bluuebunny/crossref_metadata_2025 huggingface dataset:
A connection between bulge properties and the bimodality of galaxies
Authors: Drory Niv , Fisher David B.
Published: July 2008

The global colors and structure of galaxies have recently been shown to follow bimodal distributions. Galaxies separate into a “red sequence”, populated prototypically by early-type galaxies, and a “blue cloud”, whose typical objects are late-type disk galaxies. Intermediate-type (Sa-Sbc) galaxies populate both regions. It has been suggested that this bimodality reflects the two-component nature of disk-bulge galaxies. However, it has now been established that there are two types of bulges: “classical bulges” that are dynamically hot systems resembling (little) ellipticals, and “pseudobulges”, dynamically cold, flattened, disk-like structures that could not have formed via violent relaxation. Alas, given the different formation mechanisms of these bulges, the question is whether at types Sa-Sbc, where both bulge types are found, the red-blue dichotomy separates galaxies at some value of disk-to-bulge ratio,B/T, or, whether it separates galaxies of different bulge type, irrespective of theirB/T. In this paper, we identify classical bulges and pseudobulges morphologically with HST images in a sample of nearby galaxies. Detailed surface photometry reveals that: (1) The red – blue dichotomy is a function of bulge type: at the sameB/T, pseudobulges are in globally blue galaxies and classical bulges are in globally red galaxies. (2) Bulge type also predicts where the galaxy lies in other (bimodal) global structural parameters: global Sérsic index and central surface brightness. Hence, the red – blue dichotomy is not due to decreasing bulge prominence alone, and the bulge type of a galaxy carries significance for the galaxy's evolutionary history.
Kinematics of globular cluster systems in galaxy mergers
Authors: Hayward Christopher C. , Cox T. J. , Hernquist Lars
Published: July 2008

We use numerical simulations to study how the spatial distribution and kinematics of globular cluster systems (GCS) are affected by galaxy mergers. Each progenitor galaxy is given a GCS modeled after the Galactic GCS. We then study how a major merger affects the spatial distribution and kinematics of the GCS. Here we present our methodology. Future work will investigate the effects of varying galaxy parameters, merger orbital parameters, and initial GCS number density profile and kinematics. We hope to be able to extract information about the merger history of a galaxy from observations of its GCS spatial distribution and kinematics.
GAMA: a new galaxy survey
Authors: Baldry I. , Liske J. , Driver S. P. ,   the GAMA Team
Published: July 2008

The case is outlined for a new galaxy survey, including spectroscopy with AAOmega and sub-arcsecond multi-band imaging, that bridges a crucial gap between the SDSS and VVDS surveys. The science focus is to study structure and the relationship between matter and light on kpc-to-Mpc scales. The range of scales probed will enable direct constraints on the Cold Dark Matter model by: (1) measuring the halo mass function down to $10^{12}{\cal M}_{\odot}$ and its evolution to z ~ 0.4; (2) measuring the galaxy stellar mass function to very low mass limits of $10^{7}{\cal M}_{\odot}$ constraining baryonic feedback processes; and (3) quantifying the environment-dependent merger rate since z ~ 0.4. Here, we highlight the fact that the high-resolution imaging will enable the bulge-disk decomposition of ~200000 galaxies in u–K, providing a valuable resource for statistical studies of bulge properties.
Tidal interactions and mergers in compact groups
Authors: Plauchu–Frayn I. , Coziol R.
Published: July 2008

Based on a NIR morphological study of 25 galaxies in eight Compact Groups (CGs), we find that the galaxies are not in equilibrium but in a process of transformation: late-type galaxies morphological change into earlier types. As much as half of the galaxies in our sample show evidence of ongoing or past mergers.We identify tidal stripping and mergers as the process responsible of this transformation. Our observations also suggest that galaxies in CGs merge more frequently under “dry” conditions (i.e. once they have lost most of their gas).
Boxy/peanut and discy bulges: formation, evolution and properties
Authors: Athanassoula E.
Published: July 2008

The class ‘bulges’ contains objects with very different formation and evolution paths and very different properties. I review two types of ‘bulges’, the boxy/peanut bulges (B/Ps) and the discy bulges. The former are parts of bars seen edge-on, have their origin in vertical instabilities of the disc and are somewhat shorter in extent than bars. Their stellar population is similar to that of the inner part of the disc from which they formed. Discy bulges have a disc-like outline, i.e., seen face-on they are circular or oval and seen edge-on they are thin. Their extent is of the order of 5 times smaller than that of the boxy/peanut bulges. They form from the inflow of mainly gaseous material to the centre of the galaxy and from subsequent star formation. They thus contain a lot of young stars and gas. Bulges of different types often coexist in the same galaxy. I review the main known results on these two types of bulges and present new simulation results.

B/Ps form about 1Gyr after the bar, via a vertical buckling. At that time the bar strength decreases, its inner part becomes thicker – forming the peanut or boxy shape – and the ratio $\sigma_z^2/\sigma_r^2$ increases. A second buckling episode is seen in simulations with strong bars, also accompanied by a thickening of the peanut and a weakening of the bar. The properties of the B/Ps correlate strongly with those of the bar: stronger bars have stronger peanuts, a more flat-topped vertical density distribution and have experienced more bucklings.

I also present simulations of disc galaxy formation, which include the formation of a discy bulge. Decomposition of their radial density profile into an exponential disc and a Sérsic bulge gives realistic values for the disc and bulge scale-lengths and mass ratios, and a Sérsic shape index of the order of 1.

