Jeremy Darling

THE ARECIBO LEGACY FAST ALFA SURVEY. I. SCIENCE GOALS, SURVEY DESIGN, AND STRATEGY

The recently initiated Arecibo Legacy Fast ALFA (ALFALFA) survey aims to map ~7000 deg2 of the high Galactic latitude sky visible from Arecibo, providing a H I line spectral database covering the redshift range between -1600 and 18,000 km s-1 with ~5 km s-1 resolution. Exploiting Arecibos large collecting area and small beam size, ALFALFA is specifically designed to probe the faint end of the H I mass function in the local universe and will provide a census of H I in the surveyed sky area to faint flux limits, making it especially useful in synergy with wide-area surveys conducted at other wavelengths. ALFALFA will also provide the basis for studies of the dynamics of galaxies within the Local Supercluster and nearby superclusters, allow measurement of the H I diameter function, and enable a first wide-area blind search for local H I tidal features, H I absorbers at z < 0.06, and OH megamasers in the redshift range 0.16 < z < 0.25. Although completion of the survey will require some 5 years, public access to the ALFALFA data and data products will be provided in a timely manner, thus allowing its application for studies beyond those targeted by the ALFALFA collaboration. ALFALFA adopts a two-pass, minimum intrusion, drift scan observing technique that samples the same region of sky at two separate epochs to aid in the discrimination of cosmic signals from noise and terrestrial interference. Survey simulations, which take into account large-scale structure in the mass distribution and incorporate experience with the ALFA system gained from tests conducted during its commissioning phase, suggest that ALFALFA will detect on the order of 20,000 extragalactic H I line sources out to z ~ 0.06, including several hundred with H I masses M < 107.5 M⊙.

A Search for OH Megamasers at z > 0.1. III. The Complete Survey

We present the final results from the Arecibo Observatory 1 OH megamaser survey. We discuss in detail the properties of the remaining 18 OH megamasers detected in the survey, including three redetections. We place upper limits on the OH emission from 85 nondetections and examine the properties of 25 ambiguous cases for which the presence or absence of OH emission could not be determined. The complete survey has discovered 50 new OH megamasers (OHMs) in (ultra)luminous infrared galaxies ([U]LIRGs), which doubles the sample of known OHMs and increases the sample at z > 0.1 sevenfold. The Arecibo OH megamaser survey indicates that the OHM fraction in LIRGs is an increasing function of the far-IR luminosity (LFIR) and farIR color, reaching a fraction of roughly 1 in the warmest ULIRGs. Significant relationships between OHMs and their hosts are few, primarily because of a mismatch in size scales of measured properties and an intrinsic scatter in OHM properties roughly equal to the span of the data set. We investigate relationships between OHMs and their hosts with a variety of statistical tools including survival analysis, partial correlation coefficients, and a principal component analysis. There is no apparent OH megamaser ‘‘ fundamental plane.’’ We compile data on all previously known OHMs and evaluate the possible mechanisms and relationships responsible for OHM production in merging systems. The OH-FIR relationship is reexamined by using the doubled OHM sample and found to be significantly flatter than previously thought: LOH / L 1:2� 0:1 FIR . This nearly linear dependence suggests a mixture of saturated and unsaturated masers, either within individual galaxies or across the sample.

FORMALDEHYDE DENSITOMETRY OF STARBURST GALAXIES

With a goal toward deriving the physical conditions in external galaxies, we present a survey of the formaldehyde emission in a sample of starburst systems. By extending a technique used to derive the spatial density in star formation regions in our own Galaxy, we show how the relative intensity of the 110-111 and 211-212 K-doublet transitions of H2CO can provide an accurate densitometer for the active star formation environments found in starburst galaxies. Relying on an assumed kinetic temperature and cospatial emission and absorption from both H2CO transitions, our technique is applied to a sample of 19 infrared-bright galaxies which exhibit various forms of starburst activity. In the five galaxies of our sample where both H2CO transitions were detected, we have derived spatial densities. We also use H2CO to estimate the dense gas mass in our starburst galaxy sample, finding similar mass estimates for the dense gas-forming stars in these objects as derived using other dense gas tracers. A related trend can be seen when one compares LIR to our derived n(H2) for the five galaxies within which we have derived spatial densities. Even though our number statistics are small, there appears to be a trend toward higher spatial density for galaxies with higher infrared luminosity. This is likely another representation of the LIR-Mdense correlation.

PROPERTIES OF ACTIVE GALAXIES DEDUCED FROM H i OBSERVATIONS

We have completed a new survey for H I emission for a large, well-defined sample of 154 nearby ( -->z 0.1) galaxies with type 1 (broad-line) active galactic nuclei (AGNs). We make use of the extensive database of H I and optical parameters, presented in a companion paper, to perform a comprehensive appraisal of the cold gas content in active galaxies and to seek new strategies to investigate the global properties of the host galaxies and their relationship to their central black holes. After excluding objects with kinematically anomalous line profiles, which occur with high frequency in the sample, we show that the black hole mass obeys a strong, roughly linear relation with the host galaxys dynamical mass, calculated by combining the H I line width and the optical size of the galaxy. Black hole mass follows a looser, though still highly significant, correlation with the maximum rotation velocity of the galaxy, as expected from the known scaling between rotation velocity and central velocity dispersion. Neither of these H I-based correlations is as tight as the more familiar relations between black hole mass and bulge luminosity or velocity dispersion, but they offer the advantage of being insensitive to the glare of the nucleus and therefore are promising new tools for probing the host galaxies of both nearby and distant AGNs. We present evidence for substantial ongoing black hole growth in the most actively accreting AGNs. In these nearby systems, black hole growth appears to be delayed with respect to the assembly of the host galaxy but otherwise has left no detectable perturbation to its mass-to-light ratio, as judged from the Tully-Fisher relation, or its global gas content. The host galaxies of type 1 AGNs, including those luminous enough to qualify as quasars, are generally gas-rich systems, possessing a cold interstellar medium reservoir at least as abundant as that in inactive galaxies of the same morphological type. This calls into question current implementations of AGN feedback in models of galaxy formation that predict strong cold gas depletion in unobscured AGNs.

