bluuebunny/crossref_metadata_2025 huggingface dataset:
Stellar Population Analysis on a Large Sample of Low Surface Brightness Galaxies
Authors: Chen Xiaoyan , Luo Ali , Liang Yanchun
Published: March 2013

We study the stellar populations of a large sample of nearly face-on disk Low Surface Brightness Galaxies (LSBGs), with B-band central surface brightness μ0(B) > 22 mag arcsec−2, selected from the Sloan Digital Sky Survey Data Release 4 (SDSS-DR4) main galaxy sample (similar to Zhong et al. 2008; Liang et al. 2010).
Study of the Byurakan-IRAS galaxy sample
Authors: Mickaelian Areg M. , Harutyunyan Gohar S.
Published: March 2013

The Byurakan-IRAS Galaxy (BIG) sample (Mickaelian 1995) is the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra (Markarian et al. 1989). Among the 1577 objects 1178 galaxies have been identified. Most are dusty spiral galaxies and there are a number of ULIRGs among these objects. Our spectroscopic observations carried out with three telescopes (Byurakan Astrophysical Observatory 2.6m, Russian Special Astrophysical Observatory 6m and Observatoire de Haute Provence 1.93m) (Mickaelian & Sargsyan 2010) for 172 galaxies, as well as the SDSS DR8 spectra for 83 galaxies make up the list of 255 spectroscopically studied BIG objects. The classification to activity types for narrow-line emission galaxies has been carried out using the diagnostic diagrams by Veilleux & Osterbrock (1987). All possible physical characteristics have been measured and/or calculated, including radial velocities and distances, angular and physical sizes, absolute magnitudes and luminosities (both optical and IR). IR luminosities and star-formation rates have been calculated from the IR fluxes (Duc et al. 1997).

Among the 172 observed galaxies, 102 starburst (HII) ones, 29 AGN (Sy or LINER), and 19 galaxies with composite spectrum have been revealed; spectra of 12 galaxies show emission features but without a possibility for more accurate classification, 9 galaxies are presented as galaxies where the star formation rate does not exceed normal one, and 1 galaxy is an absorption galaxy. Among the 83 objects having SDSS spectra, there are 55 HIIs, 8 Seyferts, 2 LINERs, 4 other AGN (without accurate classification), 6 composite spectrum objects and 8 other emission-line galaxies. In our spectroscopic sample we have 43 (17%) AGN, 25 (10%) composite spectrum objects, 157 (62%) starbursts, 29 emission-line galaxies without a definite type, and 1 absorption-line galaxy. There are 3 Ultra-Luminous InfraRed Galaxies (ULIRG).

Various multiwavelength (MW) data have been retrieved for the full sample of 1178 objects from recent catalogs from X-ray to radio (ROSAT, GALEX, APM, MAPS, USNO, GSC, SDSS, 2MASS, WISE, IRAS, AKARI, NVSS, FIRST, etc.) to make a complete study of these galaxies possible. MW SEDs have been built, which have been matched to their optical classifications. Star-formation rates have been calculated to compare to their other physical characteristics, such as morphology, activity types, UV, optical, IR and radio luminosities, etc.
Photometry and Stellar Structure Analysis of the Central Regions of the M33 galaxy
Authors: Nikzat Fatemeh , Javadi Atefeh , Mirtorabi Mohammad Taghi , van Loon Jacco Th. , Khosroshahi Habib
Published: March 2013

The UK InfraRed Telescope/UFTI instrument was used to analyse stars in the central region (square kpc) of the M33 galaxy over 3 nights in August 2005 with observations in K-band. Photometry was obtained for all stars by fitting appropriate PSF models, using DAOPHOT package (Stetson 1987). Around 18500 stars were detected. A master image was produced by applying an appropriate shift to each image and combining all 30 images. The final catalogue was obtained by assigning unique ID numbers to all stars and calibrating instrumental magnitudes. Comparing the UFTI and the UIST catalogues (Javadi et al. 2011) shows that a larger number of stars were detected with the UFTI, reaching a K-band limiting magnitude of 18.5 mag. Cross correlation methods were employed to cross match our catalogue with a previous monitoring survey in the near-infrared, the UIST catalogue. As a result, we assigned J magnitude and J-K color index to those stars which were found in both catalogues. Using these stars, a color-magnitude diagram was produced which shows populations of RGB, AGB and Carbon stars. Isochrones from Marigo et al. (2008) for solar metallicity and a distance modulus of 24.9 magnitude were used to identify different populations in the central region of the M33 galaxy. We will merge the UFTI catalogue with the UIST and the WFCAM, to get better coverage of stars in the central square kiloparsec.
HI and optical studies of Wolf-Rayet galaxies
Authors: Omar A. , Jaiswal S.
Published: March 2013

The tidal interactions between galaxies are believed to be the main mechanism responsible for Wolf-Rayet (WR) phases in galaxies. The HI 21 cm-line is the best tracer for detecting tidal features in galaxies. We are studying WR galaxies in the HI line using GMRT and in the Hα line using Devasthal Optical telescope. Signatures of tidal interactions in Mrk 996 and Mrk 005, previously believed to be in non-interacting environment, have been detected using both HI and Hα images.
A search for intervening HI absorption
Authors: Reeves Sarah N. , Sadler Elaine M. , Allison James R. , Koribalksi Baerbel S. , Curran Stephen J.
Published: March 2013