It is thus clear that classical bulges, B/P bulges and discy bulges are three distinct classes of objects and that lumping them together can lead to confusion. To avoid this, the two latter could be called B/P features and inner discs, respectively.
Boxy/peanut bulges, vertical buckling and galactic bars
Authors: Martinez-Valpuesta Inma , Athanassoula E.
Published: July 2008

Boxy/peanut bulges in disk galaxies have been associated to stellar bars. In this talk, we discuss the different properties of such bulges and their relation with the corresponding bar, using a very large sample of a few hundred numerical N-body simulations. We present and inter-compare various methods of measuring the boxy/peanut bulge properties, namely its strength, shape and possible asymmetry. Some of these methods can be applied to both simulations and observations. Our final goal is to get correlations that will allow us to obtain information on the boxy/peanut bulge for a galaxy viewed face-on as well as information on the bars of galaxies viewed edge-on.
Internal secular evolution in disk galaxies: the growth of pseudobulges
Authors: Kormendy John
Published: July 2008

Observational and theoretical evidence that internal, slow (“secular”) evolution reshapes galaxy disks is reviewed in Kormendy & Kennicutt (2004). This update has three aims. First, I emphasize that this evolution is very general – it is as fundamental to the evolution of galaxy disks as (e. g.) core collapse is to globular clusters, as the production of hot Jupiters is to the evolution of protoplanetary disks, and as evolution to red giants containing proto-white-dwarfs is to stellar evolution. One consequence for disk galaxies is the buildup of dense central components that get mistaken for classical (i. e., merger-built) bulges but that were grown out of disk stars and gas. We call these pseudobulges. Second, I review new results on pseudobulge star formation and structure and on the distinction between boxy and disky pseudobulges. Finally, I highlight how these results make a galaxy formation problem more acute. How can hierarchical clustering produce so many pure disk galaxies with no evidence for merger-built bulges?
The coexistence of classical bulges and disky pseudobulges in early-type disk galaxies
Authors: Erwin Peter
Published: July 2008

Close examination of “pseudobulges” in several early-type disk galaxies indicates that they are actually composite structures consisting of both a flattened, kinematically cool disklike structure (“disky pseudobulge”) and a rounder, kinematically hot spheroidal structure (“classical bulge”). This indicates that pseudobulges, thought to form from internal secular evolution, and classical bulges, thought to form from rapid mergers, are not exclusive phenomena: some galaxies can have both.
The structural parameters of bulges, bars and discs in the local Universe
Authors: Gadotti Dimitri Alexei
Published: July 2008

Image decomposition of galaxies is now routinely used to estimate the structural parameters of galactic components. In this work, I address questions on the reliability of this technique. In particular, do bars and AGN need to be taken into account to obtain the structural parameters of bulges and discs? And to what extent can we trust image decomposition when the physical spatial resolution is relatively poor? With this aim, I performed multi-component (bar/bulge/disc/AGN) image decomposition of a sample of very nearby galaxies and their artificially redshifted images, and verified the effects of removing the bar and AGN components from the models. Neglecting bars can result in a overestimation of the bulge-to-total luminosity ratio of a factor of two, even if the resolution is low. Similar effects result when bright AGN are not considered in the models, but only when the resolution is high. I also show that the structural parameters of more distant galaxies can in general be reliably retrieved, at least up to the point where the physical spatial resolution is ≈ 1.5 Kpc, but bulge parameters are prone to errors if its effective radius is small compared to the seeing radius, and might suffer from systematic effects. I briefly discuss the consequences of these results to our knowledge of the stellar mass budget in the local universe, and finish by showing preliminary results from a large SDSS sample on the dichotomy between classical and pseudo-bulges.
Vertical surface brightness profiles of boxy bulges
Authors: Aronica G. , Bureau M. , Athanassoula E. , Dettmar R. -J.
Published: July 2008

The thickening of the bar in barred disk galaxies has a strong influence in shaping the morphology in the inner regions of a disk galaxy above the galactic plane. The result of such a secular evolutionary process can be observed in galaxies with box/peanut shaped (b/ps) bulges. We have applied a one–dimensional fitting method to our sample of 30 edge–on disk galaxies using different fitting function approaches. A clear increase in scale height can be observed in the area of the most prominent b/ps isophotes compared to the neighbouring disk and bulge areas, in agreement with the predictions of the bar thickening model.
Strong magnetic spiral pattern in a ringed galaxy NGC 4736
Authors: Chyży Krzysztof T. , Buta Ronald
Published: July 2008

We present high sensitivity radio polarimetric (VLA) observations of a galaxy with strong orbital resonances – NGC 4736. The total radio intensity at 8.4 GHz covers smoothly the whole galaxy bulge and reveals a distinct ring of radio emission closely related to the ring morphology visible in infrared, CO and Hα emission. However, the magnetic field reveals a very coherent spiral pattern. The magnetic field vectors are crossing the inner starbursting ring, the dust lanes within the ring and other rather circularly shaped features visible in other gas traces. Either the magnetic field uncovers the pattern of gas motions not seen in other spectral ranges, or the spiral magnetic field is of a pure dynamo origin, ignoring the ringed morphology of the galaxy.
Lenticular galaxies in the process of evolution
Authors: Kemp S. N. , Grana J. A. Pérez , Meaburn J. , de la Fuente Eduardo
Published: July 2008

