Possible Local Spiral Counterparts to Compact Blue Galaxies at Intermediate Redshift

We identify nearby disk galaxies with optical structural parameters similar to those of intermediate-redshift compact blue galaxies. By comparing HI and optical emission-line widths, we show that the optical widths substantially underestimate the true kinematic widths of the local galaxies. By analogy, optical emission-line widths may underrepresent the masses of intermediate-z compact objects. For the nearby galaxies, the compact blue morphology is the result of tidally-triggered central star formation: we argue that interactions and minor mergers may cause apparently compact morphology at higher redshift.Comment: 5 pages, uses emulateapj5 and psfig. To appear in ApJ

Seismic Risk Assessment Tools Workshop

Held in the European Crisis Management Laboratory on 11-12 May 2017, the Workshop brought together on one side the developers of some of the most widely used modern seismic risk assessment tools and on the other a number of Civil Protection authorities from countries of the European Civil Protection Mechanism. The objective was to demonstrate the use and capabilities of the tools, explore the possible use in near-real-time impact assessment and promote their use in risk planning and disaster response. The systems presented in the workshop demonstrated a very high sophistication and increased flexibility in accepting data from a large number of sources and formats. Systems that were initially developed on a national scale can now work on a global level with little effort and the use of global-scale exposure data is almost seamless. An urgent need for more accurate exposure data being openly available was identified, as well as the need of proper use of the fragility curves. Inter-system collaboration and interoperability in some cases to increase ease of use was greatly appreciated and encouraged. All systems participated in a real-time simulation exercise on previously unknown seismic data provided by the JRC; some additional automation might be in order, but in general all systems demostrated a capacity to produce results on a near-real-time basis. The demonstrations were unanimously welcomed as very useful by the participating Civil Protection Authorities, most of which are either using a locally-developed system of moving towards using one of those presented in the workshop.JRC.E.1-Disaster Risk Managemen

CO-bandhead spectroscopy of IC 342: mass and age of the nuclear star cluster

We have used the NASA Infra-Red Telescope Facility (IRTF) to observe the nuclear stellar cluster in the nearby, face-on, giant Scd spiral IC 342. From high resolution (R = 21500) spectra at the 12CO (2-0) bandhead at 2.3 micron we derive a line-of-sight stellar velocity dispersion sigma = (33 +- 3) km/s. To interpret this observation we construct dynamical models based on the Jeans equation for a spherical system. The light distribution of the cluster is modeled using an isophotal analysis of an HST V-band image from the HST Data Archive, combined with new ground-based K-band imaging. Under the assumption of an isotropic velocity distribution, the observed kinematics imply a K-band mass-to-light ratio M/L_K = 0.05, and a cluster mass M ~ 6 times 10^6 Msun. We model the mass-to-light ratio with the `starburst99' stellar population synthesis models of Leitherer and collaborators, and infer a best-fitting cluster age in the range 63-630 Myears. Although this result depends somewhat on a number of uncertainties in the modeling (e.g., the assumed extinction along the line-of-sight towards the nucleus, the IMF of the stellar population model, and the velocity dispersion anisotropy of the cluster), none of these can be plausibly modified to yield a significantly larger age. We discuss the implications of this result on possible scenarios for the frequency of nuclear starbursts and their impact on secular evolution of spiral galaxy nuclei. As a byproduct of our analysis, we infer that IC 342 cannot have any central black hole more massive than 0.5 million solar masses. This is ~ 6 times less massive than the black hole inferred to exist in our Galaxy, consistent with the accumulating evidence that galaxies with less massive bulges harbor less massive black holes.Comment: 27 pages, incl. 9 figures, submitted to The Astronomical Journa

Optical observations of a newly identified compact galaxy group near the Zone of Avoidance

We have identified a new group of galaxies, CG J0247+44.9, at low Galactic latitude (l=143.64 deg, b=-13.29 deg), which satisfies Hickson's criteria (Hickson 1997) for Compact Groups (CGs). Our group consists of six members, two of which are in close interaction (IRAS 02443+4437). We present here optical photometry (BVRI) and low resolution spectroscopy of the individual galaxies and investigate the global properties of the group. Our morphological analysis reveals that two out of the six objects are lenticular galaxies. The others are spirals showing emission lines in their spectra through which we could classify them as a starburst galaxy (the spiral member of the IRAS 02443+4437 close pair), a Seyfert 2, a LINER and a weak H II galaxy. Since the S0/Sa is the prevailing morphology for the galaxies of this group, which is also characterized by a short crossing time and a relatively high velocity dispersion, we suggest that CG J0247+44.9 is a dynamically old compact group.Comment: 17 pages, 5 figures out of which 4 are in jpg format. A postscript version of the paper including all figures is available at: http://astro.uibk.ac.at/~giovanna/preprints/Temporins.ps.gz Accepted for publication in Astronomy and Astrophysic