HI absorption-line studies provide a unique probe of the gas distribution and kinematics in galaxies well beyond the local universe (z ≳ 0.3). HI absorption-line surveys with next-generation radio telescopes will provide the first large-scale studies of HI in a redshift regime which is poorly understood. However, we currently lack the understanding to infer galaxy properties from absorption-line observations alone. To address this issue, we are conducting a search for intervening HI absorption in a sample of 20 nearby galaxies. Our aim is to investigate how the detection rate varies with distance from the galaxy. We target sight-lines to bright continuum sources, which intercept known gas-rich galaxies, selected from the HIPASS Bright Galaxy Catalogue (Koribalski et al. 2004). In our pilot sample, six galaxies with impact parameters < 20 kpc, we do not detect any absorption lines — although all are detected in 21cm emission. This indicates that an absorption non-detection cannot simply be interpreted as an absence of neutral gas – see Fig. 1. Our detection rate is low compared to previous surveys e.g. Gupta et al. (2010). This is, at least partially, due to the high resolution of the observations reducing the flux of the background source, which will also be an issue in future surveys, such as ASKAP-FLASH.
Colour and stellar population gradients of galaxies in poor groups of galaxies
Authors: Vennik Jaan , Kuutma Teet
Published: March 2013

We studied the color distribution of satellite galaxies in three groups of galaxies and found that nearly a half of galaxies show statistically significant radial color gradients, which are indicative of changing stellar ages and metallicities. We found that the disk-dominated satellite galaxies with positive color and age gradients (i.e., evolving in outside-in fashion) are residing, predominantly, in the inner, dense group regions, within the characteristic radius R200, while those galaxies, residing in the outer group in-fall region, show typically zero or negative gradients.
Radio and Submillimeter Continuum Observations of High-Redshift Galaxies
Authors: Wang Wei-Hao , Barger Amy J. , Cowie Lennox L. , Chen Chian-Chou , Williams Jonathan P. , Owen Frazer N.
Published: March 2013

Observing galaxies in the radio and submillimeter continuum has the advantage of being unaffected by dust extinction, which is a major drawback of studying galaxy evolution using optical data. Submillimeter single-dish surveys have made tremendous progress in understanding the high-redshift dusty population, but the low angular resolution of single-dish telescopes has also hampered these studies. Our recent JCMT and SMA imaging of high-redshift submillimeter sources revealed z > 4 objects that are radio and optically faint. Such objects cannot be easily identified with the combination of submillimeter single-dish and radio imaging. We also found a large fraction of multiple objects that are blended in single-dish images. Such objects may be early-stage mergers, or dusty starbursts in group environments. Since our work, larger surveys with PdBI and ALMA have been carried out to further address these issues. Additional to submillimeter imaging, future ultradeep EVLA imaging at 20 cm can also detect large samples of ultraluminous star forming galaxies at z ≳ 2. Sensitivities in radio and submillimeter observations have different redshift and dust temperature dependencies. Radio observations are also less affected by confusion. It will be necessary to combine deep surveys in both wavebands in order to achieve a more complete picture of the evolution of high-redshift star forming galaxies.
Star Formation in Quasar Host Galaxies at Redshift 6: Millimeter Surveys and New Insights from ALMA
Authors: Wang Ran , Wagg Jeff , Carilli Chris L. , Walter Fabian , Fan Xiaohui , Bertoldi Frank , Riechers Dominik. A. , Omont Alain , Menten Karl M. , Cox Pierre , Strauss Michael A. , Narayanan Desika
Published: March 2013

We have been carrying out a systematic survey of the star formation and ISM properties in the host galaxies of z∼6 quasars. Our 250 GHz observations, together with available data from the literature, yield a sample of 14 z∼6 quasars that are bright in millimeter dust continuum emission with estimated FIR luminosities of a few 1012 to 1013 L⊙. Most of these millimeter-detected z∼6 quasars have also been detected in molecular CO line emission, indicating molecular gas masses on order of 1010 M⊙. We have searched for [C II] 158 micron fine structure line emission toward four of the millimeter bright z∼6 quasars with ALMA and all of them have been detected. All these results suggest massive star formation at rates of about 600 to 2000 M⊙ yr−1 over the central few kpc region of these quasar host galaxies.
Statistical Properties of Gamma-Ray Burst Host Galaxies
Authors: Chen J. M. , Jia L. W. , Liang E. W.
Published: March 2013

GRBs are the most luminous events in the Universe. They are detectable from local to high-z universe and may serve as probes for high-z galaxies (e.g., Savaglio et al. 2009; Kewley & Dopita 2002). We compile the observations for 61 GRB host galaxies from literature. Their redshifts range from 0.0085 to 6.295. We present the statistical properties of the GRB host galaxies, including the stellar mass (M*), star-forming rate (SFR), metallicity (Z), extinction (AV), and neutral hydrogen column density (NH). We explore possible correlations among the properties of gamma-ray burst host galaxies and their cosmic evolution with observations of 61 GRB host galaxies. Our results are shown in Figure 1. A clear Z-M* relation is found in our sample, which is Z ~ M0.4. The host galaxies of local GRBs with detection of accompanied supernovae also share the same relation with high-z GRB host galaxies. A trend that a more massive host galaxy tends to have a higher star-formation rate is found. The best linear fit gives a tentative relation, i.e, SFR ~ M0.75. No any correlation is found between AV and NH. A GRB host galaxy at a higher redshift also tends to have a higher SFR. Even in the same redshift, the SFR may vary over three orders of magnitude. The metallicity of the GRB host galaxies is statistically higher than that of the QSO DLAs. The full version of our results please refer to Chen et al. (2012).
Molecules as tracers of galaxy evolution
Authors: Aalto Susanne
Published: March 2013