We present images of a number of lenticular galaxies which appear to be undergoing evolutionary processes such as ram-pressure stripping or gravitational interactions, or possess features indicative of some evolutionary process in the recent past, such as fossil spiral arms, a polar ring-like structure, or a warped disk with box-peanut bulge. All the galaxies were originally identified on digitally co-added photographic plates or films from the UK Schmidt Telescope, showing that such material is still useful in spite of the modern digital surveys available. In some cases CCD follow up is presented.
The formation of young B/PS bulges in edge-on barred galaxies
Authors: Wozniak H. , Michel-Dansac L.
Published: July 2008

We report about the fact that the stellar population that is born in the gas inflowing towards the central regions can be vertically unstable leading to a B/PS feature remarkably bluer that the surrounding bulge. Using new chemodynamical simulations we show that this young population does not remain as flat as the gaseous nuclear disc and buckles out of the plane to form a new boxy bulge. We show that such a young B/PS bulge can be detected in colour maps.
Fueling-controlled growth of massive black holes
Authors: Escala Andrés
Published: July 2008

We study the relation between nuclear massive black holes and their host spheroid gravitational potential. Using AMR numerical simulations, we analyze how gas is transported into the nuclear (central kpc) regions of galaxies. We study gas fueling onto the inner accretion disk (sub-pc scale) and star formation in a massive nuclear disk like those generally found in proto-spheroids (ULIRGs, SCUBA Galaxies). These sub-pc resolution simulations of gas fueling, which is mainly depleted by star formation, naturally satisfy the ‘MBH- Mvirial’ relation, with a scatter considerably less than that observed. We find that a generalized version of the Kennicutt-Schmidt Law for starbursts is satisfied, in which the total gas depletion rate (Ṁgas= ṀBH+ ṀSF) scales as Mgas/torbital.
Building up mass in the centers of late type galaxies
Authors: Schinnerer E. , Böker T. , Emsellem E. , Lisenfeld U. , Downes D.
Published: July 2008

We present highest angular resolution (~ 1″ and 0.35″) mm-interferometric observations of the HCN(1-0), 12CO(1-0) and 12CO(2-1) line emission in the central 300 pc of the late-type spiral galaxy NGC 6946. The data, obtained with the IRAM Plateau de Bure Interferometer (PdBI) shows for the first time a molecular gas spiral in the inner ~ 10″ (270 pc) with a large concentration of molecular gas ($M_{H_2} \sim\,1.6\times10^7\,M_{\odot}$) within the inner 60 pc, The gas distribution in the central 50 pc has been resolved and is consistent with a gas ring or spiral driven by a bar. Both the distribution of the molecular gas as well as its kinematics can be well explained by the influence of an inner stellar bar of about 400 pc length as tested via a qualitative model for the gas flow. NGC 6946 is a prime example of molecular gas kinematics being driven by a small-scale, secondary stellar bar.

For the first time, it is possible to directly compare the location of (dense) giant molecular clouds with that of (optically) visible HII regions in space-based images. We use the 3 mm continuum and the HCN emission to estimate in the central 50 pc the star formation rates in young clusters that are still embedded in their parent clouds and hence are missed in optical and near-IR surveys of star formation. The amount of embedded star formation is about 1.6 times as high as that measured from HII regions alone, and appears roughly evenly split between ongoing dust-obscured star formation and very young giant molecular cloud cores that are just beginning to form stars. The build-up of central mass seems to have continued over the past ≥ 10 Myrs, to have occurred in an extended (albeit small) volume around the nucleus, and to be closely related to the presence of an inner bar.
Disk growth in bulge-dominated galaxies: molecular gas and morphological evolution
Authors: Young Lisa , Bureau Martin , Crocker Alison , Combes Francoise
Published: July 2008

Substantial numbers of morphologically regular early-type (elliptical and lenticular) galaxies contain molecular gas, and the quantities of gas are probably sufficient to explain recent estimates of the current level of star formation activity. This gas can also be used as a tracer of the processes that drive the evolution of early-type galaxies. For example, in most cases the gas is forming dynamically cold stellar disks with sizes in the range of hundreds of pc to more than one kpc, although there is typically only 1% of the total stellar mass currently available to form young stars. The numbers are still small, but the molecular kinematics indicate that some of the gas probably originated from internal stellar mass loss while some was acquired from outside. Future studies will help to quantify the role of molecular gas (dissipational processes) in the formation of early-type galaxies and their evolution along the red sequence.
A SINFONI view of circum-nuclear star-forming rings in spiral galaxies
Authors: Falcón-Barroso Jesús , Böker Torsten , Schinnerer Eva , Knapen Johan H. , Ryder Stuart
Published: July 2008

We present near-infrared (H- and K-band) SINFONI integral-field observations of the circumnuclear star formation rings in five nearby spiral galaxies. We made use of the relative intensities of different emission lines (i.e. [FeII], HeI, Brγ) to age date the stellar clusters present along the rings. This qualitative, yet robust, method allows us to discriminate between two distinct scenarios that describe how star formation progresses along the rings. Our findings favour a model where star formation is triggered predominantly at the intersection between the bar major axis and the inner Lindblad resonance and then passively evolves as the clusters rotate around the ring (‘Pearls on a string’ scenario), although models of stochastically distributed star formation (‘Popcorn’ model) cannot be completely ruled out.
LINER-like emission in red galaxies: evolutionary phase or recurring phenomenon?
Authors: Graves Genevieve J.
Published: July 2008

