scholarly journals Properties of the outer regions of spiral disks: abundances, colors and ages

2016 ◽  
Vol 11 (S321) ◽  
pp. 102-104
Author(s):  
Mercedes Mollá ◽  
Angeles I. Díaz ◽  
Brad K. Gibson ◽  
Oscar Cavichia ◽  
Ángel-R. López-Sánchez
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Molecular Gas ◽  
Disk Galaxies ◽  
Gas Formation ◽  
Radial Profiles ◽  
Potential Origin

AbstractWe summarize the results obtained from our suite of chemical evolution models for spiral disks, computed for different total masses and star formation efficiencies. Once the gas, stars and star formation radial distributions are reproduced, we analyze the Oxygen abundances radial profiles for gas and stars, in addition to stellar averaged ages and global metallicity. We examine scenarios for the potential origin of the apparent flattening of abundance gradients in the outskirts of disk galaxies, in particular the role of molecular gas formation prescriptions.

scholarly journals Galaxy chemical evolution models: the role of molecular gas formation

2017 ◽  
Vol 468 (1) ◽  
pp. 305-318 ◽  
Author(s):  
Mercedes Mollá ◽  
Ángeles I. Díaz ◽  
Yago Ascasibar ◽  
Brad K. Gibson
Keyword(s):  
Chemical Evolution ◽  
Molecular Gas ◽  
Gas Formation

scholarly journals The influence of bars in the star formation history and chemical evolution of disk galaxies

2009 ◽  
Vol 5 (S262) ◽  
pp. 188-191
Author(s):  
Patricia Sánchez-Blázquez
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Pilot Study ◽  
Chemical Evolution ◽  
Star Formation History ◽  
Disk Galaxies ◽  
Formation History ◽  
Observational Program

AbstractThis is a pilot study part of a larger program devoted to understand the influence of bars in the evolution of galaxy disks. Some of the goals of this observational program are to compare the stellar metallicity gradients of galaxies with and without bars, the role of bars in the redistribution of mass and angular momentum and to study the evolution of the metallicity gradients with time. Some promising results are presented as well as some words of caution.

scholarly journals Evolution of the star formation efficiency in galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 341-341
Author(s):  
Jonathan Braine
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Conversion Factor ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Molecular Gas ◽  
Present Evidence ◽  
Ngc 6822 ◽  
Physical And Chemical ◽  
Formation Efficiency

AbstractThe physical and chemical evolution of galaxies is intimately linked to star formation, We present evidence that molecular gas (H2) is transformed into stars more quickly in smaller and/or subsolar metallicity galaxies than in large spirals – which we consider to be equivalent to a star formation efficiency (SFE). In particular, we show that this is not due to uncertainties in the N(H2)/Ico conversion factor. Several possible reasons for the high SFE in galaxies like the nearby M33 or NGC 6822 are proposed which, separately or together, are the likely cause of the high SFE in this environment. We then try to estimate how much this could contribute to the increase in cosmic star formation rate density from z = 0 to z = 1.

scholarly journals SDSS-IV MaNGA: the indispensable role of bars in enhancing the central star formation of low-z galaxies

2020 ◽  
Vol 499 (1) ◽  
pp. 1406-1423 ◽  
Author(s):  
Lin Lin ◽  
Cheng Li ◽  
Cheng Du ◽  
Enci Wang ◽  
Ting Xiao ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Local Environment ◽  
Central Star ◽  
Barred Galaxies ◽  
Secular Evolution ◽  
Integral Field Spectroscopy ◽  
Radial Profiles ◽  
Order Of Magnitude

ABSTRACT We analyse two-dimensional maps and radial profiles of EW(Hα), EW(HδA), and Dn(4000) of low-redshift galaxies using integral field spectroscopy from the MaNGA survey. Out of ≈1400 nearly face-on late-type galaxies with a redshift z < 0.05, we identify 121 “turnover” galaxies that each have a central upturn in EW(Hα), EW(HδA), and/or a central drop in Dn(4000), indicative of ongoing/recent star formation. The turnover features are found mostly in galaxies with a stellar mass above ∼1010 M⊙ and NUV – r colour less than ≈5. The majority of the turnover galaxies are barred, with a bar fraction of 89 ± 3 per cent. Furthermore, for barred galaxies, the radius of the central turnover region is found to tightly correlate with one-third of the bar length. Comparing the observed and the inward extrapolated star formation rate surface density, we estimate that the central SFR have been enhanced by an order of magnitude. Conversely, only half of the barred galaxies in our sample have a central turnover feature, implying that the presence of a bar is not sufficient to lead to a central SF enhancement. We further examined the SF enhancement in paired galaxies, as well as the local environment, finding no relation. This implies that the environment is not a driving factor for central SF enhancement in our sample. Our results reinforce both previous findings and theoretical expectation that galactic bars play a crucial role in the secular evolution of galaxies by driving gas inflow and enhancing the star formation and bulge growth in the centre.