Studying the molecular phase of the interstellar medium in galaxies is fundamental for the understanding of the onset and evolution of star formation and the growth of supermassive black holes. We can use molecules as observational tools exploiting them as tracers of chemical, physical and dynamical conditions. In this short review, key molecules (e.g. HCN, HCO+, HNC, HC3N, CN, H3O+) in identifying the nature of buried activity and its evolution are discussed including some standard astrochemical scenarios. Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminous infrared galaxies (LIRGs) allowing us to get past the optically thick dust barrier of the compact obscured nuclei, e.g. in the dusty LIRG NGC4418. High resolution studies are often necessary to separate effects of excitation and radiative transport from those of chemistry - one example is absorption and effects of stimulated emission in the ULIRG Arp220. Finally, molecular gas in large scale galactic outflows is briefly discussed.
Diagnostics of the ISM in star formation regions
Authors: Baan Willem A. , Loenen Edo , Lian Xiaoli
Published: March 2013

Line emissions of high- and low-density molecular tracers serve as powerful diagnostic tools for the ISM in both Galactic and extragalactic star formation environments. The emission line strengths and line ratios may be interpreted using detailed modeling of both the dominant physics and the chemistry of the molecular constituents. Observed molecular line ratios will thus reveal the signatures of dominant UV, X-ray, and CR radiation fields and of mechanical heating and feedback from the star formation process. In addition, certain line ratios reflect the physical and chemical changes resulting from the time-evolution of a star formation region. In this paper, we present results of Galactic sources and extragalactic starbursts covering a large range of FIR luminosities and illustrate the similarities between the diagnostics of these environments.
Star Formation and the Atomic-Molecular Transition
Authors: Krumholz Mark R.
Published: March 2013

In the last decade large surveys have allowed us to separate the atomic and molecular phases of the interstellar media in a wide variety of galaxies, and to determine how each of these phases correlates with star formation. The most striking results of these observations have been that the transition from H i to H2 occurs at a characteristic gas column density that depends on metallicity, and that star formation correlates primarily with the molecular phase. These observations have stimulated a burst of theoretical work, which I review here. The work can be broken into three primary questions: what physical mechanisms control the H i to H2 transition? Why does star formation correlate with H2 and not with some other phase of the ISM? Finally, what are the implications of the answers to the previous two questions for our understanding of star formation on the cosmological scale? I discuss our current best answers to each of these questions, and conclude with prospects for future work.
GOT C+ Survey of [CII] 158 μm Emission: Atomic to Molecular Cloud Transitions in the Inner Galaxy
Authors: Velusamy T. , Langer W. D. , Willacy K. , Pineda J. L. , Goldsmith P. F.
Published: March 2013

We present the results of the distribution of CO-dark H2 gas in a sample of 2223 interstellar clouds in the inner Galaxy (l=−90° to +57°) detected in the velocity resolved [CII] spectra observed in the GOT C+ survey using the Herschel HIFI. We analyze the [CII] intensities along with the ancillary HI, 12CO and 13CO data for each cloud to determine their evolutionary state and to derive the H2 column densities in the C+ and C+/CO transition layers in the cloud. We discuss the overall Galactic distribution of the [CII] clouds and their properties as a function Galactic radius. GOT C+ results on the global distribution of [CII] clouds and CO-dark H2 gas traces the FUV intensity and star formation rate in the Galactic disk.
An ALMA and ATCA Molecular Line Survey Toward Centaurus A
Authors: Ott Jürgen , McCoy Mark , Meier David
Published: March 2013

We present Atacama Large Millimeter/submillimeter Array (ALMA) and Australia Telescope Compact Array (ATCA) data of molecular absorption lines toward the bright central core of the prominent, nearby (d ∼ 3.8 Mpc) radio galaxy Centaurus A, at 13, 7, 3, and 1mm wavelengths. The line of sight crosses the prominent dust lane and continues through the disk and eventually through gas that may be very close to the central supermassive black hole. The goal of our survey is to determine the physical conditions of the gas via analyses of molecular line tracers including molecular abundances and excitation conditions that are sensitive to changes in temperature, density, ionization, and shocks. This study allows us to derive the physical processes that are shaping each molecular environment.
The Mid-IR Extinction Law in the LMC
Authors: Gao Jian , Xue Mengyao , Jiang B. W.
Published: March 2013

The mid-infrared (MIR) extinction law in the Large Magellanic Cloud (LMC) at four IRAC bands is derived using the data of the Spitzer/SAGE Program. The derived mean extinctions are A[3.6]/AKs = 0.68±0.03, A[4.5]/AKs = 0.97±0.03, A[5.8]/AKs = 0.54±0.04, and A[8.0]/AKs = 0.58±0.07. The results show that: (1) The extinctions at [3.6], [5.8] and [8.0] of the LMC consist a flat curve, similar to that of the Milky Way (MW) predicted by the interstellar grain model at Rv = 5.5; (2) The extinction at [4.5] is clearly higher than the other three bands, which may be caused by the additional absorption of the 4.27μm CO2 ice and/or the 4.67μm CO ice in the LMC molecular clouds; (3) As far as individual sightlines are concerned, the MIR interstellar extinction law Aλ/AKs in the LMC varies with sightlines as the MW does.
The effects of dust on the derived photometric parameters of disks and bulges in spiral galaxies
Authors: Pastrav B. A. , Popescu C. C. , Tuffs R. J. , Sansom A. E.
Published: March 2013

