Bulges and discs of spiral galaxies: edge-on perspective
N. Ya. Sotnikova, V. P. Reshetnikov, A. V. Mosenkov
备注:
10 pages, 5 figures, submitted to Astron. Astrophys. Trans., talk presented at the meeting "Dynamics and Evolution of Disc Galaxies" held in Moscow and Pushchino, Russia, May 31 - June 4th, 2010
We present a sample of edge-on spiral galaxies both of early and late types.The sample consists of 175 galaxies in the Ks-filter, 169 galaxies in the H-filter and 165 galaxies in the J-filter. Bulge and disc decompositions of each galaxy image, taken from the Two Micron All Sky Survey (2MASS), were performed. We discuss several scaling relations for bulges and discs which indicate a tight link between their formation and evolution. We show that galaxies with bulges fitted by the Sersic index n<2 (pseudobulges) have quite different distributions of their structural parameters than galaxies with n>=2 bulges (classical bulges). First of all, the distribution of the apparent bulge axis ratio q_b for the subsample with n<2 can be attributed to triaxial, nearly prolate bulges, while n>=2 bulges seem to be oblate spheroids with moderate flattening. Secondly, the Photometric Plane of the sample bulges is not flat and has a prominent curvature towards small values of n. Thirdly, despite of the existence of a clear relation between the flattening of stellar discs h/z_0 and the relative mass of a spherical component, the distributions over both parameters are quite different for galaxies possesing bulges and pseudobulges.
We present a comparison of azimuthally averaged radial surface brightness mu(r) profiles and analytical bulge-disc decompositions (de Vaucouleurs, r^(1/4) bulge plus exponential disc) for spiral galaxies using Hubble Space Telescope/Advanced Camera for Surveys V-band imaging from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). In the established classification scheme, antitruncated mu(r) profiles (Type III) have a broken exponential disc with a shallower region beyond the break radius r_brk. The excess light at large radii (r > r_brk) can either be caused by an outer exponential d…
The similar stellar populations of quiescent spiral and elliptical galaxies
我们比较了星系动物园和SDSS DR 7中视觉分类的非恒星形成螺旋星系和椭圆星系中心区域的恒星星族特性。这些星系位于红移范围$0.04<z<0.1$内,恒星质量大于$logM_*=10.4$。我们只选择正面的螺旋星系,以避免污染的光从光盘的SDSS光纤,使强大的视觉识别的螺旋结构。总的来说,我们发现,星系与较大的中央恒星速度色散,无论形态类型,有年龄较大,较高的金属丰度,和增加过剩的α-元素。年龄和α增强,在固定的速度分散,不依赖于形态类型。唯一的参数,在一个给定的速度色散,与形态类型相关的是金属丰度,在那里的螺旋星系的凸起的金属丰度是0.07德克斯高于椭圆星系。然而,对于具有给定总恒星质量的星系,这种对形态的依赖性消失了。假设,对于我们的样本,速度色散跟踪的质量单独的凸起,而不是总质量(凸起+磁盘)的星系,我们的研究结果意味着星系的形成时代和恒星形成期的持续时间与质量的凸起。金属保留在星系中的程度,而不是由于流出而被移除,由星系的总质量决定。
We present observations of pseudobulges in S0 and spiral galaxies using imaging data taken with the Spitzer Infra-Red Array Camera. We have used 2-d bulge-disk-bar decomposition to determine structural parameters of 185 S0 galaxies and 31 nearby spiral galaxies. Using the Sersic index and the position on the Kormendy diagram to classify their bulges as either classical or pseudo, we find that 25 S0s (14%) and 24 spirals (77%) host pseudoblges. The fraction of pseudobulges we find in spiral galaxies is consistent with previous results obtained with optical data and show that the evolution of a …
The populations of bright planetary nebulae in the discs of spirals appear to differ in their spectral properties from those in ellipticals and the bulges of spirals. The bright planetary nebulae from the bulge of the Milky Way are entirely compatible with those observed in the discs of spiral galaxies. The similarity might be explained if the bulge of the Milky Way evolved secularly from the disc, in which case the bulge should be regarded as a pseudo-bulge.
Based on SDSS data, we have selected a sample of nine edge-on spiral galaxies with bulges whose major axes show a high inclination to the disk plane. Such objects are called polar-bulge galaxies. They are similar in their morphology to polar-ring galaxies, but the central objects in them have small size and low luminosity. We have performed a photometric analysis of the galaxies in the g and r bands and determined the main characteristics of their bulges and disks. We show that the disks of such galaxies are typical for the disks of spiral galaxies of late morphological types. The integrated c…
The role of disk instabilities, such as bars and spiral arms, and the associated resonances, in growing bulges in the inner regions of disk galaxies have long been studied in the low-redshift nearby Universe. There it has long been probed observationally, in particular through peanut-shaped bulges. This secular growth of bulges in modern disk galaxies is driven by weak, non-axisymmetric instabilities: it mostly produces pseudo-bulges at slow rates and with long star-formation timescales. Disk instabilities at high redshift (z>1) in moderate-mass to massive galaxies (10^10 to a few 10^11 Msun o…