bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Clouds: Internal Properties, Turbulence, Star Formation and Feedback
Authors: Tan Jonathan C. , Shaske Suzanne N. , Van Loo Sven 
Published: March 2013

AbstractAll stars are born in molecular clouds, and most in giant molecular clouds (GMCs), which thus set the star formation activity of galaxies. We first review their observed properties, including measures of mass surface density, Σ, and thus mass,M. We discuss cloud dynamics, concluding most GMCs are gravitationally bound. Star formation is highly clustered within GMCs, but overall is very inefficient. We compare properties of star-forming clumps with those of young stellar clusters (YSCs). The high central densities of YSCs may result via dynamical evolution of already-formed stars during and after star cluster formation. We discuss theoretical models of GMC evolution, especially addressing how turbulence is maintained, and emphasizing the importance of GMC collisions. We describe how feedback limits total star formation efficiency, ε, in clumps. A turbulent and clumpy medium allows higher ε, permitting formation of bound clusters even when escape speeds are less than the ionized gas sound speed.
An evolutionary sequence for high-mass star formation
Authors: Breen S. L. , Ellingsen S. P. 
Published: March 2013

AbstractDetermining an evolutionary clock for high-mass star formation is an important step towards realizing a unified theory of star formation, as it will enable qualitative studies of the associated high-mass stars to be executed. Our recent studies have shown that masers have great potential to accurately trace the evolution of these regions. We have investigated the relative evolutionary phases associated with the presence of combinations of water, methanol and hydroxyl masers. Comparison between the characteristics of coincident sources has revealed strong evidence for an evolutionary sequence for the different maser species, a result that we now aim to corroborate through comparisons with chemical clocks.Using our new, large samples of methanol masers at 6.7 GHz (MMB survey; Green et al. (2009)) and 12.2 GHz (Breen et al. 2012), 22 GHz water masers (Breen & Ellingsen 2012), OH masers together with complementary data, we find strong evidence that it is not only the presence or absence of the different maser species that indicates the evolutionary stage of the associated high-mass star formation region (see e.g. Breen et al. (2010)), but that the properties of those masers can give even finer evolutionary details. Most notably, the intensity and velocity range of detected maser emission increases as the star forming region evolves (Breen et al. 2011).Subsequent work we have undertaken (Ellingsen et al. 2011) has shown that the presence of rare 37.7 GHz methanol masers may signal the end of the methanol maser phase. They show that 37.7 GHz methanol masers are associated only with the most luminous 6.7 and 12.2 GHz methanol masers, which combined with the rarity of these objects is consistent with them being a short lived phase towards the end of the 6.7 GHz methanol maser lifetime.An independent confirmation of our maser evolutionary timeline can be gained through comparisons with chemical clocks. MALT90 is a legacy survey of 1000s of dense star forming cores at 90GHz, simultaneously observing 16 molecular lines with the Mopra radio telescope (see e.g. Foster et al. 2011). It provides the perfect dataset to test the maser evolutionary timeline due to the targeted lines and the fact that at least one-quarter of the MALT90 sources correspond to maser sites, providing a large enough sample for meaningful analysis. From our preliminary analysis, we find that star formation regions showing similar maser properties also show similar thermal line properties; as would be expected if our evolutionary scenario were accurate.
NIR integral field spectroscopy of high mass young stellar objects
Authors: Murakawa K. , Lumsden S. L. , Oudmaijer R. D. , Davies B. , Hoare M. G. 
Published: March 2013

AbstractWe present K-band Integral Field Spectroscopy of six high mass young stellar objects (IRAS~18151–1208, AFGL~2136, S106~IRS4, V645 Cyg, IRAS~19065+0526, and G082.5682+ 00.4040) obtained using the adaptive optics assisted NIFS instrument mounted on the Gemini North telescope. The targets are chosen from the Red MSX Source survey led by University of Leeds. The data show the spectral features of Brγ, H2, and gas phase CO emissions and absorptions with a spectral resolution of R ≈ 5500, which allow a three-dimensional spectro-astrometric analysis of the line emissions. We discuss the results of the ionized jets and winds, and rotating CO torus.
The Roles of Protostellar Outflow Feedback in Clustered Star Formation
Authors: Nakamura Fumitaka , Li Zhi-Yun 
Published: March 2013