Here we present results on the effects of dust on the derived Sérsic index of disks and bulges. This is part of a larger study (see Pastrav et al. 2012a, Pastrav et al. 2012b) that quantifies the dust effects on all photometric parameters, including scale-lengths, axis-ratios, central surface brightness and effective radii of individual and decomposed (from B/D decomposition) disks and bulges. The effects of dust are derived for both broadband and narrow line (Balmer lines) images. The changes in the derived photometric parameters from their intrinsic values (as seen in the absence of dust) were obtained by fitting simulated images of disks and bulges produced using radiative transfer calculations and the model of Popescu et al. (2011). This study follows on the analysis of Möllenhoff et al. (2006), who quantified the effects of dust on the photometry of old stellar disks seen at low and intermediate inclination. We extend the study to disks at all inclinations and we investigate the changes in the photometry of young stellar disks and bulges. For the individual components, in the majority of cases: 1) the dust lowers the Sérsic index from its intrinsic value; 2) the Sérsic index decreases as the inclination and the B band central face-on dust opacity, τBf, increase. For the decomposed disks and bulges, dust slightly increases the Sérsic index as compared with the one derived on individual components (e.g. Fig. 1); this effect is stronger for higher values of the inclination, τBf and B/D.
Dust reddening in star-forming galaxies
Authors: Xiao Ting , Wang Tinggui , Wang Huiyuan , Zhou Hongyan , Lu Honglin , Dong Xiaobo
Published: March 2013

Dust is a crucial component of galaxies in modifying the observed properties of galaxies. Previous studies have suggested that dust reddening in star-forming galaxies is correlated with star formation rate (SFR), luminosity, gas-phase metallicity (Z), stellar mass (M*) and inclination. In this work we investigate the fundamental relations between dust reddening and physical properties of galaxies, and obtain a well-defined empirical recipe for dust reddening. The empirical formulae can be incorporated into semi-analytical models of galaxy formation and evolution to estimate the dust reddening and facilitate comparison with observations.
[FeII] as a shock tracer in NGC 253
Authors: Rosenberg Marissa J. F. , van der Werf Paul P. , Israel Frank P.
Published: March 2013

Supernovae play an integral role in the feedback of processed material back into the interstellar medium (ISM) of galaxies and are responsible for most of the chemical enrichment of the universe. The rate of supernovae can also reveal the star formation histories. In a sample of 11 nearby galaxies observed with SINFONI, a strong linear correlation between [FeII]1.26 luminosity and Starburst 99-derived supernova rate is found on a pixel-pixel basis. In the very nearby archetypal starburst galaxy NGC 253, the excitation of molecular gas is a subject of debate. Using the correlation between [FeII] and supernova rate, we can determine if supernovae can account for the excitation of the bright observed near-infrared H2 emission.
Fitting the spectral energy distributions of galaxies with CIGALE : Code Investigating GALaxy Emission
Authors: Giovannoli E. , Buat V.
Published: March 2013

We use the code CIGALE (Code Investigating Galaxies Emission: Burgarella et al. 2005; Noll et al. 2009) which provides physical information about galaxies by fitting their UV (ultraviolet)-to-IR (infrared) spectral energy distribuition (SED). CIGALE is based on the use of a UV-optical stellar SED plus a dust IR-emitting component. We study a sample of 136 Luminous Infrared Galaxies (LIRGs) at z∼0.7 in the ECDF-S previously studied in Giovannoli et al. (2011). We focus on the way the empirical Dale & Helou (2002) templates reproduce the observed SEDs of the LIRGs. Fig. 1 shows the total infrared luminosity (LIR) provided by CIGALE using the 64 templates (x axis) and using 2 templates (y axis) representative of the whole sample. Despite the larger dispersion when only 1 or 2 Herschel data are available, the agreement between both values is good with Δ log LIR = 0.0013 ± 0.045 dex. We conclude that 2 IR SEDs can be used alone to determine the LIR of LIRGs at z∼0.7 in an SED-fitting procedure.
The Schmidt-Kennicutt Law of Matched-Age Star Forming Regions
Authors: Komugi S. , Tateuchi K. , Motohara K. , Takagi T. , Iono D. , Kaneko H. , Ueda J. , Saitoh T. R. ,   the miniTAO team
Published: March 2013

We show that the dispersion in the Schmidt-Kennicutt (SK) law in galaxies is affected significantly by the evolutionary stage of star forming molecular gas, using narrow band Paα imaging of Taffy I, an interacting pair of galaxies. Star forming regions in the system show very uniform ages except for the bridge region, and the SK law of regions at the same age show a exceptionally tight SK law.
Using the Milky Way as a template for understanding star formation in extreme environments across cosmological timescales
Authors: Longmore Steven N.
Published: March 2013

Recent surface- and volume-density star formation relations have been proposed which potentially unify our understanding of how gas is converted into stars, from the nearest star forming regions to ultra-luminous infrared galaxies. The inner 500 pc of our Galaxy – the Central Molecular Zone – contains the largest concentration of dense, high-surface density molecular gas in the Milky Way, providing an environment where the validity of these star-formation prescriptions can be tested.

