Science.gov

Sample records for active star-forming region

  1. Sejong Open Cluster Survey (SOS) - V. The Active Star Forming Region SH 2-255-257

    NASA Astrophysics Data System (ADS)

    Lim, Beomdu; Sung, Hwankyung; Hur, Hyeonoh; Lee, Byeong-Cheol; Bessell, Michael S.; Kim, Jinyoung S.; Lee, Kang Hwan; Park, Byeong-Gon; Jeong, Gwanghui

    2015-12-01

    There is much observational evidence that active star formation is taking place in the H II regions Sh 2-255-257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B-V) = 0.8 mag, and the reddening law toward the region is normal (R_V = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J-H) color-magnitude diagram. The slope of the IMF is about Γ = -1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169 M_{⊙}). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.

  2. Carbon Dioxide in Star-forming Regions.

    PubMed

    Charnley; Kaufman

    2000-02-01

    We consider the gas-phase chemistry of CO2 molecules in active regions. We show that CO2 molecules evaporated from dust in hot cores cannot be efficiently destroyed and are in fact copiously produced in cooler gas. When CO2-rich ices are sputtered in strong MHD shock waves, the increase in atomic hydrogen, due to H2 dissociation by ion-neutral streaming, means that CO2 can be depleted by factors of approximately 500 from its injected abundance. We find that a critical shock speed exists at higher preshock densities below which CO2 molecules can be efficiently sputtered but survive in the postshock gas. These calculations offer an explanation for the low gas/solid CO2 ratios detected by the Infrared Space Observatory in star-forming cores as being due to shock destruction followed by partial reformation in warm gas. The presence of high abundances of CO2 in the strongly shocked Galactic center clouds Sgr B2 and Sgr A also find a tentative explanation in this scenario. Shock activity plays an important role in determining the chemistry of star-forming regions, and we suggest that most hot cores are in fact shocked cores.

  3. Multiline Study of Galactic Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Mookerjea, B.; Kramer, C.; Jakob, H.; Stutzki, J.

    We present first results of observations with SMART at KOSMA of selected Galactic star forming regions in mid-J (4-3) and (7-6) rotational transitions of CO and the two fine structure transitions of C I at 492 and 810 GHz. The aim of this study is to understand the interplay of the physical and chemical structure of the interstellar matter and the UV radiation field from the stars within the molecular clouds by observing the Photon Dominated Regions (PDRs). During this ongoing observational programme, regions around Orion BN/KL, W3, S106, S140 have been observed. Here we present the first results of observations of the W3 region (Jakob et al. 2002). These observations will be combined with existing observations of the emission due to low-J transitions of CO and other tracers of PDRs. The database of intensities of different lines from each of these regions will be used to derive a self-consistent interpretation using the PDR model developed by Störzer, Stutzki, & Sternberg (1996).

  4. Star-forming Activity in the H II Regions Associated with the IRAS 17160–3707 Complex

    NASA Astrophysics Data System (ADS)

    Nandakumar, G.; Veena, V. S.; Vig, S.; Tej, A.; Ghosh, S. K.; Ojha, D. K.

    2016-11-01

    We present a multiwavelength investigation of star formation activity toward the southern H ii regions associated with IRAS 17160–3707, located at a distance of 6.2 kpc with a bolometric luminosity of 8.3 × 105 L ⊙. The ionized gas distribution and dust clumps in the parental molecular cloud are examined in detail using measurements at infrared, submillimeter and radio wavelengths. The radio continuum images at 1280 and 610 MHz obtained using the Giant Metrewave Radio Telescope reveal the presence of multiple compact sources as well as nebulous emission. At submillimeter wavelengths, we identify seven dust clumps and estimate their physical properties such as temperature: 24–30 K, mass: 300–4800 M ⊙ and luminosity: 9–317 × 102 L ⊙ using modified blackbody fits to the spectral energy distributions (SEDs) between 70 and 870 μm. We find 24 young stellar objects (YSOs) in the mid-infrared, with a few of them coincident with the compact radio sources. The SEDs of the YSOs have been fitted by the Robitaille models and the results indicate that those having radio compact sources as counterparts host massive objects in early evolutionary stages with best fit age ≤0.2 Myr. We compare the relative evolutionary stages of clumps using various signposts such as masers, ionized gas, presence of YSOs and infrared nebulosity, and find six massive star-forming clumps and one quiescent clump. Of the former, five are in a relatively advanced stage and one in an earlier stage.

  5. [Molecular spectral diagnosis of star forming regions].

    PubMed

    Xi, S; Qin, S; Deng, L; Yang, J

    2001-08-01

    Stars are the basic building blocks of our universe, therefore it is one of the most important research topics in astrophysics to understand the origin and the early evolution of these objects. The current picture is that stars are formed during the collapse of a large enough self-gravitating interstellar molecular cloud. The early collapse gives birth to a fetus of a star, which is surrounded by a rotating accretion disk. The proto-star accretes interstellar matter through the disk which in turn transfer the accumulated matter to the central proto-star, then the star gets weight during the process. Observation shows that gorgeous ejection of matter always come along with the accretion process. In the presence of disks, these outflows usually escape from the system along the axis of the disk, forming so called bipolar outflows. Typical tracers of these activities are rich molecules such as CO, SiC2, C3H, C3H2 etc. Observationally, such typical molecular outflows can be detected using Doppler effect by spectroscopic measurements. Using the 13.7 m radio telescope in Delingha station of Purple Mountain Observatory, we performed a survey for 12 low temperature IRAS objects, some of the sources show high velocity properties. Detailed analysis of the Doppler profiles of IRS34 is presented. Star forming activities are clearly seen in this field. PMID:12945260

  6. Extreme Variables in Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Contreras Peña, Carlos Eduardo

    2015-01-01

    in two multi-epoch infrared surveys: the UKIDSS Galactic Plane Survey (GPS) and the Vista Variables in the Via Lactea (VVV). In order to further investigate the nature of the selected variable stars, we use photometric information arising from public surveys at near- to far-infrared wavelengths. In addition we have performed spectroscopic and photometric follow-up for a large subset of the samples arising from GPS and VVV. We analyse the widely separated two-epoch K-band photometry in the 5th, 7th and 8th data releases of the UKIDSS Galactic Plane Survey. We find 71 stars with ΔK > 1 mag, including 2 previously known OH/IR stars and a Nova. Even though the mid-plane is mostly excluded from the dataset, we find the majority (66%) of our sample to be within known star forming regions (SFRs), with two large concentrations in the Serpens OB2 association (11 stars) and the Cygnus-X complex (27 stars). The analysis of the multi-epoch K-band photometry of 2010-2012 data from VVV covering the Galactic disc at |b| < 1° yields 816 high amplitude variables, which include known variables of different classes such as high mass X-ray binaries, Novae and eclipsing binaries among others. Remarkably, 65% of the sample are found concentrated towards areas of star formation, similar to the results from GPS. In both surveys, sources in SFRs show spectral energy distributions (SEDs) that support classification as YSOs. This indicates that YSOs dominate the Galactic population of high amplitude infrared variable stars at low luminosities and therefore likely dominate the total high amplitude population. Spectroscopic follow-up allows us to confirm the pre-main sequence nature of several GPS and VVV Objects. Most objects in both samples show spectroscopic signatures that can be attributed to YSOs undergoing high states of accretion, such as veiling of photospheric features and CO emission, or show FUor-like spectra. We also find a large fraction of objects with 2.12 μm H2 emission that

  7. Disk Evaporation in Star Forming Regions

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Young stars produce sufficient ultraviolet photon luminosity and mechanical luminosity in their winds to significantly affect the structure and evolution of the accretion disks surrounding them. The Lyman continuum photons create a nearly static, ionized, isothermal 10(exp 4) K atmosphere forms above the neutral disk at small distances from the star. Further out, they create a photoevaporative flow which relatively rapidly destroys the disk. The resulting slow (10-50 km/s) ionized outflow, which persists for approx. greater than 10(exp 5) years for disk masses M(sub d) approx. 0.3M(sub *), may explain the observational characteristics of many ultracompact HII regions. We compare model results to the observed radio free-free spectra and luminosities of ultracompact HII regions and to the interesting source MWC349, which is observed to produce hydrogen masers. We apply the results to Ae and Be stars in order to determine the lifetimes of disks around such stars. We also apply the results to the early solar nebula to explain the the dispersal of the solar nebula and the differences in hydrogen content in the giant planets. Finally, we model the small bright objects ("proplyds") observed in the Orion Nebula as disks around young, low mass stars which are externally illuminated by the UV photons from the nearby massive star Theta(sup 1) C.

  8. Chemistry of star-forming regions.

    PubMed

    Herbst, Eric

    2005-05-12

    The space between stars is not empty but contains gas-phase and particulate matter under varying conditions. Neutral matter is found mainly in large regions of the interstellar medium known as "clouds", the largest of which, termed "giant molecular clouds", are essentially molecular in nature. Stars and planetary systems form inside these giant clouds when portions collapse and heat up. The details of the collapse can be followed by observation of the chemical changes in the molecular composition of the gas and dust particles. Moreover, an understanding of the chemical processes yields much information on the time scales and histories of the assorted stages. Among the most recent additions to our chemical knowledge of star formation are a deeper understanding of isotopic fractionation, especially involving deuterium, and a realization that the role of neutral-neutral reactions is more salient than once thought possible.

  9. Chemical evolution of star-forming regions.

    PubMed

    van Dishoeck, E F; Blake, G A

    1998-01-01

    Recent advances in the understanding of the chemical processes that occur during all stages of the formation of stars, from the collapse of molecular clouds to the assemblage of icy planetesimals in protoplanetary accretion disks, are reviewed. Observational studies of the circumstellar material within 100-10,000 AU of the young star with (sub)millimeter single-dish telescopes, millimeter interferometers, and ground-based as well as space-borne infrared observatories have only become possible within the past few years. Results are compared with detailed chemical models that emphasize the coupling of gas-phase and grain-surface chemistry. Molecules that are particularly sensitive to different routes of formation and that may be useful in distinguishing between a variety of environments and histories are outlined. In the cold, low-density prestellar cores, radicals and long unsaturated carbon chains are enhanced. During the cold collapse phase, most species freeze out onto the grains in the high-density inner region. Once young stars ignite, their surroundings are heated through radiation and/or shocks, whereupon new chemical characteristics appear. Evaporation of ices drives a ''hot core'' chemistry rich in organic molecules, whereas shocks propagating through the dense envelope release both refractory and volatile grain material, resulting in prominent SiO, OH, and H2O emission. The role of future instrumentation in further developing these chemical and temporal diagnostics is discussed.

  10. Disc accretion in star forming regions

    NASA Astrophysics Data System (ADS)

    Kalari, V. M.

    2015-05-01

    In this thesis, I present new ultraviolet/optical/infrared photometric and spectroscopic observations of pre-main sequence stars that have formed in either metal-poor conditions, or in the vicinity of strong ionising radiation. This includes observations of 235 Classical T Tauri stars in the Lagoon Nebula; 63 Classical T Tauri/Herbig Ae stars in the Carina Nebula open cluster Trumpler 14; 24 intermediate mass T Tauri stars in the low-Z Sh 2-284 SFR; and one Herbig B[e] PMS candidate in the metal-poor 30 Doradus SFR. I measure the accretion rates of these PMS stars using the intensities of the U/Hα band excess measured through either optical spectra or imaging. Where possible, I use archive infrared photometry in the 1.2-8 micron wavelength range to measure the PMS disc evolutionary stage. The influence of the surrounding environment on the accretion rate evolution of pre-main sequence stars in these regions is explored using the spatial, and temporal distributions of accretion rate, mass, age and disc stage of PMS stars.

  11. NUCLEAR ACTIVITY IS MORE PREVALENT IN STAR-FORMING GALAXIES

    SciTech Connect

    Rosario, D. J.; Lutz, D.; Berta, S.; Popesso, P.; Genzel, R.; Saintonge, A.; Tacconi, L.; Wuyts, S. E-mail: lutz@mpe.mpg.de E-mail: popesso@mpe.mpg.de E-mail: amelie@mpe.mpg.de E-mail: swuyts@mpe.mpg.de; and others

    2013-07-01

    We explore the question of whether low and moderate luminosity active galactic nuclei (AGNs) are preferentially found in galaxies that are undergoing a transition from active star formation (SF) to quiescence. This notion has been suggested by studies of the UV-optical colors of AGN hosts, which find them to be common among galaxies in the so-called Green Valley, a region of galaxy color space believed to be composed mostly of galaxies undergoing SF quenching. Combining the deepest current X-ray and Herschel/PACS far-infrared (FIR) observations of the two Chandra Deep Fields with redshifts, stellar masses, and rest-frame photometry derived from the extensive and uniform multi-wavelength data in these fields, we compare the rest-frame U - V color distributions and star formation rate distributions of AGNs and carefully constructed samples of inactive control galaxies. The UV-to-optical colors of AGNs are consistent with equally massive inactive galaxies at redshifts out to z {approx} 2, but we show that such colors are poor tracers of SF. While the FIR distributions of both star-forming AGNs and star-forming inactive galaxies are statistically similar, we show that AGNs are preferentially found in star-forming host galaxies, or, in other words, AGNs are less likely to be found in weakly star-forming or quenched galaxies. We postulate that, among X-ray-selected AGNs of low and moderate accretion luminosities, the supply of cold gas primarily determines the accretion rate distribution of the nuclear black holes.

  12. A kinematic study of the Lupus star-forming region

    NASA Astrophysics Data System (ADS)

    Galli, P. A. B.; Bertout, C.; Teixeira, R.; Ducourant, C.

    2014-10-01

    In this paper, we study the southern star-forming region located in Lupus that constitutes one of the richest associations of T Tauri stars. Based on the convergent point (CP) method combined with a k-NN analysis we identify 109 pre-main sequence stars in this region that define the Lupus association of comoving stars, and derive individual distances for all group members.

  13. Intermediate-Mass Star-Forming Regions: What are the Most Massive Stars Formed?

    NASA Astrophysics Data System (ADS)

    Kobulnicky, Chip; Vargas, Carlos; Kerton, Charles; Arvidsson, Kim

    2010-08-01

    High-mass star formation cannot be viewed as simply a scaled-up version of the paradigm for low-mass star formation. The high-mass regime (M> 10 Msun) appears to require significant differences in cloud fragmentation, accretion, radiation, turbulence, and overall molecular density compared to the low-mass regime. We have identified a sample of intermediate-mass star-forming regions (IM SFRs) hosting embedded clusters that straddle the boundary of these two regimes and can be used to understand the factors that govern the transition between these extremes. Most notable among these factors is the possibility of a critical cloud mass column density that appears to divide high-mass SFRs from IM SFRs. Yet, the very nature of IM SFRs and their stellar content are almost completely unknown, primarily because of the previous difficulty in identifying such objects. We propose HK band spectroscopy of the brightest stellar sources near nine IM SFRs to identify probable members, confirm the IM nature of the most massive stars, and characterize their evolutionary state. Three nights with FLAMINGOS on the 4 m (or equivalent IR spectrograph) will suffice to obtain classification spectra and several spectral diagnostics sensitive to accretion for at least 8-10 stars per object.

  14. New Molecular Views of Southern Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Fukui, Y.

    1999-10-01

    I will present new molecular views of southern sky based on the CO survey for star forming regions conducted by Nagoya University with the NANTEN 4-m millimeter wave telescope. The NANTEN telescope is installed at the Las Campanas Observatory in Chile under a mutual agreement between Nagoya University and the Carnegie Institution of Washington. Through the survey, molecular gas distribution and the physical properties of cluster forming regions in the Magellanic Clouds, Galactic star forming GMCs, dark clouds, high latitude clouds, and interacting clouds with HII regions and/or SNRs are studied at a beam size of 2.'7 in the 12CO, 13CO, and C18O (J=1-0) molecular emission. I will review the expected contribution of the southern CO survey to the ALMA project, and discuss the scientific targets related with star formation at the time the ALMA becomes available.

  15. Accurate positions of SiO masers in active star-forming regions - Orion-KL, W51-IRS2, and Sagittarius-B2 MD5

    NASA Astrophysics Data System (ADS)

    Morita, Koh-Ichiro; Hasegawa, Tetsuo; Ukita, Nobuharu; Okumura, Sachiko K.; Ishiguro, Masato

    1992-08-01

    Accurate positional measurements of SiO J = 1-0 masers in active star-forming regions, Orion-KL, W51-IRS2, and Sgr-B2 MD5, were made with the Nobeyama Millimeter Array. Absolute positional accuracies of 0.12-0.6 arcsec were achieved. The SiO maser in W51-IRS2 is located within 0.4 arcsec (0.5 x 10 exp 17 cm at the distance of W51-IRS2) of the strongest H2O masers. In Sgr-B2 MD5, the SiO maser coincides with the strongest H2O masers, most of the strong OH masers, and the peak of radio continuum emission from the ultracompact H II region within 0.7 arcsec (0.8 x 10 exp 17 cm at the distance of Sgr-B2). Peaks of the emission from hot NH3 were found to exist within about 1 arcsec of the SiO masers in both regions. The precise positional coincidence confirms our former conclusion that the SiO masers in W51-IRS2 and Sgr-B2 MD5 are actually associated with the ongoing activity of star formation, as is the case of Orion-KL.

  16. Abundances of hydrogen sulfide in star-forming regions.

    PubMed

    Minh, Y C; Ziurys, L M; Irvine, W M; McGonagle, D

    1991-01-01

    Interstellar hydrogen sulfide (H2S) and its isotopic variant H2 34S have been observed toward several star-forming regions via their 1(10)-1(01) transitions at 2 mm, using the FCRAO telescope. In sources where both isotopic species H2S and H2 34S were observed, column densities of approximately 10(16) cm-2 were measured. Column density lower limits of approximately 10(14) cm-2 for H2S were found for other sources, where only the main isotopic line was observed. The fractional abundances of H2S relative to molecular hydrogen appear to be enhanced by at least an order of magnitude relative to quiescent cloud values (approximately 10(-9)) for many of the observed sources. Such enhancement toward star-forming clouds suggests that some process involving elevated temperature aids in producing this species; this could be gas-phase reactions, grain-related processes, or both.

  17. The Eagle Nebula: a spectral template for star forming regions

    NASA Astrophysics Data System (ADS)

    Flagey, Nicolas; Boulanger, Francois; Carey, Sean; Compiegne, Mathieu; Dwek, Eli; Habart, Emilie; Indebetouw, Remy; Montmerle, Thierry; Noriega-Crespo, Alberto

    2008-03-01

    IRAC and MIPS have revealed spectacular images of massive star forming regions in the Galaxy. These vivid illustrations of the interaction between the stars, through their winds and radiation, and their environment, made of gas and dust, still needs to be explained. The large scale picture of layered shells of gas components, is affected by the small scale interaction of stars with the clumpy medium that surrounds them. To understand spatial variations of physical conditions and dust properties on small scales, spectroscopic imaging observations are required on a nearby object. The iconic Eagle Nebula (M16) is one of the nearest and most observed star forming region of our Galaxy and as such, is a well suited template to obtain this missing data set. We thus propose a complete spectral map of the Eagle Nebula (M16) with the IRS/Long Low module (15-38 microns) and MIPS/SED mode (55-95 microns). Analysis of the dust emission, spectral features and continuum, and of the H2 and fine-structure gas lines within our models will provide us with constraints on the physical conditions (gas ionization state, pressure, radiation field) and dust properties (temperature, size distribution) at each position within the nebula. Only such a spatially and spectrally complete map will allow us to characterize small scale structure and dust evolution within the global context and understand the impact of small scale structure on the evolution of dusty star forming regions. This project takes advantage of the unique ability of IRS at obtaining sensitive spectral maps covering large areas.

