later than Sbc.

scholarly journals Galaxy properties as revealed by MaNGA – III. Kinematic profiles and stellar population gradients in S0s

2020 ◽  
Vol 495 (3) ◽  
pp. 2894-2908 ◽  
Author(s):  
H Domínguez Sánchez ◽  
M Bernardi ◽  
F Nikakhtar ◽  
B Margalef-Bentabol ◽  
R K Sheth
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Signal To Noise Ratio ◽  
Elliptical Galaxies ◽  
Element Abundance ◽  
High Signal ◽  
Galactocentric Distance ◽  
Massive Galaxies ◽  
Nearby Galaxies ◽  
Mass Functions

ABSTRACT This is the third paper of a series where we study the stellar population gradients (SP; ages, metallicities, α-element abundance ratios, and stellar initial mass functions) of early-type galaxies (ETGs) at $z$ ≤ 0.08 from the Mapping Nearby Galaxies at APO Data Release 15 (MaNGA-DR15) survey. In this work, we focus on the S0 population and quantify how the SP varies across the population as well as with galactocentric distance. We do this by measuring Lick indices and comparing them to SP synthesis models. This requires spectra with high signal-to-noise ratio which we achieve by stacking in bins of luminosity (Lr) and central velocity dispersion (σ0). We find that: (1) there is a bimodality in the S0 population: S0s more massive than $3\times 10^{10}\, \mathrm{M}_\odot$ show stronger velocity dispersion and age gradients (age and σr decrease outwards) but little or no metallicity gradient, while the less massive ones present relatively flat age and velocity dispersion profiles, but a significant metallicity gradient (i.e. [M/H] decreases outwards). Above $2\times 10^{11}\, \mathrm{M}_\odot$, the number of S0s drops sharply. These two mass scales are also where global scaling relations of ETGs change slope. (2) S0s have steeper velocity dispersion profiles than fast-rotating elliptical galaxies (E-FRs) of the same luminosity and velocity dispersion. The kinematic profiles and SP gradients of E-FRs are both more similar to those of slow-rotating ellipticals (E-SRs) than to S0s, suggesting that E-FRs are not simply S0s viewed face-on. (3) At fixed σ0, more luminous S0s and E-FRs are younger, more metal rich and less α-enhanced. Evidently for these galaxies, the usual statement that ‘massive galaxies are older’ is not true if σ0 is held fixed.

scholarly journals The relation between the gas, dust and total mass in edge-on spiral galaxies

2014 ◽  
Vol 10 (S309) ◽  
pp. 297-297
Author(s):  
Flor Allaert
Keyword(s):  
Dark Matter ◽  
Total Mass ◽  
Spiral Galaxies ◽  
3D Structure ◽  
Early Type ◽  
Interstellar Gas ◽  
Data Set ◽  
Unique Role ◽  
Radio Data ◽  
Multi Wavelength

AbstractEach component of a galaxy plays its own unique role in regulating the galaxy's evolution. In order to understand how galaxies form and evolve, it is therefore crucial to study the distribution and properties of each of the various components, and the links between them, both radially and vertically. The latter is only possible in edge-on systems. We present the HEROES project, which aims to investigate the 3D structure of the interstellar gas, dust, stars and dark matter in a sample of 7 massive early-type spiral galaxies based on a multi-wavelength data set including optical, NIR, FIR and radio data.

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