scholarly journals Quantifying the Redistribution of Mass in Galactic Disks due to Bars

2010 ◽  
Vol 6 (S277) ◽  
pp. 242-245
Author(s):  
Patricia Sánchez-Blázquez ◽  
Isabel Pérez ◽  
Pierre Ocvirk
Keyword(s):  
Evolutionary Process ◽  
Disk Galaxies ◽  
Galactic Disks ◽  
Chemical Abundance ◽  
Star Forming ◽  
Barred Galaxies ◽  
The Galaxy ◽  
Bulge Region ◽  
Disc Region ◽  
Inside Out

AbstractNumerical simulations have shown that strong gravitational torque by non-axisymmetric components induce evolutionary processes such as redistribution of mass and angular momentum in the galactic disks and consequent change of chemical abundance profiles. If we hope to understand chemical evolution gradients and their evolution we must understand the secular processes and re-arrangement of material by non-axisymmetric components and vice-versa. The most obvious of these aforementioned non-axisymmetric components are bars - at least 2/3 of spiral galaxies host a bar, and possibly all disk galaxies have hosted a bar at some point in their evolution. While observationally it has been found that barred galaxies have shallower gas-phase metallicity gradients than non-barred galaxies, a complementary analysis of the stellar abundance profiles has not yet been undertaken. This is unfortunate because the study of both gas and stars is important in providing a complete picture, as the two components undergo (and suffer from) very different evolutionary process. We present here a pilot study of the gas and stellar metallicity and age distributions in a sample of barred and non-barred galaxies using 2D spectroscopic observations. We found that the majority of the stellar mass in our sample is composed of old (~10 Gyr) stars. This is true in the bulge and the disc region, even beyond two disc scalelengths. In the disc region, a larger fraction of young stars is present in the external parts of the disc compared with the inner disc. The disc growth is, therefore, compatible with a moderate inside-out formation scenario, where the luminosity-weighted age changes from ~10 Gyrs in the centre, to ~4 Gyrs at two disc scalelengths, depending upon the galaxy. However, the presence of substructure, like star forming rings, can produce stellar population trends that are not directly related with the growing of the disc but to the bar potential. In the disc region, the metallicity gradient always decrease with the radius. In the bulge region this is not always true and we find inverse metallicity gradients in several galaxies.

scholarly journals A star-forming dwarf galaxy candidate in the halo of NGC 4634

2018 ◽  
Vol 620 ◽  
pp. A29 ◽  
Author(s):  
Y. Stein ◽  
D. J. Bomans ◽  
P. Kamphuis ◽  
E. Jütte ◽  
M. Langener ◽  
...  
Keyword(s):  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Disk Galaxies ◽  
Oxygen Abundance ◽  
Star Forming ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Projected Distance

Context. The halos of disk galaxies form a crucial connection between the galaxy disk and the intergalactic medium. Massive stars, H II regions, or dwarf galaxies located in the halos of galaxies are potential tracers of recent accretion and/or outflows of gas, and are additional contributors to the photon field and the gas phase metallicity. Aims. We investigate the nature and origin of a star-forming dwarf galaxy candidate located in the halo of the edge-on Virgo galaxy NGC 4634 with a projected distance of 1.4 kpc and a Hα star formation rate of ∼4.7 × 10−3 M⊙ yr−1 in order to increase our understanding of these disk-halo processes. Methods. With optical long-slit spectra we measured fluxes of optical nebula emission lines to derive the oxygen abundance 12 + log(O/H) of an H II region in the disk of NGC 4634 and in the star-forming dwarf galaxy candidate. Abundances derived from optical long-slit data and from Hubble Space Telescope (HST) r-band data, Hα data, Giant Metrewave Radio Telescope (GMRT) H I data, and photometry of SDSS and GALEX data were used for further analysis. With additional probes of the luminosity–metallicity relation in the B-band from the Hα-luminosity, the H I map, and the relative velocities, we are able to constrain a possible origin of the dwarf galaxy candidate. Results. The high oxygen abundance (12 + log(O/H) ≈ 8.72) of the dwarf galaxy candidate leads to the conclusion that it was formed from pre-enriched material. Analysis of auxiliary data shows that the dwarf galaxy candidate is composed of material originating from NGC 4634. We cannot determine whether this material has been ejected tidally or through other processes, which makes the system highly interesting for follow up observations.