We present recent results showing that a large fraction of red sequence galaxies contain ionized gas with LINER-like optical emission line ratios. This emission is more frequently found in galaxies with lower central velocity dispersion (σ) and these galaxies typically have younger mean ages than galaxies at the same σ which do not host emission. We suggest that the presence of LINER-like emission may be determined by the quantity of interstellar material in these galaxies and may be associated with the recent accretion of a gas-rich satellite galaxy or alternatively with stellar mass loss that declines as the galaxy stellar population ages.
Why are some brightest cluster galaxies forming stars?
Authors: O'Dea Christopher P. , Quillen Alice , Zufelt Nicholas , Park Jaehong , Edge Alastair , Russell Helen , Fabian Andy , Baum Stefi ,   The Spitzer BCG Project
Published: July 2008

We present first results from an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission located in the cores of X-ray luminous clusters selected from the ROSAT All-Sky Survey. We find that 1/3 of these sources have signs of excess infrared emission; 22 objects of 62 are detected at 70 μm and 19 have 8 to 5.8 μm flux ratios above 0.98. The strength of the excess emission correlates with the luminosity of the optical emission lines. Excluding the four systems dominated by an AGN, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely powered by star formation. We find a correlation between mass deposition rate from a cooling flow model for the X-ray emission and the star formation rate estimated from the infrared luminosity. The star formation rates are 1/10 to 1/100 of the mass deposition rates expected in the absence of heating suggesting that the re-heating of the ICM is generally very effective in reducing the amount of mass cooling from the hot phase.
Star formation in the Galactic bulge: the role of collisions
Authors: Cropper Mark , Putte Dave Vande
Published: July 2008

Prompted by the possibility that we have observed star formation triggered by globular cluster and dwarf spheroidal transits through galactic disks, we have examined kinematic evidence as to whether the superstar clusters in the Galactic bulge could have been formed from such transits. From their trajectores, we cannot exclude such a possibility. We note also that the high frequency of these transits may have generated rapid star formation at early times, and that remnant cluster cores may themselves nucleate further star formation.
Early-type galaxy formation history from GALEX-SAURON
Authors: Jeong Hyunjin , Yi Sukyoung K. , Bureau Martin , Kranović Davor , Davies Roger L.
Published: July 2008

One of long-standing debates in modern astrophysics is the formation mechanism of early-type galaxies. The classical model, proposed by Eggel et al. (1962), explains that early-type stellar populations form in an initial highly efficient burst and evolve without further star formation until present day. The high Mg and alpha abundances found in bright elliptical galaxies support such scenarios. Early-type galaxies, therefore, are traditionally believed that they are dynamically simple stellar systems with homogeneous stellar populations (e.g. Gott 1977). The popular Lambda Cold Dark Matter (LCDM) paradigm (e.g. Toomre and Toomre 1972), however, strongly suggested a hierarchical merger picture for massive elliptical galaxies. In this model, early-type galaxies form as a result of major mergers and are thought to have continued star formation. Evidence is growing that a substantial fraction of early-type galaxies has secondary star formation. Furthermore, SAURON survey has revealed a rich diversity in the kinematics, discovering numerous central disks and kinematically decoupled cores (e.g. Emsellem et al. 2004; Sarzi et al. 2006). Early-type galaxies are thus likely to have had complex and varied formation histories.
Recent star formation in high-redshift early-type galaxies: insights from the rest-frame UV
Authors: Kaviraj S. , Yi S. K. , Gawiser E. , van Dokkum P. G. , Khochfar S. , Schawinski K. , Silk J.
Published: July 2008

We combine deep UBV RIzJK photometry from the MUSYC survey with redshifts from the COMBO-17 survey to study the rest-frame ultraviolet (UV) properties of 674 high-redshift (0.5 < z < 1) early-type galaxies, drawn from the Extended Chandra Deep Field South (E-CDFS). Galaxy morphologies are determined through visual inspection of Hubble Space Telescope (HST) images taken from the GEMS survey. We harness the sensitivity of the UV to young (<1 Gyrs old) stars to quantify the recent star formation history of the early-type population. We find compelling evidence that early-types of all luminosities form stars over the lifetime of the Universe, although the bulk of their star formation is already complete at high redshift. Luminous (−23 < M(V) < −20.5) early-types form 10-15 percent of their mass after z = 1, while their less luminous (M(V) > −20.5) counterparts form 30-60 percent of their mass in the same redshift range.
A black hole fundamental plane
Authors: Hopkins Philip F.
Published: July 2008

We study observed correlations between supermassive black hole (BHs) and the properties of their host galaxies, and show that the observations define a BH “fundamental plane” (BHFP), of the form $\mbh\propto\sigma^{3.0\pm0.3}\,\re^{0.43\pm0.19}$ or $\mbh\propto\mstar^{0.54\pm0.17}\,\sigma^{2.2\pm0.5}$, analogous to the FP of elliptical galaxies. The BHFP is preferred over a simple relation between MBH and any of σ, M*, Mdyn, or Re alone at > 3 σ (99.9%) significance. The existence of this BHFP has important implications for the formation of supermassive BHs and the masses of the very largest black holes, and immediately resolves several apparent conflicts between the BH masses expected and measured for outliers in both the MBH − σ and MBH − M* relations.
Co-evolution of bulges and black holes
Authors: Woo Jong-Hak , Treu Tommaso , Malkan Matthew A. , Blandford Roger D.
Published: July 2008

