bluuebunny/crossref_metadata_2025_split huggingface dataset:
The star formation rate in the inner Milky Way Galaxy
Authors: Cavichia Oscar , Mollá Mercedes , Costa Roberto D. D. , Maciel Walter J. 
Published: March 2013

AbstractThe present star formation rate (SFR) in the inner Galaxy is puzzling for the chemical evolution models (CEM). No static CEM is able to reproduce the peak of the SFR in the 4 kpc ring. The main reason is probably a shortage of gas, which could be due to the dynamical effects produced by the galactic bar, not considered by these models. We developed a CEM that includes radial gas flows in order to mimic the effects of the galactic bar in the first 5 kpc of the galactic disk. In this model, the star formation (SF) is a two-step process: first, the diffuse gas forms molecular clouds. Then, stars form from cloud-cloud collisions or by the interaction between massive stars and the molecular gas. The former is called spontaneous and the latter induced SF. The mass in the different phases of each region changes by the processes associated with the stellar formation and death by: the SF due to spontaneous fragmentation of gas in the halo; formation of gas clouds in the disk from the diffuse gas; induced SF in the disk due to the interaction between massive stars and gas clouds; and finally, the restitution of the diffuse gas associated to these process of cloud and star formation. In the halo, the star formation rate for the diffuse gas follows a Schmidt law with a power n = 1.5. In the disk, the stars form in two steps: first, molecular clouds are formed from the diffuse gas also following a Schmidt law with n=1.5 and a proportionality factor. Including a specific pattern of radial gas flows, the CEM is able to reproduce with success the peak in the SFR at 4 kpc (fig. 1).
UKIRT Widefield Infrared Survey for H2
Authors: Froebrich Dirk , Ioannidis Georgios ,   UWISH2 Survey Team
Published: March 2013

AbstractWe perform an unbiased search for outflows from YSOs along the Galactic Plane (GP). Our data has been taken as part of the UWISH2 survey (Froebrich et al. 2011). It uses as tracer the 1-0S(1) emission line of H2, and here we focus on a continuous 33 square degree sized region in Serpens and Aquila. We identify 130 outflows from which 94% are new discoveries. Thus, we increased the number of known MHOs by a factor of 15 in this area (Ioannidis & Froebrich 2012). The flux completeness limit for the flows is 3ċ10−18Wm−2. Typically, the known flows occupy the bright end of the flux distribution. Our survey thus increases the known integrated 1-0S(1) H2 flux from outflows only by a factor of two. We are able to assign possible driving sources to half of the outflows. Brighter MHOs are more likely to have a source candidate assigned to them.Foreground star counts to GMCs associated with the outflows and the Besancon Galaxy model are used to determine distances. The method is calibrated using objects from the RMS survey. This allows us to estimate distances with a scatter of 25% (Ioannidis & Froebrich 2012). The spatial distribution of the outflows shows that they follow the GMC complexes in the GP. However, there are large areas with high extinction where no flows are detected. About 2/3 of the survey area is more or less devoid of outflows. The flows typically occur in groups of 3–5 members with a size of 5pc. The scale height of flows is ∼25–30pc, similar to young clusters and OB stars. The 1-0S(1) luminosities range from a few 10−4L⊙ to 0.1L⊙, ten times brighter than in nearby SF regions. Our sample is complete for objects brighter than 10−3L⊙ at 5kpc. This corresponds to HH211 behind AK = 1mag. The luminosity distribution of the outflows is a power law with N ∝ LH2−1.9 and the integrated luminosities indicate a Milky Way SF rate (averaged over a typical jet lifetime) of more than 0.4M⊙yr−1. The energy and momentum of the jets is insufficient to sustain the typical local turbulence levels in their parental clouds.The projected jet length drops exponentially in number for longer jets. The fraction of parsec scale flows is 25%, twice as high as in nearby SF regions. A Monte-Carlo type model of jet speeds of 40–130kms−1 and ages between 4–20 × 103yrs can reproduce the length distribution. These lifetimes are an order of magnitude below estimates for the protostellar phase. For typical jet speeds the time gaps between the ejection of larger amounts of material are about 103yrs. According to the burst mode of SF models the creation of H2 knots is hence linked to low level fluctuations of the mass accretion rate and not FU-Ori type events. Their duty cycle is more in agreement with the total jet lifetime, which suggests these outburst as trigger (or stopping point or both) of a jet ejection phase. However, better constraints of the FU-Ori duty cycle and mechanism as well as more detailed models are required to draw any further conclusions.
Submillimeter-wave Observations of Complex Organic Molecules in Southern Massive Star Forming Regions
Authors: Kamegai Kazuhisa , Sakai Takeshi , Sakai Nami , Hirota Tomoya , Yamamoto Satoshi 
Published: March 2013