Two dimensional bulge disk decomposition

We propose a two dimensional galaxy fitting algorithm to extract parameters of the bulge, disk, and a central point source from broad band images of galaxies. We use a set of realistic galaxy parameters to construct a large number of model galaxy images which we then use as input to our galaxy fitting program to test it. We find that our approach recovers all structural parameters to a fair degree of accuracy. We elucidate our procedures by extracting parameters for 3 real galaxies -- NGC 661, NGC 1381, and NGC 1427.Comment: 23 pages, LaTeX, AASTEX macros used, 7 Postscript figures, submitted to Ap

Angular Sizes of Faint Field Disk Galaxies: Intrinsic Luminosity Evolution

In order to explain the small scale-lengths detected in the recent deep field observations performed from large ground-based telescopes and from the Hubble Space Telescope, we investigate the predictions at high redshifts for disk galaxies that formed by infall. Changes with redshift in the observed properties of field galaxies are directly related to the evolution of the disks and of the stellar populations. We see that changes in the rest frame luminosity of a galaxy induce smaller values of half-light radii than are predicted assuming no evolution. Comparisons are presented with two observed samples from Mutz et al. (1994) and Smail et al. (1995).Comment: plain tex file + 3 postscript figures. To be published in ApJ

Formation of central massive objects via tidal compression

For a density that is not too sharply peaked towards the center, the local tidal field becomes compressive in all three directions. Available gas can then collapse and form a cluster of stars in the center, including or even being dominated by a central black hole. We show that for a wide range of (deprojected) Sersic profiles in a spherical potential, the tidal forces are compressive within a region which encloses most of the corresponding light of observed nuclear clusters in both late-type and early-type galaxies. In such models, tidal forces become disruptive nearly everywhere for relatively large Sersic indices n >= 3.5. We also show that the mass of a central massive object (CMO) required to remove all radial compressive tidal forces scales linearly with the mass of the host galaxy. If CMOs formed in (progenitor) galaxies with n ~ 1, we predict a mass fraction of ~ 0.1-0.5%, consistent with observations of nuclear clusters and super-massive black holes. While we find that tidal compression possibly drives the formation of CMOs in galaxies, beyond the central regions and on larger scales in clusters disruptive tidal forces might contribute to prevent gas from cooling.Comment: 19 pages, 4 figures. Accepted for publication in ApJ. High resolution version available at http://www-obs.univ-lyon1.fr/labo/perso/eric.emsellem/preprint

Near-Infrared Adaptive Optics Imaging of the Central Regions of Nearby Sc Galaxies: I. M33

Near-infrared images obtained with the Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Bonnette (AOB) are used to investigate the stellar content within 18 arcsec of the center of the Local Group spiral galaxy M33. AGB stars with near-infrared spectral-energy distributions similar to those of giants in the solar neighborhood and Baade's Window are detected over most of the field. The bolometric luminosity function (LF) of these stars has a discontinuity near M_{bol} = -5.25, and comparisons with evolutionary tracks suggest that most of the AGB stars formed in a burst of star formation 1 - 3 Gyr in the past. The images are also used to investigate the integrated near-infrared photometric properties of the nucleus and the central light concentration. The nucleus is bluer than the central light concentration, in agreement with previous studies at visible wavelengths. The CO index of the central light concentration 0.5 arcsec from the galaxy center is 0.05, which corresponds to [Fe/H] = -1.2 for simple stellar systems. Hence, the central light concentration could not have formed from the chemically-enriched material that dominates the present-day inner disk of M33.Comment: 23 pages of text + 11 figures; to appear in A

Correlations among global photometric properties of disk galaxies

Using a two-dimensional galaxy image decomposition technique, we extract global bulge and disk parameters for a complete sample of early type disk galaxies in the near infrared K band. We find significant correlation of the bulge parameter n with the central bulge surface brightness $\mu_b(0)$ and with effective radius r_e. Using bivar iate analysis techniques, we find that $\log n$, $\log r_e$ and $\mu_b(0)$ are distributed in a plane with small scatter. We do not find a strong correlation of n with bulge-to-disk luminosity ratio, contrary to earlier reports. r_e and the disk scale length r_d are well correlated for these early type disk galaxies, but with large scatter. We examine the implications of our results to various bulge formation scenarios in disk galaxies.Comment: 14 pages, LaTeX including 14 figures. To appear in the Astrophysical Journa