The Bar-Bulge Relation in Non-dwarf SB0 Galaxies in the Central Region of Coma Cluster

In this paper we explore the formation of bars and present the bulge and bar properties and their correlations for a sample of lenticular barred(SB0)and lenticular unbarred(S0)galaxies in the central region of the Coma Cluster using HST/ACS data.In our sample,we identified bar features using the luminosity profile decomposition software GALFIT.We classified the bulges based on Sérsic index and Kormendy relation.We found that the average mass of the bulge in SB0 galaxies is 1.48×10^(10)M☉whereas the average mass of the bulge in S0 galaxies is 4.3×10^(10)M☉.We observe that SB0 galaxies show lower bulge concentration,low mass and also smaller B/T values compared to S0 galaxies.Using the Kormendy relation,we found that among the lenticular barred galaxies,82%have classical bulges and 18%have pseudo bulges.These classical bulges have low masses compared to the classical bulges of unbarred galaxies.S0,galaxies with massive classical bulges do not host bars.We also found that for all SB0s the bulge effective radius is less than the bar effective radius.SB0 galaxies with classical bulges suggest that the bar may have formed by mergers.

Stellar and HI Mass Functions Predicted by a Simple Preheating Galaxy Formation Model

According to the new preheating mechanism of galaxy formation suggested by Mo et al., we construct a simple model of formation of disk galaxies within the current paradigm of galaxy formation. It incorporates preheating, gas cooling, bulge formation and star for- mation. The predicted stellar and HI mass functions of galaxies are discussed and compared with the observations. It is found that our model can roughly match both the observed galaxy luminosity function and the observed HI-mass function.

On the Black Hole - Bulge Mass Ratios in Narrow-Line Seyfert 1 Galaxies

We present estimated ratios of the central black hole mass to the bulge mass (Mbh/Mbulge) for 15 Narrow Line Seyfert 1 galaxies (NLS1s). It is found that NLS1s apparently have lower mass ratios: the average mass ratio is about 1 × 10-4 with a spread of 2, which is one order of magnitude lower than for Broad Line AGNs and quiescent galaxies. This lower value, as compared to that established essentially for all other types of galaxies, can be accounted for by an underestimation of the black hole masses and an overestimation of the bulge masses in the NLS1s.

Low Surface Brightness Galaxies Selected by Different Model Fitting

We present a study of low surface brightness galaxies(LSBGs) selected by fitting the images for all the galaxies inα.40 SDSS DR7 sample with two kinds of single-component models and two kinds of two-component models(disk+bulge):single exponential,single sersic,exponential+deVaucular(exp+deV),and exponential+sérsic(exp+ser).Under the criteria of the B band disk central surface brightness μ_(0,disk)(B)≥22.5 mag arcsec^(-2) and the axis ratio b/a> 0.3,we selected four none-edge-on LSBG samples from each of the models which contain 1105,1038,207,and 75 galaxies,respectively.There are 756 galaxies in common between LSBGs selected by exponential and sersic models,corresponding to 68.42% of LSBGs selected by the exponential model and 72.83% of LSBGs selected by the sersic model,the rest of the discrepancy is due to the difference in obtaining μ_(0) between the exponential and sersic models.Based on the fitting,in the range of 0.5≤n≤1.5,the relation of μ_(0) from two models can be written as μ_(0,sérsic)-μ_(0,exp)=-1.34(n-1).The LSBGs selected by disk+bulge models(LSBG_(2)comps) are more massive than LSBGs selected by single-component models(LSBG_1comp),and also show a larger disk component.Though the bulges in the majority of our LSBG_(2)comps are not prominent,more than 60% of our LSBG_(2)comps will not be selected if we adopt a single-component model only.We also identified 31 giant low surface brightness galaxies(gLSBGs) from LSBG_(2)comps.They are located at the same region in the color-magnitude diagram as other gLSBGs.After we compared different criteria of gLSBGs selection,we find that for gas-rich LSBGs,M_(*)> 10^(10)M_⊙ is the best to distinguish between gLSBGs and normal LSBGs with bulge.