AbstractSubmillimeter-wave observations of complex organic molecules toward southern massive star forming regions were carried out with ASTE 10m telescope. Methyl formate (HCOOCH3) and dimethyl ether (CH3OCH3) were detected in some molecular cloud cores with young protostars. Differences in chemical composition among neighboring cores were also found.
TRAO 13CO Outer Galaxy Survey
Authors: Lee Youngung , Kim Y. S. , Kang H. W. , Jung J. H. , Lee C. H. , Yim I. S. , Kim B. G. , Kim H. G. , Kim K. T. 
Published: March 2013

AbstractWe have observed the parts of the second quadrant of the Galactic Plane in 13CO(1-0) using the multibeam receiver system installed on the 14 m telescope at Taeduk Radio Astronomy Observatory (TRAO). The first target region A (L=108° to 112°.5) is the part of the 12CO Outer Galactic Plane Survey (OGS; Heyer et al. 1998), and it is for the exact Galactic plane with the latitude range of +1 and -1 degree. A total of 48,000 spectra (about 9 square degrees) were obtained on 50″ grid. Two following regions were also observed; Region B: L = 120° ∼ 121°.7, B = −1° ∼ +1° (38,000 spectra) Region C: L = 130° 132°, B = −1° ∼ +1° (42,000 spectra). Eventually all the regions of the OGS will be covered. The selected velocity resolution is 0.63 km s−1 and the covered velocity is 320 km s−1, from −210 to 110 km s−1. The typical system temperature is ranging from 400 to 800 K, and average sensitivity per channel is 0.17 K.We developed a new reduction method, which effectively deals with a relatively noisy 3-dimensional database. After using simple linear baseline subtraction, we mainly used the IRAF twod.longslit.background task in 3D within some scripts, as well as IRAF tasks dealing with statistics, and a revised FCRAO reduction package, which is working within IRAF as external user's tasks. The collected 13CO database will be manipulated with pre-existing 12CO data to get several physical parameters. As it is located in the second quadrant, the kinematic distances of the individual clouds, which will be identified, can be estimated straightforwardly without any distance ambiguity. In this meeting we present the reduction method, integrated intensity maps, and spatial-velocity maps. We intend to clarify any difference of their characteristics between the clouds in the Outer Galaxy and Inner Galaxy using our data base.The present TRAO receiver system has aged, and thus its performance level degraded. However, we have a plan to renovate our receiver system to a brand new one within the next two years. This will speed up the TOGS project. At present, it costs substantial amount of time to homogeneously reduce the spectra obtained with our present receiver system. To compensate this, we invested more integration time, and developed more advanced reduction methods (see above). A future multibeam array receiver system at the TRAO would be at least 16 beams with most recent mixers (Tsys ∼ 150 K at 110GHz), hopefully.
Morphology, Kinematics and Star Formation in Spiral Galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G)
Authors: Erroz-Ferrer Santiago , Knapen Johan H. , Font Joan , Beckman John E. ,   the S4G team
Published: March 2013

AbstractWe present a study of the morphology, kinematics and star formation of a sample of 27 isolated spiral galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G), on the basis of Hα Fabry-Perot (FP) data from the GHαFaS instrument at the William Herschel Telescope (WHT) in La Palma, complemented with images at 3.6 micron from the Spitzer Space Telescope, and with images in the R-band and in Hα taken with the ACAM instrument mounted on the WHT. With the FP data we can investigate the gas kinematics in terms of velocity maps and position-velocity diagrams, keys to constrain the secular evolution processes. We can also analyse the morphology and compute the star formation rate (SFR) with the ancillary data.
Molecular gas and star formation in extreme starbursts at low redshift
Authors: Gonçalves T. S. , Basu-Zych A. , Borthakur S. , Baker A. , Sheth K. , Overzier R. , Martin D. C. 
Published: March 2013

