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>

Plastic Surgery and Aggressive Skating: Can Business Mix with Pleasure?

Sody A Naimer 대한성형외과학회 2014 Archives of Plastic Surgery Vol.41 No.1

Significance of the tethered maxillary frenulum: a questionnaire-based observational cohort study

Naimer, Sody A.,Israel, Ariel,Gabbay, Aviezer The Korean Pediatric Society 2021 Clinical and Experimental Pediatrics (CEP) Vol.64 No.3

Background: The clinical significance of lip-tie, or a tethered maxillary frenulum, remains under debate. Clinicians and parents are often perplexed when deciding whether procedures available to relieve a seemingly tight or severe maxillary frenulum are needed. Purpose: No previous studies have assessed the consequences of not subjecting a tethered maxillary frenulum in newborns to surgical intervention. This study aimed to contribute the first prospective trial on this topic with a relatively extended follow-up of these newborn infants. Methods: This prospective observational questionnaire-based cohort trial was performed in a community setting and aimed to determine whether lip-tie is associated with an increased likelihood of eventual feeding or oral disorders. Results: The convenience sample comprised of 61 consecutively arriving infants with concomitant tethered frenula who were treated at the clinic for various reasons. This cohort was compared with a random sample of 66 age-matched children for a mean follow-up period of 6.42 years. Infants undergoing oropharyngeal procedures were excluded. Awareness of a deviation in oral structures was reported by 18% of the study group versus 0% of the controls. Mothers participating in the study group (24.6%) less frequently recalled painful nipples or discomfort during breastfeeding than those in the control group (47.0%) (P<0.01). There were no intergroup differences in other types of feeding difficulty, dental hygiene, pronunciation, or speech development. Conclusion: Our findings suggest that a tethered labial frenulum is not associated with an increase in breastfeeding disturbances or oral disorders. These data encourage clinicians to question the need to intervene in cases of tethered maxillary frenula.

Clues on the origin of galactic angular momentum from looking at galaxy pairs

Cervantes-Sodi, B.,Hernandez, X.,Park, Changbom Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.402 No.3

<P>ABSTRACT</P><P>We search for correlations between the spins in pairs of spiral galaxies, to study if the angular momentum gain for each galaxy was the result of tidal torques imprinted by the same tidal field. To perform our study we made use of a sample of galaxy pairs identified using the Sloan Digital Sky Survey. We find a weak, but statistically significant correlation between the spin magnitudes of neighbouring galaxies, but no clear alignment between their orientations. We show that events such as interactions with close neighbours play an important role in the value of the spin for the final configuration, as we find that these interactions tend to reduce the value of the λ spin parameter of late-type galaxies considerably, with dependence on the morphology of the neighbour. This implies that the original tidal field for each pair could have been similar, but the redistribution of angular momentum at later stages of evolution is important.</P>

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>

The spin of spiral galaxies in different environments

Bernardo Cervantes-Sodi 한국천문학회 2010 天文學會報 Vol.35 No.1

Quantifying galactic morphological transformations in the cluster environment

Bernardo Cervantes-Sodi,ChangbomPark,X.Hernandez 한국천문학회 2010 天文學會報 Vol.35 No.2

On dark matter haloes of barred disc galaxies

Bernardo Cervantes Sodi,Cheng Li,Changbom Park,Lixin Wang,Ye Lin 한국천문학회 2014 天文學會報 Vol.39 No.2

Quantifying galactic morphological transformations in the cluster environment

Cervantes‐,Sodi, B.,Park, Changbom,Hernandez, X.,Hwang, Ho Seong Blackwell Publishing Ltd 2011 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.414 No.1

<P><B>ABSTRACT</B></P><P>We study the effects of the cluster environment on galactic morphology by defining a dimensionless angular momentum parameter, λ<SUB>d</SUB>, to obtain a quantitative and objective measure of galaxy type. The use of this physical parameter allows us to take the study of morphological transformations in clusters beyond the measurements of merely qualitative parameters, e.g. spiral/elliptical (S/E) ratios, to a more physical footing. To this end, we employ an extensive Sloan Digital Sky Survey sample (Data Release 7) with galaxies associated with Abell galaxy clusters. The sample contains 121 relaxed Abell clusters and over 51 000 individual galaxies, which guarantees a thorough statistical coverage over a wide range of physical parameters. We find that the median λ<SUB>d</SUB> value tends to decrease as we approach the cluster centre, with different dependences according to the mass of the galaxies and the hosting cluster; low‐ and intermediate‐mass galaxies show a strong dependence, while massive galaxies seem to show, at all radii, low λ<SUB>d</SUB> values. By analysing trends in λ<SUB>d</SUB> as functions of the nearest neighbour environment, clustercentric radius and velocity dispersion of clusters, we can identify clearly the leading physical processes at work. We find that in massive clusters (σ > 700 km s<SUP>−1</SUP>), the interaction with the cluster central region dominates, whilst in smaller clusters galaxy–galaxy interactions are chiefly responsible for driving galactic morphological transformations.</P>

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>