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RISS 인기검색어
- 검색키워드
- 저자 : Bernardo Cervantes-Sodi (검색결과 7 건)
- 무료
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THE GALACTIC SPIN OF AGN GALAXIES
Cervantes-Sodi, Bernardo,Hernandez, X.,Park, Changbom,Choi, Yun-Young IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.735 No.1
<P>Using an extensive sample of galaxies selected from the Sloan Digital Sky Survey Data Release 5, we compare the angular momentum distribution of active galactic nuclei (AGNs) with non-AGN hosting late-type galaxies. To this end we characterize galactic spin through the dimensionless angular momentum parameter lambda, which we estimate through simple dynamical considerations. Using a volume-limited sample, we find a considerable difference when comparing the empirical distributions of lambda for AGNs and non-AGN galaxies, the AGNs showing typically low lambda values and associated dispersions, while non-AGNs present higher lambda values and a broader distribution. A more striking difference is found when looking at lambda distributions in thin M-r cuts; while the spin of non-AGN galaxies presents an anticorrelation with M-r, with bright (massive) galaxies having low spins, AGN host galaxies present uniform values of lambda at all magnitudes, a behavior probably imposed by the fact that most late-type AGN galaxies present a narrow range in color, with a typical constant lambda value. We also find that the fraction of AGN hosting galaxies in our sample strongly depends on galactic spin, increasing dramatically for decreasing lambda. For AGN host galaxies, we compute the mass of their supermassive black holes and find that this value tends to be higher for low spin galaxies, even at fixed luminosity, a result that could account, to a certain extent, for the spread on the luminosity-black-hole mass relation.</P>
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DARK MATTER HALOS OF BARRED DISK GALAXIES
Sodi, Bernardo Cervantes,Li, Cheng,Park, Changbom IOP Publishing 2015 The Astrophysical journal Vol.807 No.1
<P>We use a large volume-limited sample of disk galaxies drawn from the Sloan Digital Sky Survey Data Release 7 to study the dependence of the bar fraction on the stellar-to-halo mass ratio, making use of a group catalog, and we identify central and satellite galaxies in our sample. For the central galaxies in the sample we estimate the stellar-tohalo mass ratio (M-*/M-h) and find that the fraction of barred galaxies is a strong function of this ratio, especially for the case of strong bars. Bars are more common in galaxies with high M-*/M-h values, as expected from early theoretical works that showed that systems with massive dark matter halos are more stable against bar instabilities. We find that the change of the bar fraction with M-h and M-* is stronger if we consider a relation with the form f(bar) = f(bar)(M-*(alpha)/M-h) with alpha = 1.5, and that the bar fraction is largely independent of other physical properties such as color and spin parameter when M-*(3/2)/M-h is fixed. With our sample of galaxies segregated into centrals and satellites, we also compare the fraction of barred galaxies in each group, finding a slightly higher bar fraction for satellites when compared with centrals at fixed stellar mass, but at fixed color this difference becomes very weak. This result, in agreement with previous studies, confirms that the bar fraction does not directly depend on the group/cluster environment, but the dependence exists through its dependence on internal morphology.</P>
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THE ENVIRONMENT OF BARRED GALAXIES IN THE LOW-REDSHIFT UNIVERSE
Lin, Ye,Sodi, Bernardo Cervantes,Li, Cheng,Wang, Lixin,Wang, Enci IOP Publishing 2014 The Astrophysical journal Vol.796 No.2
<P>We present a study of the environment of barred galaxies using a volume-limited sample of over 30,000 galaxies drawn from the Sloan Digital Sky Survey. We use four different statistics to quantify the environment: the projected two-point cross-correlation function, the background-subtracted number count of neighbor galaxies, the overdensity of the local environment, and the membership of our galaxies to galaxy groups to segregate central and satellite systems. For barred galaxies as a whole, we find a very weak difference in all the quantities compared to unbarred galaxies of the control sample. When we split our sample into early- and late-type galaxies, we see a weak but significant trend for early-type galaxies with a bar to be more strongly clustered on scales from a few 100 kpc to 1 Mpc when compared to unbarred early-type galaxies. This indicates that the presence of a bar in early-type galaxies depends on the location within their host dark matter halos. This is confirmed by the group catalog in the sense that for early-types, the fraction of central galaxies is smaller if they have a bar. For late-type galaxies, we find fewer neighbors within similar to 50 kpc around the barred galaxies when compared to unbarred galaxies from the control sample, suggesting that tidal forces from close companions suppress the formation/growth of bars. Finally, we find no obvious correlation between overdensity and the bars in our sample, showing that galactic bars are not obviously linked to the large-scale structure of the universe.</P>
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Star Formation Activity of Barred Spiral Galaxies
Kim, Eunbin,Hwang, Ho Seong,Chung, Haeun,Lee, Gwang-Ho,Park, Changbom,Sodi, Bernardo Cervantes,Kim, Sungsoo S. American Astronomical Society 2017 The Astrophysical journal Vol.845 No.2
<P>We study the star formation activity of nearby galaxies with bars using a sample of late-type galaxies at 0.02 <= z <= 0.05489 and M-r < -19.5 from the Sloan Digital Sky Survey. We compare the physical properties of strongly and weakly barred galaxies with those of non-barred galaxies that have stellar mass and redshift distributions similar to barred galaxies. We find that the star formation activity of strongly barred galaxies probed by starburstiness, g -r, NUV -r, and mid-infrared [3.4]-[12] colors is, on average, lower than that of non-barred galaxies. However, weakly barred galaxies do not show such a difference between barred and non-barred galaxies. The amounts of atomic and molecular gas in strongly barred galaxies are smaller than those in non-barred galaxies, and the gas metallicity is higher in strongly barred galaxies than in non-barred galaxies. The gas properties of weakly barred galaxies again show no difference from those of non-barred galaxies. We stack the optical spectra of barred and non-barred galaxies in several mass bins and fit to the stacked spectra with a spectral fitting code, STARLIGHT. We find no significant difference in stellar populations between barred and non-barred galaxies for both strongly and weakly barred galaxies. Our results are consistent with the idea that the star formation activity of barred galaxies was enhanced in the past along with significant gas consumption, and is currently lower than or similar to that of non-barred galaxies. The past star formation enhancement depends on the strength of bars.</P>
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