bluuebunny/crossref_metadata_2025_split huggingface dataset:
Too Small to Form a Galaxy: How the UV Background Determines the Baryon Fraction
Authors: Hoeft M. , Yepes G. , Gottlöber S. 
Published: February 2008

AbstractThe cosmic ultraviolet background (UVB) heats the intergalactic medium (IGM), as a result the gas in dark matter halos below a certain mass is too hot to cool within a Hubble time. The UVB effectively suppresses the formation of dwarf galaxies. Using high resolution cosmological hydrodynamical simulations we show that photo heating leads to small baryon fractions in halos below ~ 6× 109h−1M⊙, independent of the cosmic environment. The simulations are carried out assuming a homogeneous UVB with flux densities as given by Haardt, &, Madau (1996). A halo may stop to condense gas significantly after the universe is reionised, namely when its mass falls below the characteristic mass scale set by the photo heating. Assuming a spherical halo model we derive this characteristic mass analytically and identify the main mechanisms that prevent the gas from cooling in small halos. The theoretically derived characteristic mass is smaller than the one obtained from observations. Increasing the energy per ionising photon by a factor between four and eight would be sufficient to reconcile both. This is equivalent to an average temperature of the IGM of ~ 104K. In this sense the faint end of the luminosity function may serve as a calorimeter for the IGM.
Baryonic Properties of the Darkest Galaxies
Authors: Grebel Eva K. 
Published: February 2008

AbstractThe faintest and darkest galaxies that we know of today are the dwarf spheroidal (dSph) galaxies. They appear to be plausible counterparts of cosmologically predicted small subhalos though their numbers do not (yet?) suffice to resolve the substructure crisis. Their mass-to-light ratios may go up to 1000 for the faintest objects, and their total masses are of the order of a few 106to 107M⊙. Though most dSphs are dominated by old populations, they all show extended and presumably slow star formation histories with considerable enrichment. While environment has certainly affected their evolution, as evidenced by the morphology-gas-distance relations, intrinsic properties such as their (initial) baryon content may also have played a major role. The complexity and diversity of their star formation histories is surprising, and there are no obvious evolutionary connections to dwarf irregulars.
The Dwarf Low Surface Brightness Population in Different Environments of the Local Universe
Authors: Sabatini S. , Davies J. I. , Roberts S. , Scaramella R. 
Published: February 2008

AbstractThe nature of the dwarf galaxy population as a function of location in the cluster and within different environments is investigated. We have previously described the results of a search for low surface brightness objects in data drawn from an East-West strip of the Virgo cluster (Sabatiniet al(2004)) and have compared this to a large area strip outside of the cluster (Robertset al(2004)). In this talk I compare the East-West data (sampling sub-cluster A and outward) to new data along a North-South cluster strip that samples a different region (part of sub-cluster A, and the N, M clouds) and with data obtained for the Ursa Major cluster and fields around the spiral galaxy M101. The sample of dwarf galaxies in different environments is obtained from uniform datasets that reach central surface brightness values of 26 B mag/arcsec2and an apparent B magnitude of 21 (MB=−10 for a Virgo Cluster distance of 16 Mpc). We discuss and interpret our results on the properties and distribution of dwarf low surface brightness galaxies in the context of variuos physical processes that are thought to act on galaxies as they form and evolve.
A Flat Faint End of the Fornax Cluster Galaxy Luminosity Function
Authors: Mieske S. , Hilker M. , Infante L. , de Oliveira C. Mendes 
Published: February 2008

AbstractWe analyse the photometric properties of the early-type Fornax cluster dwarf galaxy population (MV > −17 mag), based on a wide field imaging study of the central cluster area in V and I band-passes with IMACS/Magellan at Las Campanas Observatory. We create a fiducial sample of ~ 100 Fornax cluster dwarf ellipticals (dEs) with −16.6 < MV < −8.8 mag in the following three steps: (1) To verify cluster membership, we measured I-band surface brightness fluctuations (SBF) distances to candidate dEs known from previous surveys; (2) We re-assessed morphological classifications for those candidate dEs that are too faint for SBF detection; and (3) We searched for new candidate dEs in the size-luminosity regime close to the resolution limit of previous surveys. The resulting fiducial dE sample follows a well-defined surface brightness – magnitude relation, showing that Fornax dEs are about 40% larger than Local Group dEs. The sample also defines a colour-magnitude relation similar to that of Local Group dEs. The early-type dwarf galaxy luminosity function in Fornax has a very flat faint end slope α ≃ −1.1 ± 0.1. We compare the number of dwarfs per unit mass with those in other environments and find that the Fornax cluster fits well into a general trend of a lack of high-mass dwarfs in more massive environments.
Can Massive Dark Haloes Destroy the Discs of Dwarf Galaxies?
Authors: Fuchs B. , Esquivel O. 
Published: February 2008

