The Evolution of Galaxies through the Neutral Hydrogen Window

Abstracts

Name: Stephen Schneider
Title: HI mass function: open questions
Abstract:
Characterizing the population of extragalactic HI sources by their HI mass is an important step toward understanding how galaxies have evolved. If there is one conclusion to draw from past attempts at defining the HI mass function (HIMF) and the longer history of defining the galaxy luminosity function, it’s that we will not converge on a single answer anytime soon. Part of this is certainly because there is not a single universal HIMF, and one of the goals of current and future surveys is to characterize what other parameters, such as local density, affect it. Already there are puzzles suggesting that the evolution of HI content in a population follows a complicated path. For example, the faint end of the function shows contradictory behaviors depending on how density is measured. This points toward environments that are important to explore more deeply with future surveys. HI surveys for the present, and probably even into the era of the SKA, will remain noise-limited to a far greater degree than optical surveys. Working close to the noise limit, we face a variety of statistical perils. However, by examining the characteristics of the noise statistics in our surveys, it may be possible to extract more information than we have previously.

Name: Jacqueline van Gorkom
Title: HI gas in galaxies from z=0 to z=0.2
Abstract:
The evolution of galaxies through the neutral hydrogen window becomes obvious when we look at galaxies in different environments. In the densest parts of clusters the morphological mix and colors of galaxies is very different from galaxy properties in lower density regions. More recent evidence indicates that these properties change very smoothly over several Abell radii. I will focus on the fate of the gas in galaxies. When and where do galaxies stop accreting, how do they loose the cool gas and when does star formation stop? I will argue that it is the assembly of clusters that may affect the evolution of the galaxies.

Name: Danail Obreschkow
Title: Cold Gas Composition - a Key Between HI-Surveys and Cosmological Simulations
Abstract:
We revisit the atomic (HI) to molecular (H2) composition of neutral hydrogen in local galaxies. This work is particularly motivated by the need for accurate comparisons between the precisely measured HI-mass function (Zwaan et al. 2005) and various simulated cold gas mass functions. In a first step, we correct the H2 mass function obtained by Keres et al. (2003), using a variable conversion between observed CO-line intensities and H2 masses (similar to Boselli et al. 2002). In a second step, we derive a phenomenological prescription for the H2-to-HI ratio in HI-detected galaxies, using again a variable CO-to-H2 conversion. This prescription is used to predict an H2-mass for each galaxy in HICAT, the largest catalog of HI-detected galaxies today. The hereby recovered H2 mass function closely matches our corrected H2 mass function, thus demonstrating the self-consistency of the present approach.

Name: Nissim Kanekar
Title: HI 21cm absorption studies of damped Lyman-alpha systems
Abstract:
I will describe our recent deep HI 21cm absorption studies of high redshift damped Lyman-alpha systems (DLAs) with the Green Bank Telescope and the Giant Metrewave Radio Telescope. Absorption studies of DLAs towards compact quasars provide an estimate of the HI spin temperature of the absorbing gas, thus yielding information on the evolution of the fraction of gas in the warm and cold phases of neutral hydrogen as a function of redshift. I will discuss the repercussions of our GBT and GMRT observations for the nature of high-z DLAs and physical conditions in them. I will also describe our HI 21cm absorption studies of DLAs towards extended radio sources, which provide direct estimates of the transverse size of DLAs at intermediate redshifts. Finally, I will discuss how the SKA and its precursors will revolutionize this field in the near future.

Name: Martin Zwaan
Title: What we learn from comparing DLAs with 21-cm-selected galaxies
Abstract:
At present the techniques we use to study HI in the local Universe and at higher z are completely different. At z=0 we observe the hyperfine transition in emission with radio telescopes, whereas at higher z we use optical telescopes to study the Ly alpha line in absorption. In this talk I compare the results from these different survey techniques in detail: What can we learn from comparing e.g., the kinematics, the HI column density distribution function f(N), and the optical characteristics of Damped Lyman Alpha (DLA) systems with the properties of local 21-cm selected galaxies? What does such a comparison tell us about the star formation in DLAs and the evolution of the cosmic gas content. How does it help us to plan future surveys with telescopes such as the SKA and ALMA?