  18. Astronomers Discover New Star-Forming Regions in Milky Way

    NASA Astrophysics Data System (ADS)

    2010-05-01

    Astronomers studying the Milky Way have discovered a large number of previously-unknown regions where massive stars are being formed. Their discovery provides important new information about the structure of our home Galaxy and promises to yield new clues about the chemical composition of the Galaxy. "We can clearly relate the locations of these star-forming sites to the overall structure of the Galaxy. Further studies will allow us to better understand the process of star formation and to compare the chemical composition of such sites at widely different distances from the Galaxy's center," said Thomas Bania, of Boston University. Bania worked with Loren Anderson of the Astrophysical Laboratory of Marseille in France, Dana Balser of the National Radio Astronomy Observatory (NRAO), and Robert Rood of the University of Virginia. The scientists presented their findings to the American Astronomical Society's meeting in Miami, Florida. The star-forming regions the astronomers sought, called H II regions, are sites where hydrogen atoms are ionized, or stripped of their electrons, by the intense radiation of the massive, young stars. To find these regions hidden from visible-light detection by the Milky Way's gas and dust, the researchers used infrared and radio telescopes. "We found our targets by using the results of infrared surveys done with NASA's Spitzer Space Telescope and of surveys done with the National Science Foundation's (NSF) Very Large Array (VLA) radio telescope," Anderson said. "Objects that appear bright in both the Spitzer and VLA images we studied are good candidates for H II regions," he explained. The astronomers then used the NSF's giant Robert C. Byrd Green Bank Telescope (GBT) in West Virginia, an extremely sensitive radio telescope. With the GBT, they were able to detect specific radio frequencies emitted by electrons as they recombined with protons to form hydrogen. This evidence of recombination confirmed that the regions contained ionized

  19. Chemical Herschel Surveys of Star Forming Regions (chess)

    NASA Astrophysics Data System (ADS)

    Emprechtinger, Martin

    2011-06-01

    CHESS is an unbiased line survey of low-, intermediate-, and high-mass star forming regions at different stages of their evolution. The eight sources in the CHESS program are observed with the HIFI instrument on board of the Herschel Space Telescope, which provides a high spectral resolution (R˜ 10^6) and covers a frequency range from 480 to 1910 GHz. The objective of CHESS is to study the chemical composition and physical conditions in star forming regions and their variation with mass and evolutionary stage. To date about 50% of the program have been completed. One of the eight objects in the CHESS program is the hot core NGC 6334 I. With an envelope mass of 200 M_⊙ and temperatures 100 K, NGC 6334 I is very line rich. In this object emission lines of more than 40 species have been identified, including first detections of H_2Cl^+ (Lis et al. 2010) and H_2O^+ (Ossenkopf et al. 2010). Furthermore, several lines of ortho and para water and ammonia have been detected, allowing to determine the ortho/para ratio of these crucial species. In addition many hydrides (HF, CH) and hydride ions (SH^+, OH^+, CH^+) have been found. In the low mass protostar IRAS 16293-2422, another source of our sample, several deuterated species, including the first detection of ND (Bacmann et al. 2010), were found. The data allowed also the first determination of the ortho/para ratio of D_2H^+ (>2.6) (Vastel et al. 2010). In this talk I will give a summary of the conducted observation and highlight the most important results.

  20. VLBA Helps Build New Picture of Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    2007-01-01

    New, high-precision distance measurements by the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope are providing a major advance for astronomers trying to understand how stars form. "A large improvement in measuring the distance to a young, still-forming star means a large improvement in measuring characteristics such as its mass and intrinsic brightness," said Laurent Loinard, of the National University of Mexico (UNAM). Loinard, Amy Mioduszewski of the National Radio Astronomy Observatory, UNAM graduate student Rosa Torres and UNAM professor Luis Rodriguez presented their findings to the American Astronomical Society's meeting in Seattle, Washington. Parallax Diagram Trigonometric Parallax method determines distance to star by measuring its slight shift in apparent position as seen from opposite ends of Earth's orbit. CREDIT: Bill Saxton, NRAO/AUI/NSF Image and Animation Files Parallax Diagram (above image, JPEG, 153K) Animation of apparant motion on sky of young star T Tauri S (MPEG, 891K) Still Frame from above animation (JPEG, 14K) B&W Plot of T Tauri S Parallax motion (JPEG, 51K) "Most of what we know about the processes of star formation has come from studying young stars in a few, relatively nearby regions," Loinard said. "However, estimates of the distance to these regions have been imprecise. That imprecision has limited the ability of real-world observations to improve theoretical models for star formation," he added. The new VLBA distance measurements are great improvements over earlier estimates. For example, earlier work placed a famous young stellar system in the constellation Taurus between 423 and 489 light-years from Earth. The new VLBA measurements narrow the range to 418-422 light-years. "Our observations brought the error in this measurement down from 66 light-years to four," Mioduszewski said. The new VLBA observations also refined the distance estimate to another star-forming region in the constellation Ophiuchus

  1. A STRUCTURAL ANALYSIS OF STAR-FORMING REGION AFGL 490

    SciTech Connect

    Masiunas, L. C.; Gutermuth, R. A.; Pipher, J. L.; Megeath, S. T.; Myers, P. C.; Kirk, H. M.; Fazio, G. G.; Allen, L. E.

    2012-06-20

    We present Spitzer IRAC and MIPS observations of the star-forming region containing intermediate-mass young stellar object (YSO) AFGL 490. We supplement these data with near-IR Two Micron All Sky Survey photometry and with deep Simultaneous Quad Infrared Imaging Device observations off the central high-extinction region. We have more than doubled the known membership of this region to 57 Class I and 303 Class II YSOs via the combined 1-24 {mu}m photometric catalog derived from these data. We construct and analyze the minimum spanning tree of their projected positions, isolating one locally overdense cluster core containing 219 YSOs (60.8% of the region's members). We find this cluster core to be larger yet less dense than similarly analyzed clusters. Although the structure of this cluster core appears irregular, we demonstrate that the parsec-scale surface densities of both YSOs and gas are correlated with a power-law slope of 2.8, as found for other similarly analyzed nearby molecular clouds. We also explore the mass segregation implications of AFGL 490's offset from the center of its core, finding that it has no apparent preferential central position relative to the low-mass members.

  2. Looking Closely at "Medusa": Star Forming Regions in NGC 4194

    NASA Technical Reports Server (NTRS)

    Weistrop, D.; Eggers, D.; Nelson, C. H.; Kaiser, M. E.

    2004-01-01

    The "Medusa" (NGC 4194, Mrk 201) is a blue compact galaxy, with strong far infrared and radio emission. Ground-based observations exhibit a distorted image with a tidal tail and regions of strong star formation. A population of massive O and early B stars is evident from the IUE spectra HST survey of Seyfert and starburst galaxies notes NCG 4194 is an HII galaxy with lumpy HII regions and knots. The central starburst is apparently produced by a galaxy merger. As part of an investigation of star formation in interacting galaxies, we have obtained ultraviolet and visible images of the central regions of NGC 4194 with the Space Telescope Imaging Spectrograph on HST. Imaging was obtained in two ultraviolet (FUV-MAMA+F25QTZ, NUV-MAMA+F25CN182) and one visible (CCD+F28X50LP) band. Individual star forming knots (at HST resolution) have been identified. We present sized and luminosities for the individual knots, and the knot luminosity function. We compare our data to current starburst models to constrain stellar ages and populations. Knot characteristics as a function of location in the galaxy will also be discussed.

  3. VLBA Changes Picture of Famous Star-Forming Region

    NASA Astrophysics Data System (ADS)

    2007-10-01

    Using the supersharp radio "vision" of the National Science Foundation's Very Long Baseline Array (VLBA), astronomers have made the most precise measurement ever of the distance to a famous star-forming region. The measurement -- to the heavily studied Orion Nebula -- changes scientists' understanding of the characteristics of the young stars in the region. Parallax Diagram Trigonometric Parallax method determines distance to star by measuring its slight shift in apparent position as seen from opposite ends of Earth's orbit. CREDIT: Bill Saxton, NRAO/AUI/NSF Star Track Apparent track of star GMR A in the Orion Nebula Cluster, showing shift caused by Earth's orbital motion and star's movement in space. CREDIT: Sandstrom et al., NRAO/AUI/NSF Click on Images for Larger Files "This measurement is four times more precise than previous distance estimates. Because our measurement reduces the distance to this region, it tells us that the stars there are less bright than thought before, and changes the estimates of their ages," said Geoff Bower, an astronomer at the University of California at Berkeley. Bower, along with Karin Sandstrom, J.E.G. Peek, Alberto Bolatto and Richard Plambeck, all of Berkeley, published their findings in the October 10 edition of the Astrophysical Journal. The scientists determined the distance to a star called GMR A, one of a cluster of stars in the Orion Nebula, by measuring the slight shift in the star's apparent position in the sky caused by the Earth's motion around the Sun. Observing the star when the Earth is on opposite sides of its annual orbit allows astronomers to measure the angle of this small shift and thus provides a direct trigonometric calculation of its distance. "By using this technique, called parallax, we get a direct measurement that does not depend on various assumptions that are required to use less-direct methods," Bower said. "Only a telescope with the remarkable ability to see fine detail that is provided by the VLBA is

  4. Dynamical evolution of star-forming regions - II. Basic kinematics

    NASA Astrophysics Data System (ADS)

    Parker, Richard J.; Wright, Nicholas J.

    2016-04-01

    We follow the dynamical evolution of young star-forming regions with a wide range of initial conditions and examine how the radial velocity dispersion, σ, evolves over time. We compare this velocity dispersion to the theoretically expected value for the velocity dispersion if a region were in virial equilibrium, σvir and thus assess the virial state (σ/σvir) of these systems. We find that in regions that are initially subvirial, or in global virial equilibrium but subvirial on local scales, the system relaxes to virial equilibrium within several million years, or roughly 25-50 crossing times, according to the measured virial ratio. However, the measured velocity dispersion, σ, appears to be a bad diagnostic of the current virial state of these systems as it suggests that they become supervirial when compared to the velocity dispersion estimated from the virial mass, σvir. We suggest that this discrepancy is caused by the fact that the regions are never fully relaxed, and that the early non-equilibrium evolution is imprinted in the one-dimensional velocity dispersion at these early epochs. If measured early enough (<2 Myr in our simulations, or ˜20 crossing times), the velocity dispersion can be used to determine whether a region was highly supervirial at birth without the risk of degeneracy. We show that combining σ, or the ratio of σ to the interquartile range (IQR) dispersion, with measures of spatial structure, places stronger constraints on the dynamical history of a region than using the velocity dispersion in isolation.

  5. Locating star-forming regions in quasar host galaxies

    NASA Astrophysics Data System (ADS)

    Young, J. E.; Eracleous, M.; Shemmer, O.; Netzer, H.; Gronwall, C.; Lutz, Dieter; Ciardullo, R.; Sturm, Eckhard

    2014-02-01

    We present a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope. Our observations are motivated by recent evidence for a close relationship between black hole growth and the stellar mass evolution in its host galaxy. We use narrow-band [O II]λ3727, Hβ, [O III]λ5007 and Paα images, taken with the Wide Field Planetary Camera 2 and NICMOS instruments, to map the morphology of line-emitting regions, and, after extinction corrections, diagnose the excitation mechanism and infer star-formation rates. Significant challenges in this type of work are the separation of the quasar light from the stellar continuum and the quasar-excited gas from the star-forming regions. To this end, we present a novel technique for image decomposition and subtraction of quasar light. Our primary result is the detection of extended line-emitting regions with sizes ranging from 0.5 to 5 kpc and distributed symmetrically around the nucleus, powered primarily by star formation. We determine star-formation rates of the order of a few tens of M⊙ yr-1. The host galaxies of our target quasars have stellar masses of the order of 1011 M⊙ and specific star-formation rates on a par with those of M82 and luminous infrared galaxies. As such they fall at the upper envelope or just above the star-formation mass sequence in the specific star formation versus stellar mass diagram. We see a clear trend of increasing star-formation rate with quasar luminosity, reinforcing the link between the growth of the stellar mass of the host and the black hole mass found by other authors.

  6. Star-forming region BBW 36 in puppis

    NASA Astrophysics Data System (ADS)

    Gyulbudahgian, A. L.; May, J.

    2008-07-01

    Recent studies of the star formation region BBW 36 and associated molecular clouds are presented. The 12CO (1-0) observations, carried out with the 15-m SEST (Swedish-ESO) telescope (Cerro La Silla, Chile), revealed the existence of cloud a, connected with BBW 36 and of cloud b, having elongation in SE-NW direction. A red-shifted molecular outflow with velocity ˜+5 km/s (with respect to cloud a), having a direction parallel to the line of sight, was also observed. VLA observations showed the presence of a source VLA 2 at 3.6 cm with an elongation in the N-S direction. It is suggested that the VLA 2 source coincides with a dust disc (surrounding the object BBW 36). The star 3, which is one of the YSOs in the star-forming region BBW 36 and is connected with a bright comma-like nebula, can be the source of the molecular outflow. The star 3 has very high IR colors and is associated with an IRAS point source IRAS 07280-1829, which has IR colors, typical for an IRAS point source, connected with a water maser. On the 2MASS K image of BBW 36 we can see the existence of a bright nebula; a group of stars is embedded in that nebula, and among these stars there are stars with dust discs (or envelopes). On the 2MASS K image several spiral jets are also present, some of them with a condensation at the end.

  7. Hydride Ions, HCO+ and Ionizing Irradiation in Star Forming Region

    NASA Astrophysics Data System (ADS)

    Benz, Arnold O.; Bruderer, Simon; van Dishoeck, Ewine

    2016-06-01

    Hydrides are fundamental precursor molecules in cosmic chemistry and many hydride ions have become observable in high quality for the first time thanks to the Herschel Space Observatory. Ionized hydrides, such as CH+ and OH+ and also HCO+ affect the chemistry of molecules such as water. They also provide complementary information on irradiation by far UV (FUV) or X-rays and gas temperature.We explore hydrides of the most abundant heavier elements in an observational survey covering star forming regions with different mass and evolutionary state. Twelve YSOs were observed with HIFI on Herschel in 6 spectral settings providing fully velocity-resolved line profiles. The YSOs include objects of low (Class 0 and I), intermediate, and high mass, with luminosities ranging from 4 Ls to 2 105 Ls.The targeted lines of CH+, OH+, H2O+, and C+ are detected mostly in blue-shifted absorption. H3O+ and SH+ are detected in emission and only toward some high-mass objects. For the low-mass YSOs the column density ratios of CH+/OH+ can be reproduced by simple chemical models implying an FUV flux of 2 - 400 times the ISRF at the location of the molecules. In two high-mass objects, the UV flux is 20 - 200 times the ISRF derived from absorption lines, and 300 - 600 ISRF using emission lines. Upper limits for the X-ray luminosity can be derived from H3O+ observations for some low-mass objects.If the FUV flux required for low-mass objects originates at the central protostar, a substantial FUV luminosity, up to 1.5 Ls, is required. For high-mass regions, the FUV flux required to produce the observed molecular ratios is smaller than the unattenuated flux expected from the central object(s) at the Herschel beam radius. This is consistent with an FUV flux reduced by circumstellar extinction or by bloating of the protostar.The ion molecules are proposed to form in FUV irradiated cavity walls that are shocked by the disk wind. The shock region is turbulent, broadening the lines to some 1 - 12 km

  8. Mapping Magnetic Fields in Star Forming Regions with BLASTPol

    NASA Astrophysics Data System (ADS)

    Fissel, Laura M.; Ade, Peter; Angilè, Francesco E.; Ashton, Peter; Benton, Steven J.; Devlin, Mark J.; Dober, Bradley; Fukui, Yasuo; Galitzki, Nicholas B.; Gandilo, Natalie; Klein, J. R.; Li, Zhi-Yun; Korotkov, Andrei; Martin, Peter G.; Matthews, Tristan; Moncelsi, Lorenzo; nakamura, fumitaka; Barth Netterfield, Calvin; Novak, Giles; Pascale, Enzo; Poidevin, Frédérick; Pereira Santos, Fábio; Savini, Giorgio; Scott, Douglas; Shariff, Jamil; Soler, Juan D.; Thomas, Nicholas; tucker, carole; Tucker, Gregory S.; Ward-Thompson, Derek

    2016-01-01

    A key outstanding question in our understanding of star formation is whether magnetic fields provide support against the gravitational collapse of their parent molecular clouds and cores. Direct measurement of magnetic field strength is observationally challenging, however observations of polarized thermal emission from dust grains aligned with respect to the local cloud magnetic field can be used to map out the magnetic field orientation in molecular clouds. Statistical comparisons between these submillimeter polarization maps and three-dimensional numerical simulations of magnetized star-forming clouds provide a promising method for constraining magnetic field strength. We present early results from a BLASTPol study of the nearby giant molecular cloud (GMC) Vela C, using data collected during a 2012 Antarctic flight. This sensitive balloon-borne polarimeter observed Vela C for 57 hours, yielding the most detailed submillimeter polarization map ever made of a GMC forming high mass stars. We find that most of the structure in p can be modeled by a power-law dependence on two quantities: the hydrogen column density and the local dispersion in magnetic field orientation. Our power-law model for p(N,S) provides new constraints for models of magnetized star-forming clouds and an important first step in the interpretation of the BLASTPol 2012 data set.

  9. HUBBLE'S PANORAMIC PORTRAIT OF A VAST STAR-FORMING REGION

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NASA's Hubble Space Telescope has snapped a panoramic portrait of a vast, sculpted landscape of gas and dust where thousands of stars are being born. This fertile star-forming region, called the 30 Doradus Nebula, has a sparkling stellar centerpiece: the most spectacular cluster of massive stars in our cosmic neighborhood of about 25 galaxies. The mosaic picture shows that ultraviolet radiation and high-speed material unleashed by the stars in the cluster, called R136 [the large blue blob left of center], are weaving a tapestry of creation and destruction, triggering the collapse of looming gas and dust clouds and forming pillar-like structures that are incubators for nascent stars. The photo offers an unprecedented, detailed view of the entire inner region of 30 Doradus, measuring 200 light-years wide by 150 light-years high. The nebula resides in the Large Magellanic Cloud (a satellite galaxy of the Milky Way), 170,000 light-years from Earth. Nebulas like 30 Doradus are the 'signposts' of recent star birth. High-energy ultraviolet radiation from the young, hot, massive stars in R136 causes the surrounding gaseous material to glow. Previous Hubble telescope observations showed that R136 contains several dozen of the most massive stars known, each about 100 times the mass of the Sun and about 10 times as hot. These stellar behemoths all formed at the same time about 2 million years ago. The stars in R136 are producing intense 'stellar winds' (streams of material traveling at several million miles an hour), which are wreaking havoc on the gas and dust in the surrounding neighborhood. The winds are pushing the gas away from the cluster and compressing the inner regions of the surrounding gas and dust clouds [the pinkish material]. The intense pressure is triggering the collapse of parts of the clouds, producing a new generation of star formation around the central cluster. The new stellar nursery is about 30 to 50 light-years from R136. Most of the stars in the

  10. A CO LINE AND INFRARED CONTINUUM STUDY OF THE ACTIVE STAR-FORMING COMPLEX W51

    SciTech Connect

    Kang, Miju; Lee, Youngung; Choi, Minho; Bieging, John H.; Kulesa, Craig A.; Peters, William L.

    2010-09-15

    We present the results of an extensive observational study of the active star-forming complex W51 that was observed in the J = 2 - 1 transition of the {sup 12}CO and {sup 13}CO molecules over a 1.{sup 0}25 x 1.{sup 0}00 region with the University of Arizona Heinrich Hertz Submillimeter Telescope. We use a statistical equilibrium code to estimate physical properties of the molecular gas. We compare the molecular cloud morphology with the distribution of infrared (IR) and radio continuum sources and find associations between molecular clouds and young stellar objects (YSOs) listed in Spitzer IR catalogs. The ratios of CO lines associated with H II regions are different from the ratios outside the active star-forming regions. We present evidence of star formation triggered by the expansion of the H II regions and by cloud-cloud collisions. We estimate that about 1% of the cloud mass is currently in YSOs.

  11. A CO Line and Infrared Continuum Study of the Active Star-forming Complex W51

    NASA Astrophysics Data System (ADS)

    Kang, Miju; Bieging, John H.; Kulesa, Craig A.; Lee, Youngung; Choi, Minho; Peters, William L.

    2010-09-01

    We present the results of an extensive observational study of the active star-forming complex W51 that was observed in the J = 2 - 1 transition of the 12CO and 13CO molecules over a 1fdg25 × 1fdg00 region with the University of Arizona Heinrich Hertz Submillimeter Telescope. We use a statistical equilibrium code to estimate physical properties of the molecular gas. We compare the molecular cloud morphology with the distribution of infrared (IR) and radio continuum sources and find associations between molecular clouds and young stellar objects (YSOs) listed in Spitzer IR catalogs. The ratios of CO lines associated with H II regions are different from the ratios outside the active star-forming regions. We present evidence of star formation triggered by the expansion of the H II regions and by cloud-cloud collisions. We estimate that about 1% of the cloud mass is currently in YSOs.

  12. The Connection Between Galaxy Environment and the Luminosity Function Slopes of Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Dale, Daniel A.; Lee, Janice C.; Thilker, David A.; Calzetti, Daniela; Kennicutt, Robert

    2016-06-01

    We present the first study of GALEX far ultra-violet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ~65,000 star-forming regions (i.e., FUV sources), measure each galaxy's luminosity function, and characterize the relationships between the luminosity function slope (α) and several global galaxy properties. A final sample of \

  13. Two New SiO Maser Sources in High-Mass Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Cho, Se-Hyung; Yun, Youngjoo; Kim, Jaeheon; Liu, Tie; Kim, Kee-Tae; Choi, Minho

    2016-08-01

    Silicon monoxide (SiO) masers are rare in star-forming regions, with the exception of five known SiO maser sources. However, we detected two new SiO maser sources from infrared-loud clumps of the high-mass star-forming regions G19.61‑0.23 and G75.78+0.34. High angular resolution observations toward G19.61‑0.23 suggest that the deeply embedded young stellar object (YSO) of SMA1 is powering the SiO masers. In addition, the SiO v = 1, J = 1 \\to 0 line shows four spike features, while the v = 2 maser shows combined features of one spike and broad wing components, implying energetic activities of the YSO of SMA1 in the G19.61‑0.23 hot molecular core. The SiO v = 0, J = 2 \\to 1 emission shows bipolar outflows in the NE–SW direction with respect to the center of the SiO maser source. A high angular resolution map of the SiO v = 1, J = 2 \\to 1 maser in G75.78+0.34 shows that the SiO maser is associated with the CORE source at the earliest stage of high-mass star formation. Therefore, the newly detected SiO masers and their associated outflows will provide good probes for investigating this early high-mass star formation.

