اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe environment of barred galaxies in the low-redshift Universe
60
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
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 $sim$50 kpc around the barred galaxies when compared to unbarred galaxies form 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.
قيم البحث
اقرأ أيضاً
We apply a halo-based group finder to four large redshift surveys, the 2MRS, 6dFGS, SDSS and 2dFGRS, to construct group catalogs in the low-redshift Universe. The group finder is based on that of Yang et al. but with an improved halo mass assignment
so that it can be applied uniformly to various redshift surveys of galaxies. Halo masses are assigned to groups according to proxies based on the stellar mass/luminosity of member galaxies. The performances of the group finder in grouping galaxies according to common halos and in halo mass assignments are tested using realistic mock samples constructed from hydrodynamical simulations and empirical models of galaxy occupation in dark matter halos. Our group finder finds $sim 94%$ of the correct true member galaxies for $90-95%$ of the groups in the mock samples; the halo masses assigned by the group finder are un-biased with respect to the true halo masses, and have a typical uncertainty of $sim0.2,{rm dex}$. The properties of group catalogs constructed from the observational samples are described and compared with other similar catalogs in the literature.
We investigate possible environmental and morphological trends in the $zsim0$ bar fraction using two carefully selected samples representative of a low-density environment (the isolated galaxies from the AMIGA sample) and of a dense environment (gala
xies in the Virgo cluster). Galaxies span a stellar mass range from $10^8$ to $10^{12}$M$_{odot}$ and are visually classified using both high-resolution NIR (H-band) imaging and optical texttt{rgb} images. We find that the bar fraction in disk galaxies is independent of environment suggesting that bar formation may occur prior to the formation of galaxy clusters. The bar fraction in early type spirals ($Sa-Sb$) is $sim$50%, which is twice as high as the late type spirals ($Sbc-Sm$). The higher bar fraction in early type spirals may be due to the fact that a significant fraction of their bulges are pseudo-bulges which form via the buckling instability of a bar. i.e. a large part of the Hubble sequence is due to secular processes which move disc galaxies from late to early types. There is a hint of a higher bar fraction with higher stellar masses which may be due to the susceptibility to bar instabilities as the baryon fractions increase in halos of larger masses. Overall, the $S0$ population has a lower bar fraction than the $Sa-Sb$ galaxies and their barred fraction drops significantly with decreasing stellar mass. This supports the notion that $S0s$ form via the transformation of disk galaxies that enter the cluster environment. The gravitational harassment thickens the stellar disks, wiping out spiral patterns and eventually erasing the bar - a process that is more effective at lower galaxy masses.
(Abridge) Bars are very common in the centre of the disc galaxies, and they drive the evolution of their structure. A volume-limited sample of 2106 disc galaxies extracted from the Sloan Digital Sky Survey Data Release 5 was studied to derive the bar
fraction, length, and strength as a function of the morphology, size, local galaxy density, light concentration, and colour of the host galaxy. The bars were detected using the ellipse fitting method and Fourier analysis method. The ellipse fitting method was found to be more efficient in detecting bars in spiral galaxies. The fraction of barred galaxies turned out to be 45%. A bar was found in 29% of the lenticular galaxies, in 55% and 54% of the early- and late-type spirals, respectively. The bar length (normalised by the galaxy size) of late-type spirals is shorter than in early-type or lenticular ones. A correlation between the bar length and galaxy size was found with longer bars hosted by larger galaxies. The bars of the lenticular galaxies are weaker than those in spirals. Moreover, the unimodal distribution of the bar strength found for all the galaxy types argues against a quick transition between the barred and unbarred statues. There is no difference between the local galaxy density of barred and unbarred galaxies. Besides, neither the length nor strength of the bars are correlated with the local density of the galaxy neighbourhoods. In contrast, a statistical significant difference between the central light concentration and colour of barred and unbarred galaxies was found. Bars are mostly located in less concentrated and bluer galaxies. These results indicate that the properties of bars are strongly related to those of their host galaxies, but do not depend on the local environment.
In the local Universe, there is a handful of dwarf compact star-forming galaxies with extremely low oxygen abundances. It has been proposed that they are young, having formed a large fraction of their stellar mass during their last few hundred Myr. H
owever, little is known about the fraction of young stellar populations in more massive galaxies. In a previous article, we analyzed 280 000 SDSS spectra to identify a surprisingly large sample of more massive Very Young Galaxies (VYGs), defined to have formed at least $50%$ of their stellar mass within the last 1 Gyr. Here, we investigate in detail the properties of a subsample of 207 galaxies that are VYGs according to all three of our spectral models. We compare their properties with those of control sample galaxies (CSGs). We find that VYGs tend to have higher surface brightness and to be more compact, dusty, asymmetric, and clumpy than CSGs. Analysis of a subsample with HI detections reveals that VYGs are more gas-rich than CSGs. VYGs tend to reside more in the inner parts of low-mass groups and are twice as likely to be interacting with a neighbour galaxy than CSGs. On the other hand, VYGs and CSGs have similar gas metallicities and large scale environments (relative to filaments and voids). These results suggest that gas-rich interactions and mergers are the main mechanisms responsible for the recent triggering of star formation in low-redshift VYGs, except for the lowest mass VYGs, where the starbursts may arise from a mixture of mergers and gas infall.
We present a new suite of mock galaxy catalogs mimicking the low-redshift Universe, based on an updated halo occupation distribution (HOD) model and a scaling relation between optical properties and the neutral hydrogen (HI) content of galaxies. Our
algorithm is constrained by observations of the luminosity function and luminosity- and colour-dependent clustering of SDSS galaxies, as well as the HI mass function and HI-dependent clustering of massive HI-selected galaxies in the ALFALFA survey. Mock central and satellite galaxies with realistic values of $r$-band luminosity, $g-r$ and $u-r$ colour, stellar mass and HI mass are populated in an $N$-body simulation, inheriting a number of properties of the density and tidal environment of their host halos. The host halo of each central galaxy is also `baryonified with realistic spatial distributions of stars as well as hot and cold gas, along with the corresponding rotation curve. Our default HOD assumes that galaxy properties are a function of group halo mass alone, and can optionally include effects such as galactic conformity and colour-dependent galaxy assembly bias. The mocks predict the relation between the stellar mass and HI mass of massive HI galaxies, as well as the 2-point cross-correlation function of spatially co-located optical and HI-selected samples. They enable novel null tests for galaxy assembly bias, provide predictions for the HI velocity width function, and clarify the origin and universality of the radial acceleration relation in the $Lambda$CDM framework.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