AbstractLyman Break Analogs (LBAs) are a population of star-forming galaxies at low redshift (z ∼ 0.2). These objects present metallicities, morphologies and other physical properties similar to higher redshift Lyman Break Galaxies (LBGs), motivating their detailed study as potential local analogs to high-redshift starburst galaxies (Hoopes et al. 2007, Basu-Zych et al. 2009, Overzier et al. 2010, Overzier et al. 2011).Our recent integral-field spectroscopy survey of LBAs with Keck/OSIRIS shows that these galaxies have the same nebular gas kinematic properties as high-redshift LBGs. We argue that such kinematic studies are not an appropriate diagnostic to rule out major merger events as the trigger for the observed starburst. Comparison between kinematic analysis and morphological indices from HST imaging disagree with respect to merger identification, with no correlation between the two methods. Artificial redshifting of our data indicates the merger detection rate is even worse at high redshift due to surface brightness dimming and resolution loss. For more details, we refer the reader to Gonçalves et al. (2010).More recently, we have initiated a program with the CARMA array to detect molecular gas in these galaxies (Gonçalves et al. 2013, in prep.). Our results show that LBAs present strong emission in CO(1-0), with similar gas fractions to those observed in high-redshift starburst galaxies. Moreover, the objects observed thus far follow the same Schmidt-Kennicutt law as local galaxies, albeit at much higher surface densities, as found in BzK galaxies at z ∼ 2 (Daddi et al. 2010). This distinguishes our sample from dusty starburst galaxies, such as ULIRGs and SMGs.The upcoming operations of ALMA will definitely make a great impact on this project. We will be able to observe fainter, lower metallicity objects, and at the same time we will map the CO emission at sub-kpc resolutions. Once those data become available, we hope the scenario for the physical processes regarding the collapse of the molecular clouds and subsequent star formation will become clearer.
Obscured quasars: the link between star-formation and black hole activity
Authors: Mainieri Vincenzo , Bongiorno Angela ,   the COSMOS team
Published: March 2013

AbstractWe explore the connection between black hole growth at the center of obscured quasars selected from the XMM-COSMOS survey and the physical properties of their host galaxies. We study a bolometric regime (<Lbol> ∼ 8 × 1045 erg s−1) where several theoretical models invoke major galaxy mergers as the main fueling channel for black hole accretion. To derive robust estimates of the host galaxy properties, we use an SED fitting technique to distinguish the AGN and host galaxy emission. We find that at z ∼ 1, ≈ 62% of Type-2 QSOs hosts are actively forming stars and that their rates are comparable to those measured for normal star-forming galaxies. The fraction of star-forming hosts increases with redshift: ≈ 71% at z ∼ 2, and 100% at z ∼ 3. We also find that the evolution from z ∼ 1 to z ∼ 3 of the specific star-formation rate of the Type-2 QSO hosts is in excellent agreement with that measured for star-forming galaxies.
Molecular Gas and Star-formation in Selected H-ATLAS SDP Lensed SMGs
Authors: Leeuw Lerothodi L. , Riechers Dominik A. , Carpenter John M. , Negrello Mattia , Ivison Rob J. ,   H-ATLAS Lensing and Core
Published: March 2013

AbstractWe present detections of spatially resolved CO(J = 2→1) and CO(J = 3→2) emission, respectively, from the lensed submillimeter (submm) galaxies (SMGs), ID 9 (z = 1.577) and ID 17b (z = 2.308), found in the Science Demonstration Phase (SDP) of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS, www.h-atlas.org). The detections were obtained using the Combined Array for Research in Millimeter-wave Astronomy (CARMA, www.mmarray.org) and confirm redshifts of the lensed galaxies. We exploit the CARMA data together with existing high-J observations, to determine, among other physical properties of the lensed SMGs, the CO line luminosities, brightness temperature ratios, gas masses, and spatial sizes.
Influence of AGN on the properties of galaxies during the (U)LIRG phase
Authors: Lin Ming-Yi , Foucaud Sébastien , Hashimoto Yasuhiro 
Published: March 2013

AbstractMerging, resulting from galaxy interaction and collision, is one essential scenario to interpret the distinct evolutionary stages of galaxy formation. However AGNs are believed to play an essential role towards the final stages of this scenario, in particular to clear the galaxy from a large excess of dust. Selecting galaxies with both 70μm and X-ray detection will help to understand the relation between star formation and AGN. We are taking advantage of the extensive multi-wavelength coverage of the Cosmic Evolution Survey (COSMOS) field to dissect the AGN influence on infrared luminous objects. We demonstrate that enhanced star formation is more probably responsible for additional obscuration of the central AGN than the dust torus, in agreement with current galaxy formation theory. Furthermore, we demonstrate that the presence of an AGN does not increase the galaxy dust temperature significantly.
Complete Ionisation of the Neutral Gas in High Redshift Radio Galaxies and Quasars
Authors: Curran S. J. , Whiting M. T. 
Published: March 2013