  14. A new star-forming region in Canis Major

    NASA Astrophysics Data System (ADS)

    Magakian, T. Yu.; Movsessian, T. A.; Bally, J.

    2016-07-01

    A new southern star-formation region, located at an estimated distance of ˜1.5 kpc in the Lynds 1664 dark cloud in Canis Major, is described. Lynds 1664 contains several compact star clusters, small stellar groups and young stars associated with reflection nebulae. Narrow-band H α and [S II] images obtained with the 4-m telescope at the Cerro Tololo Inter-American Observatory reveal more than 20 new Herbig-Haro objects associated with several protostellar outflows.

  15. Cosmic-Ray Injection from Star-Forming Regions.

    PubMed

    Carlson, Eric; Profumo, Stefano; Linden, Tim

    2016-09-01

    At present, all physical models of diffuse Galactic γ-ray emission assume that the distribution of cosmic-ray sources traces the observed populations of either OB stars, pulsars, or supernova remnants. However, since H_{2}-rich regions host significant star formation and numerous supernova remnants, the morphology of observed H_{2} gas (as traced by CO line surveys) should also provide a physically motivated, high-resolution tracer for cosmic-ray injection. We assess the impact of utilizing H_{2} as a tracer for cosmic-ray injection on models of diffuse Galactic γ-ray emission. We employ state-of-the-art 3D particle diffusion and gas density models, along with a physical model for the star-formation rate based on global Schmidt laws. Allowing a fraction, f_{H_{2}}, of cosmic-ray sources to trace the observed H_{2} density, we find that a theoretically well-motivated value f_{H_{2}}∼0.20-0.25 (i) provides a significantly better global fit to the diffuse Galactic γ-ray sky and (ii) highly suppresses the intensity of the residual γ-ray emission from the Galactic center region. Specifically, in models utilizing our best global fit values of f_{H_{2}}∼0.20-0.25, the spectrum of the galactic center γ-ray excess is drastically affected, and the morphology of the excess becomes inconsistent with predictions for dark matter annihilation. PMID:27661675

  16. Cosmic-Ray Injection from Star-Forming Regions.

    PubMed

    Carlson, Eric; Profumo, Stefano; Linden, Tim

    2016-09-01

    At present, all physical models of diffuse Galactic γ-ray emission assume that the distribution of cosmic-ray sources traces the observed populations of either OB stars, pulsars, or supernova remnants. However, since H_{2}-rich regions host significant star formation and numerous supernova remnants, the morphology of observed H_{2} gas (as traced by CO line surveys) should also provide a physically motivated, high-resolution tracer for cosmic-ray injection. We assess the impact of utilizing H_{2} as a tracer for cosmic-ray injection on models of diffuse Galactic γ-ray emission. We employ state-of-the-art 3D particle diffusion and gas density models, along with a physical model for the star-formation rate based on global Schmidt laws. Allowing a fraction, f_{H_{2}}, of cosmic-ray sources to trace the observed H_{2} density, we find that a theoretically well-motivated value f_{H_{2}}∼0.20-0.25 (i) provides a significantly better global fit to the diffuse Galactic γ-ray sky and (ii) highly suppresses the intensity of the residual γ-ray emission from the Galactic center region. Specifically, in models utilizing our best global fit values of f_{H_{2}}∼0.20-0.25, the spectrum of the galactic center γ-ray excess is drastically affected, and the morphology of the excess becomes inconsistent with predictions for dark matter annihilation.

  17. Characterizing Warm Molecular Hydrogen in Active Star-Forming Systems

    NASA Astrophysics Data System (ADS)

    Rangwala, Naseem

    2014-10-01

    Herschel observations of nearby star-forming galaxies have determined that the warm component of the molecular gas traced by the high-J CO lines dominates the luminosity (~90% of the total CO luminosity) and hence the energetics of the molecular ISM. At the temperatures (T = 300 - 2000 K) and densities (n_H < 1E6 per cubic cm) typically found in our survey, H2 emission is the dominant gas coolant, much more important than CO. A fundamental assumption of all analyses of CO emission has been that CO emission traces H2 over the entire range of physical conditions in the observed sources. However, a direct observational comparison of spatial distributions and kinematics of CO and H2 has never been made for the warm molecular gas. We propose to observe the warm H2, in S(1) and S(2) transitions, with the SOFIA-EXES instrument in a diverse sample of star-forming systems: NGC 253 (starburst nucleus), NGC 6240 (luminous infrared galaxy), NGC 1068 (Seyfert-2), and SgrB2(M)/(N) (Galactic hot cores). The primary goal is to compare these measurements with the warm CO (J = 6-5 transition) observed with the Atacama Large Millimeter Array (ALMA) to investigate differences in the kinematics and spatial distributions (for the extended targets) of the two molecules and thereby confirm whether CO is a reliable tracer of H2 in the warm gas.

  18. Testing Grain Surface Chemistry in Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Keane, Jacqueline; Boogert, Adwin

    2008-03-01

    The key chemical reactions that produce the first generation ice mantles in dense molecular clouds are still poorly known. Within cold, dense clouds, species formed in the gas and on the grain surfaces will stick to the grains and form icy mantles. However, during star-formation, materials in the general cloud medium are subjected to numerous chemical and physical processes that are driven mostly by thermal and energetic radiation. The comparison between background stars and protostars is a proven excellent tool for this purpose. By comparing observed interstellar solid state abundances with models of grain surface chemistry it is possible to elucidate the efficiency and hence relevancy of a number of chemical reactions, in particular the CO_2 formation pathways. In part because of Spitzer, significant progress has been made towards understanding the various effects of these radiation processes on the ices around a large sample of high- and low-mass protostars. First results suggest that two different CO2 formation pathways play a role in these harsh environments. Though which reaction initially dominated the chemistry is unknown due to the numerous physical processes. Unfortunately, only a small sample of background field stars have been observed, most notably Taurus. In Taurus, only one reaction pathway appears to be efficient in quiescent regions, but this result is sample limited. We propose to take low resolution spectra from 5 to 22 microns along the line of sight toward 31 field stars behind the LDN 673 molecular cloud. Differences in near-IR ice chemistry have already been observed and we will use these mid-infrared data to provide more stringent constraints on chemical models of grain surface chemistry. With this sample it is possible to address fundamental questions in astrochemistry: what are the dominant grain surface chemistry pathways? What is the composition of the first generation ice mantles in molecular clouds?

  19. The role of energetic processing on solid-phase chemistry in star forming regions

    NASA Astrophysics Data System (ADS)

    Palumbo, M. E.; Urso, R. G.; Kaňuchová, Z.; Scirè, C.; Accolla, M.; Baratta, G. A.; Strazzulla, G.

    2016-05-01

    It is generally accepted that complex molecules observed in star forming regions are formed in the solid phase on icy grain mantles and are released to the gas-phase after desorption of icy mantles. Most of our knowledge on the physical and chemical properties of ices in star forming regions is based on the comparison between observations and laboratory experiments performed at low temperature (10-100 K). Here we present some recent laboratory experiments which show the formation of (complex) molecular species after ion bombardment of simple ices.

  20. NEAR-INFRARED CIRCULAR POLARIZATION SURVEY IN STAR-FORMING REGIONS: CORRELATIONS AND TRENDS

    SciTech Connect

    Kwon, Jungmi; Tamura, Motohide; Hough, James H.; Lucas, Phil W.; Kusakabe, Nobuhiko; Kandori, Ryo; Nagata, Tetsuya; Nakajima, Yasushi; Nagayama, Takahiro

    2014-11-01

    We have conducted a systematic near-infrared circular polarization (CP) survey in star-forming regions, covering high-mass, intermediate-mass, and low-mass young stellar objects. All the observations were made using the SIRPOL imaging polarimeter on the Infrared Survey Facility 1.4 m telescope at the South African Astronomical Observatory. We present the polarization properties of 10 sub-regions in 6 star-forming regions. The polarization patterns, extents, and maximum degrees of linear and circular polarizations are used to determine the prevalence and origin of CP in the star-forming regions. Our results show that the CP pattern is quadrupolar in general, the CP regions are extensive, up to 0.65 pc, the CP degrees are high, up to 20%, and the CP degrees decrease systematically from high- to low-mass young stellar objects. The results are consistent with dichroic extinction mechanisms generating the high degrees of CP in star-forming regions.

  1. VizieR Online Data Catalog: Parallaxes of high mass star forming regions (Reid+, 2014)

    NASA Astrophysics Data System (ADS)

    Reid, M. J.; Menten, K. M.; Brunthaler, A.; Zheng, X. W.; Dame, T. M.; Xu, Y.; Wu, Y.; Zhang, B.; Sanna, A.; Sato, M.; Hachisuka, K.; Choi, Y. K.; Immer, K.; Moscadelli, L.; Rygl, K. L. J.; Bartkiewicz, A.

    2016-04-01

    Table1 lists the parallaxes and proper motions of 103 regions of high-mass star formation measured with Very Long Baseline Interferometry (VLBI) techniques, using the National Radio Astronomy Observatory's Very Long Baseline Array (VLBA), the Japanese VLBI Exploration of Radio Astrometry (VERA; http://veraserver.mtk.nao.ac.jp) project, and the European VLBI Network (EVN). We have include three red supergiants (NML Cyg, S Per, VY CMa) as indicative of high-mass star forming regions. (2 data files).

  2. Observations of Star-Forming Regions with the Midcourse Space Experiment

    NASA Astrophysics Data System (ADS)

    Kraemer, Kathleen E.; Shipman, Russell F.; Price, Stephan D.; Mizuno, Donald R.; Kuchar, Thomas; Carey, Sean J.

    2003-09-01

    We have imaged seven nearby star-forming regions, the Rosette Nebula, the Orion Nebula, W3, the Pleiades, G300.2-16.8, S263, and G159.6-18.5, with the Spatial Infrared Imaging Telescope on the Midcourse Space Experiment (MSX) satellite at 18" resolution at 8.3, 12.1, 14.7, and 21.3 μm. The large angular scale of the regions imaged (~7.2-50 deg2) makes these data unique in terms of the combination of size and resolution. In addition to the star-forming regions, two cirrus-free fields (MSXBG 160 and MSXBG 161) and a field near the south Galactic pole (MSXBG 239) were also imaged. Point sources have been extracted from each region, resulting in the identification over 500 new sources (i.e., no identified counterparts at other wavelengths), as well as over 1300 with prior identifications. The extended emission from the star-forming regions is described, and prominent structures are identified, particularly in W3 and Orion. The Rosette Nebula is discussed in detail. The bulk of the mid-infrared emission is consistent with that of photon-dominated regions, including the elephant trunk complex. The central clump, however, and a line of site toward the northern edge of the cavity show significantly redder colors than the rest of the Rosette complex.

  3. Ultraviolet and Visible Analysis of Star-Forming Regions in Several Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Zernow, Lea; Hunter, D. A.

    2007-12-01

    As some of the smallest and most numerous galaxies in the universe, dwarf irregular (dIm) galaxies give many opportunities for developing an understanding of the manner in which the universe operates. In particular, these galaxies offer challenges to standard models of star formation. The concentration of gas is sufficiently small that the standard models cannot account for the presence of stars in the galaxies. In order to examine this paradox, we used ultraviolet images obtained with the GALEX satellite and optical ground-based imaging to examine the properties of star-forming regions in three dIm galaxies: DDO 50, IC 1613, and WLM. We identified candidate young star-forming regions on near ultraviolet (NUV, 2270 Angstroms) images. We then measured the brightness of the regions in the NUV, far ultraviolet (FUV, 1520 Angstroms), and UBV images. Colors were compared to cluster evolutionary models to estimate ages of the regions, which enabled an estimate of the visual magnitude at a fiducial age of ten million years. We divided the galaxies into three broad annuli in order to compare properties of the star-forming regions as a function of radius. We discuss the properties of star-forming regions in the three galaxies in the context of current star formation models that predict star formation on the basis of large-scale gravitational instability and local-scale gas compression. LZ extends gratitude for funding from the National Science Foundation's Research Experiences for Undergraduates (REU) program at Northern Arizona University through grant AST-0453611. DAH gratefully acknowledges funding for this research from the NASA GALEX program through grant NNX07AJ36G.

  4. Photometric and spectroscopic studies of star-forming regions within Wolf-Rayet galaxies

    NASA Astrophysics Data System (ADS)

    Karthick, M. Chrisphin; López-Sánchez, Ángel R.; Sahu, D. K.; Sanwal, B. B.; Bisht, Shuchi

    2014-03-01

    We present a study of the properties of star-forming regions within a sample of seven Wolf-Rayet (WR) galaxies. We analyse their morphologies, colours, star-formation rates (SFRs), metallicities and stellar populations, combining broad-band and narrow-band photometry with low-resolution optical spectroscopy. The UBVRI observations were made with the 2-m HCT (Himalayan Chandra Telescope) and 1-m ARIES telescope. The spectroscopic data were obtained using the Hanle Faint Object Spectrograph Camera (HFOSC) mounted on the 2-m HCT. The observed galaxies are NGC 1140, IRAS 07164+5301, NGC 3738, UM 311, NGC 6764, NGC 4861 and NGC 3003. The optical spectra were used to search for the faint WR features, to confirm that the ionization of the gas is caused by the massive stars, and to quantify the oxygen abundance of each galaxy using several independent empirical calibrations. We detected broad features originating in WR stars in NGC 1140 and 4861 and used them to derive the massive star populations. For these two galaxies we also derived the oxygen abundance using a direct estimation of the electron temperature of the ionized gas. The N/O ratio in NGC 4861 is ˜0.25-0.35 dex higher than expected, which may be a consequence of the chemical pollution by N-rich material released by WR stars. Using our Hα images we identified tens of star-forming regions within these galaxies, for which we derived the SFR. Our Hα-based SFR usually agrees with the SFR computed using the far-infrared and the radio-continuum flux. For all regions we found that the most recent star-formation event is 3-6 Myr old. We used the optical broad-band colours in combination with Starburst99 models to estimate the internal reddening and the age of the dominant underlying stellar population within all these regions. Knots in NGC 3738, 6764 and 3003 generally show the presence of an important old (400-1000 Myr) stellar population. However, the optical colours are not able to detect stars older than 20

  5. WIDE-FIELD INFRARED SURVEY EXPLORER OBSERVATIONS OF THE EVOLUTION OF MASSIVE STAR-FORMING REGIONS

    SciTech Connect

    Koenig, X. P.; Leisawitz, D. T.; Benford, D. J.; Padgett, D. L.; Rebull, L. M.

    2012-01-10

    We present the results of a mid-infrared survey of 11 outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE). Using a newly developed photometric scheme to identify young stellar objects and exclude extragalactic contamination, we have studied the distribution of young stars within each region. These data tend to support the hypothesis that latter generations may be triggered by the interaction of winds and radiation from the first burst of massive star formation with the molecular cloud material leftover from that earlier generation of stars. We dub this process the 'fireworks hypothesis' since star formation by this mechanism would proceed rapidly and resemble a burst of fireworks. We have also analyzed small cutout WISE images of the structures around the edges of these massive star-forming regions. We observe large (1-3 pc size) pillar and trunk-like structures of diffuse emission nebulosity tracing excited polycyclic aromatic hydrocarbon molecules and small dust grains at the perimeter of the massive star-forming regions. These structures contain small clusters of emerging Class I and Class II sources, but some are forming only a single to a few new stars.

  6. Wide-Field Infrared Survey Explorer Observations of the Evolution of Massive Star-Forming Regions

    NASA Technical Reports Server (NTRS)

    Koenig, X. P.; Leisawitz, D. T.; Benford, D. J.; Rebull, L. M.; Padgett, D. L.; Assef, R. J.

    2011-01-01

    We present the results of a mid-infrared survey of 11 outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE). Using a newly developed photometric scheme to identify young stellar objects and exclude extragalactic contamination, we have studied the distribution of young stars within each region. These data tend to support the hypothesis that latter generations may be triggered by the interaction of winds and radiation from the first burst of massive star formation with the molecular cloud material leftover from that earlier generation of stars.We dub this process the "fireworks hypothesis" since star formation by this mechanism would proceed rapidly and resemble a burst of fireworks.We have also analyzed small cutout WISE images of the structures around the edges of these massive star-forming regions. We observe large (1-3 pc size) pillar and trunk-like structures of diffuse emission nebulosity tracing excited polycyclic aromatic hydrocarbon molecules and small dust grains at the perimeter of the massive star-forming regions. These structures contain small clusters of emerging Class I and Class II sources, but some are forming only a single to a few new stars.

  7. Wide-Field Infrared Survey Explorer Observations of the Evolution of Massive Star-Forming Regions

    NASA Technical Reports Server (NTRS)

    Koenig, X. P.; Leisawitz, D. T.; Benford, D. J.; Rebull, L. M.; Padgett, D. L.; Asslef, R. J.

    2012-01-01

    We present the results of a mid-infrared survey of II outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE). Using a newly developed photometric scheme to identify young stellar objects and exclude extragalactic contamination, we have studied the distribution of young stars within each region. These data tend to support the hypothesis that latter generations may be triggered by the interaction of winds and radiation from the first burst of massive star formation with the molecular cloud material leftover from that earlier generation of stars. We dub this process the "fireworks hypothesis" since star formation by this mechanism would proceed rapidly and resemble a burst of fireworks. We have also analyzed small cutout WISE images of the structures around the edges of these massive star-forming regions. We observe large (1-3 pc size) pillar and trunk-like structures of diffuse emission nebulosity tracing excited polycyclic aromatic hydrocarbon molecules and small dust grains at the perimeter of the massive star-forming regions. These structures contain small clusters of emerging Class I and Class II sources, but some are forming only a single to a few new stars.

  8. YOUNG STELLAR OBJECTS IN THE MASSIVE STAR-FORMING REGION W49

    SciTech Connect

    Saral, G.; Hora, J. L.; Willis, S. E.; Koenig, X. P.; Gutermuth, R. A.; Saygac, A. T.

    2015-11-01

    We present the initial results of our investigation of the star-forming complex W49, one of the youngest and most luminous massive star-forming regions in our Galaxy. We used Spitzer/Infrared Array Camera (IRAC) data to investigate massive star formation with the primary objective of locating a representative set of protostars and the clusters of young stars that are forming around them. We present our source catalog with the mosaics from the IRAC data. In this study we used a combination of IRAC, MIPS, Two Micron All Sky Survey, and UKIRT Deep Infrared Sky Survey (UKIDSS) data to identify and classify the young stellar objects (YSOs). We identified 232 Class 0/I YSOs, 907 Class II YSOs, and 74 transition disk candidate objects using color–color and color–magnitude diagrams. In addition, to understand the evolution of star formation in W49, we analyzed the distribution of YSOs in the region to identify clusters using a minimal spanning tree method. The fraction of YSOs that belong to clusters with ≥7 members is found to be 52% for a cutoff distance of 96″, and the ratio of Class II/I objects is 2.1. We compared the W49 region to the G305 and G333 star-forming regions and concluded that W49 has the richest population, with seven subclusters of YSOs.

  9. Distribution of HNCO 505-404 in massive star-forming regions

    NASA Astrophysics Data System (ADS)

    Li, J.; Wang, J. Z.; Gu, Q. S.; Zheng, X. W.

    2013-07-01

    Aims: The goal of this paper is to study the spatial distribution of HNCO in massive star-forming region and to investigate both its spatial association with infrared sources and physical conditions in region of HNCO emission. Methods: We mapped nine massive star-forming regions in HNCO 505-404 with the Purple Mountain Observatory 13.7 m telescope. The C18O maps of these sources were obtained simultaneously. Results: The HNCO emission shows compact distribution, with the emission peak centered on water masers. Nearly all the HNCO clumps show signs of embedded mid-infrared or far-infrared sources. The FWHM sizes of HNCO clumps are significantly smaller than C18O clumps but rather similar to HC3N clumps. We find a good correlation between the integrated intensities, linewidths, and LSR velocities of HNCO and HC3N emission, implying similar excitation mechanisms for these two species. As such, collisional excitation is likely to be the dominant excitation mechanism for HNCO 505 - 404 emission in galactic massive star-forming regions.

  10. PARALLAXES OF STAR-FORMING REGIONS IN THE OUTER SPIRAL ARM OF THE MILKY WAY

    SciTech Connect

    Hachisuka, K.; Choi, Y. K.; Reid, M. J.; Dame, T. M.; Brunthaler, A.; Menten, K. M.; Sanna, A.