scholarly journals 2D-Galactic chemical evolution: the role of the spiral density wave

2019 ◽  
Vol 490 (1) ◽  
pp. 665-682 ◽  
Author(s):  
M Mollá ◽  
S Wekesa ◽  
O Cavichia ◽  
Á I Díaz ◽  
B K Gibson ◽  
...  
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Formation Rate ◽  
Density Wave ◽  
Spiral Wave ◽  
Elemental Abundance ◽  
Abundance Pattern ◽  
Spiral Density Wave ◽  
Azimuthal Symmetry

ABSTRACT We present a 2D chemical evolution code applied to a Milky Way type Galaxy, incorporating the role of spiral arms in shaping azimuthal abundance variations, and confront the predicted behaviour with recent observations taken with integral field units. To the usual radial distribution of mass, we add the surface density of the spiral wave and study its effect on star formation and elemental abundances. We compute five different models: one with azimuthal symmetry which depends only on radius, while the other four are subjected to the effect of a spiral density wave. At early times, the imprint of the spiral density wave is carried by both the stellar and star formation surface densities; conversely, the elemental abundance pattern is less affected. At later epochs, however, differences among the models are diluted, becoming almost indistinguishable given current observational uncertainties. At the present time, the largest differences appear in the star formation rate and/or in the outer disc (R ≥ 18 kpc). The predicted azimuthal oxygen abundance patterns for t ≤ 2 Gyr are in reasonable agreement with recent observations obtained with VLT/MUSE for NGC 6754.

scholarly journals Molecular Gas and Star Formation in Local Early–type Galaxies

2010 ◽  
Vol 6 (S277) ◽  
pp. 55-58
Author(s):  
M. Bureau ◽  
T. A. Davis ◽  
K. Alatalo ◽  
A. F. Crocker ◽  
L. Blitz ◽  
...  
Keyword(s):  
Star Formation ◽  
Far Infrared ◽  
Gas Content ◽  
Molecular Gas ◽  
Disk Galaxies ◽  
Formation Processes ◽  
Early Type ◽  
High Detection Rate ◽  
Physical Conditions ◽  
Multi Wavelength

AbstractThe molecular gas content of local early-type galaxies is constrained and discussed in relation to their evolution. First, as part of the ATLAS3D survey, we present the first complete, large (260 objects), volume-limited single-dish survey of CO in normal local early-type galaxies. We find a surprisingly high detection rate of 22%, independent of luminosity and at best weakly dependent on environment. Second, the extent of the molecular gas is constrained with CO synthesis imaging, and a variety of morphologies is revealed. The kinematics of the molecular gas and stars are often misaligned, implying an external gas origin in over a third of the systems, although this behaviour is drastically diffferent between field and cluster environments. Third, many objects appear to be in the process of forming regular kpc-size decoupled disks, and a star formation sequence can be sketched by piecing together multi-wavelength information on the molecular gas, current star formation, and young stars. Last, early-type galaxies do not seem to systematically obey all our usual prejudices regarding star formation, following the standard Schmidt-Kennicutt law but not the far infrared-radio correlation. This may suggest a greater diversity in star formation processes than observed in disk galaxies. Using multiple molecular tracers, we are thus starting to probe the physical conditions of the cold gas in early-types.

scholarly journals Cold Molecular Gas as a Possible Component of Dark Matter in the Outer Parts of Disk Galaxies

2004 ◽  
Vol 220 ◽  
pp. 249-250
Author(s):  
Ronald J. Allen ◽  
Rosa Diaz-Miller
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Small Area ◽  
Physical State ◽  
Filling Factor ◽  
Massive Star ◽  
Molecular Gas ◽  
Disk Galaxies ◽  
Dust Grain ◽  
New Evidence

In the last few years new evidence has been presented for the presence of ongoing massive star formation in the outer HI disks of galaxies. These discoveries strongly suggest that precursor molecular gas must also be present in some physical state which is escaping detection by the usual means (CO(1-0), IR, etc.). We present a model for such a gas in a framework which views the HI as the result of an ongoing “photodissociation ↔ dust grain reformation” equilibrium in a cold, clumpy molecular medium with a small area filling factor.