scholarly journals Warps and Accretion

2010 ◽  
Vol 6 (S277) ◽  
pp. 71-74 ◽  
Author(s):  
Gyula I. G. Józsa
Keyword(s):  
Star Formation ◽  
Intergalactic Medium ◽  
Ambient Medium ◽  
Basic Feature ◽  
Optical Disk ◽  
Disk Galaxies ◽  
Galactic Disks ◽  
Star Forming ◽  
Show Evidence ◽  
Excitation Mechanisms

AbstractWarps are a basic feature of disk galaxies. Usually they occur at radii where the optical disk fades and become most pronounced in the outermost gaseous disks.As such, warps present a massive reservoir to replenish star forming material in the inner, star forming disks. Furthermore, some possible excitation mechanisms for warps connect their formation to the accretion of extragalctic material. Interactions or mergers with gas-rich companions or the direct accretion of the ambient intergalactic medium might lead to the formation of warps, at the same time supplementing fuel to maintain star formation in galactic disks.Employing a number of H i studies of warped galaxies, including ultra-deep observations of the prototype warped galaxies NGC 5907 and NGC 4013, I discuss whether the observed kinematics may show evidence for a connection of warps and accretion from the ambient medium.

scholarly journals The dual origin of the Galactic thick disc and halo from the gas-rich Gaia–Enceladus Sausage merger

2020 ◽  
Vol 497 (2) ◽  
pp. 1603-1618 ◽  
Author(s):  
Robert J J Grand ◽  
Daisuke Kawata ◽  
Vasily Belokurov ◽  
Alis J Deason ◽  
Azadeh Fattahi ◽  
...  
Keyword(s):  
Rotation Velocity ◽  
Orbital Eccentricity ◽  
Chemical Abundance ◽  
Thick Disc ◽  
Rapid Formation ◽  
The Galaxy ◽  
Stellar Halo ◽  
Disc Region ◽  
Magnetohydrodynamic Simulations ◽  
Dual Origin

ABSTRACT We analyse a set of cosmological magnetohydrodynamic simulations of the formation of Milky Way-mass galaxies identified to have a prominent radially anisotropic stellar halo component similar to the so-called ‘Gaia Sausage’ found in the Gaia data. We examine the effects of the progenitor of the Sausage (the Gaia–Enceladus Sausage, GES) on the formation of major galactic components analogous to the Galactic thick disc and inner stellar halo. We find that the GES merger is likely to have been gas-rich and contribute 10–50 ${{\ \rm per\ cent}}$ of gas to a merger-induced centrally concentrated starburst that results in the rapid formation of a compact, rotationally supported thick disc that occupies the typical chemical thick disc region of chemical abundance space. We find evidence that gas-rich mergers heated the proto-disc of the Galaxy, scattering stars on to less-circular orbits such that their rotation velocity and metallicity positively correlate, thus contributing an additional component that connects the Galactic thick disc to the inner stellar halo. We demonstrate that the level of kinematic heating of the proto-galaxy correlates with the kinematic state of the population before the merger, the progenitor mass, and orbital eccentricity of the merger. Furthermore, we show that the mass and time of the merger can be accurately inferred from local stars on counter-rotating orbits.

scholarly journals Barred Galaxies: Intrinsic or Extrinsic?

1996 ◽  
Vol 157 ◽  
pp. 339-348 ◽  
Author(s):  
M. Noguchi
Keyword(s):  
Simple Model ◽  
Gravitational Instability ◽  
Dynamical Property ◽  
Disk Galaxies ◽  
Early Type ◽  
Late Type ◽  
Galactic Disks ◽  
Barred Galaxies ◽  
Tidal Interactions ◽  
Key Parameter

AbstractA unified picture is presented for the formation of bars in galaxies of different morphological types based on a simple model of the growth of galactic disks by gas infall from haloes. The infall timescale is found to be a key parameter which determines the dynamical property of the resulting disk. It is suggested that the bars in early-type disk galaxies have been formed in tidal interactions with other galaxies whereas those in late-type galaxies formed spontaneously due to gravitational instability (bar instability) in their disks.

scholarly journals SPATIALLY RESOLVED Hα MAPS AND SIZES OF 57 STRONGLY STAR-FORMING GALAXIES AT z ∼ 1 FROM 3D-HST: EVIDENCE FOR RAPID INSIDE-OUT ASSEMBLY OF DISK GALAXIES