Methods for constraining fine structure constant evolution with OH microwave transitions.

We investigate the constraints that OH microwave transitions in megamasers and molecular absorbers at cosmological distances may place on the evolution of the fine structure constant alpha=e(2)/ variant Plancks over 2pi c. The centimeter OH transitions are a combination of hyperfine splitting and lambda doubling that can constrain the cosmic evolution of alpha from a single species, avoiding systematic errors in alpha measurements from multiple species which may have relative velocity offsets. The most promising method compares the 18 and 6 cm OH lines, includes a calibration of systematic errors, and offers multiple determinations of alpha in a single object. Comparisons of OH lines to the HI 21 cm line and CO rotational transitions also show promise.

A Search for OH Megamasers at z > 0.1. II. Further Results

We present current results of an ongoing survey for OH megamasers in luminous infrared galaxies at the Arecibo Observatory.1 The survey is now two-thirds complete, and has resulted in the discovery of 35 new OH megamasers at z > 0.1, 24 of which are presented in this paper. We discuss the properties of each source in detail, including an exhaustive survey of the literature. We also place upper limits on the OH emission from 107 nondetections and list their IR, radio, and optical properties. The survey detection rate is one OH megamaser for every six candidates overall, but is a strong function of the far-IR luminosity of candidates and may depend on merger stage or on the central engine responsible for the IR luminosity in the merging galaxy pair. We also report the detection of IRAS 12032+1707, a new OH gigamaser.

An ALMA Early Science survey of molecular absorption lines toward PKS 1830−211 - Analysis of the absorption profiles

We present the first results of an ALMA spectral survey of strong absorption lines for common interstellar species in the z = 0.89 molecular absorber toward the lensed blazar PKS 1830-211. The dataset brings essential information on the structure and composition of the absorbing gas in the foreground galaxy. In particular, we find absorption over large velocity intervals (greater than or similar to 100 km s(-1)) toward both lensed images of the blazar. This suggests either that the galaxy inclination is intermediate and that we sample velocity gradients or streaming motions in the disk plane, that the molecular gas has a large vertical distribution or extraplanar components, or that the absorber is not a simple spiral galaxy but might be a merger system. The number of detected species is now reaching a total of 42 different species plus 14 different rare isotopologues toward the SW image, and 14 species toward the NE line-of-sight. The abundances of CH, H2O, HCO+, HCN, and NH3 relative to H-2 are found to be comparable to those in the Galactic diffuse medium. Of all the lines detected so far toward PKS 1830-211, the ground-state line of ortho-water has the deepest absorption. We argue that ground-state lines of water have the best potential for detecting diffuse molecular gas in absorption at high redshift.

A SEARCH FOR OH MEGAMASERS AT z ( 0.1. I. PRELIMINARY RESULTS

We present the preliminary results of a survey for OH megamasers underway at the Arecibo Observatory1. The goals of the survey are to calibrate the luminosity function of OH megamasers to the low-redshift galaxy merger rate (0.1 0.1. The new megamasers show a wide range of spectral properties but are consistent with the extant set of 55 previously reported objects, only eight of which have z > 0.1.

New searches for H I 21 cm in damped Lyman α absorption systems

We present the results of three separate searches for H I 21-cm absorption in a total of twelve damped Lyman-� absorption systems (DLAs) and sub-DLAs over the redshift range zabs = 0:86 3:37. We find no absorption in the five systems for which we obtain re asonable sensitivities and add the results to those of other rece nt surveys in order to investigate factors which could have an effect on the detection rate: We provide evidence that the mix of spin temperature/covering factor ratios seen at low redshift may also exist at high redshift, with a correlation between the 21-cm line strength and the total neutral hydrogen column density, indicating a roughly constant spin temperature/cove ring factor ratio for all of the DLAs searched. Also, by considering the geometry of a flat expandi ng Universe together with the projected sizes of the background radio emission regions, we find, for the detections, that the 21-cm line strength is correlated with the size of the absorb er. For the non-detections it is apparent that larger absorbers (covering factors) are requ ired in order to exhibit 21-cm absorption, particularly if these DLAs do not arise in spiral g alaxies. We also suggest that the recent zabs = 2:3 detection towards TXS 0311+430 arises in a spiral galaxy, but on the basis of a large absorption cross-section and high metallicity, r ather than a low spin temperature (York et al. 2007).

SPITZER MID-INFRARED SPECTROSCOPY OF COMPACT SYMMETRIC OBJECTS: WHAT POWERS RADIO-LOUD ACTIVE GALACTIC NUCLEI?

We present low- and high-resolution mid-infrared (mid-IR) spectra and photometry for eight compact symmetric objects (CSOs) taken with the Infrared Spectrograph on the Spitzer Space Telescope. The hosts of these young, powerful radio galaxies show significant diversity in their mid-IR spectra. This includes multiple atomic fine-structure lines, H2 gas, polycyclic aromatic hydrocarbon (PAH) emission, warm dust from T = 50to150 K, and silicate features in both emission and absorption. There is no evidence in the mid-IR of a single template for CSO hosts, but 5/8 galaxies show similar moderate levels of star formation ( 108 M ? likely exist in all of the CSOs in the sample; however, there is no direct evidence from these data that BH spin energy is being tapped as an alternative mode for powering the radio jets.