scholarly journals Redistribution of stars and gas in the star formation deserts of barred galaxies

2019 ◽  
Vol 489 (4) ◽  
pp. 4992-5003 ◽  
Author(s):  
C E Donohoe-Keyes ◽  
M Martig ◽  
P A James ◽  
K Kraljic
Keyword(s):  
Star Formation ◽  
Time Scales ◽  
Age Distribution ◽  
Young Stars ◽  
Host Galaxies ◽  
Radial Migration ◽  
Barred Galaxies ◽  
Central Regions ◽  
Zoom In ◽  
Bar Formation

ABSTRACT Bars strongly influence the distribution of gas and stars within the central regions of their host galaxies. This is particularly pronounced in the star formation desert (SFD) which is defined as two symmetrical regions either side of the bar that show a deficit in young stars. Previous studies proposed that, if star formation is truncated because of the influence of the bar, then the age distribution of stars within the SFD could be used to determine the epoch of bar formation. To test this, we study the properties of SFDs in six galaxies from zoom-in cosmological re-simulations. Age maps reveal old regions on both sides of the bars, with a lack of stars younger than 10 Myr, confirming the SFD phenomenon. Local star formation is truncated in the SFDs because after the bar forms, gas in these regions is removed on 1 Gyr time-scales. However, the overall age distribution of stars in the SFD does not show a sharp truncation after bar formation but rather a gradual downturn in comparison to that of the bar. This more subtle signature may still give information on bar formation epochs in observed galaxies, but the interpretation will be more difficult than originally hoped. The gradual drop in the SFD age distribution, instead of a truncation, is due to radial migration of stars born in the disc. The SFD is thus one of the only regions where an uncontaminated sample of stars only affected by radial migration can be studied.

scholarly journals “The mass distribution of the young stellar population in Chamaeleon I and in Rho Ophiuchi”

1991 ◽  
Vol 147 ◽  
pp. 427-429
Author(s):  
Jane C. Gregório Hetem ◽  
J.R.D. Lépine ◽  
R. Ortiz
Keyword(s):  
Star Formation ◽  
Mass Distribution ◽  
Formation Process ◽  
Stellar Population ◽  
Age Distribution ◽  
Young Stars ◽  
Rho Ophiuchi ◽  
Hr Diagram

We obtain the mass distribution and the age distribution of the young stars associated with Chamaeleon I and Rho Ophiuchi, two nearby sites of star formation. Our method consists in determining the temperature and the luminosity of each object in order to locate it on the HR diagram, and then comparing the position on the HR diagram with the evolutionary tracks and isochrones presented by Cohen and Kuhi (1979). The star-formation process is found to have started more recently in ρ Oph than in Cham I.

scholarly journals Secular evolution in galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 19-23 ◽  
Author(s):  
F. Combes
Keyword(s):  
Star Formation ◽  
Numerical Simulations ◽  
Significant Role ◽  
High Frequency ◽  
Central Star ◽  
Barred Galaxies ◽  
Secular Evolution ◽  
Gas Accretion ◽  
Bar Formation

AbstractNew observations in favour of a significant role of secular evolution are reviewed: central star formation boosted in pseudo-bulge barred galaxies, relations between bulge and disk, evidence for rejuvenated bulges. Numerical simulations have shown that secular evolution can occur through a cycle of bar formation and destruction, in which the gas plays a major role. Since bars are weakened or destroyed in gaseous disks, the high frequency of bars observed today requires external cold gas accretion, to replenish the disk and allow a new bar formation. The rate of gas accretion from external filaments is compatible with what is observed in cosmological simulations.

scholarly journals Quasar Metal Abundances & Host Galaxy Evolution

2009 ◽  
Vol 5 (S265) ◽  
pp. 171-178
Author(s):  
Fred Hamann ◽  
Leah E. Simon
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
High Redshift ◽  
Big Bang ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Massive Galaxies ◽  
Central Regions ◽  
Metal Abundances ◽  
The Big Bang

AbstractHigh-redshift quasars provide a unique glimpse into the early evolution of massive galaxies. The physical processes that trigger major bursts of star formation in quasar host galaxies (mergers and interactions) probably also funnel gas into the central regions to grow the super-massive black holes (SMBHs) and ignite the luminous quasar phenomenon. The globally dense environments where this occurs were probably also among the first to collapse and manufacture stars in significant numbers after the big bang. Measurements of the elemental abundances near quasars place important constraints on the nature, timing and extent of this star formation. A variety of studies using independent emission and absorption line diagnostics have shown that quasar environments have gas-phase metallicities that are typically a few times solar at all observed redshifts. These results are consistent with galaxy evolution scenarios in which large amounts of star formation (e.g., in the central regions) precede the visibly bright quasar phase. An observed trend for higher metallicities in more luminmous quasars (powered by more massive SMBHs) is probably tied to the well-known mass–metallicity relation among ordinary galaxies. This correlation and the absence of a trend with redshift indicate that mass is a more important parameter in the evolution than the time elapsed since the big bang.