2012 ◽  
Vol 747 (2) ◽  
pp. L28 ◽  
Author(s):  
Erica June Nelson ◽  
Pieter G. van Dokkum ◽  
Gabriel Brammer ◽  
Natascha Förster Schreiber ◽  
Marijn Franx ◽  
...  
Keyword(s):  
Disk Galaxies ◽  
Star Forming ◽  
Spatially Resolved ◽  
Inside Out

scholarly journals Quantifying the mixing due to bars

2012 ◽  
Vol 10 (H16) ◽  
pp. 353-353
Author(s):  
Patricia Sanchez-Blazquez
Keyword(s):  
Angular Momentum ◽  
Gas Phase ◽  
Galaxy Evolution ◽  
Spiral Galaxies ◽  
Solar Neighborhood ◽  
Stellar Disk ◽  
Galactic Disks ◽  
Chemical Abundance ◽  
Evolutionary Processes ◽  
Barred Galaxies

AbstractWe will present star formation histories and the stellar and gaseous metallicity gradients in the disk of a sample of 50 face-on spiral galaxies with and without bars observed with the integral field unit spectrograph PMAS. The final aim is to quantify the redistribution of mass and angular momentum in the galactic disks due to bars by comparing both the gas-phase and star-phase metallicity gradients on the disk of barred and non-barred galaxies. Numerical simulations have shown that strong gravitational torque by non-axisymmetric components induce evolutionary processes such as redistribution of mass and angular momentum in the galactic disks (Sellwood & Binney 2002) and consequent change of chemical abundance profiles. If we hope to understand chemical evolution gradients and their evolution we must understand the secular processes and re-arrangement of material by non-axisymmetric components and vice-versa. Furthermore, the re-arrangement of stellar disk material influences the interpretation of various critical observed metrics of Galaxy evolution, including the age-metallicity relation in the solar neighborhood and the local G-dwarf metallicity distribution. Perhaps the most obvious of these aforementioned non-axisymmetric components are bars - at least 2/3 of spiral galaxies host a bar, and possibly all disk galaxies have hosted a bar at some point in their evolution. While observationally it has been found that barred galaxies have shallower gas-phase metallicity gradients than non-barred galaxies, a complementary analysis of the stellar abundance profiles has not yet been undertaken. This is unfortunate because the study of both gas and stars is important in providing a complete picture, as the two components undergo (and suffer from) very different evolutionary processes.

scholarly journals Constraints on Bars in the Local Universe from 5000 SDSS Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 76-76 ◽  
Author(s):  
Fabio D. Barazza ◽  
Shardha Jogee ◽  
Irina Marinova
Keyword(s):  
Large Scale ◽  
Major Axis ◽  
Disk Galaxies ◽  
Semi Major Axis ◽  
Local Universe ◽  
Barred Galaxies ◽  
Sky Survey ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Local Disk

AbstractWe present the first study of bars in the local Universe, based on the Sloan Digitized Sky Survey (SDSS). The large sample of ~5000 local galaxies provides the largest study to date of local bars and minimizes the effect of cosmic variance. The sample galaxies have Mg ≤ −18.5 mag and cover the redshift range 0.01 ≤ z < 0.04. We use a color cut in the color-magnitude diagram and the Sérsic index n to identify disk galaxies. We characterize bars and disks using r-band images and the method of iterative ellipse fits and quantitative criteria developed in Jogee at al. (2004, ApJL, 615, L105). After excluding highly inclined (i>60°) systems our results are: (1) the optical (r-band) fraction of barred galaxies among local disk galaxies is 43% (Figure 1, left panel), which confirms the ubiquity of local bars, in agreement with other optical studies based on smaller samples (e.g. Eskridge et al 2000, AJ, 119, 536, Marinova & Jogee 2006, astro-ph/0608039); (2) the optical bar fraction rises for bluer galaxies, suggesting a relation between bars and star formation (Figure 1, middle panel); (3) preliminary analyzes suggest that the optical bar fraction increases steeply with the galaxy effective radius (reff, Figure 1, right panel); (4) the optical bar fraction at z ~ 0 is ~35% for bright disks (Mg ≤ −19.3 mag) and strong (bar ellipticity >0.4), large-scale (bar semi-major axis >1.5 kpc) bars, which is comparable to the value of ~30 ± 6% reported earlier (Jogee et al 2004) for similar disks and bars at z ~ 0.2 − 1.0.

scholarly journals Simulating non-axisymmetric flows in disk galaxies

2018 ◽  
Vol 618 ◽  
pp. A106 ◽  
Author(s):  
T. H. Randriamampandry ◽  
N. Deg ◽  
C. Carignan ◽  
L. M. Widrow
Keyword(s):  
Surface Brightness ◽  
Initial Conditions ◽  
Major Axis ◽  
Second Step ◽  
Disk Galaxies ◽  
Distribution Models ◽  
Step Method ◽  
Barred Galaxies ◽  
The Galaxy ◽  
Oriented Parallel