We have used recently-available data from HOPS, MALT90 and HiGAL at wavelengths where the Galaxy is transparent, to find the dense, star-forming molecular gas across the Milky Way [Longmore et al. (2012a), Longmore et al. (2012b)]. We use water and methanol maser emission to trace star formation activity within the last 105 years and 30 GHz radio continuum emission from the Wilkinson Microwave Anisotropy Satellite (WMAP) to estimate the high-mass star formation rate averaged over the last ∼ 4 × 106 years.

We find the dense gas distribution is dominated by the very bright and spatially-extended emission within a few degrees of the Galactic centre [Purcell et al. (2012)]. This region accounts for ∼80% of the NH3(1,1) integrated intensity but only contains 4% of the survey area. However, in stark contrast, the distribution of star formation activity tracers is relatively uniform across the Galaxy.

To probe the dense gas vs SFR relationship towards the Galactic centre region more quantitatively, we compared the HiGAL column density maps to the WMAP-derived SFR across the same region. The total mass and SFR derived using these methods agree well with previous values in the literature. The main conclusion from this analysis is that both the column-density threshold and volumetric SF relations over-predict the SFR by an order of magnitude given the reservoir of dense gas available to form stars. The region 1° < l < 3.5°, |b| < 0.5° is particular striking in this regard. It contains ∼107 M⊙ of dense molecular gas — enough to form 1000 Orion-like clusters — but the present-day star formation rate within this gas is only equivalent to that in Orion. This implication of this result is that any universal column/volume density relations must be a necessary but not sufficient condition for SF to occur.

Understanding why such large reservoirs of dense gas deviate from commonly assumed SF relations is of fundamental importance and may help in the quest to understand SF in more extreme (dense) environments, like those found in interacting galaxies and at earlier epochs of the Universe.
Stochastic star formation and early galactic nucleosynthesis
Authors: Nguyen Lan , Mathews Grant
Published: March 2013

We discuss calculations of the star formation, nucleosynthesis, and stochastic evolution of proto-galactic clouds in a galactic chemical evolution model which is motivated by cold dark matter simulations of hierarchical galaxy formation (Saleh et al. 2006; Lan et al. 2010). We utilize SN-induced and dark matter halo formation-induced star formation within a model that follows the evolution of chemical enrichment and energy input to the clouds via Type II, Ia supernovae and stellar winds.
Multi-wavelength Studies of Cluster Star Forming Galaxies at z∼0.54
Authors: Randriamampandry S. M. , Crawford S. M. , Cress C. M. , Hess K. M. , Giovannoli E. , Vaccari M.
Published: March 2013

We carry out a multi-wavelength analysis of star forming galaxies in the massive cluster MS0451.6-0305 at z∼0.54 to shed light on the evolution of the far-infrared-radio relationship in rich clusters. We have performed Spectral Energy Distribution (SED) fitting of IRAC 3.6μ, IRAC 4.5μ and MIPS 24μ photometry from Spitzer to derive the total infrared bolometric luminosity of spectroscopically confirmed cluster members with radio counterparts. The radio flux densities were measured from deep Very Large Array (VLA) radio continuum observations. The relationship between the infrared and radio luminosities for our sources show the strong correlation found between these two parameters for star forming galaxies. The far-infrared to radio luminosity ratio (qIR) values measured for these sources are comparable to those measured in low redshift clusters and indicative of an excess of radio emission.
Off-nuclear starburst in a triple merger
Authors: Väisänen Petri , Reunanen Juha , Kotilainen Jari , Mattila Seppo
Published: March 2013

We present SINFONI observations of IRAS 19115-2124, dubbed the Bird, an intriguing triple galaxy encounter. NIR line strengths and line ratios are used to study the sequence of events in this complex system. The most massive and obscured component shows LINER-like activity, while the least massive irregular component is the source of 3/4 of the current total SF. This most recent compact starburst lies 3 kpc away from the dynamically dominant components. Cool and warm gas inflows and outflows are detected at the locations of the progenitor nuclei.
Lyα vs. fundamental properties of galaxies
Authors: Wofford Aida , Leitherer Claus , Salzer John ,   COS Science Team
Published: March 2013

We obtained HST COS Lyα spectroscopy for 20 galaxies that were Hα-selected from the Kitt Peak International Spectroscopic Survey data release. We cover redshifts of z=0.02–0.06 and a broad range in metallicity, reddening, and luminosity. We investigate correlations between the properties of the Lyα-lines and fundamental properties of the galaxies. Our seven emitters have: equivalent widths in the range EW(Lyα)=1–12 Å, i.e., below the completeness limits of higher redshift studies; extinction corrected Lyα/Hα ratios of at most 12–15% of the case B recombination theory value; and O I λ1302 ISM absorptions blueshifted to 〈v(O I)〉= − 117±40 km/s, which are consistent with H I gas outflows. Six emitters have P-Cygni-like Lyα profiles with peaks redshifted to 〈v〉=172±25 km/s, and one of our face-on spiral galaxies has two Lyα peaks separated by 370 km/s. The latter peaks are such that the blueshifted peak is twice as strong as the redshifted peak. The rest of the galaxies show Lyα absorption troughs centered at 〈v〉=19 km/s and O I λ1302 absorptions centered at 〈v(O I)〉= − 34±25 km/s, which is consistent with static or low velocity H I gas. Our two most metal poor and least reddened galaxies, which have large Hα equivalent widths are absorbers. The spiral galaxies in our sample have Lyα in single emission, double emission, or absorption. There appears to be a correlation between the Hα derived SFR and the strength of the Lyα emission but our sample is small. Our observations cover regions of at most 3 kpc in diameter and may miss a significant fraction of the resonantly scattered Lyα emission. This work is supported by NASA grant N1317.
Molecular gas in galaxies: much more than just the fuel of star formation
Authors: Nesvadba Nicole , Boulanger Francois , Herrera Cinthya , Guillard Pierre , Lehnert Matt , Salome Philippe , Falgarone Edith
Published: March 2013