scholarly journals Molecular Gas in the Central Regions of Barred Galaxies

1996 ◽  
Vol 157 ◽  
pp. 150-156 ◽  
Author(s):  
Jeffrey Kenney
Keyword(s):  
Star Formation ◽  
Solid Body ◽  
Rotation Curve ◽  
Molecular Gas ◽  
Star Forming ◽  
Barred Galaxies ◽  
Central Regions ◽  
Early Phases ◽  
Intense Star Formation

AbstractThe morphology and kinematics of molecular gas in the central regions of barred galaxies are described. The largest gas concentrations are often located near ILRs, although there is a range of morphologies. The gas motions associated with star-forming rings are predominantly circular, while motions just beyond the rings are often non-circular and in some cases show clear radial inflow. In barred galaxies with circumnuclear starbursts in early phases of evolution, the CO is centrally peaked, perhaps inside IILRs. The most intense star formation occurs where the gas motions are circular, and where the rotation curve rises steeply and is nearly solid body.

scholarly journals Tracing the Origin of Bars and Bulges through the Study of their Stellar and Ionised Gas Properties

2010 ◽  
Vol 6 (S277) ◽  
pp. 166-169
Author(s):  
Isabel Pérez ◽  
Patricia Sánchez-Blázquez ◽  
Almudena Zurita ◽  
Estrella Florido
Keyword(s):  
Star Formation ◽  
Velocity Dispersion ◽  
Age Distribution ◽  
Central Component ◽  
Early Type ◽  
Barred Galaxies ◽  
Stellar Properties ◽  
Metallicity Distribution ◽  
Similar Sample ◽  
Gas Properties

AbstractWe have carried out a detailed analysis of stellar properties of bars and bulges of a sample of early-type galaxies. We have also compared the results of the bulge properties with the bulges of a similar sample of unbarred galaxies, deriving the SSP equivalent stellar parameters in the same way as for our sample. We are currently characterising the nebular gas in the bulges of the sample galaxies. We have found differences in the bulge stellar population properties between barred and unbarred galaxies. The bulges of barred galaxies seem to be more metal rich, at a given velocity dispersion (σ), than the bulges of unbarred galaxies, as measured by some metallicity sensitive indices. There are indications that the ratio of relative abundance of alpha-elements with respect to iron, [E/Fe], derived for the bulges of barred galaxies tend to lie above the values of the unbarred galaxies at a given σ. We also find three different types of bars according to their metallicity and age distribution along the radius: 1) Bars with negative metallicity gradients. They show mean young/intermediate population (<2 Gyr), and have amongst the lowest stellar maximum central velocity dispersion of the sample. 2) Bars with null metallicity gradients. These galaxies that do not show any gradient in their metallicity distribution along the bar and have negative age gradients (i.e younger populations at the bar end). 3) Bars with positive metallicity gradients, i.e. more metal rich at the bar ends. These galaxies are predominantly those with higher velocity dispersion and older mean population. We find no significant correlation between the age and metallicity distribution, and bar/galaxy parameters such as the AGN presence, size or the bar strength. From the kinematics, we find that all the galaxies show a disk–like central component. Regarding the ionised gas properties, we find that the nebular metallicity gradients are shallower than the stellar ones, indicating an efficient mixing of the material currently forming. The nebular central metallicities do not show a correlation with the central σ, and, furthermore, in some cases the nebular metallicities are clearly lower than the stellar ones, indicating an external origin for the gas fueling the current star formation. All these results point to a scenario, at least for early-type galaxies, where bars are long-lived and where the formation of the bulge and the bar are closely linked. Later accretion of gas can then be funneled towards the center forming nuclear discs and rings, producing substructures with low level of star formation, but that would not contain enough stars to produce a change in the SSP-equivalent metallicities and [E/Fe].

scholarly journals Young stellar population gradients in central cluster galaxies from NUV and optical spectroscopy

2020 ◽  
Vol 500 (3) ◽  
pp. 3368-3381
Author(s):  
N Salvador-Rusiñol ◽  
M A Beasley ◽  
A Vazdekis ◽  
F La Barbera
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Stellar Populations ◽  
Young Stars ◽  
Galactocentric Distance ◽  
Potential Wells ◽  
Cluster Galaxies ◽  
Central Cluster ◽  
Central Regions ◽  
Galaxy Cores

ABSTRACT Central cluster galaxies are the largest and most massive galaxies in the Universe. Although they host very old stellar populations, several studies found the existence of blue cores in some BCGs indicating ongoing star formation. We analyse VLT/X-Shooter stacked spectra of 6 nearby massive central galaxies with high central velocity dispersions (σ &gt; 300 km s−1) at different galactocentric distances. We quantify the young stellar population out to 4 kpc by fitting near-UV and optical absorption line indices with predictions of composite stellar populations modelled by an old and a young stellar component. We also use IMF-sensitive indices since these galaxies have been found to host a bottom-heavy IMF in their central regions. We derive negative young stellar populations gradients, with mass fractions of stars younger than 1 Gyr decreasing with galactocentric distance, from 0.70 per cent within 0.8 kpc to zero beyond 2 kpc. We also measure the mass fraction in young stars for individual galaxies in the highest S/N central regions. All the galaxies have young components of less than one percent. Our results clearly suggest that the star formation in massive central cluster galaxies takes place in their galaxy cores (&lt;2 kpc), which, with deeper gravitational potential wells, are capable of retaining more gas. Among the possible sources for the gas required to form these young stars, our results are consistent with an in situ origin via stellar evolution, which is sufficient to produce the observed young stellar populations.