    2015-02-10

    We report parallaxes and proper motions of three water maser sources in high-mass star-forming regions in the Outer Spiral Arm of the Milky Way. The observations were conducted with the Very Long Baseline Array as part of Bar and Spiral Structure Legacy Survey and double the number of such measurements in the literature. The Outer Arm has a pitch angle of 14.°9 ± 2.°7 and a Galactocentric distance of 14.1 ± 0.6 kpc toward the Galactic anticenter. The average motion of these sources toward the Galactic center is 10.7 ± 2.1 km s{sup –1} and we see no sign of a significant fall in the rotation curve out to 15 kpc from the Galactic center. The three-dimensional locations of these star-forming regions are consistent with a Galactic warp of several hundred parsecs from the plane.

  11. The connection between galaxy environment and the luminosity function slopes of star-forming regions

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Dale, Daniel A.; Lee, Janice C.; Thilker, David; Calzetti, Daniela; Kennicutt, Robert C.

    2016-11-01

    We present the first study of GALEX far-ultraviolet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ˜65 000 star-forming regions (i.e. FUV sources), measure each galaxy's luminosity function, and characterize the relationships between the luminosity function slope (α) and several global galaxy properties. A final sample of 82 galaxies with reliable luminosity functions are used to define these relationships and represent the largest sample of galaxies with the largest range of galaxy properties used to study the connection between luminosity function properties and galaxy environment. We find that α correlates with global star formation properties, where galaxies with higher star formation rates and star formation rate densities (ΣSFR) tend to have flatter luminosity function slopes. In addition, we find that neither stochastic sampling of the luminosity function in galaxies with low-number statistics nor the effects of blending due to distance can fully account for these trends. We hypothesize that the flatter slopes in high ΣSFR galaxies is due to higher gas densities and higher star formation efficiencies which result in proportionally greater numbers of bright star-forming regions. Finally, we create a composite luminosity function composed of star-forming regions from many galaxies and find a break in the luminosity function at brighter luminosities. However, we find that this break is an artefact of varying detection limits for galaxies at different distances.

  12. 13C Isotopic Fractionation of HC3N in Star-forming Regions: Low-mass Star-forming Region L1527 and High-mass Star-forming Region G28.28-0.36

    NASA Astrophysics Data System (ADS)

    Taniguchi, Kotomi; Saito, Masao; Ozeki, Hiroyuki

    2016-10-01

    We observed the J = 9–8 and 10–9 rotational lines of three 13C isotopologues of HC3N in L1527 and G28.28-0.36, with the 45 m radio telescope of the Nobeyama Radio Observatory, in order to constrain the main formation mechanisms of HC3N in each source. The abundance ratios of the three 13C isotopologues of HC3N are found to be 0.9 (±0.2) : 1.00 : 1.29 (±0.19) (1σ), and 1.0 (±0.2) : 1.00 : 1.47 (±0.17) (1σ), for [H13CCCN : HC13CCN : HCC13CN] in L1527 and G28.28-0.36, respectively. We recognize, from a similar 13C isotopic fractionation pattern, that the abundances of H13CCCN and HC13CCN are comparable, and HCC13CN is more abundant than the others. Based on the results, we discuss the main formation pathway of HC3N. The 13C isotopic fractionation pattern derived from our observations can be explained by the neutral-neutral reaction between C2H2 and CN in both the low-mass (L1527) and high-mass (G28.28-0.36) star-forming regions.

  13. The comparison of physical properties derived from gas and dust in a massive star-forming region

    SciTech Connect

    Battersby, Cara; Bally, John; Ginsburg, Adam; Darling, Jeremy; Dunham, Miranda; Longmore, Steve

    2014-05-10

    We explore the relationship between gas and dust in a massive star-forming region by comparing the physical properties derived from each. We compare the temperatures and column densities in a massive star-forming Infrared Dark Cloud (G32.02+0.05), which shows a range of evolutionary states, from quiescent to active. The gas properties were derived using radiative transfer modeling of the (1,1), (2,2), and (4,4) transitions of NH{sub 3} on the Karl G. Jansky Very Large Array, while the dust temperatures and column densities were calculated using cirrus-subtracted, modified blackbody fits to Herschel data. We compare the derived column densities to calculate an NH{sub 3} abundance, χ{sub NH{sub 3}} = 4.6 × 10{sup –8}. In the coldest star-forming region, we find that the measured dust temperatures are lower than the measured gas temperatures (mean and standard deviations T {sub dust,} {sub avg} ∼ 11.6 ± 0.2 K versus T {sub gas,} {sub avg} ∼ 15.2 ± 1.5 K), which may indicate that the gas and dust are not well-coupled in the youngest regions (∼0.5 Myr) or that these observations probe a regime where the dust and/or gas temperature measurements are unreliable. Finally, we calculate millimeter fluxes based on the temperatures and column densities derived from NH{sub 3}, which suggest that millimeter dust continuum observations of massive star-forming regions, such as the Bolocam Galactic Plane Survey or ATLASGAL, can probe hot cores, cold cores, and the dense gas lanes from which they form, and are generally not dominated by the hottest core.

  14. The complex high-mass star-forming region IRAS 15507-5359

    NASA Astrophysics Data System (ADS)

    Persi, P.; Tapia, M.; Roth, M.; Elia, D.; López-Vázquez, J. A.

    2016-06-01

    The far-infrared IRAS 15507-5359 source is known to be a medium-mass star-forming region associated with a compact H II region and a near-infrared embedded cluster. We present a survey of infrared-calibrated images ranging from 1.2 to 500 μm obtained with the Baade telescope at Las Campanas Observatory, and the Herschel space telescope with additional archive Spitzer data. We confirm the distance to the complex to be 5.0 kpc. Three Herschel far-infrared sources are found, I, II, III, identified with dense cores at different evolutionary stages. One (III) is a starless infrared dark cloud showing, near its edge, two infrared reflection nebulae (R1) and (R2) with dispersed young stellar populations, including a knot of shocked H2 line emission. Both show considerable polycyclic aromatic hydrocarbon emission. Core II has associated a radio H II region and a deeply embedded one-million-year-old cluster (Cl 1) that contains more than 45 young stellar objects, reddened by at least 20 visual magnitudes. About 20 per cent of them show considerable infrared excess emission. Core I appears void of a near-infrared population, and coincides with a long emission bar that resembles a photodissociation front. We determine the properties of the two most luminous Class I sources in the region by fitting models of young stars with accreting discs and envelopes to their 1-500 μm spectral energy distributions. This is another example of a medium-mass region with at least three well-defined active centres of star formation separated by about 1 pc and at different evolutionary stages.

  15. 13CO Survey of Northern Intermediate-Mass Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Lundquist, Michael J.; Kobulnicky, H. A.; Kerton, C. R.

    2014-01-01

    We conducted a survey of 13CO with the OSO 20-m telescope toward 68 intermediate-mass star-forming regions (IM SFRs) visible in the northern hemisphere. These regions have mostly been excluded from previous CO surveys and were selected from IRAS colors that specify cool dust and large PAH contribution. These regions are known to host stars up to, but not exceeding, about 8 solar masses. We detect 13CO in 57 of the 68 IM SFRs down to a typical RMS of ~50 mK. We present kinematic distances, minimum column densities, and minimum masses for these IM SFRs.

  16. VizieR Online Data Catalog: YSOs in 9 LMC star forming regions (Carlson+, 2012)

    NASA Astrophysics Data System (ADS)

    Carlson, L. R.; Sewilo, M.; Meixner, M.; Romita, K. A.; Lawton, B.

    2012-04-01

    We introduce a new set of selection criteria for the identification of infrared bright young stellar object (YSO) candidates and apply them to nine HII regions in the Large Magellanic Cloud (LMC), focusing particularly on lower mass candidates missed by most surveys. Data are from the Spitzer Space Telescope legacy program SAGE (Surveying the Agents of Galaxy Evolution; Meixner et al. 2006, Cat. J/AJ/132/2268, see also II/305), combined with optical photometry from the Magellanic Clouds Photometric Survey (MCPS; Zaritsky et al. 1997AJ....114.1002Z) and near-infrared photometry from the InfraRed Survey Facility (IRSF; Kato et al. 2007, Cat. II/288). We choose regions of diverse physical size, star formation rates (SFRs), and ages. We also cover a wide range of locations and surrounding environments in the LMC. These active star-forming regions are LHA 120-N 11, N 44, N 51, N 105, N 113, N 120, N 144, N 160, and N 206. Some have been well-studied (e.g., N11, N44, N160) in the past, while others (e.g., N51, N144) have received little attention. We identify 1045 YSO candidates, including 918 never before identified and 127 matching previous candidate lists. We characterize the evolutionary stage and physical properties of each candidate using the spectral energy distribution (SED) fitter of Robitaille et al. (2007ApJS..169..328R) and estimate mass functions and SFRs for each region. (4 data files).

  17. Identifying young stellar objects in nine Large Magellanic Cloud star-forming regions

    NASA Astrophysics Data System (ADS)

    Carlson, L. R.; Sewiło, M.; Meixner, M.; Romita, K. A.; Lawton, B.

    2012-06-01

    We introduce a new set of selection criteria for the identification of infrared bright young stellar object (YSO) candidates and apply them to nine Hii regions in the Large Magellanic Cloud (LMC), focusing particularly on lower mass candidates missed by most surveys. Data are from the Spitzer Space Telescope legacy program SAGE (Surveying the Agents of Galaxy Evolution; Meixner et al. 2006, AJ, 132, 2268), combined with optical photometry from the Magellanic Clouds Photometric Survey (MCPS; Zaritsky et al. 1997, AJ, 114, 1002) and near-infrared photometry from the InfraRed Survey Facility (IRSF; Kato et al. 2007, PASJ, 59, 615). We choose regions of diverse physical size, star formation rates (SFRs), and ages. We also cover a wide range of locations and surrounding environments in the LMC. These active star-forming regions are LHA 120-N 11, N 44, N 51, N 105, N 113, N 120, N 144, N 160, and N 206. Some have been well-studied (e.g., N11, N44, N160) in the past, while others (e.g., N51, N144) have received little attention. We identify 1045 YSO candidates, including 918 never before identified and 127 matching previous candidate lists. We characterize the evolutionary stage and physical properties of each candidate using the spectral energy distribution (SED) fitter of Robitaille et al. (2007, ApJS, 169, 328) and estimate mass functions and SFRs for each region. Full Tables 1-3, 5 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A66

  18. From the H II Region to the Molecular Cloud: Determining Physical Conditions in Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Abel, N. P.

    2004-12-01

    Infrared missions such as Spitzer offer new insights into the chemical evolution and star formation history of the universe. Although objects such as starburst galaxies, which are among the most luminous objects in the universe, are the primary focus, OMC-1, a lower luminosity region with superb spatial resolution, serves as a benchmark to test the physics of newly formed O stars interacting with the surrounding molecular environment. The classical approach in determining conditions in the ionized, photodissociated, and molecular regions is to treat each problem separately. In actuality, however, this is a single continuous phenomenon, linked through the transport of gas and radiation. Here we self-consistently calculate the physical conditions and emission from the hot HII region to the cold, molecular gas as a continuous hydrostatic layer. The ion states of the first 30 elements, along with the abundances of 70 molecules, are determined with the temperature and electron density. The grain physics is treated self-consistently, with grain charge transfer, single photon heating, and PAH effects all included. Additionally, level populations of all the rotational/vibrational levels of the ground electronic state of molecular hydrogen are determined (see the dissertation talk of Gargi Shaw). As a benchmark, we consider the physical conditions through OMC-1 1' west of the Trapezium, where emission-line observations of the HII region and the PDR/molecular cloud all exist. Accurately interpreting this spectrum will give us confidence that we can apply our calculations to more luminous and distant starburst galaxies. We predict the sometimes significant contribution of the HII region to important PDR emission-line diagnostics. This has consequences for the interpretation of IR observations, the deduced values of n(H) and G0 in PDRs, and hence the overall conditions in star forming regions. All calculations were developed with the spectral synthesis code Cloudy, which is

  19. A {sup 13}CO SURVEY OF INTERMEDIATE-MASS STAR-FORMING REGIONS

    SciTech Connect

    Lundquist, Michael J.; Kobulnicky, Henry A.; Kerton, Charles R.; Arvidsson, Kim

    2015-06-10

    We have conducted a {sup 13}CO survey of a sample of 128 infrared color-selected intermediate-mass star-forming region (IM SFR) candidates. We utilized the Onsala 20 m telescope to observe {sup 13}CO (1–0) toward 67 northern IM SFRs, used the 12 m Atacama Pathfinder Experiment telescope to observe {sup 13}CO (2–1) toward 22 southern IM SFRs, and incorporated an additional 39 sources from the Boston University Five College Radio Astronomy Observatory Galactic Ring Survey which observed {sup 13}CO (1–0). We detect {sup 13}CO (1–0) in 58 of the 67 northern sources and {sup 13}CO (2–1) in 20 of the 22 southern sources. The mean molecular column densities and {sup 13}CO linewidths in the inner Galaxy are higher by factors of 3.4 and 1.5, respectively, than the outer Galaxy. We attribute this difference to molecular clouds in the inner Galaxy being more massive and hosting star forming regions with higher luminosities on average than the outer Galaxy. IM SFRs have mean a molecular column density of 7.89 × 10{sup 21} cm{sup −2}, a factor of 3.1 lower than that for a sample of high-mass regions, and have a mean {sup 13}CO linewidth of 1.84 km s{sup −1}, a factor of 1.5 lower than that for high-mass regions. We demonstrate a correlation between {sup 13}CO linewidth and infrared luminosity as well as between molecular column density and infrared luminosity for the entire sample of intermediate-mass and high-mass regions. IM SFRs appear to form in distinctly lower-density environments with mean linewidths and beam-averaged column densities a factor of several lower than high-mass star-forming regions.

  20. A 13CO Survey of Intermediate-mass Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Lundquist, Michael J.; Kobulnicky, Henry A.; Kerton, Charles R.; Arvidsson, Kim

    2015-06-01

    We have conducted a 13CO survey of a sample of 128 infrared color-selected intermediate-mass star-forming region (IM SFR) candidates. We utilized the Onsala 20 m telescope to observe 13CO (1-0) toward 67 northern IM SFRs, used the 12 m Atacama Pathfinder Experiment telescope to observe 13CO (2-1) toward 22 southern IM SFRs, and incorporated an additional 39 sources from the Boston University Five College Radio Astronomy Observatory Galactic Ring Survey which observed 13CO (1-0). We detect 13CO (1-0) in 58 of the 67 northern sources and 13CO (2-1) in 20 of the 22 southern sources. The mean molecular column densities and 13CO linewidths in the inner Galaxy are higher by factors of 3.4 and 1.5, respectively, than the outer Galaxy. We attribute this difference to molecular clouds in the inner Galaxy being more massive and hosting star forming regions with higher luminosities on average than the outer Galaxy. IM SFRs have mean a molecular column density of 7.89 × 1021 cm-2, a factor of 3.1 lower than that for a sample of high-mass regions, and have a mean 13CO linewidth of 1.84 km s-1, a factor of 1.5 lower than that for high-mass regions. We demonstrate a correlation between 13CO linewidth and infrared luminosity as well as between molecular column density and infrared luminosity for the entire sample of intermediate-mass and high-mass regions. IM SFRs appear to form in distinctly lower-density environments with mean linewidths and beam-averaged column densities a factor of several lower than high-mass star-forming regions.

  1. High angular resolution observations of star-forming regions with BETTII and SOFIA

    NASA Astrophysics Data System (ADS)

    Rizzo, Maxime; Rinehart, Stephen; Mundy, Lee G.; Benford, Dominic J.; Dhabal, Arnab; Fixsen, Dale J.; Leisawitz, David; Maher, Stephen F.; Mentzell, Eric; Silverberg, Robert F.; Staguhn, Johannes; Veach, Todd; Cardiff BETTII Team

    2016-01-01

    High angular resolution observations in the far-infrared are important to understand the star formation process in embedded star clusters where extinction is large and stars form in close proximity. The material taking part in the star forming process is heated by the young stars and emits primarily in the far-IR; hence observations of the far-IR dust emission yields vital information about the gravitational potential, the mass and energy distribution, and core/star formation process. Previous observatories, such as Herschel, Spitzer and WISE lack the angular resolution required to study these dense star forming cores and are further limited by saturation in bright cores.The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is pioneering the path to sub-arcsecond resolution at far-IR wavelengths. This thesis talk discusses the instrumental challenges in building BETTII, as well as results from our SOFIA survey to illustrate the potential of higher-angular resolution observations. The 8m-long two element interferometer is being tested at NASA GSFC and is scheduled for first flight in fall 2016. BETTII will provide 0.5 to 1 arcsecond spatial resolution and spectral resolving power of 10 to 100 between 30 and 90 microns, where most of the dust continuum emission peaks in local star forming regions. It will achieve spatially-resolved spectroscopy of bright, dense cores with unprecedented high definition. This talk focuses on the main challenges and solutions associated with building BETTII: thermal stability, attitude/pointing control, and path length stabilization. In each of these areas we look at the trade-off between design, control, and knowledge in order to achieve the best-possible instrumental capability and sensitivity.As a first step towards resolving cluster cores, we surveyed 10 nearby star-forming clusters with SOFIA FORCAST at 11, 19, 31 and 37 microns. The FORCAST instrument has the highest angular resolution currently available in

  2. Molecular cloud/HII region interfaces in the star forming region NGC 6357.

    NASA Astrophysics Data System (ADS)

    Massi, F.; Brand, J.; Felli, M.

    1997-04-01

    We have performed ^12^CO(1-0), ^12^CO(2-1), ^13^CO(1-0), ^13^CO(2-1), C^18^O(1-0), C^18^O(2-1), HCO^+^(1-0) and H^13^CO^+^(1-0) observations towards two selected areas in the star forming complex NGC 6357 with angular resolutions from 21" to 55". In particular, we have mapped the molecular gas around the two HII regions G353.1+0.6 and G353.2+0.9 in the ^12^CO(1-0) and ^13^CO(1-0) transitions with a resolution of ~43". This improves on the coarser ^12^CO(1-0) observations previously carried out by others. We have also studied the physical properties of gas along strips through the molecular cloud/HII region interfaces. For G353.1+0.6, the observations confirm that an ionization front is eroding a warm, dense molecular cloud located to the north of the optical nebula. The molecular gas appears fragmented on a scale size >0.5pc and not all the components are related to the HII region. There is evidence of a density increase near the front and indications of temperature gradients toward the exciting stars. This is further suggested by the presence of ^12^CO(1-0) self-absorption produced by a cooler external layer. The isotopic ratio X(^13^CO)/X(C^18^O) decreases from the inner part of the clouds towards the front, contrary to what is theoretically predicted and observed in many other regions. This may be due to excitation or optical depths effects. An evolutionary scenario is proposed where the exciting stars form at the edge of a molecular cloud. The morphology of G353.2+0.9 is rather different from what previously believed. Only a weak "bar" of molecular material was found to the south of the sharp ionization front observed optically and in the radio-continuum, and most of the molecular emission arises from regions behind or to the north of the HII region. This indicates that we are viewing a late stage "blister" configuration face-on. This region is fragmented on a scale size >0.5pc, and a warm, dense and compact molecular fragment coincides with the elephant trunk

  3. The Schmidt Law in Six Galactic Massive Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Willis, S.; Guzman, A.; Marengo, M.; Smith, H. A.; Martínez-Galarza, J. R.; Allen, L.

    2015-08-01

    We present a census of young stars in five massive star-forming regions in the 4th Galactic quadrant, G305, G326-4, G326-6, G333 (RCW 106), and G351, and combine this census with an earlier census of young stars in NGC 6334. Each region was observed at J, H, and Ks with the NOAO Extremely Wide-Field Infrared Imager and combined with deep observations taken with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope at the wavelengths 3.6 and 4.5 μm. We derived a five band point-source catalog containing >200,000 infrared sources in each region. We have identified a total of 2871 YSO candidates, 363 Class I YSOs, and 2508 Class II YSOs. We mapped the column density of each cloud using observations from Herschel between 160 and 500 μm and near-infrared extinction maps in order to determine the average gas surface density above AV > 2. We study the surface density of the YSOs and the star-formation rate as a function of the column density within each cloud and compare them to the results for nearby star-forming regions. We find a range in power-law indices across the clouds, with the dispersion in the local relations in an individual cloud much lower than the average over the six clouds. We find the average over the six clouds to be {{{Σ }}}{SFR}∼ {{{Σ }}}{gas}2.15+/- 0.41 and power-law exponents ranging from 1.77 to 2.86, similar to the values derived within nearby star-forming regions, including Taurus and Orion. The large dispersion in the power-law relations between individual Milky Way molecular clouds reinforces the idea that there is not a direct universal connection between Σgas and a cloud's observed star-formation rate.

  4. A Multi-Wavelength Survey of Intermediate-Mass Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Lundquist, Michael J.; Kobulnicky, Henry A.; Kerton, Charles R.