In the present-day universe, the global properties of bulges and early-type galaxies correlate with the mass of their central black holes, indicating a connection between galaxy evolution and nuclear activity. Understanding the origin of this relation is a major challenge for cosmological models. Using Keck spectra and HST images, we present direct measurements of the correlations between black hole mass and host spheroid luminosity and velocity dispersion at z=0.36, showing that the relations evolved significantly in the past 4 billion years. It appears that black holes of a few 108M⊙completed their growth before their host galaxies, and that the current scaling relations are only the final point of the co-evolution of galaxies and black holes.
The Vc − σ0 relation of galaxies
Authors: Courteau Stéphane , McDonald Michael , Widrow Lawrence M.
Published: July 2008

Courteau et al. (2007a) reported on the dependence of the ratio of a galaxy's maximum circular velocity, Vc, to its central velocity dispersion, σ0, on morphology, or equivalently total light concentration. This Vc − σ0–concentration relation, which involves details about the local and global galaxy physics, poses a fundamental challenge for galaxy structure models. Furthermore, not only must these models reproduce the Vc − σ0 relation and its various dependences, they must simultaneously match other fundamental scaling relations such as the velocity-size-luminosity and color-luminosity relations. We focus here on the interpretation of parameters that enter the Vc − σ0 relation to enable proper data-model comparisons and follow-up studies by galaxy modelers and observers.
Searching for mergers in early-type QSO host galaxies and a control sample of inactive ellipticals
Authors: Bennert Nicola , Canalizo Gabriela , Jungwiert Bruno , Stockton Alan , Schweizer François , Peng Chien , Lacy Mark
Published: July 2008

We present very deep HST/ACS images of five QSO host galaxies, classified as undisturbed ellipticals in earlier studies. For four of the five objects, our images reveal strong signs of interaction such as tidal tails, shells, and other fine structure, suggesting that a large fraction of QSO host galaxies may have experienced a relatively recent merger event. Our preliminary results for a control sample of inactive elliptical galaxies do not reveal comparable fine structure.
The spectral decomposition of Active Galactic Nuclei with double-peaked Balmer lines from SDSS
Authors: Bian W.
Published: July 2008

For a sample of 52 double-peaked broad-lines AGNs from the Sloan Digital Sky Survey (SDSS), we do the spectral decomposition to obtain the host spectrum and the nuclei spectrum from their SDSS spectra, as well as the bulge luminosity (Lbulge), stellar velocity dispersion (σ*). A strong correlation is found between the σ* and the gaseous velocity dispersion in narrow line regions. With the Mbh − σ* relation, we estimate the black hole masses, range from 1.0 × 107 to 6 × 108 M⊙, and the Eddington ratio from about 0.01 to about 1. It is consistent with the result from Mbh − Lbulge relation. However, it is not consistent with the mass from the Hβ FWHM. It seems that the empirical size-luminosity relation for broad line regions dose not hold for double-peaked AGNs, otherwise the calibration factor is as small as 0.185, suggesting the non-virial dynamics of broad line regions.
Simulating the dynamics of binary black holes in nuclear gaseous discs
Authors: Dotti Massimo , Colpi Monica , Haardt Francesco , Mayer Lucio
Published: July 2008

We study the pairing of massive black holes embedded in a massive circum–nuclear, rotationally supported disc, until they form a close binary. Using high resolution SPH simulations, we follow the black hole dynamics, and in particular the eccentricity evolution, as a function of the composition in stars and gas of the disc. Binary–disc interaction always leads to orbital decay and, in case of co–rotating black holes, to orbit circularization. We present also a higher resolution simulation performed using the particle–splitting technique showing that the binary orbital decay is efficient down to a separation of ~ 0.1 pc, comparable to our new resolution limit. We detail the gaseous mass profile bound to each black hole. Double nuclear activity is expected to occur on an estimated timescale of ≲ 10 Myrs.
Brightness temperature for radio sources
Authors: Fan J. H. , Huang Y. , Liu Y. , Gao Y. , Hua T. X. , Yang J. H.
Published: July 2008

In this work, using the database of the university of Michigan Radio Astronomy Observatory (UMRAO), we determined the brightness temperatures, TB for a sample of 167 radio sources. The value of TB is in a range of log TB(K) = 10.46 to 20.08, which suggested that the boosting factors are in a range of δ = 0.41 to 41.26.
12CO observations on narrow-line Seyfert 1 galaxies
Authors: Kawaguchi Toshihiro , Nakanishi K. , Kohno K. , Ohta K. , Aoki K.
Published: July 2008

In order to investigate how the growth of galactic bulges is accompanied with the growth of central black holes (BHs), we observed molecular gas (fuel for the coming star formation) in possibly young active galaxies, narrow-line Seyfert 1 galaxies (NLS1s). We present the results of pilot observations of 12CO (1→0) line using the Nobeyama Millimeter Array for two FIR-bright NLS1s, ending in the first detection of their CO emission. Corresponding molecular-gas masses M(H2) of (1−3)×109M⊙ are the 2nd and 4th largest ones among NLS1s. Together with CO data for other NLS1s (including our sub-kpc observations) and for broad-line Seyfert 1 galaxies (BLS1s), we found that NLS1s and BLS1s contain a similar amount of molecular–gas. We do not see a significant difference in M(H2)/MBH ratios and in M(H2)/Mbulge ratios between NLS1s and BLS1s. The lack of a clear difference in M(H2) between them indicates either that bulge and BH growth phases are not overlapped or that the duration of star formation is much longer than that of active galaxies.
Black holes in low-mass bulges and pseudobulges
Authors: Nowak N. , Saglia R. P. , Thomas J. , Erwin P. , Bender R.
Published: July 2008