It is well known that shocks can heat molecular gas, but we are only starting to understand what the consequences might be for galaxy evolution. Observations are now revealing a growing number of galaxies undergoing phases of strong injection of kinetic energy through galaxy interactions or feedback from powerful AGN, which have bright line emission from shock-heated molecular gas that is likely powered by the dissipation of turbulent energy. These observations demonstrate that turbulence – now recognized as an important mechanism regulating star formation – may also be key in regulating galaxy growth. We report on our on-going efforts to quantify the role of molecular gas for the dissipation of kinetic energy through observations on two very different examples, the Antennae galaxy merger and the radio galaxy 3C326 N, a site of strong mechanical AGN feedback. Both galaxies show signatures of strong dissipation of kinetic energy through shocks. We will illustrate how key parameters of these processes like bulk and turbulent velocities, gas masses, and dissipation timescales can be measured with multi-wavelength data, and how this furthers our understanding of how galaxy evolution and star formation in galaxies depend on each other.
Effects of large-scale AGN feedback in local galaxies
Authors: Shabala Stanislav , Kaviraj Sugata , Silk Joseph
Published: March 2013

The effects of active galactic nucleus (AGN) feedback on group and cluster galaxies are investigated. We examine the colors of non-AGN hosts (i.e. satellite galaxies) by comparing galaxies overrun by radio AGN with similar galaxies located outside the radio AGN contours. We find that powerful Fanaroff-Riley type II (edge-brightened) radio AGN truncate star formation in the galaxies overrun by AGN-driven bow shocks. On the other hand, the ubiquitous Fanaroff-Riley type I (core-dominated) AGN do not affect neighboring galaxies. This result shows that, despite their rarity, feedback from powerful radio AGN is an important factor in the evolution of group/cluster galaxies.
Analytic description, measurements, and modeling of 3D-embedded silicon inductance for High-Performance Hybrid Systems Applications
Authors: Descamps Philippe , Tesson Olivier , Duplessis Magali , Pasquet Daniel , Murray Hugues
Published: March 2013

In this paper, the design and the measurements of three-dimensional through silicon vias (TSVs) based-integrated solenoids embedded within high-resistive silicon is presented. Prior to silicon implementation, a rigorous theoretical analysis is proposed to put in obviousness the advantages of using such coil architecture for L and S band applications. This analysis, demonstrates a clear reduction of the footprint passive function lying on the external substrate together with a reduced capacitive coupling with the local environment. Two-port radio frequency measurements have been performed in a wide-frequency range (100 MHz – 50 GHz) in order to support the theoretical investigations. Solenoids exhibit high-quality factors below 4 GHz – Q = 25 @ 2 GHz for a 800 pH device – and clearly outperforms classical planar architecture considered in most of the integrated circuit processes. Two different modeling approaches (compact modeling and EM modeling) are then proposed in order to speed-up their design implementation in a typical CAD design flow. Based on the available data, a good agreement is shown between and simulated data.
Taurine transport in human placental trophoblast is important for regulation of cell differentiation and survival
Authors: Desforges M , Parsons L , Westwood M , Sibley C P , Greenwood S L
Published: March 2013

The outer epithelial cell layer of human placenta, the syncytiotrophoblast, is a specialised terminally differentiated multinucleate tissue. It is generated and renewed from underlying cytotrophoblast cells that undergo proliferation, differentiation and fusion with syncytiotrophoblast. Acquisition of fresh cellular components is thought to be balanced by apoptosis and shedding of aged nuclei. This process of trophoblast cell turnover maintains a functional syncytiotrophoblast, capable of sufficient nutrient transfer from mother to foetus. Foetal growth restriction (FGR) is a pregnancy complication associated with aberrant trophoblast turnover and reduced activity of certain amino acid transporters, including the taurine transporter (TauT). Taurine is the most abundant amino acid in human placenta implying an important physiological role within this tissue. Unlike other amino acids, taurine is not incorporated into proteins and in non-placental cell types represents an important osmolyte involved in cell volume regulation, and is also cytoprotective. Here, we investigated the role of taurine in trophoblast turnover using RNA interference to deplete primary human trophoblast cells of TauT and reduce intracellular taurine content. Trophoblast differentiation was compromised in TauT-deficient cells, and susceptibility of these cells to an inflammatory cytokine that is elevated in FGR was increased, evidenced by elevated levels of apoptosis. These data suggest an important role for taurine in trophoblast turnover and cytoprotection.
Global marine bacterial diversity peaks at high latitudes in winter
Authors: Ladau Joshua , Sharpton Thomas J , Finucane Mariel M , Jospin Guillaume , Kembel Steven W , O’Dwyer James , Koeppel Alexander F , Green Jessica L , Pollard Katherine S
Published: March 2013