    2015-01-01

    Current research into Galactic star formation has focused on either massive star-forming regions or nearby low-mass regions. We present results from a survey of Galactic intermediate-mass star-forming regions (IM SFRs). These regions were selected from IRAS colors that specify cool dust and large PAH contribution, suggesting that they produce stars up to but not exceeding about 8 solar masses. Using WISE data we have classified 984 candidate IM SFRs as star-like objects, galaxies, filamentary structures, or blobs/shells based on their mid-infrared morphologies. Focusing on the blobs/shells, we combined follow-up observations of deep near-infrared (NIR) imaging with optical and NIR spectroscopy to study the stellar content, confirming the intermediate-mass nature of these regions. We also gathered CO data from OSO and APEX to study the molecular content and dynamics of these regions. We compare these results to those of high-mass star formation in order to better understand their role in the star-formation paradigm.

  5. Neutral and ionized hydrides in star-forming regions. Observations with Herschel/HIFI.

    PubMed

    Benz, Arnold O; Bruderer, Simon; van Dishoeck, Ewine F; Stäuber, Pascal; Wampfler, Susanne F

    2013-10-01

    The cosmic abundance of hydrides depends critically on high-energy UV, X-ray, and particle irradiation. Here we study hydrides in star-forming regions where irradiation by the young stellar object can be substantial, and density and temperature can be much enhanced over interstellar values. Lines of OH, CH, NH, and SH and their ions OH(+), CH(+), NH(+), SH(+), H2O(+), and H3O(+) were observed in star-forming regions by the HIFI spectrometer onboard the Herschel Space Observatory. Molecular column densities are derived from observed ground-state lines, models, or rotational diagrams. We report here on two prototypical high-mass regions, AFGL 2591 and W3 IRS5, and compare them to chemical calculations by making assumptions on the high-energy irradiation. A model assuming no ionizing protostellar emission is compared with (i) a model assuming strong protostellar X-ray emission and (ii) a two-dimensional (2D) model including emission in the far UV (FUV, 6-13.6 eV), irradiating the outflow walls that separate the outflowing gas and infalling envelope material. We confirm that the effect of FUV in two-dimensional models with enlarged irradiated surfaces is clearly noticeable. A molecule that is very sensitive to FUV irradiation is CH(+), enhanced in abundance by more than 5 orders of magnitude. The HIFI observations of CH(+) lines agree with the two-dimensional FUV model by Bruderer et al., which computes abundances, non-LTE excitation, and line radiative transfer.20 It is concluded that CH(+) is a good FUV tracer in star-forming regions. The effect of potential X-ray irradiation is not excluded but cannot be demonstrated by the present data.

  6. The Initial Mass Function in the Taurus Star-forming Region

    NASA Astrophysics Data System (ADS)

    Briceño, César; Luhman, K. L.; Hartmann, Lee; Stauffer, John R.; Kirkpatrick, J. Davy

    2002-11-01

    By combining a deep optical imaging (I,z') survey of 8 deg2 in the Taurus star-forming region with data from the Two-Micron All-Sky Survey (2MASS) and follow-up spectroscopy, we have performed a search for low-mass Taurus members that is complete to 0.02 Msolar for reddenings of AV<~4. We report the discovery of nine new members with spectral types of M5.75-M9.5, corresponding to masses of 0.1-0.015 Msolar by recent evolutionary models. The new M9.5 member is the least massive brown dwarf found to date in the Taurus star-forming region. We derive an initial mass function (IMF) for the fields surveyed in this work and in our previous studies, which encompass 54% of the known Taurus membership. We compare the Taurus IMF with a similarly derived one for the Trapezium Cluster and to mass functions for the M35 and Pleiades open clusters. While the IMFs in all of these regions flatten near ~0.8 Msolar, the mass function in Taurus is more narrow and sharply peaked at this mass. Our survey indicates that Taurus has ~2 × fewer brown dwarfs at 0.02-0.08 Msolar than the Trapezium. We discuss the implications of these results for theories of the IMF, and suggest that the lower frequency of brown dwarfs in Taurus relative to the Trapezium may result from the low-density star-forming environment, leading to larger minimum Jeans masses. Based on observations obtained at the Kitt Peak National Observatory, Keck Observatory, Steward Observatory, and the MMT Observatory. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

  7. Trigonometric parallaxes of star forming regions in the Perseus spiral arm

    SciTech Connect

    Choi, Y. K.; Brunthaler, A.; Menten, K. M.; Hachisuka, K.; Reid, M. J.; Dame, T. M.; Xu, Y. E-mail: ykchoi@kasi.re.kr

    2014-08-01

    We report trigonometric parallaxes and proper motions of water masers for 12 massive star forming regions in the Perseus spiral arm of the Milky Way as part of the Bar and Spiral Structure Legacy (BeSSel) Survey. Combining our results with 14 parallax measurements in the literature, we estimate a pitch angle of 9.°9 ± 1.°5 for a section of the Perseus arm. The three-dimensional Galactic peculiar motions of these sources indicate that on average they are moving toward the Galactic center and slower than the Galactic rotation.

  8. Kinematic Distances of Pre-main Sequence Stars in the Lupus Star-Forming Region

    NASA Astrophysics Data System (ADS)

    Galli, P. A. B.; Teixeira, R.; Ducourant, C.; Bertout, C.

    2014-06-01

    The problem of the determination of distances has always played a central role in astronomy. However, little recent progress has been made in the distance determination of faint young stellar objects such as pre-main sequence (PMS) stars. Many of the PMS stars were neither observed by the Hipparcos satellite due to their magnitude nor have any trigonometric parallax measured from the ground due to their distance. Here we investigate the kinematic properties of the Lupus moving group with the primary objective of deriving individual parallaxes for each group member of this star-forming region.

  9. Looking for phase-space structures in star-forming regions: an MST-based methodology

    NASA Astrophysics Data System (ADS)

    Alfaro, Emilio J.; González, Marta

    2016-03-01

    We present a method for analysing the phase space of star-forming regions. In particular we are searching for clumpy structures in the 3D sub-space formed by two position coordinates and radial velocity. The aim of the method is the detection of kinematic segregated radial velocity groups, that is, radial velocity intervals whose associated stars are spatially concentrated. To this end we define a kinematic segregation index, tilde{Λ }(RV), based on the Minimum Spanning Tree graph algorithm, which is estimated for a set of radial velocity intervals in the region. When tilde{Λ }(RV) is significantly greater than 1 we consider that this bin represents a grouping in the phase space. We split a star-forming region into radial velocity bins and calculate the kinematic segregation index for each bin, and then we obtain the spectrum of kinematic groupings, which enables a quick visualization of the kinematic behaviour of the region under study. We carried out numerical models of different configurations in the sub-space of the phase space formed by the coordinates and the that various case studies illustrate. The analysis of the test cases demonstrates the potential of the new methodology for detecting different kind of groupings in phase space.

  10. The First Detections of the Key Prebiotic Molecule PO in Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Rivilla, V. M.; Fontani, F.; Beltrán, M. T.; Vasyunin, A.; Caselli, P.; Martín-Pintado, J.; Cesaroni, R.

    2016-08-01

    Phosphorus is a crucial element in biochemistry, in particular the P‑O bond, which is key in the formation of the backbone of deoxyribonucleic acid. So far, PO has only been detected toward the envelope of evolved stars, but never toward star-forming regions. We report the first detection of PO toward two massive star-forming regions, W51 e1/e2 and W3(OH), using data from the IRAM 30 m telescope. PN has also been detected toward the two regions. The abundance ratio PO/PN is 1.8 and 3 for W51 and W3(OH), respectively. Our chemical model indicates that the two molecules are chemically related and are formed via gas-phase ion–molecule and neutral–neutral reactions during cold collapse. The molecules freeze out onto grains at the end of the collapse and desorb during the warm-up phase once the temperature reaches ˜35 K. Similar abundances of the two species are expected during a period of ˜5 × 104 yr at the early stages of the warm-up phase, when the temperature is in the range 35–90 K. The observed molecular abundances of 10‑10 are predicted by the model if a relatively high initial abundance of 5 × 10‑9 of depleted phosphorus is assumed.

  11. The First Detections of the Key Prebiotic Molecule PO in Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Rivilla, V. M.; Fontani, F.; Beltrán, M. T.; Vasyunin, A.; Caselli, P.; Martín-Pintado, J.; Cesaroni, R.

    2016-08-01

    Phosphorus is a crucial element in biochemistry, in particular the P-O bond, which is key in the formation of the backbone of deoxyribonucleic acid. So far, PO has only been detected toward the envelope of evolved stars, but never toward star-forming regions. We report the first detection of PO toward two massive star-forming regions, W51 e1/e2 and W3(OH), using data from the IRAM 30 m telescope. PN has also been detected toward the two regions. The abundance ratio PO/PN is 1.8 and 3 for W51 and W3(OH), respectively. Our chemical model indicates that the two molecules are chemically related and are formed via gas-phase ion-molecule and neutral-neutral reactions during cold collapse. The molecules freeze out onto grains at the end of the collapse and desorb during the warm-up phase once the temperature reaches ˜35 K. Similar abundances of the two species are expected during a period of ˜5 × 104 yr at the early stages of the warm-up phase, when the temperature is in the range 35-90 K. The observed molecular abundances of 10-10 are predicted by the model if a relatively high initial abundance of 5 × 10-9 of depleted phosphorus is assumed.

  12. Class I methanol masers in low-mass star-forming regions

    NASA Astrophysics Data System (ADS)

    Kalenskii, S. V.; Kurtz, S.; Bergman, P.

    2013-02-01

    Results of observations of Class I methanol masers in regions of low-mass star formation (MMIL) are summarized and analyzed. Four masers were detected at 44, 84, and 95 GHz towards "chemically active" bipolar outflows in the low-mass star-forming regions NGC1333 I4A, NGC 1333 I2A, HH 25, and L1157. Another maser was found at 36 GHz towards a similar outflow in NGC 2023. Thus, all the detected MMILs are associated with chemically active outflows. The brightness temperatures of the strongest 44-GHz maser spots in NGC 1333 I4A, HH 25, and L1157 exceed 2000 K, whereas the brightness temperature in NGC 1333 I2A is only 176 K, although a rotational-diagram analysis shows that this last source is also amaser. The flux densities of the newly detectedmasers are no higher than 18 Jy, and are much lower than those of strong masers in regions of high-mass star formation (MMIH). The MMIL luminosities match the maser luminosity-protostar luminosity relation established earlier for MMIHs. No MMIL variability was detected in 2004-2011. The radial velocities of the newly detected masers are close to the systemic velocities of the associated regions, except for NGC 2023, where the maser radial velocity is lower than the systemic velocity by approximately 3.5 km/s. Thus, the main MMILproperties are similar to those of MMIHs. MMILs are likely to be an extension of the MMIH population toward lower luminosities of both the masers and the associated young stellar objects. The results of VLA observations of MMILs can be explained using a turbulent-cloud model, which predicts that compact maser spots can arise in extended sources because the coherence lengths along some directions randomly appear to be longer than the mean coherence length in a turbulent velocity field. However, one must assume that the column density of methanol towardM1, the strongest maser in L1157, is appreciably higher than the mean column density of the clump B0a where the maser arises. The shape of the maser lines

  13. Sulphur abundance determinations in star-forming regions - I. Ionization correction factor

    NASA Astrophysics Data System (ADS)

    Dors, O. L.; Pérez-Montero, E.; Hägele, G. F.; Cardaci, M. V.; Krabbe, A. C.

    2016-03-01

    In this work, we used a grid of photoionization models combined with stellar population synthesis models to derive reliable ionization correction factors (ICFs) for the sulphur in star-forming regions. These models cover a large range of nebular parameters and yielding ionic abundances in consonance with those derived through optical and infrared observational data of star-forming regions. From our theoretical ICFs, we suggested an α value of 3.27 ± 0.01 in the classical Stasińska formulae. We compared the total sulphur abundance in the gas phase of a large sample of objects by using our theoretical ICF and other approaches. In average, the differences between the determinations via the use of the different ICFs considered are similar to the uncertainties in the S/H estimations. Nevertheless, we noted that for some objects it could reach up to about 0.3 dex for the low-metallicity regime. Despite of the large scatter of the points, we found a trend of S/O ratio to decrease with the metallicity, independently of the ICF used to compute the sulphur total abundance.

  14. Observations of HDO in the High-Mass Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Kulczak-Jastrzębska, M.

    2016-06-01

    I present observations of the ground state (10,1-00,0) rotational transition of HDO at 464.925 GHz toward several high-mass star forming regions carried out with the Caltech Submillimeter Observatory. The spectra are modeled together with observations of higher-energy HDO transitions and submillimeter dust continuum fluxes present in the literature. Spherically symmetric radiative transfer model was used to derive the radial distribution of the HDO abundance in the target sources. The abundance profile is divided into an inner hot core region, with kinetic temperatures higher than 100 K, and a cold outer envelope. The derived HDO abundances relative to H2 are: (0.6-3.5)×10-8 and (0.1-25)×10-11 in the hot inner region and the cold outer envelope, respectively.

  15. The Stellar Content of Intermediate-Mass Star-Forming Regions.

    NASA Astrophysics Data System (ADS)

    Lundquist, Michael; Kobulnicky, H.; Alexander, M.; Vargas Alvarez, C.; Arvidsson, K.; Kerton, C.

    2012-01-01

    In an effort to understand the factors that govern the transition from low- to high-mass star formation, we report near-infrared imaging and spectroscopy of stars within a sample of intermediate-mass star-forming regions (IMSFRs). Some IMSFRs appear to contain compact <1 pc embedded clusters at an early evolutionary stage similar to compact HII regions, but lacking the massive ionizing central star(s). The IMSFRs have photodissociation regions with diameters 1 pc powered by the equivalent of an early B star, but because all sources lack radio free-free emission, they must host a collection of less massive stars. These spectroscopic observations using FLAMINGOS on the Kitt Peak 4 m telescope, coupled with 2MASS and UKIDSS infrared imaging, identify which candidate IMSFRs host probable stellar clusters and address the nature of their most massive stellar constituents.

  16. X-ray and Infrared Surveys of Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Gagne, Marc

    2005-07-01

    Since most stars in the Galaxy probably formed in giant molecular clouds, identifying nearly complete samples of low-mass stars in galactic star-forming regions is an important step in understanding the overall star-formation process. Recent X-ray, optical, and near-infrared studies of the galactic HII regions M8, M16, M17 and M20 have significantly increased the number of known cluster stars. By comparing their X-ray and infrared properties with stars in well-studied regions like the Orion Nebula Cluster, we can estimate distance, age and completeness. These studies will be used to assess the prevalence of triggered star-formation.

  17. Nitric oxide in star-forming regions: further evidence for interstellar N-O bonds.

    PubMed

    Ziurys, L M; McGonagle, D; Minh, Y; Irvine, W M

    1991-06-01

    Nitric oxide has been newly detected towards several star-forming clouds, including Orion-KL, Sgr B2(N), W33A, W51M, and DR21(OH) via its J = 3/2 --> 1/2 transitions near 150 GHz, using the FCRAO 14 m telescope. Both lambda-doubling components of NO were observed towards all sources. Column densities derived for nitric oxide in these clouds are N approximately 10(15)-10(16) cm-2, corresponding to fractional abundances of f approximately 0.5-1.0 x 10(-8), relative to H2. Towards Orion-KL, the NO line profile suggests that the species arises primarily from hot, dense gas. Nitric oxide may arise from warm material toward the other clouds as well. Nitric oxide in star-forming regions could be synthesized by high-temperature reactions, although the observed abundances do not disagree with values predicted from low-temperature, ion-molecule chemistry by more than one order of magnitude. The abundance of NO, unlike other simple interstellar nitrogen compounds, does appear to be reproduced by chemical models, at least to a good approximation. Regardless of the nature of formation of NO, it appears to be a common constituent of warm, dense molecular clouds. N-O bonds may therefore be more prevalent than previously thought.

  18. Trigonometric parallaxes to star-forming regions within 4 kpc of the galactic center

    SciTech Connect

    Sanna, A.; Menten, K. M.; Zhang, B.; Sato, M.; Brunthaler, A.; Immer, K.; Reid, M. J.; Dame, T. M.; Moscadelli, L.

    2014-02-01

    We report four trigonometric parallaxes for high-mass star-forming regions within 4 kpc of the Galactic center. These measurements were made with the Very Long Baseline Array as part of the BeSSeL Survey. By associating these sources kinematically with large-scale features in CO and H I longitude-velocity diagrams, we begin to outline some major features of the inner Milky Way: the Connecting arm, the near and far 3 kpc arms, and the Norma arm. The Connecting arm in the first Galactic quadrant lies closer to the Galactic center than the far 3 kpc arm and is offset by the long-bar's major axis near its leading edge, supporting the presence of an inner Lindblad resonance. Assuming the 3 kpc arms are a continuous physical structure, the relative Galactocentric distance of its near and far sides suggests highly elliptical streamlines of gas around the bar(s) and a bar corotation radius, r {sub CR} ≳ 3.6 kpc. At a Galactic longitude near 10° and a heliocentric distance of about 5 kpc, the near 3 kpc arm and the Norma arm intersect on a face-on view of our Galaxy, while passing at different Galactic latitudes. We provide an accurate distance measurement to the W 31 star-forming complex of 4.95{sub −0.43}{sup +0.51} kpc from the Sun, which associates it with a bright CO feature belonging to the near 3 kpc arm.

  19. Young open clusters in the Galactic star forming region NGC 6357

    NASA Astrophysics Data System (ADS)

    Massi, F.; Giannetti, A.; Di Carlo, E.; Brand, J.; Beltrán, M. T.; Marconi, G.

    2015-01-01

    Context. NGC 6357 is an active star forming region with very young massive open clusters. These clusters contain some of the most massive stars in the Galaxy and strongly interact with nearby giant molecular clouds. Aims: We study the young stellar populations of the region and of the open cluster Pismis 24, focusing on their relationship with the nearby giant molecular clouds. We seek evidence of triggered star formation "propagating" from the clusters. Methods: We used new deep JHKs photometry, along with unpublished deep Spitzer/IRAC mid-infrared photometry, complemented with optical HST/WFPC2 high spatial resolution photometry and X-ray Chandra observations, to constrain age, initial mass function, and star formation modes in progress. We carefully examine and discuss all sources of bias (saturation, confusion, different sensitivities, extinction). Results: NGC 6357 hosts three large young stellar clusters, of which Pismis 24 is the most prominent. We found that Pismis 24 is a very young (~1-3 Myr) open cluster with a Salpeter-like initial mass function and a few thousand members. A comparison between optical and infrared photometry indicates that the fraction of members with a near-infrared excess (i.e., with a circumstellar disk) is in the range 0.3-0.6, consistent with its photometrically derived age. We also find that Pismis 24 is likely subdivided into a few different subclusters, one of which contains almost all the massive members. There are indications of current star formation triggered by these massive stars, but clear age trends could not be derived (although the fraction of stars with a near-infrared excess does increase towards the Hii region associated with the cluster). The gas out of which Pismis 24 formed must have been distributed in dense clumps within a cloud of less dense gas ~1 pc in radius. Conclusions: Our findings provide some new insight into how young stellar populations and massive stars emerge, and evolve in the first few Myr after

  20. Modeling the water line emission from the high-mass star-forming region AFGL 2591

    NASA Astrophysics Data System (ADS)

    Poelman, D. R.; van der Tak, F. F. S.

    2007-12-01

    Context: Observations of water lines are a sensitive probe of the geometry, dynamics and chemical structure of dense molecular gas. The launch of Herschel with on board HIFI and PACS allows to probe the behaviour of multiple water lines with unprecedented sensitivity and resolution. Aims: We investigate the diagnostic value of specific water transitions in high-mass star-forming regions. As a test case, we apply our models to the AFGL 2591 region. Methods: A multi-zone escape probability method is used in two dimensions to calculate the radiative transfer. Similarities and differences of constant and jump abundance models are displayed, as well as when an outflow is incorporated. Results: In general, for models with a constant water abundance, the ground state lines, i.e., 110-101, 111-000, and 212-101, are predicted in absorption, all the others in emission. This behaviour changes for models with a water abundance jump profile in that the line profiles for jumps by a factor of ~10-100 are similar to the line shapes in the constant abundance models, whereas larger jumps lead to emission profiles. Asymmetric line profiles are found for models with a cavity outflow and depend on the inclination angle. Models with an outflow cavity are favoured to reproduce the SWAS observations of the 110-101 ground-state transition. PACS spectra will tell us about the geometry of these regions, both through the continuum and through the lines. Conclusions: It is found that the low-lying transitions of water are sensitive to outflow features, and represent the excitation conditions in the outer regions. High-lying transitions are more sensitive to the adopted density and temperature distribution which probe the inner excitation conditions. The Herschel mission will thus be very helpful to constrain the physical and chemical structure of high-mass star-forming regions such as AFGL 2591.