Over the past decade we have learned that probably all ellipticals and bulges contain a central supermassive black hole (SMBH). The mass of the SMBH correlates both with the mass of the bulge component (about 0.15% of the bulge mass) and with the velocity dispersion σ of the bulge. We are investigating whether these relations remain valid or how they change when galaxies with pseudobulges, very low-mass bulges or bulgeless galaxies are considered. Studying SMBH relations for both classical bulges and pseudobulges can reveal the importance of different growing mechanisms (mergers vs. secular evolution) for the evolution of SMBHs. Low-mass classical bulges and bulgeless galaxies may harbour seed black holes in their earliest evolutionary stages, and studying them is of paramount importance for understanding the link between bulge evolution and black hole growth.
Gravitational loss-cone instability in stellar clusters around massive black holes
Authors: Polyachenko Evgeny V. , Polyachenko Valerij L. , Shukhman Ilia G.
Published: July 2008

Stability of spherical and thin disk stellar clusters surrounding massive black holes are studied. Due to the black hole, stars with sufficiently low angular momenta escape from the system through the loss cone. We show that stability of spherical clusters crucially depend on whether the distribution of stars is monotonic or non-monotonic in angular momentum. It turns out that only non-monotonic distributions can be unstable. At the same time the instability in disk clusters is possible for both types of distributions.
An accreting black hole in the nucleus of the bulgeless galaxy NGC 1042
Authors: Shields Joseph C. , Walcher Carl Jakob , Böker Torsten , Ho Luis C. , Rix Hans-Walter , van der Marel Roeland P.
Published: July 2008

Compact star clusters are commonly found in the centers of galaxies and may foster formation of intermediate-mass “seed” black holes that facilitate the growth of supermassive black holes in galaxy nuclei. Such star clusters can be studied with minimal background starlight contamination in bulgeless galaxies. We present new results that point to the presence of an accreting black hole associated with the central star cluster in the Sd galaxy NGC 1042, and discuss implications for the bulge-black hole connection.
Massive galaxies with very young AGN
Authors: de Vries Nathan , Snellen I. A. G. , Schilizzi R. T. , Lehnert M. D. , Bremer M. N.
Published: July 2008

Gigahertz Peaked Spectrum (GPS) radio galaxies are generally thought to be the young counterparts of classical extended radio sources and live in massive ellipticals. GPS sources are vital for studying the early evolution of radio-loud AGN, the trigger of their nuclear activity, and the importance of feedback in galaxy evolution. We study the Parkes half-Jansky sample of GPS radio galaxies of which now all host galaxies have been identified and 80% has their redshifts determined (0.122 < z < 1.539). Analysis of the absolute magnitudes of the GPS host galaxies show that at z > 1 they are on average a magnitude fainter than classical 3C radio galaxies. This suggests that the AGN in young radio galaxies have not yet much influenced the overall properties of the host galaxy. However their restframe UV luminosities indicate that there is a low level of excess as compared to passive evolution models.
Spiral galaxies in the SAURON survey
Authors: Peletier Reynier F. , Ganda Katia , Falcón-Barroso Jesús , Bacon Roland , Cappellari Michele , Davies Roger L. , de Zeeuw P. Tim , Emsellem Eric , Krajnović Davor , Kuntschner Harald , McDermid Richard M. , Sarzi Marc , van de Ven Glenn
Published: July 2008

We discuss some recent integral field spectroscopy using the SAURON instrument of a sample consisting of 24 early-type spirals, part of the SAURON Survey, and 18 late-type spirals. Using 2-dimensional maps of their stellar radial velocity, velocity dispersion, and absorption line strength, it is now much easier to understand the nature of nearby galactic bulges. We discuss a few highlights of this work, and point out some new ideas about the formation of galactic bulges.
Age and metallicity of the bulges in lenticular galaxies
Authors: Sil'chenko Olga K.
Published: July 2008

Panoramic spectroscopy of the sample of 80 nearby lenticular galaxies is presented. The SSP-equivalent ages, [Z/H], and [Mg/Fe] are determined through the Lick indices Hβ, Mgb, and 〈Fe〉 separately for the nuclei and for the bulges. About a half of the sample contain chemically distinct nuclei, more metal-rich and younger than the bulges. The statistics of stellar population properties for the nearby S0s is discussed.
The formation and evolution of bulges as traced by globular cluster systems
Authors: Forbes Duncan A. , Spitler Lee
Published: July 2008

Globular Clusters provide a unique method for tracing the formation and evolution of their host galaxies. As single stellar populations they are far easier to interpret than the multi-population complexity of galaxy field stars. The scaling properties of globular clusters provide important constraints on the hierarchical assembly history of galaxies. Here we briefly review recent progress using the Hubble Space Telescope for imaging and the Keck plus Gemini telescopes for spectroscopy. We argue that the red, or metal-rich, subpopulation of GCs is associated with the bulge/spheroid component of galaxies. As one of the oldest stellar systems available for study, we discuss how globular clusters can be used to constrain the formation of galaxy bulges, in particular the role of mergers vs secular evolution. We conclude that metal-rich GCs, and hence bulges, formed very early in the Universe with more recent mergers having a small effect at most.
Stellar populations in the bulges of S0s and the formation of S0 galaxies
Authors: Aragón-Salamanca Alfonso
Published: July 2008