scholarly journals The molecular gas content in a protocluster at z = 17: Star formation and AGN feedback

2019 ◽  
Vol 15 (S352) ◽  
pp. 168-170
Author(s):  
Q. D’Amato ◽  
I. Prandoni ◽  
R. Gilli ◽  
M. Massardi ◽  
E. Liuzzo ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Gas Content ◽  
Molecular Gas ◽  
Star Forming ◽  
Physical Conditions ◽  
Radio Jets ◽  
Multi Wavelength ◽  
Data Coverage

AbstractA large-scale structure has been recently discovered at z = 1.7, around a powerful FRII radio galaxy. Eight Star Forming Galaxies (SFGs) have been discovered within Δ z ≍ 0.0095 and at < 1 Mpc from the FRII, indicating that this is a signpost of a protocluster. Furthermore, a significant X-ray diffuse emission overlapping the Eastern lobe of the FRII has been detected. Protoclusters are the ideal targets to investigate the complex assembly processes leading to the formation of local galaxy clusters. We will exploit new ALMA CO(2-1) observations (PI: R. Gilli) of the entire region around the FRII galaxy to trace the molecular gas content, in order to discover new protocluster members. Coupling these measurements with the multi-wavelength data coverage available for this field, we aim at placing constrains on the physical conditions in which star formation occurs, and ultimately infer the role of the radio jets in triggering it.

The role of AGN in galaxy star formation: A case study of a radio galaxy at z = 2.6

2019 ◽  
Vol 15 (S356) ◽  
pp. 224-224
Author(s):  
Allison Man
Keyword(s):  
Star Formation ◽  
Radio Galaxy ◽  
Star Formation History ◽  
Molecular Gas ◽  
Ob Stars ◽  
Massive Galaxies ◽  
Radio Jets ◽  
Formation History

AbstractRadio galaxies are ideal sites to scrutinize AGN feedback physics, as they are massive galaxies with jets that interact with the surrounding ISM. I will present a detailed analysis of the recent star formation history and conditions of a starbursting, massive radio galaxy at z = 2.6, PKS 0529-549. In the 8.5-hour VLT/X-Shooter spectrum, we detect unambiguous signatures of stellar photospheric absorption lines originating from OB-stars. Comparison with model spectra shows that more than one burst took place in its recent past: the most recent one at 4 − 7 Myr, and another aged ⩾20 Myr. ALMA observations of the [CI] atomic carbon emission line indicates that it has a low molecular gas fraction (∼13%) and short depletion time (∼40 Myr). Most intriguing is the modest velocity dispersion (⩽50 km/s) of these photospheric lines and the ALMA [CI] cold gas. We attribute its efficient star formation to compressive gas motions, induced by radio jets and/or interaction. Star formation works in concert with the AGN to remove any residual molecular gas and eventually leads to quenching.

scholarly journals Molecular gas in the central region of NGC 7213

2020 ◽  
Vol 641 ◽  
pp. A151
Author(s):  
F. Salvestrini ◽  
C. Gruppioni ◽  
F. Pozzi ◽  
C. Vignali ◽  
A. Giannetti ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Large Scale ◽  
Host Galaxy ◽  
Molecular Gas ◽  
X Ray ◽  
Gas Kinematics ◽  
Star Formation Activity ◽  
Multi Wavelength

We present a multi-wavelength study (from X-ray to mm) of the nearby low-luminosity active galactic nucleus NGC 7213. We combine the information from the different bands to characterise the source in terms of contribution from the AGN and the host-galaxy interstellar medium. This approach allows us to provide a coherent picture of the role of the AGN and its impact, if any, on the star formation and molecular gas properties of the host galaxy. We focused our study on archival ALMA Cycle 1 observations, where the CO(2–1) emission line has been used as a tracer of the molecular gas. Using the 3DBAROLO code on ALMA data, we performed the modelling of the molecular gas kinematics traced by the CO(2–1) emission, finding a rotationally dominated pattern. The molecular gas mass of the host galaxy was estimated from the integrated CO(2–1) emission line obtained with APEX data, assuming an αCO conversion factor. Had we used the ALMA data, we would have underestimated the gas masses by a factor ∼3, given the filtering out of the large-scale emission in interferometric observations. We also performed a complete X-ray spectral analysis on archival observations, revealing a relatively faint and unobscured AGN. The AGN proved to be too faint to significantly affect the properties of the host galaxy, such as star formation activity and molecular gas kinematics and distribution.

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