Name: Nick Gnedin
Title: HI in the early universe: expectations
Abstract:
I will give a general overview of the evolution of the neutral hydrogen in the IGM, and will highlight the prospects (and difficulties) of detection of the cosmological HI signal over a range of redshifts.

Name: Jessica Rosenberg
Title: Observing the Evolution of Star-Forming Dwarf Galaxies through the Neutral Hydrogen Window
Abstract:
The combination of HI and optical data can be a powerful tool in understanding the properties of galaxies and their evolution. Observations at 21 cm adds information on the gas mass and dynamical masses of galaxies that complement the stellar properties as measured at optical wavelengths. I will discuss a multiwavelength study of star-forming dwarf galaxies in the local universe and how the combination of optical and HI data provides information about the evolution of these systems over time. The SKA will open up an entirely new regime for this work by allowing for the observation of vastly larger numbers of galaxies at 21 cm then has been possible to date. The future of using 21 cm data to help study the evolution of star-forming dwarf galaxies (among other systems) when these large data sets are available will be discussed.

Name: Juergen Ott
Title: VLA-ANGST: Star Formation History and ISM Feedback in Nearby Galaxies
Abstract:
In recent years, HST revolutionized the field of star formation in nearby galaxies. Due to its high angular resolution it has now become possible to construct star formation histories of individual stellar populations on scales of a few arcseconds spanning a range of a several Gyr. ANGST (ACS Nearby Galaxy Survey Treasury) is an ambitious program to derive the detailed star formation histories for a volume filled sample of galaxies up to 4 Mpc distance (excluding the Local Group). The ANGST sample will be followed--up by high resolution VLA HI observations in the context of an approved Large Project ~480 hours of allocated time). The combination of ANGST/HST and VLA data is essential to understand the triggering of star formation, the feedback of massive stars into the interstellar medium (ISM), the impact of previous episodes of star formation on the present day ISM structure, and the energy budget of the ISM on local and galaxy scales. In this context, VLA B-array data is indispensable as it is a perfect match to the resolution of the maps of reconstructed star formation histories derived from HST data.

Name: Karen O'Neil
Title: Gas and Stars in Massive Low Surface Brightness Galaxies
Abstract:
Massive low surface brightness galaxies have disk central surface brightnesses at least one magnitude fainter than the night sky, but total magnitudes and masses that show they are among the largest galaxies known. Like all low surface brightness (LSB) galaxies, massive LSB galaxies are often in the midst of star formation yet their stellar light has remained diffuse, raising the question of how star formation is proceeding within these galaxies. HI observations have played a crucial role in studying these systems as LSB galaxies are typically extremely gas rich. In the past few years we have more than quadrupled the total number of massive LSB galaxies, primarily through HI surveys. To clarify the structural parameters and stellar and gas content of these enigmatic systems, we have undertaken a multi-wavelength study of them. The results of this study, which includes HI, CO, optical, near UV, and far UV images of the galaxies, will provide the most in depth study done to date of how, when, and where star formation proceeds within this unique subset of the galaxy population.

Name: Gerhardt Meurer
Title: The HI Star-Formation Connection: Open Questions
Abstract:
I will show data from the Survey of Ionization in Neutral Gas Galaxies (SINGG) and Survey of Ultraviolet emission in Neutral Gas Galaxies (SUNGG) which survey the star formation properties of HI selected galaxies as traced by H-alpha and Ultraviolet emission, respectively. The correlations found demonstrate a strong relationship between the neutral ISM and young massive stars. For example the correlation between star formation intensity and the HI cycling time is tighter than the Kennicutt-Schmidt Star Formation Law. The existence of an HI - star formation connection is somewhat of a mystery since stars form in the molecular not the neutral ISM, while the highest mass stars and the HI have very different distributions in galaxies. The star formation properties of galaxies in the UV and H-alpha differ significantly hinting at different formation mechanisms for B and O stars.