AbstractRecent high-resolution simulations together with theoretical studies of the dynamical evolution of galactic disks have shown that contrary to wide-held beliefs a ‘live’, dynamically responsive, dark halo surrounding a disk does not stabilize the disk against dynamical instabilities. We generalize Toomre's Q stability parameter for a disk-halo system and show that if a disk, which would be otherwise stable, is embedded in a halo, which is too massive and cold, the combined disk-halo system can become locally Jeans unstable. The good news is, on the other hand, that this will not happen in real dark haloes, which are in radial hydrostatic equilibrium. Even very low-mass disks are not prone to such dynamical instabilities.
“Dark Galaxies” and Local Very Metal-Poor Gas-Rich Glaxies: Possible Interrelations
Authors: Pustilnik Simon A. 
Published: February 2008

AbstractThere are only a few “dark galaxy” candidates discovered to date in the local Universe. One of the most prominent of them is the SW component of a merging system HI 1225+01. On the other hand, the number of known very metal-poor gas-rich dwarfs similar to I Zw 18 and SBS 0335–052 E, W has grown drastically during the last decade, from a dozen and a half to about five dozen. Many of them are very gas-rich, having from ~90 to 99% of all baryons in gas. For some of such objects that have the deep photometry data, no evidences for the light of old stars are found. At least a half of such galaxies with the prominent starbursts have various evidences of interactions, including advanced mergers. This suggests that a fraction of this group objects can be a kind of very stable protogalaxies (or “dark galaxies”), which have recently experienced strong disturbances from nearby massive galaxy-size bodies. Such a collision caused the gas instabilities and its collapse with the subsequent onset of starburst. We briefly discuss the morphology and gas kinematics for the subsample of the most metal-poor dwarfs that illustrate this picture. We discuss also the relation of these rare galaxies to the processes by which “dark galaxies” can occasionally transform to optically visible galaxies.
Arecibo Survey of HI Emission from Disk Galaxies at Redshift z~0.2
Authors: Catinella B. , Haynes M. P. , Gardner J. P. , Connolly A. J. , Giovanelli R. 
Published: February 2008

AbstractWe 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. Among other applications, this dataset will be used to study the evolution of disk scaling relations at intermediate redshifts. Compared to optical velocity widths, HI measurements sample a larger fraction of the disks, where the rotation curves are typically flat, and are not affected by slit smearing and misalignment or by aperture effects. Thus, in contrast to studies based on optical spectroscopy, this dataset allows for a direct comparison with the local Tully-Fisher relation that is technique independent.
Radio Observations of AGN in Low Surface Brightness Galaxies
Authors: Das M. , McGaugh S. S. , Kantharia N. , Vogel S. N. 
Published: February 2008

AbstractWe present preliminary results of a study of the low frequency radio continuum emission from the nuclei of Giant Low Surface Brightness (LSB) galaxies. We have mapped the emission and searched for extended features such as radio lobes/jets associated with AGN activity. LSB galaxies are poor in star formation and generally less evolved compared to nearby bright spirals. This paper presents low frequency observations of 3 galaxies; PGC 045080 at 1.4 GHz, 610 MHz, 325MHz, UGC 1922 at 610 MHz and UGC 6614 at 610 MHz. The observations were done with the GMRT. Radio cores as well as extended structures were detected and mapped in all three galaxies; the extended emission may be assocated with jets/lobes associated with AGN activity. Our results indicate that although these galaxies are optically dim, their nuclei can host AGN that are bright in the radio domain.
Low Surface Brightness Galaxies Around the Hubble Deep Field South
Authors: Haberzettl L. , Bomans D. J. , Dettmar R.-J. 
Published: February 2008