  1. Tracing the PAH-YSO Relationship in Nine LMC Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Carlson, Lynn R.; Galaxy Evolution), SAGE (Surveying the Agents of

    2013-01-01

    I present the discovery of over 1000 Young Stellar Objects (YSOs) in nine diverse star-forming regions in the Large Magellanic Cloud (Carlson et al. 2012 A&A 542, 66). These sources are color-selected in the infrared using SAGE Spitzer IRAC bands and MIPS 24μm, and their spectral energy distributions are fit as in Robitaille et al. (2007) to determine their approximate physical characteristics and evolutionary stages. I then look at the physical distribution of emission from polycyclic-aromatic hydrocarbons (PAHs) in these regions by comparing IRAC fluxes as in Povich et al. (2007) and identifying YSOs with significant PAH emission. The clearest PAH tracer is 8μm/4.5μm, as the [8.0] encompasses the strong 7.7μm feature, while the [4.5] has no PAH contribution. The YSO and PAH distributions are compared.

  2. Modeling the production of highly-complex molecules in star-forming regions

    NASA Astrophysics Data System (ADS)

    Garrod, R. T.

    2016-05-01

    Molecules of increasing complexity are being observed toward star-forming regions, including the recently detected iso-propyl cyanide, the first interstellar branched carbon-chain molecule. Modeling the formation of new complex organics requires new grain-surface production mechanisms, as well as gas-phase and grain-surface destruction processes. The method for constructing networks for new molecules is discussed, as well as the results of recent models of branched carbon-chain molecule chemistry. The formation of both simple and complex organics in cold regions is also discussed. New, exact kinetics models indicate that complex molecules may be formed efficiently at very low temperatures, if CO is abundant on the grain surfaces.

  3. Deep VLA observations of nearby star forming regions I: Barnard 59 and Lupus 1

    NASA Astrophysics Data System (ADS)

    Dzib, S. A.; Loinard, L.; Medina, S.-N. X.; Rodríguez, L. F.; Mioduszewski, A. J.; Torres, R. M.

    2016-04-01

    Barnard 59 and Lupus 1 are two nearby star-forming regions visible from the southern hemisphere. In this manuscript, we present deep (σ˜15 μJy) radio observations (ν=6 GHz) of these regions, and report the detection of a total of 114 sources. Thirteen of these sources are associated with known young stellar objects, nine in Barnard 59 and four in Lupus 1. The properties of the radio emission (spectral index and, in some cases, polarization) suggest a thermal origin for most young stellar objects. Only for two sources (Sz 65 and Sz 67) are there indications for a possible non-thermal origin. The remaining radio detections do not have counterparts at other wavelengths, and the number of sources detected per unit solid angle is in agreement with extragalactic number counts, suggesting that they are extragalactic sources.

  4. A kinematic analysis of the Giant star-forming Region of N11

    NASA Astrophysics Data System (ADS)

    Torres-Flores, Sergio; Barbá, Rodolfo; Maíz Apellániz, Jesús; Rubio, Mónica; Bosch, Guillermo

    2015-02-01

    In this work we present high resolution spectroscopic data of the giant star-forming region of N11, obtained with the GIRAFFE instrument at the Very Large Telescope. By using this data set, we find that most of the Hα emission lines profiles in this complex can be fitted by a single Gaussian, however, multiple emission line profiles can be observed in the central region of N11. By adding all the spectra, we derive the integrated Hα profile of this complex, which displays a width (σ) of about 12 km s-1 (corrected by instrumental and thermal width). We find that a single Gaussian fit on the integrated Hα profile leaves remaining wings, which can be fitted by a secondary broad Gaussian component. In addition, we find high velocity features, which spatially correlate with soft diffuse X-ray emission.

  5. An all-sky sample of intermediate-mass star-forming regions

    SciTech Connect

    Lundquist, Michael J.; Kobulnicky, Henry A.; Alexander, Michael J.; Kerton, Charles R.; Arvidsson, Kim

    2014-04-01

    We present an all-sky sample of 984 candidate intermediate-mass Galactic star-forming regions that are color selected from the Infrared Astronomical Satellite (IRAS) Point Source Catalog and morphologically classify each object using mid-infrared Wide-field Infrared Survey Explorer (WISE) images. Of the 984 candidates, 616 are probable star-forming regions (62.6%), 128 are filamentary structures (13.0%), 39 are point-like objects of unknown nature (4.0%), and 201 are galaxies (20.4%). We conduct a study of four of these regions, IRAS 00259+5625, IRAS 00420+5530, IRAS 01080+5717, and IRAS 05380+2020, at Galactic latitudes |b| > 5° using optical spectroscopy from the Wyoming Infrared Observatory, along with near-infrared photometry from the Two-Micron All Sky Survey, to investigate their stellar content. New optical spectra, color-magnitude diagrams, and color-color diagrams reveal their extinctions, spectrophotometric distances, and the presence of small stellar clusters containing 20-78 M {sub ☉} of stars. These low-mass diffuse star clusters contain ∼65-250 stars for a typical initial mass function, including one or more mid-B stars as their most massive constituents. Using infrared spectral energy distributions we identify young stellar objects near each region and assign probable masses and evolutionary stages to the protostars. The total infrared luminosity lies in the range 190-960 L {sub ☉}, consistent with the sum of the luminosities of the individually identified young stellar objects.

  6. A Survey of Large Molecules of Biological Interest toward Selected High Mass Star Forming Regions

    NASA Technical Reports Server (NTRS)

    Remijan, A.; Shiao, Y.-S.; Friedel, D. N.; Meier, D. S.; Snyder, L. E.

    2004-01-01

    We have surveyed three high mass Galactic star forming regions for interstellar methanol (CH3OH), formic acid (HCOOH), acetic acid (CH3COOH), methyl formate (HCOOCH3), methyl cyanide (CH3CN), and ethyl cyanide (CH3CH2CN) with the BIMA Array. From our observations, we have detected two new sources of interstellar HCOOH toward the hot core regions G19.61-0.23 and W75N. We have also made the first detections of CH3CH2CN and HCOOCH3 toward G19.61-0.23. The relative HCOOH/HCOOCH3 abundance ratio toward G19.61-0.23 is 0.18 which is comparable to the abundance ratios found by Liu and colleagues toward Sgr B2(N-LMH), Orion and W51(approximately 0.10). We have made the first detection of HCOOCH3 toward W75N. The relative HCOOH/HCOOCH3 abundance ratio toward W75N is 0.26 which is more than twice as large as the abundance ratios found by Liu and colleagues. Furthermore, the hot core regions around W75N show a chemical differentiation between the O and N cores similar to what is seen toward the Orion Hot Core and Compact Ridge and W3(OH) and W3(H2O). It is also apparent from our observations that the high mass star forming region G45.47+0.05 does not contain any compact hot molecular core and as a consequence its chemistry may be similar to cold dark clouds. Finally, the formation of CH3COOH appears to favor HMCs with well mixed N and O, despite the fact that CH3COOH does not contain a N atom. If proved to be true, this is an important constraint on CH3COOH formation and possibly other structurally similar biomolecules.

  7. Chemical characterization of the early evolutionary phases of high-mass star-forming regions

    NASA Astrophysics Data System (ADS)

    Gerner, Thomas

    2014-10-01

    The formation of high-mass stars is a very complex process and up to date no comprehensive theory about it exists. This thesis studies the early stages of high-mass star-forming regions and employs astrochemistry as a tool to probe their different physical conditions. We split the evolutionary sequence into four observationally motivated stages that are based on a classification proposed in the literature. The sequence is characterized by an increase of the temperatures and densities that strongly influences the chemistry in the different stages. We observed a sample of 59 high-mass star-forming regions that cover the whole sequence and statistically characterized the chemical compositions of the different stages. We determined average column densities of 18 different molecular species and found generally increasing abundances with stage. We fitted them for each stage with a 1D model, such that the result of the best fit to the previous stage was used as new input for the following. This is a unique approach and allowed us to infer physical properties like the temperature and density structure and yielded a typical chemical lifetime for the high-mass star-formation process of 1e5 years. The 18 analyzed molecular species also included four deuterated molecules whose chemistry is particularly sensitive to thermal history and thus is a promising tool to infer chemical ages. We found decreasing trends of the D/H ratios with evolutionary stage for 3 of the 4 molecular species and that the D/H ratio depends more on the fraction of warm and cold gas than on the total amount of gas. That indicates different chemical pathways for the different molecules and confirms the potential use of deuterated species as chemical age indicators. In addition, we mapped a low-mass star forming region in order to study the cosmic ray ionization rate, which is an important parameter in chemical models. While in chemical models it is commonly fixed, we found that it ! strongly varies with

  8. VERY LARGE ARRAY OH ZEEMAN OBSERVATIONS OF THE STAR-FORMING REGION S88B

    SciTech Connect

    Sarma, A. P.; Eftimova, M.; Brogan, C. L.; Bourke, T. L.; Troland, T. H.

    2013-04-10

    We present observations of the Zeeman effect in OH thermal absorption main lines at 1665 and 1667 MHz taken with the Very Large Array toward the star-forming region S88B. The OH absorption profiles toward this source are complicated, and contain several blended components toward a number of positions. Almost all of the OH absorbing gas is located in the eastern parts of S88B, toward the compact continuum source S88B-2 and the eastern parts of the extended continuum source S88B-1. The ratio of 1665/1667 MHz OH line intensities indicates the gas is likely highly clumped, in agreement with other molecular emission line observations in the literature. S88-B appears to present a similar geometry to the well-known star-forming region M17, in that there is an edge-on eastward progression from ionized to molecular gas. The detected magnetic fields appear to mirror this eastward transition; we detected line-of-sight magnetic fields ranging from 90 to 400 {mu}G, with the lowest values of the field to the southwest of the S88B-1 continuum peak, and the highest values to its northeast. We used the detected fields to assess the importance of the magnetic field in S88B by a number of methods; we calculated the ratio of thermal to magnetic pressures, we calculated the critical field necessary to completely support the cloud against self-gravity and compared it to the observed field, and we calculated the ratio of mass to magnetic flux in terms of the critical value of this parameter. All these methods indicated that the magnetic field in S88B is dynamically significant, and should provide an important source of support against gravity. Moreover, the magnetic energy density is in approximate equipartition with the turbulent energy density, again pointing to the importance of the magnetic field in this region.

  9. New HH objects in star-forming regions: Parsec-scale outflows in GM 2 30

    NASA Astrophysics Data System (ADS)

    Nikogossian, E. G.; Magakian, T. Yu.; Movsessian, T. A.

    2007-09-01

    We examine the star-forming region in a molecular cloud with the coordinates l = 33.30°, b = 0.25° at a distance of 1.7 kpc, in which the nebula GM 2 30 is embedded. Apart from the previously known Herbig—Haro object HH 172, several new HH objects have been found, comprising at least two HH flows. The internal structure of these objects is studied. The relationship between the line emission and kinematic data obtained through multi-pupil spectroscopy suggest the presence of bipolar outflow associated with the nebula GM 2 30 and HH 172/HH 721, which show mirror symmetry according to a number of characteristics. No optical source of this flow is observed, although the source of energy of the second flow may be a weak star associated with HH 723. The linear dimensions of the flows (more than one parsec) suggest that they are the giant outflows.

  10. The SONYC survey: Towards a complete census of brown dwarfs in star forming regions

    NASA Astrophysics Data System (ADS)

    Muzic, K.; Scholz, A.; Jayawardhana, R.; Geers, V. C.; Dawson, P.; Ray, T. P.; Tamura, M.

    2014-10-01

    Deep surveys of star forming regions are the backbone of observational studies on the origin of stars and planets: On one side, they provide large and homogeneous object samples required to study disks, accretion, and multiplicity. On the other side, such surveys determine the shape and the low-mass limit of the Initial Mass Function (IMF), which are fundamental constraints on star formation theory. SONYC, short for ``Substellar Objects in Nearby Young Clusters", is an ongoing project to provide a census of the substellar population in nearby star forming regions. We have conducted deep optical and near-infrared photometry, combined with proper motions, and followed by extensive spectroscopic follow-up campaigns with Subaru and VLT, in which we have obtained more than 700 spectra of candidate objects in NGC1333, ρ Ophiuchi, Chamaeleon-I, Upper Sco, and Lupus-3. We have identified and characterized more than 60 new substellar objects, among them a handful of objects with masses close to, or below the Deuterium burning limit. Thanks to the SONYC survey and the efforts of other groups, the substellar IMF is now well characterized down to ˜ 5 - 10 M_{J}, and we find that the ratio of the number of stars with respect to brown dwarfs lies between 2 ad 6. Another important piece of information for the star formation theories is that, down to ˜ 5 M_J, the free-floating objects with planetary masses are 20-50 times less numerous than stars, so that their total contribution to the mass budget of the clusters can be neglected. In this contribution we will present the status of the SONYC survey, discuss its main results, and focus on the latest findings in NGC1333, Lupus-3 and Upper-Sco.

  11. Extremely Bright Submillimeter Galaxies beyond the Lupus-I Star-forming Region

    NASA Astrophysics Data System (ADS)

    Tamura, Y.; Kawabe, R.; Shimajiri, Y.; Tsukagoshi, T.; Nakajima, Y.; Oasa, Y.; Wilner, D. J.; Chandler, C. J.; Saigo, K.; Tomida, K.; Yun, M. S.; Taniguchi, A.; Kohno, K.; Hatsukade, B.; Aretxaga, I.; Austermann, J. E.; Dickman, R.; Ezawa, H.; Goss, W. M.; Hayashi, M.; Hughes, D. H.; Hiramatsu, M.; Inutsuka, S.; Ogasawara, R.; Ohashi, N.; Oshima, T.; Scott, K. S.; Wilson, G. W.

    2015-08-01

    We report detections of two candidate distant submillimeter galaxies (SMGs), MM J154506.4-344318 and MM J154132.7-350320, which are discovered in the AzTEC/ASTE 1.1 mm survey toward the Lupus-I star-forming region. The two objects have 1.1 mm flux densities of 43.9 and 27.1 mJy, and have Herschel/SPIRE counterparts as well. The Submillimeter Array counterpart to the former SMG is identified at 890 μm and 1.3 mm. Photometric redshift estimates using all available data from the mid-infrared to the radio suggest that the redshifts of the two SMGs are {z}{photo}≃ 4-5 and 3, respectively. Near-infrared objects are found very close to the SMGs and they are consistent with low-z ellipticals, suggesting that the high apparent luminosities can be attributed to gravitational magnification. The cumulative number counts at {S}1.1{mm}≥slant 25 mJy, combined with the other two 1.1 mm brightest sources, are {0.70}-0.34+0.56 deg-2, which is consistent with a model prediction that accounts for flux magnification due to strong gravitational lensing. Unexpectedly, a z\\gt 3 SMG and a Galactic dense starless core (e.g., a first hydrostatic core) could be similar in the mid-infrared to millimeter spectral energy distributions and spatial structures at least at ≳ 1\\prime\\prime . This indicates that it is necessary to distinguish the two possibilities by means of broadband photometry from the optical to centimeter and spectroscopy to determine the redshift, when a compact object is identified toward Galactic star-forming regions.

  12. Probing the brown dwarf population of the Chamaeleon I star forming region

    NASA Astrophysics Data System (ADS)

    Comerón, F.; Neuhäuser, R.; Kaas, A. A.

    2000-07-01

    We present observations of a sample of 13 very low mass stars and brown dwarfs in the central region of the Chamaeleon I star forming cloud. The observations include slitless spectroscopy around Hα to identify new members, low resolution long-slit visible and near-infrared spectroscopy, deep ROSAT PSPC X-ray observations, and ISOCAM mid-infrared observations. Our sample adds seven new objects to those discussed by Comerón, Rieke, and Neuhäuser (1999, A&A, 343, 477) and extends the range of spectral types up to M8. We study different narrow-band indices as a tool for detecting and classifying very late-type young stellar objects. As to K-band spectra, we find that the visible features are not appropriate to yield a spectral classification more accurate than a few subclasses at best beyond M6. None of our sources displays K-band excess emission, but four have excess at 6.7 mu m suggesting that, although circumstellar disks are common around young very low mass stars, their inner regions are in general not hot enough to radiate significantly in the K band. Mid-infrared emission loosely correlates with Hα emission: sources without mid-IR excesses are always weak Hα emitters, while mid-IR excess sources have a broad range of Hα equivalent widths. X-ray emission is detected for 7 objects with spectral type M6 or later, including one bona-fide brown dwarf and three objects near the border separating stars and brown dwarfs. X-ray to bolometric luminosity ratios are typical of low mass, fully convective stars. The non-detection of X-ray emission at comparable levels from more evolved brown dwarfs suggests that X-ray activity may be restricted to early stages of brown dwarf evolution. We discuss in detail the temperatures and luminosities of our objects based on their magnitudes and spectra, and use the derived values to estimate masses and ages according to two different sets of pre-main sequence evolutionary tracks. Both sets of models are in good agreement

  13. Different Evolutionary Stages in the Massive Star-forming Region W3 Main Complex

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Beuther, Henrik; Zhang, Qizhou; Bik, Arjan; Rodón, Javier A.; Jiang, Zhibo; Fallscheer, Cassandra

    2012-08-01

    We observed three high-mass star-forming regions in the W3 high-mass star formation complex with the Submillimeter Array and IRAM 30 m telescope. These regions, i.e., W3 SMS1 (W3 IRS5), SMS2 (W3 IRS4) and SMS3, are in different evolutionary stages and are located within the same large-scale environment, which allows us to study rotation and outflows as well as chemical properties in an evolutionary sense. While we find multiple millimeter continuum sources toward all regions, these three subregions exhibit different dynamical and chemical properties, which indicate that they are in different evolutionary stages. Even within each subregion, massive cores of different ages are found, e.g., in SMS2, sub-sources from the most evolved ultracompact H II region to potential starless cores exist within 30,000 AU of each other. Outflows and rotational structures are found in SMS1 and SMS2. Evidence for interactions between the molecular cloud and the H II regions is found in the 13CO channel maps, which may indicate triggered star formation.

  14. Carbon gas in SMC low-metallicity star-forming regions

    NASA Astrophysics Data System (ADS)

    Requena-Torres, M. A.; Israel, F. P.; Okada, Y.; Güsten, R.; Stutzki, J.; Risacher, C.; Simon, R.; Zinnecker, H.

    2016-05-01

    This paper presents [ CII ], [ CI ] and CO emission line maps of the star-forming regions N 66, N 25+N 26, and N 88 in the metal-poor Local Group dwarf galaxy SMC. The spatial and velocity structure of the large HII region N 66 reveals an expanding ring of shocked molecular gas centered on the exciting star cluster NGC 346, whereas a more distant dense molecular cloud is being eroded by UV radiation from the same cluster. In the N 25+N 26 and N 88 maps, diffuse [ CII ] emission at a relatively low surface brightness extends well beyond the compact boundaries of the bright emission associated with the HII regions. In all regions, the distribution of this bright [ CII ] emission and the less prominent [ CI ] emission closely follows the outline of the CO complexes, but the intensity of the [ CII ] and [ CI ] emission is generally anticorrelated, which can be understood by the action of photodissociation and photoionization processes. Notwithstanding the overall similarity of CO and [ CII ] maps, the intensity ratio of these lines varies significantly, mostly due to changes in CO brightness. [ CII ] emission line profiles are up to 50% wider in velocity than corresponding CO profiles. A radiative transfer analysis shows that the [ CII ] line is the dominant tracer of (CO-dark) molecular hydrogen in the SMC. CO emission traces only a minor fraction of the total amount of gas. The similarity of the spatial distribution and line profile shape, and the dominance of molecular gas associated with [ CII ] rather than CO emission imply that in the low-metallicity environment of the SMC the small amount of dense molecular gas traced by CO is embedded in the much more extended molecular gas traced only by [ CII ] emission. The contribution from neutral atomic and ionized hydrogen zones is negligible in the star-forming regions observed. The reduced datacubes (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via

  15. A Proper-Motion Census of Star-Forming Regions in the Solar Neighborhood

    NASA Astrophysics Data System (ADS)

    Kraus, Adam; Stauffer, John; Evans, Neal; Allers, Katelyn; Dunham, Michael; Lu, Jessica; Jaffe, Daniel

    2012-09-01

    Over the past decade, Spitzer has revolutionized our understanding of the membership, mass functions, and disk populations of the star-forming regions in the solar neighborhood. However, the faintest members of these populations have remained elusive, particularly in highly-embedded regions of ongoing star formation. Mid-infrared color selection is not effective at distinguishing proto-brown dwarfs and disk-free young stars from dusty galaxies or reddened field stars, and optical/NIR spectroscopic confirmation remains too expensive. The most cost-effective method to identify this missing population is to confirm common proper motion with their host regions. The astrometric performance of IRAC has been considered insufficient for this task, but as we demonstrate, our new characterization of the IRAC optical distortion improves the astrometric noise floor from 0.1-0.2 arcsec to 0.01-0.02 arcsec at each epoch, corresponding to proper motion uncertainties as low as 2 mas/yr. We propose a Spitzer/IRAC Exploration Science program for 560 hours to conduct second-epoch imaging for a proper-motion search of six stellar populations: Ophiuchus, Lupus, Chamaeleon, Perseus, Taurus, and Corona Australis. We will observe dense mosaics that span the areas which were previously observed during the cryogenic mission. In combination with the existing first-epoch astrometry, we will measure proper motions with uncertainties of <=5 mas/yr for sources as faint as m_[3.6] = 17.5, reaching photospheric fluxes corresponding to 1-2 MJup at 1 Myr. Our census will reveal the shape and slope of the proto(sub)stellar luminosity function, identify free-floating counterparts of young giant planets, search for the dynamical signatures of star formation models, and study disk evolution/dispersal and planet formation around the youngest and lowest-mass primaries. In summary, our program will unveil the last unidentified members in the benchmark star-forming regions which have been studied so

  16. The growth of the central region by acquisition of counterrotating gas in star-forming galaxies

    PubMed Central

    Chen, Yan-Mei; Shi, Yong; Tremonti, Christy A.; Bershady, Matt; Merrifield, Michael; Emsellem, Eric; Jin, Yi-Fei; Huang, Song; Fu, Hai; Wake, David A.; Bundy, Kevin; Stark, David; Lin, Lihwai; Argudo-Fernandez, Maria; Bergmann, Thaisa Storchi; Bizyaev, Dmitry; Brownstein, Joel; Bureau, Martin; Chisholm, John; Drory, Niv; Guo, Qi; Hao, Lei; Hu, Jian; Li, Cheng; Li, Ran; Lopes, Alexandre Roman; Pan, Kai-Ke; Riffel, Rogemar A.; Thomas, Daniel; Wang, Lan; Westfall, Kyle; Yan, Ren-Bin

    2016-01-01

    Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Here, based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counter-rotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counter-rotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (<1 kpc) to form new stars. PMID:27759033

  17. A kinematic study and membership analysis of the Lupus star-forming region

    NASA Astrophysics Data System (ADS)

    Galli, P. A. B.; Bertout, C.; Teixeira, R.; Ducourant, C.