Name: Liese van Zee
Title: SF in low mass galaxies: overview
Abstract:
As the evolution of galaxies is largely driven by their conversion of gas into stars, understanding the relationship between gas distribution and star formation activity is of critical importance for galaxy evolution models. I will review the star formation activity and gas distributions found in isolated low mass galaxies and discuss the implications for star formation efficiency in low density environments. I will also review the current status of the SMUDGES survey to investigate star formation modes in low mass galaxies, with an emphasis on new directions that should be explored within the next decade.

Name: Tobias Kaufmann
Title: Cold Cloud Infall and Galaxy Formation
Abstract:
I will discuss the fragmentation and cooling of halo gas using very high-resolution galaxy formation simulations set within the context of LCDM cosmology. Disk formation proceeds via the infall of cool clouds, and the residual population resembles the high-velocity cloud population of the Milky Way. Neutral cloud observations provide an important constraint on galaxy formation models and proposed feedback schemes.

Name: John Beckman/Valeria Buenrostro-Leiter
Title: High velocity clouds around nearby galxies from THINGS
Abstract:
As a sub-set of activities within the THINGS collaboration we have used the HI maps of the complete set of galaxies observed in the THINGS survey with the VLA to search for the presence of high velocity clouds around them. Detections were made in 30% of the cases, with a lower detection limit of just under 10⁵ solar masses. Given the column density limit of the survey, and assuming that these clouds would have underlying structures comparable to those HVC's around the Milky Way which are known not to be galactic fountain objects (Complex C or Complex H) we estimate that our detections would account for less than 10% of the total HI masses of the newly detected cloudlets. We draw some tentative concusions about the rate of infall of HI to the disks of the galaxies observed.

Name: Sheila Kannappan
Title: Gas Fractions and Scaling Relations
Abstract:
I will show that both early and late type galaxies increase sharply in typical HI gas richness below a threshold stellar mass of ~1-2 x 10¹⁰ Msun, and I will suggest that probing the possible downsizing of this threshold mass is a key observational goal for the future. These results draw on an extraordinarily tight correlation between atomic gas mass/stellar mass ratio (G/S) and U-K color, previously discovered by cross-matching catalogs and now confirmed using HI data for a statistically well-defined and broadly representative survey (the Nearby Field Galaxy Survey, or NFGS). The correlation holds over more than three decades in G/S, with scatter <0.4 dex, enabling statistical detection of the gas-richness threshold mass using "photometric gas fractions" based on U-K. For comparison, I will present and interpret the G/S vs. global emission-line EW(Halpha) correlation, which has greater scatter than the G/S vs. U-K relation as well as differentially higher scatter for early types (the G/S vs. U-K correlation shows more uniform scatter for all types). Finally, I will discuss efforts to add molecular gas into these analyses.

Name: Matthew Bershady
Title: Growth and Destruction of Disks: Combined HI and HII View
Abstract:
How large disk galaxies have evolved in the blue cloud as a function of environment and time is an outstanding question. Some of the largest disks become systems like M31, M33 and the Milky Way today. In denser environments, it appears they transform onto the red sequence. Tracking disk systems since z<1 as a function HI mass, dynamical mass, and environment should be possible in the coming decade. HI and optical data combined can sample outer and inner disk dynamics to connect halo properties with regions of most intense star-formation, and the gas reservoir to the consumption rate. We describe existing and future IFUs on 4-10m telescopes that complement upcoming HI surveys for studying disks at z<1. Multiple units, deployable over large fields-of-view, and with logarithmic sampling will yield kinematic and SF maps resolving the core but retaining sensitivity to disk outskirts. While detailed spatial information falls away between 0

Name: Steven Myers
Title: The Radio Synoptic Survey Telescope (RSST): A SKA Concept
Abstract:
The next generation of radio arrays are being designed under the umbrella of the "Square Kilometer Array" project. The leading concept for a "mid-frequency" (0.3-3 GHz) SKA is the Radio Synoptic Survey Telescope (RSST), which is being developed for presentation to the upcoming Astronomy and Astrophysics Decadal Survey. The RSST is targeted at obtaining HI observations of a billion galaxies out to redshift z=1.5 over 10000 square degrees, and synoptic mapping of the radio sky for transient detection and monitoring. In this talk I will outline the design and technical challenges facing the RSST, and discuss the path forward towards construction and operation of the RSST.