AbstractWe present results from a study of the SFH of a sample of LSB galaxies around the HDF-S. For the selection of the LSB galaxy candidates we used color–color diagrams, from which we selected the candidates based on their different location in comparison to the HSB galaxy redshift tracks. We compared measured spectra to synthetic SEDs from synthesis evolution models. We were able to fit SEDs in the range of 2 to 5 Gyr to the spectra of the LSB galaxies, while applying the same method to a sample of HSB galaxies resulted in an averaged stellar population of about 10 to 14 Gyr. Therefore, LSB galaxies tend to show much younger averaged stellar populations. This implies that the major star formation event of LSB galaxies took place at a redshift of z ~ 0.2 to 0.4 while for HSB galaxies this tends to be at z ~ 2 to 4.
Spitzer Observations of Tidal Dwarf Galaxies
Authors: Higdon Sarah J. U. , Higdon James L. 
Published: February 2008

AbstractWe present Spitzer observations of Tidal Dwarf Galaxies (TDGs) in three interacting systems: NGC 5291, Arp 105 & Stephan's Quintet. The spectra show bright emission from polyaromatic hydrocarbons (PAHs), nebular lines and warm molecular hydrogen, characteristic of recent episodes of star formation. The PAH emission that falls in the IRAC 8.0 μm band leads to the TDGs having an extremely red IRAC color, with [4.5] − [8.0] > 3. The emission from PAHs is characterized by a model with mainly neutral 100-C PAH atoms.
A 500 kpc HI Tail of the Virgo Pair NGC4532/DDO137 Detected by ALFALFA
Authors: Koopmann Rebecca A. 
Published: February 2008

AbstractHI observations of the Virgo Cluster pair NGC 4532/DDO 137, conducted as part of the Arecibo Legacy Fast ALFA Survey, reveal an HI feature extending ~500kpc to the southwest. The structure has a total mass of up to 7 x 108M⊙, equivalent to 10% of the pair HI mass. Optical R imaging reveals no counterparts to a level of 26.5 mag arcsec−2. The structure is likely the result of galaxy harassment.
Virgo Early-Type Dwarfs in ALFALFA
Authors: Koopmann Rebecca A. 
Published: February 2008

AbstractEarly-type dwarf galaxies dominate cluster populations, but their formation and evolutionary histories are poorly understood. The ALFALFA (Arecibo Legacy Fast ALFA) survey has completed observations of the Virgo Cluster in the declination range of 6 – 16 degrees. Less than 2% of the early-type dwarf population is detected, a significantly lower fraction than reported in previous papers based on more limited samples. In contrast ~30% of the irregular/BCD dwarf population is detected. The detected early-type galaxies tend to be located in the outer regions of the cluster, with a concentration in the direction of the M Cloud. Many show evidence for ongoing/recent star formation. Galaxies such as these may be undergoing morphological transition due to cluster environmental effects.
Neutral Hydrogen Gas in Star Forming Galaxies at z=0.24
Authors: Lah Philip , Chengalur Jayaram N. , Briggs Frank H. , Colless Matthew , De Propris Roberto , Pracy Michael B. , de Blok W. J. G. 
Published: February 2008

AbstractWe use observations from the Giant Metrewave Radio Telescope (GMRT) to measure the atomic hydrogen gas content of star-forming galaxies at z = 0.24 (i.e. a look-backtime of ~3 Gyr). To measure the HI 21 cm emission signal we stack the signal from 121 galaxies with known optical positions and redshifts. We find an average HI mass for the galaxies of (2.26 ± 0.90) × 109 M⊙. We translate this HI measurement into a cosmic density of neutral gas at z=0.24 of Ωgas = (0.91 ± 0.42) × 10−3. This value is consistent with that estimated from damped Lyα systems around this redshift.
The Distribution of ALFALFA Galaxies
Authors: Martin Ann M. 
Published: February 2008

AbstractThe ALFALFA2 blind HI survey will enable a census of the distribution of gas-rich galaxies in the local Universe. Sensitive to an HI mass of 107 solar masses at the distance of the Virgo cluster, ALFALFA will probe the smallest objects locally and provide a new consideration of near-field cosmology. Additionally, with a larger, cosmologically significant sample volume and wider bandwidth than previous blind surveys, a much larger number of detections in each mass bin is possible, with adequate angular resolution to eliminate the need for extensive follow-up observations. This increased sensitivity will greatly enhance the utility of cosmological probes in HI. ALFALFA will eventually measure the correlation function of HI selected galaxies in a large local volume. The larger sample and volume size of the ALFALFA dataset will also robustly measure the HI mass function (HIMF). Here, we present the preliminary results on the distribution of local gas-rich galaxies from a first ALFALFA catalog covering 540 deg2.
Dark Galaxies: How about this one?
Authors: Struve Christian , Józsa Gyula I.G. , Kenn Franz , Klein Uli , Gentile Gianfranco 
Published: February 2008