    2013-10-01

    Aims: A precise determination of the distance to individual stars is required to reliably determine the fundamental parameters (mass and age) of young stellar objects. This paper is dedicated to investigating the kinematic properties of the Lupus moving group of young stars with the primary objective of deriving individual parallaxes for each group member. Methods: We identify those stars in the Lupus star-forming region that define the comoving association of young stars by utilizing our new and improved convergent point search method that allows us to derive the precise position of the convergent point of the comoving association from the stars' proper motions. We used published proper motion catalogs and searched the literature for radial velocities, which are needed to compute individual parallaxes. We supplemented the radial velocity data with new measurements from spectroscopic observations performed with the FEROS spectrograph mounted on the MPG/ESO 2.2 m telescope at La Silla. Results: We identify a comoving group with 109 pre-main sequence stars and candidates that define the kinematic properties of the Lupus low-mass star-forming region. We derive individual parallaxes for stars with known radial velocity and tentative parallaxes for the remaining group members by assuming that all stars share the same space motion. The convergent point method, combined with the k-NN algorithm, makes it possible to distinguish the Lupus and Upper Centaurus Lupus stars from the adjacent Scorpius-Centaurus association. We find significant depth effects in this region and show that the classical T Tauri stars, located in the close vicinity of the Lupus molecular clouds, form a background population, while the weak-emission line T Tauri stars are dispersed not only in angular extent but also in depth. Conclusions: The newly derived individual parallaxes will be used in a forthcoming paper to refine the masses and ages of Lupus T Tauri stars, with the aim of better

  18. AN INFRARED/X-RAY SURVEY FOR NEW MEMBERS OF THE TAURUS STAR-FORMING REGION

    SciTech Connect

    Luhman, K. L.; Allen, P. R.; Mamajek, E. E.; Cruz, K. L.

    2009-09-20

    We present the results of a search for new members of the Taurus star-forming region using data from the Spitzer Space Telescope and the XMM-Newton Observatory. We have obtained optical and near-infrared spectra of 44 sources that exhibit red Spitzer colors that are indicative of stars with circumstellar disks and 51 candidate young stars that were identified by Scelsi and coworkers using XMM-Newton. We also performed spectroscopy on four possible companions to members of Taurus that were reported by Kraus and Hillenbrand. Through these spectra, we have demonstrated the youth and membership of 41 sources, 10 of which were independently confirmed as young stars by Scelsi and coworkers. Five of the new Taurus members are likely to be brown dwarfs based on their late spectral types (>M6). One of the brown dwarfs has a spectral type of L0, making it the first known L-type member of Taurus and the least massive known member of the region (M {approx} 4-7 M{sub Jup}). Another brown dwarf exhibits a flat infrared spectral energy distribution, which indicates that it could be in the protostellar class I stage (star+disk+envelope). Upon inspection of archival images from various observatories, we find that one of the new young stars has a large edge-on disk (r = 2.''5 = 350 AU). The scattered light from this disk has undergone significant variability on a timescale of days in optical images from the Canada-France-Hawaii Telescope. Using the updated census of Taurus, we have measured the initial mass function for the fields observed by XMM-Newton. The resulting mass function is similar to previous ones that we have reported for Taurus, showing a surplus of stars at spectral types of K7-M1 (0.6-0.8 M{sub sun}) relative to other nearby star-forming regions, such as IC 348, Chamaeleon I, and the Orion Nebula Cluster.

  19. Star and jet multiplicity in the high-mass star forming region IRAS 05137+3919

    NASA Astrophysics Data System (ADS)

    Cesaroni, R.; Massi, F.; Arcidiacono, C.; Beltrán, M. T.; Persi, P.; Tapia, M.; Molinari, S.; Testi, L.; Busoni, L.; Riccardi, A.; Boutsia, K.; Bisogni, S.; McCarthy, D.; Kulesa, C.

    2015-09-01

    Context. We present a study of the complex high-mass star forming region IRAS 05137+3919 (also known as Mol8), where multiple jets and a rich stellar cluster have been described in previous works. Aims: Our goal is to determine the number of jets and shed light on their origin, and thus determine the nature of the young stars powering these jets. We also wish to analyse the stellar clusters by resolving the brightest group of stars. Methods: The star forming region was observed in various tracers and the results were complemented with ancillary archival data. The new data represent a substantial improvement over previous studies both in resolution and frequency coverage. In particular, adaptive optics provides us with an angular resolution of 80 mas in the near IR, while new mid- and far-IR data allow us to sample the peak of the spectral energy distribution and thus reliably estimate the bolometric luminosity. Results: Thanks to the near-IR continuum and millimetre line data we can determine the structure and velocity field of the bipolar jets and outflows in this star forming region. We also find that the stars are grouped into three clusters and the jets originate in the richest of these, whose luminosity is ~ 2.4 × 104L⊙. Interestingly, our high-resolution near-IR images allow us to resolve one of the two brightest stars (A and B) of the cluster into a double source (A1+A2). Conclusions: We confirm that there are two jets and establish that they are powered by B-type stars belonging to cluster C1. On this basis and on morphological and kinematical arguments, we conclude that the less extended jet is almost perpendicular to the line of sight and that it originates in the brightest star of the cluster, while the more extended one appears to be associated with the more extincted, double source A1+A2. We propose that this is not a binary system, but a small bipolar reflection nebula at the root of the large-scale jet, outlining a still undetected circumstellar

  20. The Disk Population of the Chamaeleon I Star-forming Region

    NASA Astrophysics Data System (ADS)

    Luhman, K. L.; Allen, L. E.; Allen, P. R.; Gutermuth, R. A.; Hartmann, L.; Mamajek, E. E.; Megeath, S. T.; Myers, P. C.; Fazio, G. G.

    2008-03-01

    We present a census of circumstellar disks in the Chamaeleon I star-forming region. Using the Infrared Array Camera and the Multiband Imaging Photometer on board the Spitzer Space Telescope, we have obtained images of Chamaeleon I at 3.6, 4.5, 5.8, 8.0, and 24 μm. To search for new disk-bearing members of the cluster, we have performed spectroscopy on objects that have red colors in these data. Through this work, we have discovered four new members of Chamaeleon I with spectral types of M4, M6, M7.5, and L0. The first three objects are highly embedded (AJ ~ 5) and reside near known protostars, indicating that they may be among the youngest low-mass sources in the cluster (τ < 1 Myr ). The L0 source is the coolest known member of Chamaeleon I. Its luminosity implies a mass of 0.004-0.01 M⊙, making it the least massive brown dwarf for which a circumstellar disk has been reliably detected. To characterize the disk population in Chamaeleon I, we have classified the infrared spectral energy distributions of the 203 known members that are encompassed by the Spitzer images. Through these classifications, we find that the disk fraction in Chamaeleon I is roughly constant at ~50% from 0.01 to 0.3 M⊙. These data are similar to the disk fraction of IC 348, which is a denser cluster at the same age as Chamaeleon I. However, the disk fraction at Mgtrsim 1 M⊙ is significantly higher in Chamaeleon I than in IC 348 (65% vs. 20%), indicating longer disk lifetimes in Chamaeleon I for this mass range. Thus, low-density star-forming regions like Chamaeleon I may offer more time for planet formation around solar-type stars than denser clusters. Based on observations performed with the Magellan Telescopes at Las Campanas Observatory, Gemini Observatory, and the Spitzer Space Telescope. Gemini Observatory is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NSF (United States), the Particle Physics and Astronomy Research Council

  1. TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. VI. GALACTIC STRUCTURE, FUNDAMENTAL PARAMETERS, AND NONCIRCULAR MOTIONS

    SciTech Connect

    Reid, M. J.; Sato, M.; Menten, K. M.; Brunthaler, A.; Xu, Y.; Choi, Y. K.; Zheng, X. W.; Zhang, B.; Moscadelli, L.; Honma, M.; Hirota, T.; Hachisuka, K.; Moellenbrock, G. A.; Bartkiewicz, A.

    2009-07-20

    We are using the Very Long Baseline Array and the Japanese VLBI Exploration of Radio Astronomy project to measure trigonometric parallaxes and proper motions of masers found in high-mass star-forming regions across the Milky Way. Early results from 18 sources locate several spiral arms. The Perseus spiral arm has a pitch angle of 16 deg. {+-} 3 deg., which favors four rather than two spiral arms for the Galaxy. Combining positions, distances, proper motions, and radial velocities yields complete three-dimensional kinematic information. We find that star-forming regions on average are orbiting the Galaxy {approx}15 km s{sup -1} slower than expected for circular orbits. By fitting the measurements to a model of the Galaxy, we estimate the distance to the Galactic center R {sub 0} = 8.4 {+-} 0.6 kpc and a circular rotation speed {theta}{sub 0} = 254 {+-} 16 km s{sup -1}. The ratio {theta}{sub 0}/R {sub 0} can be determined to higher accuracy than either parameter individually, and we find it to be 30.3 {+-} 0.9 km s{sup -1} kpc{sup -1}, in good agreement with the angular rotation rate determined from the proper motion of Sgr A*. The data favor a rotation curve for the Galaxy that is nearly flat or slightly rising with Galactocentric distance. Kinematic distances are generally too large, sometimes by factors greater than 2; they can be brought into better agreement with the trigonometric parallaxes by increasing {theta}{sub 0}/R {sub 0} from the IAU recommended value of 25.9 km s{sup -1} kpc{sup -1} to a value near 30 km s{sup -1} kpc{sup -1}. We offer a 'revised' prescription for calculating kinematic distances and their uncertainties, as well as a new approach for defining Galactic coordinates. Finally, our estimates of {theta}{sub 0} and {theta}{sub 0}/R{sub 0}, when coupled with direct estimates of R {sub 0}, provide evidence that the rotation curve of the Milky Way is similar to that of the Andromeda galaxy, suggesting that the dark matter halos of these two

  2. Molecular emission in dense massive clumps from the star-forming regions S231-S235

    NASA Astrophysics Data System (ADS)

    Ladeyschikov, D. A.; Kirsanova, M. S.; Tsivilev, A. P.; Sobolev, A. M.

    2016-04-01

    The paper is concerned with the study of the star-forming regions S231-S235 in radio lines of molecules of the interstellar medium—carbon monoxide (CO), ammonia (NH3), cyanoacetylene (HC3N), in maser lines—methanol (CH3OH) and water vapor (H2O). The regions S231-S235 belong to the giant molecular cloudG174+2.5. The goal of this paper is to search for new sources of emission toward molecular clumps and to estimate their physical parameters from CO and NH3 molecular lines. We obtained new detections ofNH3 andHC3Nlines in the sources WB89673 and WB89 668 which indicates the presence of high-density gas. From the CO line, we derived sizes, column densities, and masses of molecular clumps. From the NH3 line, we derived gas kinetic temperatures and number densities in molecular clumps. We determined that kinetic temperatures and number densities of molecular gas are within the limits 16-30 K and 2.8-7.2 × 103 cm-3 respectively. The shock-tracing line of CH3OH molecule at a frequency of 36.2 GHz was detected in WB89 673 for the first time.

  3. THE MASSIVE STAR-FORMING REGIONS OMNIBUS X-RAY CATALOG

    SciTech Connect

    Townsley, Leisa K.; Broos, Patrick S.; Feigelson, Eric D.; Getman, Konstantin V.; Kuhn, Michael A.; Garmire, Gordon P.; Bouwman, Jeroen; Povich, Matthew S.

    2014-07-01

    We present the Massive Star-forming Regions (MSFRs) Omnibus X-ray Catalog (MOXC), a compendium of X-ray point sources from Chandra/ACIS observations of a selection of MSFRs across the Galaxy, plus 30 Doradus in the Large Magellanic Cloud. MOXC consists of 20,623 X-ray point sources from 12 MSFRs with distances ranging from 1.7 kpc to 50 kpc. Additionally, we show the morphology of the unresolved X-ray emission that remains after the cataloged X-ray point sources are excised from the ACIS data, in the context of Spitzer and WISE observations that trace the bubbles, ionization fronts, and photon-dominated regions that characterize MSFRs. In previous work, we have found that this unresolved X-ray emission is dominated by hot plasma from massive star wind shocks. This diffuse X-ray emission is found in every MOXC MSFR, clearly demonstrating that massive star feedback (and the several-million-degree plasmas that it generates) is an integral component of MSFR physics.

  4. The Nature of Transition Disks in Nearby Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Cieza, Lucas A.; Schreiber, M. R.; Romero, G. A.; Orellana, M.; Williams, J. P.; Merin, B.

    2011-01-01

    We present an update on our ongoing project to characterize a large sample of Spitzer selected transition disks located in several star-forming regions. Transition objects are pre-main-sequence stars with optically thin inner disks and optically thick outer disks. Different mechanisms have been proposed to explain their inner opacity holes: planet formation, grain growth, photoevaporation, and tidal truncation in tight binaries. These mechanisms, all relevant to disk evolution in general, can be distinguished when disk masses, accretion rates, and multiplicity information are available. We have already completed our study of Ophiuchus objects, presenting the results from Adaptive Optics (AO) imaging, submillimeter photometry, and echelle spectroscopy observations. We are currently working on several other regions, including Taurus-Auriga, Perseus, Serpens, and Lupus. Our results show that transition disks are a very heterogeneous group of objects with a wide range of SED morphologies, disk masses ( < 0.5 to 40 Mjup), and accretion rates (<10E-11 to 10E-7 Msolar/yr). Since the properties of our transition disks point toward distinct processes driving the evolution of each disk, we have been able to identify very strong candidates for the following disk categories: circumbinary disks, grain-growth dominated disks, photoevaporating disks, debris disks, and (giant) planet-forming disks.

  5. YOUNG STELLAR OBJECTS IN THE LARGE MAGELLANIC CLOUD STAR-FORMING REGION N206

    SciTech Connect

    Romita, Krista Alexandra; Meixner, M.; Sewilo, M.; Shiao, B.; Carlson, Lynn Redding; Whitney, B.; Babler, B.; Meade, M.; Indebetouw, R.; Hora, J. L. E-mail: carlson@stsci.ed E-mail: brian@sal.wisc.ed E-mail: jhora@cfa.harvard.ed

    2010-09-20

    We present analysis of the energetic star-forming region Henize 206 (N206) located near the southern edge of the Large Magellanic Cloud (LMC) based on photometric data from the Spitzer Surveying the Agents of Galaxy Evolution (SAGE-LMC; IRAC 3.6, 4.5, 5.8, 8.0 {mu}m and MIPS 24 {mu}m), Infrared Survey Facility near-infrared survey (J, H, K{sub s}), and the Magellanic Clouds Photometric Survey (MCPS UBVI) covering a wavelength range of 0.36-24 {mu}m. Young stellar object (YSO) candidates are identified based upon their location in infrared color-magnitude space and classified by the shapes of their spectral energy distributions in comparison with a pre-computed grid of YSO models. We identify 116 YSO candidates: 102 are well characterized by the YSO models, predominately Stage I, and 14 may be multiple sources or young sources with transition disks. Careful examination of the individual sources and their surrounding environment allows us to identify a factor of {approx}14.5 more YSO candidates than have already been identified. The total mass of these well-fit YSO candidates is {approx}520 M{sub sun}. We calculate a current star formation rate of 0.27 x 10{sup -1} M{sub sun} yr{sup -1} kpc{sup -2}. The distribution of YSO candidates appears to follow shells of neutral material in the interstellar medium.

  6. Phosphorus-bearing molecules in solar-type star forming regions: First PO detection.

    NASA Astrophysics Data System (ADS)

    Lefloch, Bertrand; Vastel, C.; Viti, S.; Jimenez-Serra, I.; Codella, C.; Podio, L.; Ceccarelli, C.; Mendoza, E.; Lepine, J. R. D.; Bachiller, R.

    2016-08-01

    As part of the Large Program ASAI (Astrochemical Surveys At IRAM), we have used the IRAM 30m telescope to lead a systematic search for the emission of rotational transitions of P-bearing species between 80 and 350 GHz towards L1157-B1, a shock position in the solar-type star forming region L1157. We report the detection of several transitions of PN and, for the first time, of prebiotic molecule PO. None of these species are detected towards the driving protostar of the outflow L1157-mm. Analysis of the line profiles shows that PN arises from the outflow cavity, where SiO, a strong shock tracer, is produced. Radiative transfer analysis yields an abundance of 2.5 × 10-9 and 0.9 × 10-9 for PO and PN, respectively. These results imply a strong depletion (≈100) of Phosphorus in the quiescent cloud gas. Shock modelling shows that atomic N plays a major role in the chemistry of PO and PN. The relative abundance of PO and PN brings constraints both on the duration of the pre-shock phase, which has to be ˜ 106 yr, and on the shock parameters. The maximum temperature in the shock has to be larger than 4000 K, which implies a shock velocity of 40 km s-1.

  7. Phosphorus-bearing molecules in solar-type star-forming regions: first PO detection

    NASA Astrophysics Data System (ADS)

    Lefloch, Bertrand; Vastel, C.; Viti, S.; Jimenez-Serra, I.; Codella, C.; Podio, L.; Ceccarelli, C.; Mendoza, E.; Lepine, J. R. D.; Bachiller, R.

    2016-11-01

    As part of the Large Program Astrochemical Surveys At IRAM, we have used the IRAM 30 m telescope to lead a systematic search for the emission of rotational transitions of P-bearing species between 80 and 350 GHz towards L1157-B1, a shock position in the solar-type star-forming region L1157. We report the detection of several transitions of PN and, for the first time, of pre-biotic molecule PO. None of these species are detected towards the driving protostar of the outflow L1157-mm. Analysis of the line profiles shows that PN arises from the outflow cavity, where SiO, a strong shock tracer, is produced. Radiative transfer analysis yields an abundance of 2.5 × 10-9 and 0.9 × 10-9 for PO and PN, respectively. These results imply a strong depletion (≈100) of phosphorus in the quiescent cloud gas. Shock modelling shows that atomic N plays a major role in the chemistry of PO and PN. The relative abundance of PO and PN brings constraints both on the duration of the pre-shock phase, which has to be ˜106 yr, and on the shock parameters. The maximum temperature in the shock has to be larger than 4000 K, which implies a shock velocity of 40 km s-1.

  8. Extreme infrared variables from UKIDSS - I. A concentration in star-forming regions

    NASA Astrophysics Data System (ADS)

    Contreras Peña, C.; Lucas, P. W.; Froebrich, D.; Kumar, M. S. N.; Goldstein, J.; Drew, J. E.; Adamson, A.; Davis, C. J.; Barentsen, G.; Wright, N. J.

    2014-04-01

    We present initial results of the first panoramic search for high-amplitude near-infrared variability in the Galactic plane. We analyse the widely separated two-epoch K-band photometry in the fifth and seventh data releases of the UKIDSS Galactic plane survey. We find 45 stars with ΔK > 1 mag, including two previously known OH/IR stars and a Nova. Even though the mid-plane is not yet included in the data set, we find the majority (66 per cent) of our sample to be within known star-forming regions (SFRs), with two large concentrations in the Serpens OB2 association (11 stars) and the Cygnus-X complex (12 stars). Sources in SFRs show spectral energy distributions that support classification as young stellar objects (YSOs). This indicates that YSOs dominate the Galactic population of high-amplitude infrared variable stars at low luminosities and therefore likely dominate the total high-amplitude population. Spectroscopic follow up of the DR5 sample shows at least four stars with clear characteristics of eruptive pre-main-sequence variables, two of which are deeply embedded. Our results support the recent concept of eruptive variability comprising a continuum of outburst events with different time-scales and luminosities, but triggered by a similar physical mechanism involving unsteady accretion. Also, we find what appears to be one of the most variable classical Be stars.