Radio Luminosity,Black Hole Mass and Eddington Ratio for Quasars from the Sloan Digital Sky Survey

We investigate the MBH-σ＊ relation for radio-loud quasars with redshifl z 〈 0.83 in Data Release 3 of the Sloan Digital Sky Survey （SDSS）. The sample consists of 3772 quasars with better models of the H/4 and [O Ⅲ] lines and available radio luminosity, including 306 radio-loud quasars, 3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity （181 radio-quiet quasars with measured radio luminosity）. The virial supermassive black hole mass （MBH） is calculated from the broad Hβline, and the host stellar velocity dispersion （σ＊） is traced by the core [O Ⅲ] gaseous velocity dispersion. The radio luminosity and radio loudness are derived from the FIRST catalog. Our results are as follows： （1） For radio-quiet quasars, we confirm that there is no obvious deviation from the MBH-σ＊ relation defined for inactive galaxies when the uncertainties in ~IBH and the luminosity bias are concerned. （2） We find that the radio-loud quasars deviate more from the MBH-σ＊ relation than do the radio-quiet quasars. This deviation is only partly due to a possible cosmological evolution of the MBH-σ＊ relation and the luminosity bias. （3） The radio luminosity is proportional to MBH1.28＋0.23-0.16（LBol/LEdd） ^1.29＋0.31-0.24 for radio-quiet quasars and to -MBH3.10＋0.60-0.70（LBol/LEdd）^4.18＋1.40-1.10 - for radio-loud quasars. The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities, such as the spin of the black hole.

Astrophysical applications of gravitational microlensing

Since the first discovery of microlensing events nearly two decades ago, gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications. The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights. （1） Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects （MACHOs）. This confirms most dark matter is non-baryonic, consistent with other observations. （2） Microlensing has discovered about 20 extrasolar planets （16 published）, including the first two Jupiter-Saturn like systems and the only five ＂cold Neptunes＂ yet de- tected. They probe a different part of the parameter space and will likely provide the most stringent test of core accretion theory of planet formation. （3） Microlensing pro- vides a unique way to measure the mass of isolated stars, including brown dwarfs and normal stars. Half a dozen or so stellar mass black hole candidates have also been pro- posed. （4） High-resolution, target-of-opportunity spectra of highly-magnified dwarf stars provide intriguing ＂age＂ determinations which may either hint at enhanced he- lium enrichment or unusual bulge formation theories. （5） Microlensing also measured limb-darkening profiles for close to ten giant stars, which challenges stellar atmo- sphere models. （6） Data from surveys also provide strong constraints on the geometry and kinematics of the Milky Way bar （through proper motions）; the latter indicates predictions from current models appear to be too anisotropic compared with observa- tions. The future of microlensing is bright given the new capabilities of current surveys and forthcoming new telescope networks from the ground and from space. Some open issues in the field are identified and briefly discussed.

Local galaxies with compact cores as the possible descendants of massive compact quiescent galaxies at high redshift

In order to test a possible evolutionary scenario of high-z compact quiescent galaxies(cQGs)that they can survive as local compact cores embedded in local massive galaxies with different morphology classes, we explore the star formation histories of local compact cores according to their spectral analysis.We build a sample of 182 massive galaxies with compact cores(M*,core> 10^10.6 M⊙) at 0.02 ≤ z ≤ 0.06 from SDSS DR7 spectroscopic catalogue. The STARLIGHT package is used to analyze the median stacked spectra and derive the stellar ages and metallicities. Our main results show that local compact cores have the average age of about 12.1 ± 0.6 Gyr, indicating their early formation at z > 3, which is consistent with the formation redshifts of cQGs at 1 < z < 3. Together with previous studies, our result that local compact cores have similar formation redshifts as those of high-z cQGs, supports that local massive galaxies with compact cores are possible descendants of cQGs. Morphological study of local galaxies with compact cores suggests that there would be multiple possible evolutionary paths for high-z cQGs: most of them(> 80%)will evolve into local massive early-type galaxies according to dry minor merger, while some of them(~ 15%) will build substantial stellar/gas discs according to the late-time gas accretion and sustaining star formation, and finally grow up into spiral galaxies.