AbstractWe report on the (serendipitous) detection and analysis of an extremely massive HI cloud without an obvious stellar counterpart nearby the relatively isolated giant spiral galaxy NGC 1030 and present first results of this dark galaxy candidate.
The Detectability of Dark Galaxies Through Image-Splitting Effects
Authors: Zackrisson E. , Riehm T. , Lietzen H. , Möller O. , Wiik K. , Nurmi P. 
Published: February 2008

AbstractIn principle, dark galaxies in the dwarf-galaxy mass range may be detectable through additional, small-scale image splitting of quasars that are already known to be multiply-imaged on arcsecond scales. Here, we derive the image separations expected for dark galaxies with density profiles favoured by recent N-body simulations. The results are compared to the angular resolution of existing and planned telescopes at X-ray, optical, near-infrared and radio wavelengths.
From Subduction to Collision: The Sunda‐Banda Arc Transition
Authors: Müller Christian , Barckhausen Udo , Ehrhardt Axel , Engels Martin , Gaedicke Christoph , Keppler Hans , Lutz Rüdiger , Lüschen Ewald , Neben Sönke , Kopp Heidrun , Flueh Ernst R. , Djajadihardja Yusuf S. , Soemantri Dzulkarnaen D. P. , Seeber Leonardo 
Published: February 2008

In the aftermath of the Mw 9.3 Indian Ocean earthquake and tsunami of 26 December 2004, which killed more than 250,000 people, numerous investigations have been commissioned near the epicenter offshore northern Sumatra to evaluate future earthquake and tsunami hazards. These projects have mapped seafloor morphology and imaged deep structures and faults in order to better understand the origin of megathrust earthquakes and tsunamis in the western portion of the Sunda Arc subduction system offshore northern Sumatra [e.g., Henstock et al., 2006].In contrast, the eastern part of the arc has received relatively little attention, even though it may be just as hazardous. Our geophysical data from the eastern Sunda Arc and the transition to the Banda Arc (Figure 1) provide evidence for recent tectonic activity and thus for a similar earthquake and tsunami risk.
Earth Science Instrumentation and Facilities Program Review
Authors: Jeanloz Raymond , Beck Susan L. , Lisowski Michael , Lorenzo Juan M. , Mora Claudia I. , Rimstidt J. Donald , Shirey Steven B. , Stein Seth , Wirth Karl 
Published: February 2008

The Instrumentation and Facilities (IF) program of the U.S. National Science Foundation's Division of Earth Sciences (NSF/EAR) supports a remarkably broad span of research, both in the science that is addressed and in the nature of awards provided, according to a review by a Committee of Visitors on 22–24 August 2007. The present article, written by committee members, provides a synopsis of our findings to promote community‐wide discussion of the size, scope, and responsibilities of the IF program.The IF program funds infrastructure ranging from an individual investigator's purchase of laboratory equipment to support for major, multiuser facilities requiring millions of dollars per year (Figure 1). Partial support is also provided for technicians (for up to 5 years, with a decreasing level of funding each year).
Protein oxidation: key to bacterial desiccation resistance?
Authors: Fredrickson James K , Li Shu-mei W , Gaidamakova Elena K , Matrosova Vera Y , Zhai Min , Sulloway Heather M , Scholten Johannes C , Brown Mindy G , Balkwill David L , Daly Michael J 
Published: February 2008

Abstract
For extremely ionizing radiation-resistant bacteria, survival has been attributed to protection of proteins from oxidative damage during irradiation, with the result that repair systems survive and function with far greater efficiency during recovery than in sensitive bacteria. Here we examined the relationship between survival of dry-climate soil bacteria and the level of cellular protein oxidation induced by desiccation. Bacteria were isolated from surface soils of the shrub-steppe of the US Department of Energy's Hanford Site in Washington State. A total of 63 isolates were used for phylogenetic analysis. The majority of isolates were closely related to members of the genus Deinococcus, with Chelatococcus, Methylobacterium and Bosea also among the genera identified. Desiccation-resistant isolates accumulated high intracellular manganese and low iron concentrations compared to sensitive bacteria. In vivo, proteins of desiccation-resistant bacteria were protected from oxidative modifications that introduce carbonyl groups in sensitive bacteria during drying. We present the case that survival of bacteria that inhabit dry-climate soils are highly dependent on mechanisms, which limit protein oxidation during dehydration.
Functional responses of prokaryotes and viruses to grazer effects and nutrient additions in freshwater microcosms
Authors: Pradeep Ram Angia Sriram , Sime-Ngando Télesphore 
Published: February 2008