AbstractCool neutral gas provides the raw material for all star formation in the Universe, and yet, from a survey of the hosts of high redshift radio galaxies and quasars, we find a complete dearth of atomic (Hi 21-cm) and molecular (OH, CO, HCO+ & HCN) absorption at redshifts z ≳ 3 (Curran et al. 2008). Upon a thorough analysis of the optical photometry, we find that all of our targets have ionising (λ ≤ 912 Å) ultra-violet continuum luminosities of LUV ≳ 1023 W Hz−1. We therefore attribute this deficit to the traditional optical selection of targets biasing surveys towards the most ultra-violet luminous objects, where the intense radiation excites the neutral gas to the point where it cannot engage in star formation (Curran & Whiting 2010). However, this hypothesis does not explain why there is a critical luminosity, rather than a continuum where the detections gradually become fewer and fewer as the harshness of the radiation increases. We show that by placing a quasar within a galaxy of gas there is always a finite ultra-violet luminosity above which all of the gas is ionised. This demonstrates that these galaxies are probably devoid of star-forming material rather than this being at abundances below the sensitivity limits of current radio telescopes.
Chemical complexity and star-formation in merging galaxies
Authors: Davis T. A. , Heiderman A. , Iono D. ,   the VIXENS team
Published: March 2013

AbstractWhen galaxies merge the resulting conditions are some of the most extreme found anywhere in nature. Large gas flows, shocks and active black holes all can affect the ISM. Nearby merging galaxies with strong starbursts are the only places where we can conduct detailed study of star formation in conditions that mimic those under which the majority of stars in the universe formed. Here we study molecular gas tracers in 8 galaxies selected from the VIRUS-P Investigation of the eXtreme ENvironments of Starbursts (VIXENS) survey. Each galaxy has also been observed using the integral field unit spectrograph VIRUS-P, allowing us to investigate the relation between the chemical state of the gas, star formation and total gas content. Full details can be found in Heiderman et al. (2011). Here we report on new results obtained from IRAM-30m/NRO-45m 3mm line surveys towards 14 positions in these 8 merging galaxies. We detect ≈ 25 different molecular transitions towards these objects, many which have never been observed in these galaxies before. Our measurements show that the mean fraction of dense gas increases in later-stage mergers (Fig. 1, left), as does the average optical depth of the gas. Molecular diagnostic diagrams (Fig. 1, right) show that molecular regions we probe are, in general, UV photon dominated. Triggered AGN activity, and/or cosmic ray ionisation (from SNe II in the starburst) are not yet energetically important in determining the state of the gas.
Testing Evolutionary Models of Dwarf Irregular Galaxies through Gas and Stellar Metallicity Determinations in HII Galaxies
Authors: Westera Pieter , Cuisinier François , Curty Didier , Buser Roland 
Published: March 2013

AbstractDwarf irregular galaxies are usually low-metallicity objects, and show ongoing or very recent star formation, giving rise to their irregular appearance. Especially HII galaxies, a sub-category of dwarf irregulars showing unusually high star formation activity, are believed to be among the least evolved galaxies in existence today. Therefore, they are very interesting objects for studies of early galaxy evolution and of metallicity enrichment mechanisms.Several groups have developed theoretical evolutionary models of galaxies of this type, describing different possible formation and evolutionary scenarii, and varying factors such as gas infall and outflow, as well as the star formation history, and making predictions about their chemical evolution. One way to evaluate these models is by determining the metallicities of the different components of these galaxies, their gas and stars.We examine a sample of HII galaxies from the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of HII galaxy spectra to date. Using very restrictive selection criteria, which guarantee a sample of high quality spectra and avoid “contamination” by spectra of objects of other nature, we defined a sample of ∼ 700 HII galaxies spectra.Through emission line strength calibrations and a detailed stellar population synthesis, we determined the metallicities of both the gas and the stellar content of these galaxies.For HII galaxies up to stellar masses of 5 × 109M⊙, we find enrichment mechanisms not to vary with galactic mass, being the same for low- and high-mass galaxies on average. They do seem to present a greater variety at the high-mass end, though, indicating a more complex assembly history. Our results favour galaxy evolutionary models featuring constantly infalling low-metallicity clouds that retain part of the galactic winds. Above 5 × 109M⊙ stellar mass, the retention of high metallicity gas by the galaxies' gravitational potential dominates.I would like to thank the Fundação de Amparo à Pesquisa do Estado do São Paulo (FAPESP) for financial support.
Global Dust Budgets of the Magellanic Clouds
Authors: Matsuura Mikako 
Published: March 2013