AbstractWe discuss the roles of protostellar outflow feedback in cluster formation using observational data of nearby cluster-forming regions like rho Oph, NGC1333, and Serpens. The observations suggest that observed protostellar outflow feedback appears to be sufficient both to maintain supersonic turbulence and to dynamically support the parent cluster-forming clumps. However, it is not enough to destroy the parent clumps by the current outflow activity. This implies that star formation process may not be too short and probably last at least for several local dynamical times.
Atomic and Molecular Gas in M17 SW
Authors: Pérez-Beaupuits J. P. , Stutzki J. , Güsten R. , Ossenkopf V. , Wiesemeyer H. 
Published: March 2013

AbstractWe probe the spatial distribution of the [C ii] μm fine-structure emission and its association with neutral and molecular gas in a 5′.7 × 3′.7 (∼3.3 × 2.1 pc2) region of the M17 SW nebula. Comparison of velocity-resolved [C ii] emission maps with other atomic and molecular tracers is possible for the first time with the dual band receiver GREAT on board the SOFIA airborne telescope. We detected [C ii] emission in a much broader velocity range than the CO-lines (Pérez-Beaupuits et al. 2012). Only [C ii] narrow channel maps at intermediate velocities (between 10 and 24 kms) show correlations with other molecular gas components, supporting a clumpy cloud scenario. At lower (< 10 kms) and higher (>24 kms) velocities instead, we see more than 60% of the region mapped in [C ii] that is not associated with other tracers of star-forming material, the so called “CO-dark” gas. Interaction with winds and outflows lead to substantial excitation of [C ii] emitting gas, so that ablation and shock-interaction have to be taken into account to model the observed [C ii] emission.
High-resolution Ammonia Mapping of the Protostellar Core Cha-MMS1
Authors: Väisälä Miikka , Harju Jorma , Mantere Maarit , Miettinen Oskari , Walmsley Malcolm 
Published: March 2013

AbstractThe nearby protostellar core Cha-MMS1 has been mapped in the NH3 (1, 1) line and the 1.2 cm continuum using the Australia Telescope Compact Array, ATCA. In addition, observations from Spitzer Space Telescope and Herschel Space Observatory are used to help the interpretation. An elongated condensation with a maximum length of 9000 AU is seen in ammonia. The condensation has a clear velocity gradient directed perpendicularly to the axis of elongation. The gradient can be interpreted as rotation around this axis. We suggest that the observed ammonia structure delineates a rotating envelope and dense gas entrained by a very young protostellar outflow.
Possible triggered star formation associated with SNR G59.5+0.1
Authors: Xu Jin-Long , Wang Jun-Jie 
Published: March 2013

AbstractWe perform the submillimeter/millimeter observations in CO lines toward the southeast of SNR G59.5+0.1 with the KOSMA 3m-Telescope, which fully covers the open cluster NGC 6823. Three molecular clumps are identified in the CO molecular arc, each clump show outflow in motion. The age of the SNR is 8.6×104 yr. The number of selected YSOs are significantly enhanced in the interacting regions, indicating the presence of some recently formed stars.
YSOs in Taurus-Auriga-Perseus and Orion
Authors: Zahorecz Sarolta , Tóth L. Viktor , Marton Gábor , Onishi Toshikazu , Balázs Lajos G. , Fehér Orsolya , Kawamura Akiko , Kitamura Yoshimi , Lisztes Mónika , Nishimura Atsushi , Pásztor László , Pintér Sándor , Rácz István , Tamura Motohide , Sese Rogel M.D. , Ueno Munetaka 
Published: March 2013

AbstractPhysical parameters were derived for 100 young stellar objects in the TAPO region.
Triggered Star Formation from Bubbles S51, N68, and N131
Authors: Zhang C. P. , Wang J. J. 
Published: March 2013

AbstractWe investigated the environment of the infrared dust bubbles S51 (Zhang & Wang 2012a), N68 (Zhang & Wang 2012b), and N131 (Zhang et al. 2012) from catalogue of Churchwell et al. (2006), and searched for evidence of triggered star formation.
Massive Star Formation: Radiation Transfer Modeling and Multiwavelength Observation
Authors: Zhang Yichen , Tan Jonathan , McKee Chris , De Buizer James 
Published: March 2013