The stellar populations in the bulges of S0s, together with the galaxies' dynamics, masses and globular clusters, contain very interesting clues about their formation. I present here recent evidence suggesting that S0s are the descendants of fading spirals whose star formation ceased.
Stellar populations in the center of barred spiral galaxies
Authors: Mollá M. , Cantin S. , Robert C. , Pellerin A.
Published: July 2008

We show observations obtained with the integral field spectrometer OASIS for the centers of a sample of barred galaxies. The high spatial resolution of the instrument allows to distinguish spatially some structures within these regions as defined by stellar populations of different ages and metallicities. From these data we deduce important clues about the star formation history. But we advise that, in order to obtain adequately the evolutionary sequence, a combination of chemical and synthesis models might be necessary.
Internal kinematics and stellar populations of early-type galaxies in the Fornax cluster
Authors: Gerken Bettina , Davies Roger L. , Kuntschner Harald
Published: July 2008

We present a study of the internal kinematics and stellar populations of early-type galaxies in the Fornax cluster. 10 galaxies in a luminosity range of −21.8≤MB≤−17.4 were observed with the integral field units (IFU) of Gemini South GMOS and VLT-VIMOS. Velocity maps and age-metallicity diagrams are presented for NGC 1404 and NGC 1419.
Stellar population in bulge of spiral galaxies
Authors: Morelli L. , Pompei E. , Pizzella A. , Coccato L. , Corsini E. M. , Abreu J. Méndez , Saglia R. P. , Sarzi M. , Bertola F.
Published: July 2008

We present extensive photometric and spectroscopic study to give a new insight in the bulge stellar population. Super-solar α/Fe and its constant value along the radial profile, in most of the galaxies, suggest that the star formation in these objects has been fast and occurred at the same time in the whole bulge.
The role of bars on bulge formation and the evolution of barred galaxies
Authors: Pérez I. , Sánchez-Blázquez P. , Zurita A.
Published: July 2008

We have started a long term project to analyse the role played by bars in bulge formation and the formation and evolution of bars from the point of view of their star formation histories and stellar populations. To this aim, we have obtained high S/N long slit spectra of 22 barred galaxies, ranging in morphological types between S0 to Sb galaxies. We have obtained Lick/IDS indices along the bar for all the sample galaxies. We used Vazdekis et al. (2007) models to derive simple stellar population ages and metallicities. Extreme care has been taken to correct the indices for any nebular contribution. Preliminary results show that the bulges of barred galaxies are similar to those of unbarred galaxies. The metalicity gradients along bars show a dependency with the central stellar velocity dispersion. The galaxies with higher central dispersion appear to have a gradient in both age and metallicity changing radially outward to a younger and more metal rich population. The galaxies with lower central velocity dispersion show a change in age and metallicity with respect to the inner part of the bar with the populations at the end of the bar being younger or same age and more metal poor. There is no correlation between the gradient and the morphological or nuclear type. There is no correlation either with the total K-band luminosity. The fact that we observe galaxies with the outer parts of the bar more metal rich than the inner parts shows that at least some bars are old, since it requires long time for the observed enrichment to take place. The gradients in these bars are opposite to what is generally found in disks. The correlation between the central velocity dispersion and the bar gradient relates both, the dynamical and stellar population aging of the bar.
The Galactic bulge: a review
Authors: Minniti Dante , Zoccali Manuela
Published: July 2008

The Milky Way is the only galaxy for which we can resolve individual stars at all evolutionary phases, from the Galactic center to the outskirt. The last decade, thanks to the advent of near IR detectors and 8 meter class telescopes, has seen a great progress in the understanding of the Milky Way central region: the bulge. Here we review the most recent results regarding the bulge structure, age, kinematics and chemical composition. These results have profound implications for the formation and evolution of the Milky Way and of galaxies in general. This paper provides a summary on our current understanding of the Milky Way bulge, intended mainly for workers on other fields.
Kinematics and composition of the Galactic bulge: recent progress
Authors: Rich R. Michael , Howard Christian , Reitzel David B. , Zhao HongSheng , de Propris Roberto
Published: July 2008

We present recent results from a Keck study of the composition of the Galactic bulge, as well as results from the bulge Bulge Radial Velocity Assay (BRAVA). Culminating a 10 year investigation, Fulbright, McWilliam, & Rich (2006, 2007) solved the problem of deriving the iron abundance in the Galactic bulge, and find enhanced alpha element abundances, consistent with the earlier work of McWilliam & Rich (1994). We also report on a radial velocity survey of 2MASS-selected M giant stars in the Galactic bulge, observed with the CTIO 4m Hydra multi-object spectrograph. This program is to test dynamical models of the bulge and to search for and map any dynamically cold substructure in the Galactic bulge. We show initial results on fields at −10° < l < + 10° and b = −4°. We construct a longitude-velocity plot for the bulge stars and the model data, and find that contrary to previous studies, the bulge does not rotate as a solid body; from −5° < l < + 5° the rotation curve has a slope of ≈ 100 km s−1 and flattens considerably at greater l and reaches a maximum rotation of 45 km s−1 (heliocentric) or ~ 70 km s−1 (Galactocentric). This rotation is slower than that predicted by the dynamical model of Zhao (1996).
The boxy bulge and stellar bar of the Milky Way
Authors: Mahoney T. J. , López-Corredoira M. , Cabrera-Lavers A. , Hammersley P. L. , González-Fernández C. , Garzón F.
Published: July 2008

