The Trouble with Hubble Types in the Virgo Cluster

Quantitative measures of central light concentration and star formation activity are derived from R and Halpha surface photometry of 84 bright S0-Scd Virgo Cluster and isolated spiral galaxies. For isolated spirals, there is a good correlation between these two parameters and assigned Hubble types. In the Virgo Cluster, the correlation between central light concentration and star formation activity is significantly weaker. Virgo Cluster spirals have systematically reduced global star formation with respect to isolated spirals, with severe reduction in the outer disk, but normal or enhanced activity in the inner disk. Assigned Hubble types are thus inadequate to describe the range in morphologies of bright Virgo Cluster spirals. In particular, spirals with reduced global star formation activity are often assigned misleading early-type classifications, irrespective of their central light concentrations. 45+-25% of the galaxies classified as Sa in the Virgo Cluster sample have central light concentrations more characteristic of isolated Sb-Sc galaxies. The misleading classification of low concentration galaxies with low star formation rates as early-type spirals may account for part of the excess of `early-type' spiral galaxies in clusters. Thus the morphology-density relationship is not all due to a systematic increase in the bulge-to-disk ratio with environmental density.Comment: Accepted for publication in ApJ Letters. Latex aaspp4.sty, 9 pages, 2 Postscript (embedded) figures. Also available at http://www.astro.yale.edu/koopmann/preprint.htm

An Atlas of H-alpha and R Images and Radial Profiles of 29 Bright Isolated Spiral Galaxies

Narrow-band H-alpha+[NII] and broadband R images and surface photometry are presented for a sample of 29 bright (M_B < -18) isolated S0-Scd galaxies within a distance of 48 Mpc. These galaxies are among the most isolated nearby spiral galaxies of their Hubble classifications as determined from the Nearby Galaxies Catalog (Tully 1987a).Comment: To appear in Astrophysical Journal Supplement Series. 17 pages, including 8 atlas pages in JPEG format. Version with high resolution figures available at http://www1.union.edu/~koopmanr/preprints.htm

Environmental Effects in Clusters: Modified Far-Infrared--Radio Relations within Virgo Cluster Galaxies

(abridged) We present a study on the effects of the intracluster medium (ICM) on the interstellar medium (ISM) of 10 Virgo cluster spiral galaxies using {\it Spitzer} far-infrared (FIR) and VLA radio continuum imaging. Relying on the FIR-radio correlation within normal galaxies, we use our infrared data to create model radio maps which we compare to the observed radio images. For 6 of our sample galaxies we find regions along their outer edges that are highly deficient in the radio compared with our models. We believe these observations are the signatures of ICM ram pressure. For NGC 4522 we find the radio deficit region to lie just exterior to a region of high radio polarization and flat radio spectral index, although the total 20 cm radio continuum in this region does not appear strongly enhanced. These characteristics seem consistent for other galaxies with radio polarization data in the literature. The strength of the radio deficit is inversely correlated with the time since peak pressure as inferred from stellar population studies and gas stripping simulations, suggesting the strength of the radio deficit is good indicator of the strength of the current ram pressure. We also find that galaxies having {\it local} radio {\it deficits} appear to have {\it enhanced global} radio fluxes. Our preferred physical picture is that the observed radio deficit regions arise from the ICM wind sweeping away cosmic-ray (CR) electrons and the associated magnetic field, thereby creating synchrotron tails as observed for some of our galaxies. We propose that CR particles are also re-accelerated by ICM-driven shocklets behind the observed radio deficit regions which in turn enhances the remaining radio disk brightness.Comment: 19 pages, 10 figures; Astrophysical Journa

Genome-Wide Identification of Expression Quantitative Trait Loci (eQTLs) in Human Heart.

In recent years genome-wide association studies (GWAS) have uncovered numerous chromosomal loci associated with various electrocardiographic traits and cardiac arrhythmia predisposition. A considerable fraction of these loci lie within inter-genic regions. The underlying trait-associated variants likely reside in regulatory regions and exert their effect by modulating gene expression. Hence, the key to unraveling the molecular mechanisms underlying these cardiac traits is to interrogate variants for association with differential transcript abundance by expression quantitative trait locus (eQTL) analysis. In this study we conducted an eQTL analysis of human heart. For a total of 129 left ventricular samples that were collected from non-diseased human donor hearts, genome-wide transcript abundance and genotyping was determined using microarrays. Each of the 18,402 transcripts and 897,683 SNP genotypes that remained after pre-processing and stringent quality control were tested for eQTL effects. We identified 771 eQTLs, regulating 429 unique transcripts. Overlaying these eQTLs with cardiac GWAS loci identified novel candidates for studies aimed at elucidating the functional and transcriptional impact of these loci. Thus, this work provides for the first time a comprehensive eQTL map of human heart: a powerful and unique resource that enables systems genetics approaches for the study of cardiac traits

The STAGES view of red spirals and dusty red galaxies: Mass-dependent quenching of star-formation in cluster infall