scholarly journals “The mass distribution of the young stellar population in Chamaeleon I and in Rho Ophiuchi”

1991 ◽  
Vol 147 ◽  
pp. 427-429
Author(s):  
Jane C. Gregório Hetem ◽  
J.R.D. Lépine ◽  
R. Ortiz
Keyword(s):  
Star Formation ◽  
Mass Distribution ◽  
Formation Process ◽  
Stellar Population ◽  
Age Distribution ◽  
Young Stars ◽  
Rho Ophiuchi ◽  
Hr Diagram

We obtain the mass distribution and the age distribution of the young stars associated with Chamaeleon I and Rho Ophiuchi, two nearby sites of star formation. Our method consists in determining the temperature and the luminosity of each object in order to locate it on the HR diagram, and then comparing the position on the HR diagram with the evolutionary tracks and isochrones presented by Cohen and Kuhi (1979). The star-formation process is found to have started more recently in ρ Oph than in Cham I.

scholarly journals Barred Galaxies: Intrinsic or Extrinsic?

1996 ◽  
Vol 171 ◽  
pp. 426-426
Author(s):  
M. Noguchi
Keyword(s):  
Star Formation ◽  
Galactic Disk ◽  
Stellar Disk ◽  
Disk Galaxies ◽  
Analytic Model ◽  
Disk Formation ◽  
Barred Galaxies ◽  
Disk Growth ◽  
Bar Formation ◽  
Disk Component

A unified picture is presented of the formation of bar structures in disk galaxies of various morphological types. In order to discuss bar formation in the context of galactic disk formation, a simple analytic model is constructed of the growth of galactic disks by infall of primordial gas from haloes and subsequent star formation in the disks. It is monitored during the course of disk growth whether or not the condition for spontaneous bar formation (i.e., bar instability) is fulfilled for the stellar disk component.

scholarly journals A Burst of Star Formation in Galaxies of the M 81 Group

1994 ◽  
Vol 161 ◽  
pp. 596-598
Author(s):  
B.P. Artamonov
Keyword(s):  
Image Processing ◽  
Star Formation ◽  
Young Stars ◽  
Active Star ◽  
Active Star Formation ◽  
Central Regions ◽  
Star Formation In Galaxies ◽  
Ubv Photometry

UBV photographic plates of galaxies (resolution ∼ ) for the M 81 Group were obtained with the 1-metre Ritchey-Chrétien (RC) Zeiss telescope at Maidanak Observatory. Some plates show a resolution ∼ . Artamonov et al. (1990) have distinguished and measured positions of starlike objects in the central regions of M 82 (69 spots) and NGC 3077 (19 spots). We have measured the position of 120 blue starlike objects in NGC 2976. Image processing was carried out using a PC 286/386 with calibration using the data of Notni &amp; Bronkalla, 1985; Bronkalla et al. 1992. The observed galaxies show active star formation which are related with intergalactic interaction. We have carried out UBV photometry of starlike objects in these galaxies. All objects emulate a population of young stars with different reddening. Figure 1 shows the two-colour plot of starlike objects in M 82 and the central regions of NGC 3077 (Price &amp; Gullixson 1989). The colours of these objects lie along the line of reddening.

scholarly journals More insights into bar quenching

2020 ◽  
Vol 644 ◽  
pp. A79
Author(s):  
K. George ◽  
P. Joseph ◽  
C. Mondal ◽  
S. Subramanian ◽  
A. Subramaniam ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Hydrogen ◽  
Neutral Hydrogen ◽  
Archival Data ◽  
Imaging Data ◽  
Gas Distribution ◽  
Barred Galaxies ◽  
Central Regions ◽  
Multi Wavelength ◽  
Disc Galaxies

The underlying nature of the process of star formation quenching in the central regions of barred disc galaxies that is due to the action of stellar bar is not fully understood. We present a multi-wavelength study of four barred galaxies using the archival data from optical, ultraviolet, infrared, CO, and HI imaging data on star formation progression and stellar and gas distribution to better understand the process of bar quenching. We found that for three galaxies, the region between the nuclear or central sub-kiloparsec region and the end of the bar (bar region) is devoid of neutral and molecular hydrogen. While the detected neutral hydrogen is very negligible, we note that molecular hydrogen is present abundantly in the nuclear or central sub-kiloparsec regions of all four galaxies. The bar co-rotation radius is also devoid of recent star formation for three out of four galaxies. One galaxy shows significant molecular hydrogen along the bar, which might mean that the gas is still being funnelled to the centre by the action of the stellar bar. Significant star formation is also present along the bar co-rotation radius of this galaxy. The study presented here supports a scenario in which gas redistribution as a result of the action of stellar bar clears the bar region of fuel for further star formation and eventually leads to star formation quenching in the bar region.

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