Name: Min Yun
Title: HI, H2, and Galaxy Evolution
Abstract:
Establishing the cosmic gas accretion history and the evolution in the HI mass function is an important and fundamental observational constraint on galaxy evolution. About 1/2 of the cold ISM in galaxies is found in the denser, molecular phase, which is also the immediate fuel for the formation of young stars. Therefore a census of molecular gas mass and its evolution is an essential complement to the HI surveys planned for the near future. I will describe how the science programs planned for the 50-m Large Millimeter Telescope (currently under construction on a 15,000 ft peak in Mexico) will address some of the key issues in galaxy evolution in terms of their molecular gas content.

Name: Aeree Chung
Title: Color Bimodality of the VIVA Sample: HI Stripping and Broadband Color
Abstract:
We present the result from our color bimodality study of spirals in a single cluster environment using the VIVA (VLA Imaging Survey of Virgo in Atomic gas) sample. The goal is to investigate whether HI gas stripping in the cluster plays a role in moving galaxies from blue cloud to red sequence. We have explored the dependence of the color-magnitude relation on HI properties such as morphology and deficiency, and compared with the SDSS sample. With a few exceptions, we find that severely gas stripped galaxies with small HI disks redder compared to gas rich galaxies with extended HI disks. In particular, five out of seven galaxies found with one-sided extended HI tails in the VIVA survey, which are thought to be entering high density regions, are found somewhere between the blue cloud and the red sequence, the region known as "green valley". This implies that galaxies become redder as they lose gas in the cluster environment and consequently have less star formation. While not the only effect, it appears that HI stripping in the cluster environment is one of the contributors to the observed color bimodality.

Name: Luca Cortese
Title: Neutral Hydrogen and Star Formation in the Coma-Abell1367 supercluster
Abstract:
The environment in clusters is known to affect the morphology, star formation activity of their member galaxies, resulting in the well known morphology-density relation. Further evidence of the effect of cluster environment on galaxy evolution comes from the observed increase in the fraction of HI deficient spiral galaxies toward the cluster core which is strongly linked to evidence that infalling cluster spirals encountering the cluster X-ray emitting intracluster medium (ICM) for the first time experience rapid ISM evolution. However our picture of galaxy clusters still remains limited since it is mostly based on the study of rest-frame optical selected objects which have already converted great part of their atomic hydrogen into stars. Moreover we lack a census of the whole gas content and star formation in galaxy clusters. This is mainly due to the lack of blind multiwavelength surveys able to trace the different baryonic components in a galaxy (gas, young and old stars and dust). In the last years, this situation is rapidly improving thanks to the advent of new generation UV (Galaxy Evolution Explorer) and HI (Arecibo L-band Feed Array) blind surveys which are providing us for the first time an unbiased view of star formation and gas content in cluster galaxies. In this talk I will present the preliminary results from blind HI and UV surveys of the Coma-Abell1367 supercluster. These observations provide an unbiased census of star formation and neutral hydrogen content in local clusters allowing us to gain more insights on the evolutionary history of cluster galaxies.

Name: Barbara Catinella
Title: Pushing Arecibo to the limit: detection of HI emission from galaxies at redshift z~0.2
Abstract:
I will present results from a targeted survey undertaken with the 305m Arecibo radiotelescope to detect HI-line emission from disk galaxies at redshift z>0.16. The targets for the observations were extracted from the Sloan Digital Sky Survey database according to their redshift, optical emission line strength, inclination, disk morphology, and relative isolation (to minimize confusion within the beam). HI profiles of adequate quality for flux and velocity width measurement for ~30 galaxies in the redshift range 0.17-0.26. The average total integration time per object varied between 2 and 6 hours, primarily depending on the redshift of the target. This sample includes the highest redshift detections of HI emission from individual, normal galaxies to date.