AbstractWe present a radiation transfer model consistently developed for a core in high pressure environment forming a massive star through core accretion. We compare this model to the massive protostar G35.2-0.74N, including SOFIA observations at 30 and 40μm. Good agreement is achieved, showing that a ~30M⊙ protostar is forming from a high surface density core via relatively ordered collapse and accretion, driving powerful outflows. This result supports the Core Accretion theory which predicts that massive stars form similarly to low-mass stars.
A Molecular Line Survey of CRL 2688 at 1 mm and 3 mm Wavelengths
Authors: Zhang Yong , Kwok Sun , Nakashima Jun-ichi , Trung Dinh-V 
Published: March 2013

AbstractIt is well established that circumstellar envelopes (CSEs) around evolved stars are active sites of molecular synthesis, and CSEs are one of the major sources of chemical enrichment in the interstellar space. The investigation of molecular compositions in CSEs is essential to understand the chemical evolution of the Galaxy. In order to study circumstellar chemistry in different environments, we have been systematically performing molecular line surveys of a sample of evolved stars from asymptotic giant branch (AGB) stars, proto-planetary nebulae (PPNs), to planetary nebulae (PNs). The dynamical time scales in different evolutionary stages can impose a time limit on the reaction time scales. Here we report our results for CRL 2688.
Modes of star formation from Herschel
Authors: Testi L. , Bressert E. , Longmore S. 
Published: March 2013

AbstractWe summarize some of the results obtained from Herschel surveys of nearby star forming regions and the Galactic plane. We show that in the nearby star forming regions the starless core spatial surface density distribution is very similar to that of the young stellar objects. This, taken together with the similarity between the core mass function and the initial mass function for stars and the relationship between the amount of dense gas and star formation rate, suggest that the cloud fragmentation process defines the global outcome of star formation. This “simple” view of star formation may not hold on all scales. In particular dynamical interactions are expected to become important at the conditions required to form young massive clusters. We describe the successes of a simple criterion to identify young massive cluster precursors in our Galaxy based on (sub-)millimeter wide area surveys. We further show that in the location of our Galaxy where the best candidate for a precursor of a young massive cluster is found, the “simple” scaling relationship between dense gas and star formation rate appear to break down. We suggest that in regions where the conditions approach those of the central molecular zone of our Galaxy it may be necessary to revise the scaling laws for star formation.
The origin and evolution of dense regions in the ISM, and their role in spectral features
Authors: Falceta-Gonçalves Diego 
Published: March 2013

AbstractIn this work we discuss the turbulent evolution of molecular clouds and the formation of dense structures within. Typically, the clumps evolution occurs apart from the secular evolution of the turbulent mother cloud due to its high density and large inertia. Despite of current theoretical assumptions we show, by means of numerical simulations, that the clump lifetimes are greater than previously thought by more than an order of magnitude. The presence of dense and long-lived clumps modifies the spectral line profiles of clouds, which are strongly related to the determination of Larson's relations. We address the main modifications of these if a realistic distribution of dense structures is taken into account.
Similarity and randomness in the molecular clouds associated with Spitzer GLIMPSE Extended Green Objects (EGOs)
Authors: He J. H. , Takahashi S. , Chen X. 
Published: March 2013

AbstractEGOs are candidates of massive star forming regions that show signatures of outflows. A 1.1mm line survey has been performed to 89 EGOs using the AROSMT. Our high detection rates of H13CO+ 3-2 and SiO 6-5 lines support EGOs to be dense clouds harboring outflows.Ubiquitous line luminosity linear correlations are found among different kinds of tracer lines: dense gas tracer H13CO+ 3-2, outflow tracer SiO 6-5, mixed dense gas and outflow tracers SO3Σ 65 − 54 and CH3OH lines, and relatively lower density gas tracers 12CO, 13CO, C18O 1-0 (see an example in Fig. 1). This can be explained if a universal similarity of density and thermal structures and probably of shock properties among all these EGO clouds are assumed. Furthermore, the outflow shocks are also required to be produced mainly inside of the natal clouds of the YSOs.The data scatter of the luminosity (and line width) correlations show a clear trend of worsening across larger cloud substructure size scales or toward larger cloud sizes, which demonstrates the growth of randomness in cloud structures and velocity fields. See more details in our paper (He et al. 2012).
First Census of Galactic Molecular Clouds
Authors: Hojaev Alisher S. , Kovaleva Anna A. , Alimova Nigina R. 
Published: March 2013