Genomic approaches to characterizing bacterial communities are revealing significant differences in diversity and composition between environments. But bacterial distributions have not been mapped at a global scale. Although current community surveys are way too sparse to map global diversity patterns directly, there is now sufficient data to fit accurate models of how bacterial distributions vary across different environments and to make global scale maps from these models. We apply this approach to map the global distributions of bacteria in marine surface waters. Our spatially and temporally explicit predictions suggest that bacterial diversity peaks in temperate latitudes across the world’s oceans. These global peaks are seasonal, occurring 6 months apart in the two hemispheres, in the boreal and austral winters. This pattern is quite different from the tropical, seasonally consistent diversity patterns observed for most macroorganisms. However, like other marine organisms, surface water bacteria are particularly diverse in regions of high human environmental impacts on the oceans. Our maps provide the first picture of bacterial distributions at a global scale and suggest important differences between the diversity patterns of bacteria compared with other organisms.
Tight knots in proteins: can they block the mitochondrial pores?
Authors: Szymczak Piotr
Published: March 2013

Proteins need to be unfolded when translocated through the pores in mitochondrial and other cellular membranes. Knotted proteins, however, might get stuck during this process since the diameter of the pore is smaller than the size of maximally tightened knot. In the present article, I briefly review the experimental and numerical studies of tight knots in proteins, with a particular emphasis on the estimates of the size of these knots. Next, I discuss the process of protein translocation through the mitochondrial pores and report the results of molecular dynamics simulations of knotted protein translocation, which show how the knot can indeed block the pore.
Enumeration of RNA complexes via random matrix theory
Authors: Andersen Jørgen E. , Chekhov Leonid O. , Penner Robert C. , Reidys Christian M. , Sułkowski Piotr
Published: March 2013

In the present article, we review a derivation of the numbers of RNA complexes of an arbitrary topology. These numbers are encoded in the free energy of the Hermitian matrix model with potential V(x)=x2/2−stx/(1−tx), where s and t are respective generating parameters for the number of RNA molecules and hydrogen bonds in a given complex. The free energies of this matrix model are computed using the so-called topological recursion, which is a powerful new formalism arising from random matrix theory. These numbers of RNA complexes also have profound meaning in mathematics: they provide the number of chord diagrams of fixed genus with specified numbers of backbones and chords as well as the number of cells in Riemann's moduli spaces for bordered surfaces of fixed topological type.
The thermodynamics of DNA loop formation, from J to Z
Authors: Levene Stephen D. , Giovan Stefan M. , Hanke Andreas , Shoura Massa J.
Published: March 2013

The formation of DNA loops is a ubiquitous theme in biological processes, including DNA replication, recombination and repair, and gene regulation. These loops are mediated by proteins bound at specific sites along the contour of a single DNA molecule, in some cases many thousands of base pairs apart. Loop formation incurs a thermodynamic cost that is a sensitive function of the length of looped DNA as well as the geometry and elastic properties of the DNA-bound protein. The free energy of DNA looping is logarithmically related to a generalization of the Jacobson–Stockmayer factor for DNA cyclization, termed the J factor. In the present article, we review the thermodynamic origins of this quantity, discuss how it is measured experimentally and connect the macroscopic interpretation of the J factor with a statistical-mechanical description of DNA looping and cyclization.
DNA thermodynamics shape chromosome organization and topology
Authors: Travers Andrew A. , Muskhelishvili Georgi
Published: March 2013

How much information is encoded in the DNA sequence of an organism? We argue that the informational, mechanical and topological properties of DNA are interdependent and act together to specify the primary characteristics of genetic organization and chromatin structures. Superhelicity generated in vivo, in part by the action of DNA translocases, can be transmitted to topologically sensitive regions encoded by less stable DNA sequences.
Metabolomics in nutrition research: current status and perspectives
Authors: Brennan Lorraine
Published: March 2013

Metabolomics is the study of metabolites present in biological samples such as biofluids, tissue/cellular extracts and culture media. Combining metabolomic data with multivariate data analysis tools allows us to study alterations in metabolic pathways following different perturbations. Examples of perturbations can be disease state, drug or nutritional interventions with successful applications in the fields of drug toxicology, biomarker development and nutrition research. Application of metabolomics to nutrition research is increasing and applications range from assessing novel biomarkers of dietary intake to application of metabolomics in intervention studies. The present review highlights the use of metabolomics in nutrition research.
Sedoheptulose kinase regulates cellular carbohydrate metabolism by sedoheptulose 7-phosphate supply
Authors: Nagy Csörsz , Haschemi Arvand
Published: March 2013

Dynamic carbon re-routing between catabolic and anabolic metabolism is an essential element of cellular transformation associated with tumour formation and immune cell activation. Such bioenergetic adaptations are important for cellular function and therefore require tight control. Carbohydrate phosphorylation has been proposed as a rate-limiting step of several metabolic networks. The recent identification of a sedoheptulose kinase indicated that free sedoheptulose is a relevant and accessible carbon source in humans. Furthermore, the bioavailability of its phosphorylated form, sedoheptulose 7-phosphate, appears to function as a rheostat for carbon-flux at the interface of glycolysis and the pentose phosphate pathway. In the present paper, we review reports of sedoheptulose metabolism, compare it with glucose metabolism, and discuss the regulation of sedoheptulose kinase as mechanism to achieve bioenergetic reprogramming in cells.
Topological Aspects of DNA Function and Protein Folding
Authors: Stasiak Andrzej , Bates Andrew D. , Buck Dorothy E. , Harris Sarah A. , Sumners De Witt
Published: March 2013