Name: Karen Masters
Title: The local velocity field.
Abstract:
The 2 Micron All-Sky Survey (2MASS) Tully-Fisher Survey (2MTF) aims to measure Tully-Fisher (TF) distances to all bright inclined spirals in the 2MASS Redshift Survey (2MRS). I will describe the current status of this project. Essential to the survey is a universal calibration of the TF relation in the 2MASS J (1.2 um), H (1.6 um) and K (2.2 um) bands. I present the first bias corrected or universal TF template in these bands. I will show that the slope of the TF relation becomes steeper as the wavelength increases being close to L ~ v^4 in K-band and L ~ v^3.6 in J and H-bands. We also investigate the dependence on galaxy morphology showing that in all three bands the relation is steeper for later type spirals which also have a dimmer TF zeropoint than earlier type spirals. Finally we study the scatter from the TF relation fitting for a width dependent intrinsic scatter which is not found to vary significantly with wavelength.

Name: Kristine Spekkens
Title: The baryonic TF relation and the dark matter content of normal spirals
Abstract:
Mass models of spiral galaxy photometry and kinematics imply that dark matter densities across the disks of normal, L* spirals are an order of magnitude lower than expected from cosmological simulations. While there is no consensus regarding the effectiveness of mechanisms proposed to reconcile this discrepancy, it is clear that progress on this front requires a multi-wavelength observational approach. In particular, HI kinematics beyond the optical disk are essential for constraining halo sizes and concentrations, while high-resolution tracers in the inner region probe the changing central attraction and resolve non-circular flows. RINGS, the RMC/Rutgers Imaging spectroscopy Nearby Galaxy Survey, will deliver aperture synthesis HI observations from the (E)VLA and Fabry-Perot Ha imaging spectroscopy from SALT for 24 nearby systems. The resulting velocity fields will be complemented with BVRI photometry to produce a dataset of the highest quality for detailed dynamical studies of nearby spirals. Numerical tools are being developed to mass model RINGS data products, and ultimately to carry out self-consistent simulations that will probe the stability and evolution of the optimal fits. RINGS will therefore make important progress towards understanding the dark matter content of normal spirals in a cosmological context.

Name: Brian Kent
Title: Clouds and Debris in the Virgo Cluster
Abstract:
The Arecibo Legacy Fast ALFA survey has yielded a complete HI dataset of the Virgo Cluster and its environs (Giovanelli et al. 2007, Kent et al. 2007). Several HI candidates have been detected in the vicinity of the Virgo Cluster, all at cz < 3000 km/s. Assuming a distance to Virgo of 16.7 Mpc, the minimum detectable HI mass is of order 2 x 10^7 Msolar masses Some objects appear to be located near low surface brightness optical counterparts, or are the result of tidal interactions with nearby large galaxies. Such detections are clearly the result of a larger group or system. However, other isolated HI detections do not coincide with any nearby counterparts visible in optical surveys. The detections lie outside the influence of effects from ram-pressure stripping in the Virgo Cluster. The observed HI properties of these objects derived from single dish Arecibo mapping, as well as aperture-synthesis followup observations obtained from the VLA will be shown. The effects of the cluster environment on the formation and evolution of such objects will corroborated with observed properties.

Name: Judd Bowman
Title: HI and Cosmology: What We Need to Know
Abstact:
There are four distinct regimes in which radio observations of HI can contribute directly to cosmology in unique ways. They are: 1) inflationary physics and the Dark Ages, 2) reionization, 3) "the doldrums" between 6>z>1, and 4) Dark Energy and accelerated expansion. The variety of observational approaches needed to study each of these regimes spans many different paradigms, from measuring the all-sky radio spectrum with exquisite precision, to surveying enormous numbers of galaxies, to characterizing fluctuations in the diffuse background and imaging ionized bubbles around quasars. Each measurement presents its own set of technical, theoretical, and observational challenges. I will review briefly the most fundamental aspects of what we need to know (and what we expect to learn in the coming years) in order to achieve the goals of the SKA and beyond.

Name: Rogier Windhorst
Title: GiGa: the billion galaxy HI survey
Abstract:
I will review the rationale and requirements of the Billion Galaxy HI survey (GiGa) with the next generation radio facilities. Its main goal.will be to map hierarchical galaxy assembly from the end of reionization to the present. It will have significant synergy with the next generation space and ground based facilities.