We describe the boxy bulge, long stellar bar and elliptical ring of the Galaxy. This model has largely evolved from NIR survey work by many teams and differs from other models with a monolithic ellipsoidal bulge. We maintain that the structure of the inner Galaxy can only be properly studied by adequately sampling the entire Galactic plane for |l| < 30°, |b| < 1.5°, and that the bulge is best studied at least 3° from the plane. We briefly report a slight radially outwardly increasing metallicity gradient along the bar and reaffirm de Vaucouleurs & Pence's (1978) suggestion that the Galaxy is probably of morphological type SAB(rs)bc II.
Proper motions in the Galactic bulge: Plaut's window
Authors: Vieira Katherine , Cassetti-Dinescu Dana , Méndez René A. , Rich R. Michael , Girard Terrence M. , Korchagin Vladimir I. , van Altena William , Majewski Steven R. , van den Bergh Sidney
Published: July 2008

A proper motion study of a field of 20′ × 20′ inside Plaut's low extinction window (l,b)=(0o, −8o), has been completed. Relative proper motions and photographicBVphotometry have been derived for ~ 21,000 stars reaching toV~ 20.5 mag, based on the astrometric reduction of 43 photographic plates, spanning over 21 years of epoch difference. Proper motion errors are typically 1 mas yr−1. Cross-referencing with the 2MASS catalog yielded a sample of ~ 8700 stars, from which predominantly disk and bulge subsamples were selected photometrically from theJHcolor-magnitude diagram. The two samples exhibited different proper-motion distributions, with the disk displaying the expected reflex solar motion. Galactic rotation was also detected for stars between ~2 and ~3 kpc from us. The bulge sample, represented by red giants, has an intrinsic proper motion dispersion of (σl, σb) = (3.39, 2.91)±(0.11, 0.09) mas yr−1, which is in good agreement with previous results. A mean distance of$6.37^{+0.87}_{-0.77}$kpc has been estimated for the bulge sample, based on the observedKmagnitude of the horizontal branch red clump. The metallicity [M/H] distribution was also obtained for a subsample of 60 bulge giants stars, based on calibrated photometric indices. The observed [M/H] shows a peak value at [M/H] ~ −0.1 with an extended metal poor tail and around 30% of the stars with supersolar metallicity. No change in proper motion dispersion was observed as a function of [M/H]. We are currently in the process of obtaining CCDUBV RIphotometry for the entire proper-motion sample of ~ 21,000 stars.
New indications on the Galactic bulge IMF by microlensing surveys
Authors: Mancini L. , Novati S. Calchi
Published: July 2008

Basing on recent microlensing observations, we analyse the mass spectrum of the Galactic bulge stellar population and study the slope of the initial mass function.
The Millennium Galaxy Catalogue: the severe attenuation of bulge flux by dusty spiral discs
Authors: Driver Simon P. ,   the MGC Team
Published: July 2008

Using the Millennium Galaxy Catalogue we quantify the dependency of the disc and bulge luminosity functions on galaxy inclination. Using a contemporary dust model we show that our results are consistent with galaxy discs being optically thick in their central regions ($\tau_B^f=3.8\pm0.7$). As a consequence the measured B-band fluxes of bulges can be severely attenuated by 50% to 95% depending on disc inclination. We argue that a galaxy's optical appearance can be radically transformed by simply removing the dust, e.g. during cluster infall, with mid-type galaxies becoming earlier, redder, and more luminous. Finally we derive the mean photon escape fraction from the integrated galaxy population over the 0.1 μm to 2.1 μm range, and use this to show that the energy of starlight absorbed by dust (in our model) is in close agreement with the total far-IR emission.
Morphological properties of massive galaxies at high−z from GOODS
Authors: Ravindranath Swara , Daddi E. , Giavalisco M. , Ferguson H. C. , Dickinson M. E.
Published: July 2008

We have used the BzK-selection to identify a composite population of passive, and star-forming galaxies at redshifts 1.4 ≤ z ≤ 2.5 from the Great Observatories Origins Deep Survey (GOODS). Using an unprecedented large sample of galaxies in this redshift range, we characterize the morphological diversity through the analysis of the surface-brightness profile shapes for 171 galaxies with passive SEDs, and 1068 star-forming galaxies. We find that the z ~ 2 galaxies display a wide range of morphologies, from spheroidals to disk-like. Interestingly, the galaxies with passively-evolving SEDs predominantly have steep profiles as seen for the classical bulges at low redshifts, although they are very compact with re < 3 kpc. The star-forming galaxies on the other hand exhibit mostly disk-like and merger morphologies, and have sizes comparable to their low−z counterparts. Our results emphasize the need for an unbiased selection in order to reveal the morphological diversities, and range of galaxy properties at high redshifts.
VIRUS-W A fiber based integral field unit spectrograph for the study of galaxy bulges
Authors: Fabricius Maximilian H. , Bender Ralf , Drory Niv , Grupp Frank , Hill Gary J. , Hopp Ulrich
Published: July 2008

We presented the design for a fiber based integral field unit spectrograph for the new two meter class Wendelstein telescope in Bavaria, Germany. The proposed spectrograph will feature a fiberhead consisting of 246 individual optical fibers and a field of view of approximately 1′ × 2′ and two different spectral resolution modes optimized for the study of bulges of local late-type galaxies.