AbstractThe first attempt at a census of all molecular clouds (MoC) in the Milky Way observed to date is presented. The catalog of MoC includes all observed and estimated physical parameters. The data will be used to compute a model of the MoC system in the Galaxy.
Herschel Galactic Cold Cloud Core Analysis
Authors: Verebelyi Erika , Pagani Laurent 
Published: March 2013

AbstractWe have compiled a sample of 106 lesser-known cores from the Herschel Galactic Cold Cloud Cores Key Program (Juvela, M. et al. 2007). Based on the assumption, that these represent the crowd of the cold cores in the galaxy well, we have started a deep individual investigation, beginning with a ground-based follow-up and molecular line measurement at IRAM 30m telescope. We present the methods and calculated values of the most important parameters on a selected source: the G130.38+11.25 molecular cloud, which is part of the L1340.
Molecular gas and dust in spiral galaxies
Authors: Wilson Christine D. 
Published: March 2013

AbstractSeveral recent surveys (HERACLES, NGLS, KINGFISH, VNGS) have provided us with sensitive high-resolution observations of the molecular gas and dust content in spiral galaxies within 25 Mpc. I review recent results on the molecular gas content and its relation to star formation, as well as on the gas to dust ratio and the dust heating in spiral galaxies. I also present new results on the effect of environment on the molecular gas content of spiral galaxies.
Results of the IRAM M33 Large Program
Authors: Braine Jonathan , Schuster Karl , Gratier Pierre , Druard Clément 
Published: March 2013

AbstractA very sensitive survey of the CO(2−1) emission of the entire disk of the Local Group galaxy M 33 is virtually complete. Hundreds of clouds down to a mass of 10000M⊙ are detected and we show that the cloud mass function (assuming a constant ratio between CO emission and H2 mass) steepens away from the center of M 33. Through comparison with dust emission and cloud Virial masses, we estimate a N(H2)/ICO factor roughly twice Galactic.
Clues from star-formation histories - does the formation scenario of S0 galaxies depend on their luminosities?
Authors: Barway Sudhanshu , Wadadekar Yogesh , Vaghmare Kaustubh , Kembhavi Ajit 
Published: March 2013

AbstractLenticular (S0) galaxies are a morphological transition class between ellipticals and early-type spirals. Recent studies indicate that the formation scenario for lenticular galaxies depends on their near-IR luminosity (Barway et al. 2007;2009;2011). Low-luminosity lenticular galaxies likely formed by the stripping of gas from the disc of late-type spiral galaxies, which in turn formed their pseudo bulges through secular evolution processes, possibly involving multiple episodes of star formation. On the other hand, more luminous lenticulars likely formed at early epochs through a rapid collapse followed by rapid star formation, similar to the formation process of elliptical galaxies, and are characterized by a old coeval stellar population in the bulge. To investigate the imprint of these distinct formation scenarios on stellar populations, we combine GALEX/SDSS/2MASS photometry to construct color-color diagrams for a carefully defined sample of ~400 lenticular galaxies. We divide the sample into bright and faint groups as suggested by Barway et al. (2007). We find the (FUV-NUV) versus (NUV-K) color-color diagram shows larger scatter for faint lenticular galaxies while bright lenticular galaxies show a much tighter relation similar to that of ellipticals. Simple Stellar Population (SSP) analysis shows that ellipticals and bright lenticulars are dominated by a stellar population of age >109 years while faint lenticular galaxies are as young as 108 years, providing evidence for relatively recent star formation activity. Further, if we use the (NUV-r) < 5.4 color criterion to identify galaxies with recent (within 500 Myr) star formation, most faint lenticular galaxies fall into this category; bright lenticulars are mostly quiescent. Most faint lenticular galaxies generally have lower velocity dispersions. If we consider velocity as a virial mass indicator, majority of faint, recently star forming, lenticular galaxies have low virial masses compared to brighter lenticular galaxies. Such systematic differences in star formation history between bright and faint lenticular galaxies are consistent with the expectations from the luminosity dependent formation scenario described above.
Stellar Population Analysis on a Large Sample of Low Surface Brightness Galaxies
Authors: Chen Xiaoyan , Luo Ali , Liang Yanchun 
Published: March 2013

AbstractWe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.