AbstractWithin galaxies, gas and dust are constantly exchanged between stars and the interstellar medium (ISM). The life-cycle of gas and dust is the key to the evolution of galaxies. Despite its importance, it is has been very difficult to trace the life-cycle of gas and dust via observations. The Spitzer Space Telescope and Herschel Space Observatory have provided a great opportunity to study the life-cycle of the gas and dust in very nearby galaxies, the Magellanic Clouds. AGB stars are more important contributors to the dust budget in the Large Magellanic Cloud (LMC), while in the Small Magellanic Cloud (SMC), SNe are dominant. However, it seems that the current estimates of the total dust production from AGB stars is insufficient to account for dust present in the ISM. Other dust sources are needed, and supernovae are promising sources. Alternatively the time scale of dust lifetime itself needs some revisions, potentially because they could be unevenly distributed in the ISM or clumps.
Gas, Dust and Star Formation in Nearby Galaxies as Seen with the JCMT
Authors: Sánchez-Gallego José Ramón 
Published: March 2013

AbstractWe combine 12CO J = 3 − 2 for 155 nearby galaxies, obtained as part of the James Clerk Maxwell Telescope (JCMT) Nearby Galaxies Legacy Survey (NGLS), with star formation rates derived from Hα luminosities to probe the relation between warm, dense gas and star formation. These data are compared with ancillary data from the literature, including infrared (IR) and 1.4 GHz radio continuum luminosities and Hi masses. We find a good correlation between CO J = 3 − 2 luminosities and Hα-derived star formation rates (SFRs), which is in agreement with previous studies. Several groups of galaxies show a peculiar behaviour in the SFR(Hα) − LCOJ = 3 − 2 plot, which disappears when using IR data. We analyse these regions and propose several hypotheses to explain this behaviour, including group interactions and very recent (≲20 Myr) bursts of star formation only traced by Hα emission. While atomic hydrogen is hardly related with SFR, molecular and total gas (Hi + H2) show similar correlations with Hα luminosities. No correlation is found between CO J = 3−2 luminosity and metallicity, although galaxies with low metallicity are more likely to not be detected. We discuss that CO J = 3 − 2 does not seem to be a significantly better tracer of the star-forming gas, but its independence from metallicity may be used to constrain the conversion factor between CO and H2.
Star Formation Efficiency at Intermediate Redshift
Authors: Combes F. , García-Burillo S. , Braine J. , Schinnerer E. , Walter F. , Colina L. 
Published: March 2013

AbstractStar formation is evolving very fast in the second half of the Universe, and it is as yet unclear whether this is due to evolving gas content, or evolving star formation efficiency (SFE). We have carried out a survey of ultra-luminous galaxies (ULIRG) between z = 0.2 and 1, to check the gas fraction in this domain of redshift which is still poorly known. Our survey with the IRAM-30m detected 33 galaxies out of 69, and we derive a significant evolution of both the gas fraction and SFE of ULIRGs over the whole period, and in particular a turning point around z = 0.35. The result is sensitive to the CO-to-H2 conversion factor adopted, and both gas fraction and SFE have comparable evolution, when we adopt the low starburst conversion factor of α = 0.8 M⊙ (K km s−1 pc2)−1. Adopting a higher α will increase the role of the gas fraction. Using α = 0.8, the SFE and the gas fraction for z∼0.2-1.0 ULIRGs are found to be significantly higher, by a factor 3, than for local ULIRGs, and are comparable to high redshift ones. We compare this evolution to the expected cosmic H2 abundance and the cosmic star formation history.
A Fundamental Plane for GAMA galaxies
Authors: Lara-López Maritza A. , Hopkins Andrew M. , López-Sánchez Angel R. ,   the GAMA team
Published: March 2013

AbstractA full appreciation of the role played by gas metallicity (Z), star-formation rate (SFR), and stellar mass (M*) is fundamental to understanding how galaxies form and evolve. Using data from the SDSS–DR7 and the GAMA surveys we study the Fundamental Plane for star-forming galaxies. Our analysis allows us to confirm the existence of a Fundamental Plane, for which stellar mass = f(Z, SFR) in star-forming galaxies.