We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ~0.17 using restframe near-UV-optical SEDs, 24 micron IR data and HST morphologies from the STAGES dataset. The cluster sample is based on COMBO-17 redshifts with an rms precision of sigma_cz~2000 km/sec. We find that 'dusty red galaxies' and 'optically passive spirals' in A901/2 are largely the same phenomenon, and that they form stars at a substantial rate, which is only 4x lower than that in blue spirals at fixed mass. This star formation is more obscured than in blue galaxies and its optical signatures are weak. They appear predominantly in the stellar mass range of log M*/Msol=[10,11] where they constitute over half of the star-forming galaxies in the cluster; they are thus a vital ingredient for understanding the overall picture of star formation quenching in clusters. We find that the mean specific SFR of star-forming galaxies in the cluster is clearly lower than in the field, in contrast to the specific SFR properties of blue galaxies alone, which appear similar in cluster and field. Such a rich red spiral population is best explained if quenching is a slow process and morphological transformation is delayed even more. At log M*/Msol<10, such galaxies are rare, suggesting that their quenching is fast and accompanied by morphological change. We note, that edge-on spirals play a minor role; despite being dust-reddened they form only a small fraction of spirals independent of environment.Comment: Accepted for publication in MNRA

Ring Star Formation Rates in Barred and Nonbarred Galaxies

Nonbarred ringed galaxies are relatively normal galaxies showing bright rings of star formation in spite of lacking a strong bar. This morphology is interesting because it is generally accepted that a typical ring forms when material collects near a resonance, set up by the pattern speed of a bar or bar-like perturbation. Our goal in this paper is to examine whether the ring star formation properties are related to the non-axisymmetric gravity potential in general. For this purpose, we obtained H{\alpha} emission line images and calculated the line fluxes and star formation rates (SFRs) for 16 nonbarred SA galaxies and four weakly barred SAB galaxies with rings. For comparison, we combine our observations with a re-analysis of previously published data on five SA, seven SAB, and 15 SB galaxies with rings, three of which are duplicates from our sample. With these data, we examine what role a bar may play in the star formation process in rings. Compared to barred ringed galaxies, we find that the inner ring SFRs and H{\alpha}+[N ii] equivalent widths in nonbarred ringed galaxies show a similar range and trend with absolute blue magnitude, revised Hubble type, and other parameters. On the whole, the star formation properties of inner rings, excluding the distribution of H ii regions, are independent of the ring shapes and the bar strength in our small samples. We confirm that the deprojected axis ratios of inner rings correlate with maximum relative gravitational force Q_g; however, if we consider all rings, a better correlation is found when local bar forcing at the radius of the ring, Q_r, is used. Individual cases are described and other correlations are discussed. By studying the physical properties of these galaxies, we hope to gain a better understanding of their placement in the scheme of the Hubble sequence and how they formed rings without the driving force of a bar.Comment: 55 pages; 21 figures and 9 tables. Article has been accepted for publication in the Astronomical Journa

Atomic and Molecular Gas Components in Spiral Galaxies of the Virgo Cluster

Based on two models, we investigate the molecular-to-atomic gas ratio in Virgo cluster galaxies in comparison with field galaxies. We show that the enhanced metallicity for cluster members and the ram pressure stripping of atomic gas from the disk periphery cannot fully explain the observed gas component ratios. The additional environmental factors affecting the interstellar medium and leading to an increase in the molecular gas fraction should be taken into account for cluster galaxies.Comment: 11 pages, 4 figure

Metal enrichment of the intra-cluster medium over a Hubble time for merging and relaxed galaxy clusters

We investigate the efficiency of galactic mass loss, triggered by ram-pressure stripping and galactic winds of cluster galaxies, on the chemical enrichment of the intra-cluster medium (ICM). We combine N-body and hydrodynamic simulations with a semi-numerical galaxy formation model. By including simultaneously different enrichment processes, namely ram-pressure stripping and galactic winds, in galaxy-cluster simulations, we are able to reproduce the observed metal distribution in the ICM. We find that the mass loss by galactic winds in the redshift regime z>2 is ~10% to 20% of the total galactic wind mass loss, whereas the mass loss by ram-pressure stripping in the same epoch is up to 5% of the total ram-pressure stripping mass loss over the whole simulation time. In the cluster formation epochs z<2 ram-pressure stripping becomes more dominant than galactic winds. We discuss the non-correlation between the evolution of the mean metallicity of galaxy clusters and the galactic mass losses. For comparison with observations we present two dimensional maps of the ICM quantities and radial metallicity profiles. The shape of the observed profiles is well reproduced by the simulations in the case of merging systems. In the case of cool-core clusters the slope of the observed profiles are reproduced by the simulation at radii below ~300 kpc, whereas at larger radii the observed profiles are shallower. We confirm the inhomogeneous metal distribution in the ICM found in observations. To study the robustness of our results, we investigate two different descriptions for the enrichment process interaction.Comment: 11 pages, 13 figures, accepted for publication in A&A, high resolution version can be found at <http://astro.uibk.ac.at/~wolfgang/kapferer.pdf

The Herschel Virgo Cluster Survey: II. Truncated dust disks in HI-deficient spirals

By combining Herschel-SPIRE observations obtained as part of the Herschel Virgo Cluster Survey with 21 cm HI data from the literature, we investigate the role of the cluster environment on the dust content of Virgo spiral galaxies.We show for the first time that the extent of the dust disk is significantly reduced in HI-deficient galaxies, following remarkably well the observed 'truncation' of the HI disk. The ratio of the submillimetre-to- optical diameter correlates with the HI-deficiency, suggesting that the cluster environment is able to strip dust as well as gas. These results provide important insights not only into the evolution of cluster galaxies but also into the metal enrichment of the intra-cluster medium.Comment: Letter accepted for publication in A&A (Herschel special issue