The bar and spiral arms in the Milky Way: structure and kinematics

The Milky Way is a spiral galaxy with the Schechter characteristic luminosity L*,thus an important anchor point of the Hubble sequence of all spiral galaxies.Yet the true appearance of the Milky Way has remained elusive for centuries.We review the current best understanding of the structure and kinematics of our home galaxy,and present an updated scientifically accurate visualization of the Milky Way structure with almost all components of the spiral arms,along with the COBE image in the solar perspective.The Milky Way contains a strong bar,four major spiral arms,and an additional arm segment(the Local arm)that may be longer than previously thought.The Galactic boxy bulge that we observe is mostly the peanut-shaped central bar viewed nearly end-on with a bar angle of^25°-30°from the SunGalactic center line.The bar transitions smoothly from a central peanut-shaped structure to an extended thin part that ends around R^5 kpc.The Galactic bulge/bar contains^30%-40%of the total stellar mass in the Galaxy.Dynamical modelling of both the stellar and gas kinematics yields a bar pattern rotation speed of^35-40 km s-1 kpc-1,corresponding to a bar rotation period of^160-180 Myr.From a galaxy formation point of view,our Milky Way is probably a pure-disk galaxy with little room for a significant merger-made,"classical"spheroidal bulge,and we give a number of reasons why this is the case.

Variation of physical properties across the green valley for local galaxies

We selected a sample of nearby galaxies from the Sloan Digital Sky Survey Data Release 7(SDSS DR7) to investigate the variation of physical properties from the blue cloud to green valley to red sequence.The sample is limited to a narrow range in the color-stellar mass diagram. After splitting green valley galaxies into two parts—a bluer green valley(green 1) and a redder one(green 2) and three stellar mass bins,we investigate the variation of physical properties across the green valley region. Our main results are as follows:(i) The percentages of pure bulge and bulge-dominated/elliptical galaxies increase gradually from blue cloud to red sequence while the percentages of pure disk and disk-dominated/spiral galaxies decrease gradually in all stellar mass bins and different environments.(ii) With the analysis of morphological and structural parameters(e.g., concentration(C) and the stellar mass surface density within the central 1 kpc(Σ1)), red galaxies show more luminous and compact cores than both green valley and blue galaxies, while blue galaxies show the opposite behavior in all stellar mass bins.(iii) A strong negative(positive) relationship between bulge-to-total light ratio(B/T) and specific star formation rate(sSFR)(D_(4000)) is found from blue to red galaxies. Our results indicate that the growth in bulge plays an important role when the galaxies change from the blue cloud, to the green valley and to the red sequence.

A revised rotation curve of the Milky Way with maser astrometry

We reconstruct the rotation curve of the Milky Way using the new trigono-metric parallax and proper motion data for masers in 43 high-mass star-forming re-gions obtained by VLBI, as well as the existing data from the literature, based on a new set of galactic constants （R0, -0） = （8.4 kpc, 254 km s^-1） measured by Reid et al. The revised rotation curve of the Milky Way is almost fiat or slightly rising in the region from about 6 to 15 kpc. The rotation velocities within 5 kpc of the Galactic center, as determined by VLBI, differ from those obtained by measurement of the HI-and CO-line tangent velocities. We fitted the revised rotation curve arising from three mass components： the bulge, disk and dark matter halo. The total mass of the Milky Way is found to be 2.3× 10^11 M⊙ （20 kpc）. This is about 10% larger than that from Sofue et al, and is comparable with the mass of M31, 3.4× 10^11 M⊙ （35 kpc）, given by Carignan et al. The limited accurate observational data, especially the VLBI data, do not permit a fully satisfactory fit to the rotation curve. The extensive par-allax and proper motion data that will be produced by the Bar and Spiral Structure Legacy Survey project in the next few years should lead to considerable progress in understanding the rotation curve and dark matter halo of the Milky Way.