Abstract
For aquatic systems, there is little data on the interactions between viruses, prokaryotes, grazers and the availability of resources. We conducted a microcosm experiment using a size fractionation approach to manipulate grazers, with a purpose to examine the effects of inorganic and organic nutrients on viral and prokaryotic standing stocks and activities, and on prokaryotic community composition as assessed by fluorescent in situ hybridization (FISH) method. Experiments were performed during periods of severe phosphate (P)-limiting conditions in the oligotrophic Sep Reservoir (Massif Central, France). In the absence of nutrient addition, the presence of grazers in microcosms stimulated prokaryotic growth and viral proliferation, likely through nutrient and substrate enrichment. Addition of nutrients had a stronger effect on viral infection of prokaryotes than grazing. Addition of P led to the most pronounced increase in prokaryotic abundance, production and growth efficiency, thus providing direct evidence of P limitation of prokaryotes. Enhanced prokaryotic activity in P treatments also stimulated viral abundance and viral-induced lyses of prokaryotes. Changes in prokaryotic community composition due to nutrient additions were evident in the grazer-free samples. Prokaryotic populations hybridizing for the probes bacteria, β-Proteobacteria and α-Proteobacteria responded to nutrient enrichment with significant increases in their relative abundances, whereas cells hybridizing for Archaea and Cytophaga-Flavobacterium (now known as Bacteroidetes) probes failed to show any functional response. Cells hybridizing for the latter cluster increased towards the end of incubation period in the control samples (that is, without nutrient additions) with grazers present, suggesting the development of grazing resistant forms. From our nutrient enrichment microcosm experiments, we conclude that the presence of grazers is a stimulating factor for prokaryotic growth and viral proliferation in the plankton, probably through nutrient regeneration process.
Renal Cytochrome P450 as a Determinant of Impaired Natriuresis by PPAR‐γ Ligands in Ovariectomized Obese Rats
Authors: Yoshioka Kyoko , Wakino Shu , Homma Koichiro , Kanda Takeshi , Tatematsu Satoru , Hasegawa Kazuhiro , Sugano Naoki , Ito Osamu , Omata Ken , Saruta Takao , Hayashi Koichi 
Published: February 2008

Objective: Peroxisome proliferator–activated receptor (PPAR)‐γ ligand, pioglitazone (PIO), is reported to induce edema especially in postmenopausal women. The aim of this study was to elucidate the mechanism for PIO‐induced sodium retention and to discover the therapeutic strategy for the PIO‐induced changes in renal sodium handling.Methods and Procedures: Zucker obese rats were ovariectomized and were given PIO for 8 weeks. Renal sodium excretion and renal expressions of several enzymes that generate natriuretic substances were examined.Results: Sodium excretion was decreased in ovariectomized (OVX) rats that were given PIO when compared with OVX rats that were not. Urinary nitrites/nitrates excretion was decreased in OVX rats, but was restored by PIO. The expressions of nitric oxide synthases (NOSs) and cyclooxygenases‐1/2 (COX‐1/2) were unaltered. Similarly, the expression of epithelial sodium channels (ENaC), identified as a PPAR‐γ‐regulated gene product, was unaffected. In contrast, the expression of cytochrome P450 4A (CYP4A) was increased in OVX rats, and was downregulated by PIO. Co‐treatment of OVX rats with PIO and PPAR‐α ligand, fenofibrate, a putative inducer of CYP4A, restored not only the impaired sodium excretion but also the downregulated CYP4A expression.Discussion: PIO‐induced sodium retention is specific in female OVX rats. Ovariectomy decreases renal NO production, but upregulates renal CYP4A expression to compensate for renal sodium balance. In this setting, PIO downregulates CYP4A, leading to sodium retention. Furthermore, PPAR‐α ligands can provide a novel strategy for preventing the PIO‐induced sodium retention.