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

The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems

We present VLA HI spectral line imaging of 5 sources discovered by ALFALFA. These targets are drawn from a larger sample of systems that were not uniquely identified with optical counterparts during ALFALFA processing, and as such have unusually high HI mass to light ratios. These candidate "Almost Dark" objects fall into 4 categories: 1) objects with nearby HI neighbors that are likely of tidal origin; 2) objects that appear to be part of a system of multiple HI sources, but which may not be tidal in origin; 3) objects isolated from nearby ALFALFA HI detections, but located near a gas-poor early-type galaxy; 4) apparently isolated sources, with no object of coincident redshift within ~400 kpc. Roughly 75% of the 200 objects without identified counterparts in the $\alpha$.40 database (Haynes et al. 2011) fall into category 1. This pilot sample contains the first five sources observed as part of a larger effort to characterize HI sources with no readily identifiable optical counterpart at single dish resolution. These objects span a range of HI mass [7.41 < log(M$_{\rm HI}$) < 9.51] and HI mass to B-band luminosity ratios (3 < M$_{\rm HI}$/L$_{\rm B}$ < 9). We compare the HI total intensity and velocity fields to SDSS optical imaging and to archival GALEX UV imaging. Four of the sources with uncertain or no optical counterpart in the ALFALFA data are identified with low surface brightness optical counterparts in SDSS imaging when compared with VLA HI intensity maps, and appear to be galaxies with clear signs of ordered rotation. One source (AGC 208602) is likely tidal in nature. We find no "dark galaxies" in this limited sample. The present observations reveal complex sources with suppressed star formation, highlighting both the observational difficulties and the necessity of synthesis follow-up observations to understand these extreme objects. (abridged)Comment: Astronomical Journal, in pres

A Generalist, Automated ALFALFA Baryonic Tully-Fisher Relation

The Baryonic Tully-Fisher Relation (BTFR) has applications in galaxy evolution as a testbed for the galaxy-halo connection and in observational cosmology as a redshift-independent secondary distance indicator. We use the 31,000+ galaxy ALFALFA sample -- which provides redshifts, velocity widths, and HI content for a large number of gas-bearing galaxies in the local universe -- to fit and test an extensive local universe BTFR. This BTFR is designed to be as inclusive of ALFALFA and comparable samples as possible. Velocity widths measured via an automated method and $M_{b}$ proxies extracted from survey data can be uniformly and efficiently measured for other samples, giving this analysis broad applicability. We also investigate the role of sample demographics in determining the best-fit relation. We find that the best-fit relations are changed significantly by changes to the sample mass range and to second order, mass sampling, gas fraction, different stellar mass and velocity width measurements. We use a subset of ALFALFA with demographics that reflect the full sample to measure a robust BTFR slope of $3.30\pm0.06$. We apply this relation and estimate source distances, finding general agreement with flow-model distances as well as average distance uncertainties of $\sim0.17$ dex for the full ALFALFA sample. We demonstrate the utility of these distance estimates by applying them to a sample of sources in the Virgo vicinity, recovering signatures of infall consistent with previous work.Comment: 23 pages, 10 figures, submitted to Ap

Kinematics of diffuse ionized gas in the disk halo interface of NGC 891 from Fabry-P\'erot observations

The properties of the gas in halos of galaxies constrain global models of the interstellar medium. Kinematical information is of particular interest since it is a clue to the origin of the gas. Here we report observations of the kinematics of the thick layer of the diffuse ionized gas in NGC 891 in order to determine the rotation curve of the halo gas. We have obtained a Fabry-P\'erot data cube in Halpha to measure the kinematics of the halo gas with angular resolution much higher than obtained from HI 21 cm observations. The data cube was obtained with the TAURUS II spectrograph at the WHT on La Palma. The velocity information of the diffuse ionized gas extracted from the data cube is compared to model distributions to constrain the distribution of the gas and in particular the halo rotation curve. The best fit model has a central attenuation tau_H-alpha=6, a dust scale length of 8.1 kpc, an ionized gas scale length of 5.0 kpc. Above the plane the rotation curve lags with a vertical gradient of -18.8 km/s/kpc. We find that the scale length of the H-alpha must be between 2.5 and 6.5 kpc. Furthermore we find evidence that the rotation curve above the plane rises less steeply than in the plane. This is all in agreement with the velocities measured in the HI.Comment: A&A, in press. 13 pages, 19 figure

A 500 kpc HI Extension of the Virgo Pair NGC4532/DDO137 Detected by the Arecibo Legacy Fast ALFA (ALFALFA) Survey

We report the discovery of a ~500 kpc H I extension southwest of the Virgo Cluster H I-rich pair NGC 4532/DDO 137, detected as part of the Arecibo Legacy Fast ALFA (ALFALFA) Survey. The feature is the longest and most massive H I tail structure so far found in the Virgo Cluster and, at 1.8 Mpc from M87, the most distant from the main concentration of the intracluster medium. The structure is spatially and spectrally separated into two ridges and is defined by diffuse emission and discrete clumps of mass (2.5–6.8) × 107 M☉. All emission is blueshifted with respect to the NGC 4532/DDO 137 pair emission. Including diffuse emission, the structure has a total mass of up to 7 × 108 M☉, equivalent to ~10% of the system\u27s H I mass. Optical R-band imaging finds no counterparts to a level of 26.5 mag arcsec−2. The characteristics of the structure appear most consistent with a tidal origin