The Topological Aspects of DNA Function and Protein Folding international meeting provided an interdisciplinary forum for biological scientists, physicists and mathematicians to discuss recent developments in the application of topology to the study of DNA and protein structure. It had 111 invited participants, 48 talks and 21 posters. The present article discusses the importance of topology and introduces the articles from the meeting's speakers.
Analytic transient analysis of radiation from hyperboloid reflector antennas via surface curvature continuation of ellipsoidal surfaces
Authors: Chou H.‐T. , Tuan S.‐C.
Published: March 2013

A transient analysis of a hyperbolic reflector antenna is performed based on a mathematic continuation of surface curvatures of an ellipsoidal reflector antenna with the analysis previously performed. This work makes the time‐domain analysis useful for the design of reflector antennas since both ellipsoidal and hyperbolic reflectors are widely used as sub‐reflectors for dual‐reflector antenna system. In particular, this work interprets the scattering phenomena in terms of reflected and diffracted fields with respect to the frameworks of geometrical theories of diffraction, and allows one to analyse the reflector based on the local scattering mechanism.
Discontinuous spectrum sensing scheme for energy‐constrained cognitive radio networks
Authors: Wang Bo , Feng Zhiyong , Huang Dongyan , Zhang Ping
Published: March 2013

Compared with traditional communication systems, cognitive radio (CR) systems consume additional sensing and reporting energy. Minimising additional energy consumption while maintaining maximum throughput is an emerging issue in CR systems. Proposed is a discontinuous spectrum sensing scheme for CR systems that adopts cooperative spectrum sensing. The simulation results show that the proposed scheme can achieve remarkable energy savings with negligible throughput loss.
Reliability Improvement of superluminescent diodes emitting at 1.0 µm band using InGaAsP barrier structure
Authors: Ohgoh T. , Asano H. , Hamamoto K.
Published: March 2013

A report is presented on the reliability evaluation of broad‐band InGaAs superluminescent diodes emitting at 1.0 µm band wavelength. The devices using the InGaAsP barrier layer showed better reliability characteristics owing to the low optical power density in the active region, compared to the devices with using the GaAs barrier layer. In the lifetime test under auto‐power‐control mode at the output power of 30 mW at 25 °C, a noticeable degradation was observed in the devices with the GaAs barrier, while the devices with the InGaAsP barrier have shown almost no degradation over 3000 h.
Miniaturised Horst‐type Wilkinson power divider with simple layout
Authors: Wang X. , Sakagami I. , Ito N. , Mase A.
Published: March 2013

A Wilkinson power divider with an open‐circuited stub and extra‐transmission lines between two output ports is presented. Compared with the modified Wilkinson power divider presented by Horst, the proposed power divider has the advantages of less occupation area on a printed circuit board and simple layout, where the isolation resistor, one open‐circuited stub and extra‐transmission lines are constants. The experimental circuit shows good agreement with theoretical simulation.
Multi‐rate real‐time model‐based parameter estimation and state identification for induction motors
Authors: Wang Song , Dinavahi Venkata , Xiao Jian
Published: March 2013

This study presents multi‐rate parameter and state estimation methods for the induction motor. Based on multi‐rate control theory and the extended Kalman filter (EKF) theory, a multi‐rate EKF algorithm including input and output algorithms is proposed for load torque estimation in the induction motor. The methods are implemented in real‐time on PC‐cluster node which acts as the controller for an induction motor experimental set‐up. Rotor time constant is a sensitive variable in indirect field‐oriented control method. A multi‐rate model reference adaptive system (MRAS) is proposed to estimate the rotor time constant in order to guarantee the high‐performance control of induction motor. Experimental result verified the effectiveness of the algorithms. Simulations compare the multi‐rate EKF algorithm with the traditional single‐rate EKF algorithm performance to show improved performance of load torque estimator. The comparison between the traditional MRAS and the multi‐rate MRAS shows the superiority of the proposed method, with a satisfactory accuracy.
Factorisation‐based transfer function estimation technique for deformation diagnostics of windings in transformers
Authors: Narayana Gunda Surya , Badgujar Ketan P. , Kulkarni Shrikrishna V.
Published: March 2013

Mechanical deformations of transformer windings are identified through variations observed in their frequency response (FR). This study proposes a new way of determining a transfer function (TF) from measured FR data using factorisation principles as against established ways of finding it through rational fitting algorithms or least‐square estimation. It is observed that some characteristics of FR of a transformer winding are similar to FR of first‐ and second‐order systems, and this has been the basic motivation for the reported work. In the proposed method, TF is expressed as a combination of first‐ and second‐order polynomials. The algorithm is applicable over a wide‐frequency range and for high‐order systems. Initial guesstimates for locations of poles/zeros, orders of TFs, and enforcement of poles to the left half of the s‐plane are not required. The algorithm is validated through three case studies and its accuracy is checked through commonly used statistical indicators. The application of the algorithm is also demonstrated on a 500 kVA distribution transformer. The method is simple and accurate in estimating TFs for their further use in the deformation diagnostics of transformer windings.