Context. We present a two-step method to simulate and study non-circular motions in strongly barred galaxies. The first step is to constrain the initial parameters using a Bayesian analysis of each galaxy’s azimuthally averaged rotation curve, the 3.6 μm surface brightness, and the gas surface density. The second step is to generate equilibrium models using the GalactICS code and evolve them via GADGET-2. Aims. The bar strengths and mock velocity maps of the resulting snapshots are compared to observations in order to determine the best representation of the galaxy. Methods. We apply our method to the unbarred galaxy NGC 3621 and the barred galaxies NGC 1300 and NGC 1530. NGC 3621 provides a validation of our method of generating initial conditions. NGC 1530 has an intermediate bar orientation that allows for a comparison to DiskFit. Finally NGC 1300 has a bar oriented parallel to the galaxy’s major axis, where other algorithms tend to fail. Results. Our models for NGC 3621 and NGC 1530 are comparable to those obtained using commonly available algorithms. Moreover, we produce one of the first mass distribution models for NGC 1300.

scholarly journals The MAD View on the Outskirts of Disks

2016 ◽  
Vol 11 (S321) ◽  
pp. 163-171
Author(s):  
C. M. Carollo ◽  
S. Erroz-Ferrer ◽  
M. den Brok ◽  
M. Fagioli ◽  
M. Onodera ◽  
...  
Keyword(s):  
Stellar Population ◽  
Theoretical Models ◽  
Spectroscopic Properties ◽  
Disk Galaxies ◽  
Star Forming ◽  
Stellar Properties ◽  
Gas Accretion ◽  
Additional Role ◽  
Inside Out

AbstractWe present the MUSE Atlas of Disks (MAD), a GTO program with the MUSE spectrograph on the ESO/VLT that is dedicated to the study of the optical spectroscopic properties of z = 0 disk galaxies on the star-forming ‘Main Sequence’ at < 100 pc physical resolution. MUSE pointings on the MAD galaxies extend out to ~ 2 disk scale lengths, enabling to investigate the bulge and inner disk properties of galaxies with different outer disks. Here we specifically compare, at constant stellar-mass, the stellar population properties of the inner components in disks with down-bending (Type II) and up-bending (Type III) outer profiles. We highlight similarities in the inner stellar properties of such different hosts, which point at a universal inside-out growth of disks, as well as differences which suggest an additional role of stellar migration and/or gas accretion in the growth of disk galaxies with an outer up-bending profile, as expected from theoretical models.

scholarly journals Significance of bar quenching in the global quenching of star formation

2019 ◽  
Vol 628 ◽  
pp. A24 ◽  
Author(s):  
K. George ◽  
S. Subramanian ◽  
K. T. Paul
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Stellar Mass ◽  
Gas Content ◽  
Disk Galaxies ◽  
Local Universe ◽  
Star Forming ◽  
Barred Galaxies

The suppression of star formation in the inner kiloparsec regions of barred disk galaxies due to the action of bars is known as bar quenching. We investigate here the significance of bar quenching in the global quenching of star formation in the barred galaxies and their transformation to passive galaxies in the local Universe. We do this by measuring the offset of quenched barred galaxies from star-forming main sequence galaxies in the star formation rate-stellar mass plane and comparing it with the length of the bar, which is considered as a proxy of bar quenching. We constructed the star formation rate-stellar mass plane of 2885 local Universe face-on strong barred disk galaxies (z <  0.06) identified by Galaxy Zoo. The barred disk galaxies studied here fall on the star formation main sequence relation with a significant scatter for galaxies above stellar mass 1010.2M⊙. We found that 34.97% galaxies are within the intrinsic scatter (0.3 dex) of the main sequence relation, with a starburst population of 10.78% (above the 0.3 dex) and a quenched population of 54.25% (below the −0.3 dex) of the total barred disk galaxies in our sample. Significant neutral hydrogen (MHI > 109M⊙ with log MHI/M⋆ ∼ −1.0 to −0.5) is detected in the quenched barred galaxies with a similar gas content to that of the star-forming barred galaxies. We found that the offset of the quenched barred galaxies from the main sequence relation is not dependent on the length of the stellar bar. This implies that the bar quenching may not contribute significantly to the global quenching of star formation in barred galaxies. However, this observed result could also be due to other factors such as the dissolution of bars over time after star formation quenching, the effect of other quenching processes acting simultaneously, and/or the effects of environment.

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