The Arecibo Legacy Fast ALFA Survey: VI. Second HI Source Catalog of the Virgo Cluster Region

We present the third installment of HI sources extracted from the Arecibo Legacy Fast ALFA extragalactic survey. This dataset continues the work of the Virgo ALFALFA catalog. The catalogs and spectra published here consist of data obtained during the 2005 and 2006 observing sessions of the survey. The catalog consists of 578 HI detections within the range 11h 36m < R.A.(J2000) < 13h 52m and +08 deg < Dec.(J2000) < +12 deg, and cz_sun < 18000 km/s. The catalog entries are identified with optical counterparts where possible through the examination of digitized optical images. The catalog detections can be classified into three categories: (a) detections of high reliability with S/N > 6.5; (b) high velocity clouds in the Milky Way or its periphery; and (c) signals of lower S/N which coincide spatially with an optical object and known redshift. 75% of the sources are newly published HI detections. Of particular note is a complex of HI clouds projected between M87 and M49 that do not coincide with any optical counterparts. Candidate objects without optical counterparts are few. The median redshift for this sample is 6500 km/s and the cz distribution exhibits the local large scale structure consisting of Virgo and the background void and the A1367-Coma supercluster regime at cz_sun ~7000 km/s. Position corrections for telescope pointing errors are applied to the dataset by comparing ALFALFA continuum centroid with those cataloged in the NRAO VLA Sky Survey. The uncorrected positional accuracy averages 27 arcsec ~(21 arcsec ~median) for all sources with S/N > 6.5 and is of order ~21 arcsec ~(16 arcsec ~median) for signals with S/N > 12. Uncertainties in distances toward the Virgo cluster can affect the calculated HI mass distribution.Comment: 25 pages, 1 Table, 8 figures, Accepted by the Astronomical Journa

Impact of long-range interactions on the disordered vortex lattice

The interaction between the vortex lines in a type-II superconductor is mediated by currents. In the absence of transverse screening this interaction is long-ranged, stiffening up the vortex lattice as expressed by the dispersive elastic moduli. The effect of disorder is strongly reduced, resulting in a mean-squared displacement correlator = characterized by a mere logarithmic growth with distance. Finite screening cuts the interaction on the scale of the London penetration depth \lambda and limits the above behavior to distances R<\lambda. Using a functional renormalization group (RG) approach, we derive the flow equation for the disorder correlation function and calculate the disorder-averaged mean-squared relative displacement \propto ln^{2\sigma} (R/a_0). The logarithmic growth (2\sigma=1) in the perturbative regime at small distances [A.I. Larkin and Yu.N. Ovchinnikov, J. Low Temp. Phys. 34, 409 (1979)] crosses over to a sub-logarithmic growth with 2\sigma=0.348 at large distances.Comment: 9 pages, no figure

Halpha Morphologies and Environmental Effects in Virgo Cluster Spiral Galaxies

We describe the various Halpha morphologies of Virgo Cluster and isolated spiral galaxies, and associate the Halpha morphologies with the types of environmental interactions which have altered the cluster galaxies. The spatial distributions of Halpha and R-band emission are used to divide the star formation morphologies of the 52 Virgo Cluster spirals into several categories: normal (37%), anemic (6%), enhanced (6%), and (spatially) truncated (52%). Truncated galaxies are further subdivided based on their inner star formation rates into truncated/normal (37%), truncated/compact (6%), truncated/anemic (8%), and truncated/enhanced (2%). The fraction of anemic galaxies is relatively small (6-13%) in both environments, suggesting that starvation is not a major factor in the reduced star formation rates of Virgo spirals. The majority of Virgo spiral galaxies have their Halpha disks truncated (52%), whereas truncated Halpha disks are rarer in isolated galaxies (12%). Most of the Halpha-truncated galaxies have relatively undisturbed stellar disks and normal-to-slightly enhanced inner disk star formation rates, suggesting that ICM-ISM stripping is the main mechanism causing the reduced star formation rates of Virgo spirals. In other galaxies, the Halpha morphologies are more consistent with a tidal origin or perhaps outer cluster HI accretion. These results indicate that most Virgo spiral galaxies experience ICM-ISM stripping, many experience significant tidal effects, and many experience both. (abridged).Comment: Accepted by Astrophysical Journal. 16 pages, 15 figures, including 9 in low-resolution jpg format. Higher resolution postscript versions of these figures are available from http://www1.union.edu/~koopmanr/radfig.htm

BVRI Light Curves for 29 Type Ia Supernovae

BVRI light curves are presented for 27 Type Ia supernovae discovered during the course of the Calan/Tololo Survey and for two other SNe Ia observed during the same period. Estimates of the maximum light magnitudes in the B, V, and I bands and the initial decline rate parameter m15(B) are also given.Comment: 17 pages, figures and tables are not included (contact first author if needed), to appear in the Astronomical Journa