  9. Trigonometric parallaxes of star forming regions in the Scutum spiral arm

    SciTech Connect

    Sato, M.; Wu, Y. W.; Immer, K.; Zhang, B.; Sanna, A.; Brunthaler, A.; Menten, K. M.; Reid, M. J.; Dame, T. M.

    2014-10-01

    We report measurements of trigonometric parallaxes for six high-mass star-forming regions in the Scutum spiral arm of the Milky Way as part of the BeSSeL Survey. Combining our measurements with 10 previous measurements from the BeSSeL Survey yields a total sample of 16 sources in the Scutum arm with trigonometric parallaxes in the Galactic longitude range from 5° to 32°. Assuming a logarithmic spiral model, we estimate a pitch angle of 19.°8 ± 3.°1 for the Scutum arm, which is larger than pitch angles reported for other spiral arms. The high pitch angle of the arm may be due to the arm's proximity to the Galactic bar. The Scutum arm sources show an average peculiar motion of 4 km s{sup –1} slower than the Galactic rotation and 8 km s{sup –1} toward the Galactic center. While the direction of this non-circular motion has the same sign as determined for sources in other spiral arms, the motion toward the Galactic center is greater for the Scutum arm sources.

  10. YSOVAR: Mid-infrared variability in the star-forming region Lynds 1688

    SciTech Connect

    Günther, H. M.; Poppenhaeger, K.; Wolk, S. J.; Hora, J. L.; Cody, A. M.; Covey, K. R.; Hillenbrand, L. A.; Plavchan, P.; Rebull, L. M.; Stauffer, J. R.; Bayo, A.; Gutermuth, R. A.; Meng, H. Y. A.; Morales-Calderón, M.; Parks, J. R.; Song, Inseok

    2014-12-01

    The emission from young stellar objects (YSOs) in the mid-infrared (mid-IR) is dominated by the inner rim of their circumstellar disks. We present IR data from the Young Stellar Object VARiability (YSOVAR) survey of ∼800 objects in the direction of the Lynds 1688 (L1688) star-forming region over four visibility windows spanning 1.6 yr using the Spitzer Space Telescope in its warm mission phase. Among all light curves, 57 sources are cluster members identified based on their spectral energy distribution and X-ray emission. Almost all cluster members show significant variability. The amplitude of the variability is larger in more embedded YSOs. Ten out of 57 cluster members have periodic variations in the light curves with periods typically between three and seven days, but even for those sources, significant variability in addition to the periodic signal can be seen. No period is stable over 1.6 yr. Nonperiodic light curves often still show a preferred timescale of variability that is longer for more embedded sources. About half of all sources exhibit redder colors in a fainter state. This is compatible with time-variable absorption toward the YSO. The other half becomes bluer when fainter. These colors can only be explained with significant changes in the structure of the inner disk. No relation between mid-IR variability and stellar effective temperature or X-ray spectrum is found.

  11. The HIFI spectral survey of massive star-forming region AFGL 2591

    NASA Astrophysics Data System (ADS)

    Kazmierczak, Maja; van der Tak, Floris; Helmich, Frank; Chvarria, Luis; Wang, Kuo-Song; Ceccarelli, Cecilia

    2013-07-01

    AFGL 2591 is a massive protostellar object with a bipolar outflow. It has been widely studied before since it is a relatively isolated and nearby star-forming region. Here we present an overview of the Herschel/HIFI spectral survey, as a part of CHESS Key Project. The survey covers a frequency range from 480 up to 1240 GHz as well as some particular lines from 1267 to 1901 GHz. From the spectral survey a total of 32 species were identified. The data analysis is divided into various families of molecules, eg. CO and its isotopologues, nitrogen-bearing molecules, sulfur-bearing species, organic molecules. We will discuss different types of observed molecules and their physical parameters. The radial abundance profiles of some molecules will be presented to learn about the chemical processes leading to their formation and destruction. One of the studied molecule is ammonia, which is concentrated in the inner part of the protostellar envelope (when T > 100K i.e. where water ice evaporates), with the abundance of 3x10e-7.

  12. THE PRESENCE OF WEAK ACTIVE GALACTIC NUCLEI IN HIGH REDSHIFT STAR-FORMING GALAXIES

    SciTech Connect

    Wright, Shelley A.; Graham, James R.; Ma, C-P; Larkin, James E.

    2010-03-10

    We present [O III 5007 A] observations of the star-forming galaxy (SFG) HDF-BMZ1299 (z = 1.598) using Keck Observatory's adaptive optics system with the near-infrared {integral} field spectrograph OSIRIS. Using previous Halpha and [N II] measurements of the same source, we are able for the first time to use spatially resolved observations to place a high-redshift galaxy's substructure on a traditional H II diagnostic diagram. We find that HDF-BMZ1299's spatially concentrated nebular ratios in the central {approx}1.5 kpc (0.''2) are best explained by the presence of an active galactic nucleus (AGN): log ([N II]/Halpha) = -0.22 +- 0.05 and 2sigma limit of log ([O III]/Hbeta) {approx}>0.26. The dominant energy source of this galaxy is star formation, and integrating a single aperture across the galaxy yields nebular ratios that are composite spectra from both AGN and H II regions. The presence of an embedded AGN in HDF-BMZ1299 may suggest a potential contamination in a fraction of other high-redshift SFGs, and we suggest that this may be a source of the 'elevated' nebular ratios previously seen in seeing-limited metallicity studies. HDF-BMZ1299's estimated AGN luminosity is L{sub Halpha} = (3.7 +- 0.5) x 10{sup 41} erg s{sup -1} and L{sub [O{sub III}]} = (5.8 +- 1.9) x 10{sup 41} erg s{sup -1}, making it one of the lowest luminosity AGNs discovered at this early epoch.

  13. DISK EVOLUTION IN THE THREE NEARBY STAR-FORMING REGIONS OF TAURUS, CHAMAELEON, AND OPHIUCHUS

    SciTech Connect

    Furlan, E.; Watson, Dan M.; McClure, M. K. E-mail: dmw@pas.rochester.ed

    2009-10-01

    We analyze samples of Spitzer Infrared Spectrograph spectra of T Tauri stars in the Ophiuchus, Taurus, and Chamaeleon I star-forming regions, whose median ages lie in the <1-2 Myr range. The median mid-infrared spectra of objects in these three regions are similar in shape, suggesting, on average, similar disk structures. When normalized to the same stellar luminosity, the medians follow each other closely, implying comparable mid-infrared excess emission from the circumstellar disks. We use the spectral index between 13 and 31 {mu}m and the equivalent width of the 10 {mu}m silicate emission feature to identify objects whose disk configuration departs from that of a continuous, optically thick accretion disk. Transitional disks, whose steep 13-31 {mu}m spectral slope and near-IR flux deficit reveal inner disk clearing, occur with about the same frequency of a few percent in all three regions. Objects with unusually large 10 {mu}m equivalent widths are more common (20%-30%); they could reveal the presence of disk gaps filled with optically thin dust. Based on their medians and fraction of evolved disks, T Tauri stars in Taurus and Chamaeleon I are very alike. Disk evolution sets in early, since already the youngest region, the Ophiuchus core (L1688), has more settled disks with larger grains. Our results indicate that protoplanetary disks show clear signs of dust evolution at an age of a few Myr, even as early as approx1 Myr, but age is not the only factor determining the degree of evolution during the first few million years of a disk's lifetime.

  14. Near-Infrared Imaging Polarimetry of the NGC 2071 Star-Forming Region with SIRPOL

    NASA Astrophysics Data System (ADS)

    Tamura, Motohide; Kandori, Ryo; Hashimoto, Jun; Kusakabe, Nobuhiko; Nakajima, Yasushi; Sato, Shuji; Nagashima, Chie; Kurita, Mikio; Nagata, Tetsuya; Nagayama, Takahiro; Hough, James H.; Matsumoto, Tomoaki; Chrysostomou, Antonio

    2007-06-01

    We conducted deep JHKs imaging polarimetry of a ˜ 8' × 8' area of the NGC 2071 star-forming region. Our polarization data revealed various infrared reflection nebulae (IRNe) associated with the central IR young star cluster NGC 2071IR and identified their illuminating sources. There are at least 4 IRNe in NGC 2071IR, and several additional IRNe were identified around nearby young stars in the same field-of-view. Each illuminating source coincides with a known near-IR source, except for IRS 3, which is only a part of IRN 2 and is illuminated by the radio source 1c. Aperture polarimetry of each cluster source was used to detect unresolved circumstellar disk/outflow systems. Aperture polarimetry of the other point-like sources within the field was conducted in this region for the first time. The magnetic field structures (from ˜ 1 pc down to ˜ 0.1 pc) were derived using both aperture polarimetry of the point-like sources and imaging polarimetry of the shocked H2 emission that is seen as the dominant knotty nebulae in the Ks band image; both are of dichroic origin and the derived field directions are consistent with each other. The magnetic field direction projected on the sky is also consistent with that inferred from the 850μm thermal continuum emission polarimetry of the central 0.2 pc region, but is running roughly perpendicular (˜ 75°) to the direction of the large-scale outflow. We argue that the field strength is too weak to align the outflow in the large-scale field direction via magnetic braking.

  15. SPITZER INFRARED SPECTROGRAPH SURVEY OF YOUNG STARS IN THE CHAMAELEON I STAR-FORMING REGION

    SciTech Connect

    Manoj, P.; Kim, K. H.; Watson, Dan M.; Forrest, W. J.; Bohac, C.; Arnold, L. A.; Furlan, E.; McClure, M. K.; Calvet, N.; Luhman, K. L.; Espaillat, C.; Najita, J. R.; D'Alessio, P.; Adame, L.; Sargent, B. A.; Green, J. D.

    2011-03-15

    We present 5-36 {mu}m mid-infrared spectra of 82 young stars in the {approx}2 Myr old Chamaeleon I star-forming region, obtained with the Spitzer Infrared Spectrograph (IRS). We have classified these objects into various evolutionary classes based on their spectral energy distributions and the spectral features seen in the IRS spectra. We have analyzed the mid-IR spectra of Class II objects in Chamaeleon I in detail, in order to study the vertical and radial structure of the protoplanetary disks surrounding these stars. We find evidence for substantial dust settling in most protoplanetary disks in Chamaeleon I. We have identified several disks with altered radial structures in Chamaeleon I, among them transitional disk candidates which have holes or gaps in their disks. Analysis of the silicate emission features in the IRS spectra of Class II objects in Cha I shows that the dust grains in these disks have undergone significant processing (grain growth and crystallization). However, disks with radial holes/gaps appear to have relatively unprocessed grains. We further find the crystalline dust content in the inner ({approx}<1-2 AU) and the intermediate ({approx}<10 AU) regions of the protoplanetary disks to be tightly correlated. We also investigate the effects of accretion and stellar multiplicity on the disk structure and dust properties. Finally, we compare the observed properties of protoplanetary disks in Cha I with those in slightly younger Taurus and Ophiuchus regions and discuss the effects of disk evolution in the first 1-2 Myr.

  16. B- AND A-TYPE STARS IN THE TAURUS-AURIGA STAR-FORMING REGION

    SciTech Connect

    Mooley, Kunal; Hillenbrand, Lynne; Rebull, Luisa; Padgett, Deborah; Knapp, Gillian

    2013-07-10

    We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B, and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral-type B. The second group consists of early-type stars compiled from (1) literature listings in SIMBAD, (2) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud, (3) magnitude- and color-selected point sources from the Two Micron All Sky Survey, and (4) spectroscopically identified early-type stars from the Sloan Digital Sky Survey coverage of the Taurus region. We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. For selected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the results with the observed spectral energy distributions to further test the plausibility of physical association of the B stars with the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445 (HD 28929), {tau} Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources including HD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though not secure, members.

  17. B- and A-Type Stars in the Taurus-Auriga Star-Forming Region

    NASA Technical Reports Server (NTRS)

    Mooley, Kunal; Hillenbrand, Lynne; Rebull, Luisa; Padgett, Deborah; Knapp, Gillian

    2013-01-01

    We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B, and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral-type B. The second group consists of early-type stars compiled from (1) literature listings in SIMBAD, (2) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud, (3) magnitude- and color-selected point sources from the Two Micron All Sky Survey, and (4) spectroscopically identified early-type stars from the Sloan Digital Sky Survey coverage of the Taurus region. We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. For selected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the results with the observed spectral energy distributions to further test the plausibility of physical association of the B stars with the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445 (HD 28929), t Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources including HD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though not secure, members.

  18. OT1_cvastel_2: Deuterated water chemistry towards high-mass star-forming regions.

    NASA Astrophysics Data System (ADS)

    Vastel, C.

    2010-07-01

    Observations of the HDO molecules are an important complement for studies of water, since they give strong constraints on the formation processes: grain surfaces versus gas-phase chemistry through energetic process as shocks. HIFI observations of multiple transitions of HDO in SgrB2(M) combined with ground-based observations allowed for the first time the determination of its abundance throughout the envelope. In the framework of the PRISMAS Key Program, a large sample of high-mass star-forming regions have been observed with the detection of many species in their line of sight. The HDO (111-000) fundamental transition has also been detected in absorption at the velocity of the hot core towards the 2 sources that have been observed so far, probably tracing the colder envelope in its surrounding. We propose to observe higher energy level HDO transitions towards a sample of three compact HII regions that will be targeted by the PRISMAS Key Program (G34.3+0.1, W33A, W49N) in order to perform a full modeling from the hot core through the envelope using a spherical Monte Carlo radiative transfer code, RATRAN, which takes into account radiative pumping by continuum emission from dust. We will use for an optimum accuracy of the modeling the HDO and D2O collision rates with H2, recently computed within our group, that are not available in the public so far. This study will hopefully give strong constrains on the formation processes of water, combining the proposed observations with published or soon to be published high resolution H2O observations with HIFI towards the same sources.

  19. Water in Star-forming Regions with Herschel (WISH): recent results and trends

    NASA Astrophysics Data System (ADS)

    van Dishoeck, E. F.

    2012-03-01

    Water is a key molecule in the physics and chemistry of star- and planet-forming regions. In the `Water in Star-forming Regions with Herschel' (WISH) Key Program, we have obtained a comprehensive set of water data toward a large sample of well-characterized protostars, covering a wide range of masses and luminosities --from the lowest to the highest mass protostars--, as well as evolutionary stages --from pre-stellar cores to disks. Lines of both ortho- and para-H_2O and their isotopologues, as well as chemically related hydrides, are observed with the HIFI and PACS instruments. The data elucidate the physical processes responsible for the warm gas, probe dynamical processes associated with forming stars and planets (outflow, infall, expansion), test basic chemical processes and reveal the chemical evolution of water and the oxygen-reservoir into planet-forming disks. In this brief talk a few recent WISH highlights will be presented, including determinations of the water abundance in each of the different physical components (inner and outer envelope, outflow) and constraints on the ortho/para ratio. Special attention will be given to trends found across the sample, especially the similarity in profiles from low to high-mass protostars and the evolution of the gas-phase water abundance from prestellar cores to disks. More details can be found at http://www.strw.leidenuniv.nl/WISH, whereas overviews are given in van Dishoeck et al. (2011, PASP 123, 138), Kristensen & van Dishoeck (2011, Astronomische Nachrichten 332, 475) and Bergin & van Dishoeck (2012, Phil. Trans. Royal Soc. A).

  20. Water in massive star-forming regions: HIFI observations of W3 IRS5

    NASA Astrophysics Data System (ADS)

    Chavarría, L.; Herpin, F.; Jacq, T.; Braine, J.; Bontemps, S.; Baudry, A.; Marseille, M.; van der Tak, F.; Pietropaoli, B.; Wyrowski, F.; Shipman, R.; Frieswijk, W.; van Dishoeck, E. F.; Cernicharo, J.; Bachiller, R.; Benedettini, M.; Benz, A. O.; Bergin, E.; Bjerkeli, P.; Blake, G. A.; Bruderer, S.; Caselli, P.; Codella, C.; Daniel, F.; di Giorgio, A. M.; Dominik, C.; Doty, S. D.; Encrenaz, P.; Fich, M.; Fuente, A.; Giannini, T.; Goicoechea, J. R.; de Graauw, Th.; Hartogh, P.; Helmich, F.; Herczeg, G. J.; Hogerheijde, M. R.; Johnstone, D.; Jørgensen, J. K.; Kristensen, L. E.; Larsson, B.; Lis, D.; Liseau, R.; McCoey, C.; Melnick, G.; Nisini, B.; Olberg, M.; Parise, B.; Pearson, J. C.; Plume, R.; Risacher, C.; Santiago-García, J.; Saraceno, P.; Stutzki, J.; Szczerba, R.; Tafalla, M.; Tielens, A.; van Kempen, T. A.; Visser, R.; Wampfler, S. F.; Willem, J.; Yıldız, U. A.

    2010-10-01

    We present Herschel observations of the water molecule in the massive star-forming region W3 IRS5. The o-H_217O 110-101, p-H_218O 111-000, p-H2O 202-111, p-H2O 111-000, o-H2O 221-212, and o-H2O 212-101 lines, covering a frequency range from 552 up to 1669 GHz, have been detected at high spectral resolution with HIFI. The water lines in W3 IRS5 show well-defined high-velocity wings that indicate a clear contribution by outflows. Moreover, the systematically blue-shifted absorption in the H2O lines suggests expansion, presumably driven by the outflow. No infall signatures are detected. The p-H2O 111-000 and o-H2O 212-101 lines show absorption from the cold material (T ~ 10 K) in which the high-mass protostellar envelope is embedded. One-dimensional radiative transfer models are used to estimate water abundances and to further study the kinematics of the region. We show that the emission in the rare isotopologues comes directly from the inner parts of the envelope (T ≳ 100 K) where water ices in the dust mantles evaporate and the gas-phase abundance increases. The resulting jump in the water abundance (with a constant inner abundance of 10-4) is needed to reproduce the o-H_217O 110-101 and p-H_218O 111-000 spectra in our models. We estimate water abundances of 10-8 to 10-9 in the outer parts of the envelope (T ≲ 100 K). The possibility of two protostellar objects contributing to the emission is discussed. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  1. GOODS-HERSCHEL: SEPARATING HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI AND STAR-FORMING GALAXIES USING INFRARED COLOR DIAGNOSTICS

    SciTech Connect

    Kirkpatrick, Allison; Pope, Alexandra; Charmandaris, Vassilis; Daddi, Emmanuele; Elbaz, David; Pannella, Maurilio; Aussel, Herve; Dasyra, Kalliopi; Leiton, Roger; Scott, Douglas; Magnelli, Benjamin; Popesso, Paola; Altieri, Bruno; Coia, Daniela; Valtchanov, Ivan; Dannerbauer, Helmut; Dickinson, Mark; Kartaltepe, Jeyhan; Magdis, Georgios

    2013-02-15

    We have compiled a large sample of 151 high-redshift (z = 0.5-4) galaxies selected at 24 {mu}m (S {sub 24} > 100 {mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-infrared spectrum into contributions from star formation and activity in the galactic nuclei. In addition, we have a wealth of photometric data from Spitzer IRAC/MIPS and Herschel PACS/SPIRE. We explore how effective different infrared color combinations are at separating our mid-IR spectroscopically determined active galactic nuclei from our star-forming galaxies. We look in depth at existing IRAC color diagnostics, and we explore new color-color diagnostics combining mid-IR, far-IR, and near-IR photometry, since these combinations provide the most detail about the shape of a source's IR spectrum. An added benefit of using a color that combines far-IR and mid-IR photometry is that it is indicative of the power source driving the IR luminosity. For our data set, the optimal color selections are S {sub 250}/S {sub 24} versus S {sub 8}/S {sub 3.6} and S {sub 100}/S {sub 24} versus S {sub 8}/S {sub 3.6}; both diagnostics have {approx}10% contamination rate in the regions occupied primarily by star-forming galaxies and active galactic nuclei, respectively. Based on the low contamination rate, these two new IR color-color diagnostics are ideal for estimating both the mid-IR power source of a galaxy when spectroscopy is unavailable and the dominant power source contributing to the IR luminosity. In the absence of far-IR data, we present color diagnostics using the Wide-field Infrared Survey Explorer mid-IR bands which can efficiently select out high-z (z {approx} 2) star-forming galaxies.

  2. SUB-STELLAR COMPANIONS AND STELLAR MULTIPLICITY IN THE TAURUS STAR-FORMING REGION

    SciTech Connect

    Daemgen, Sebastian; Bonavita, Mariangela; Jayawardhana, Ray; Lafrenière, David; Janson, Markus

    2015-02-01

    We present results from a large, high-spatial-resolution near-infrared imaging search for stellar and sub-stellar companions in the Taurus-Auriga star-forming region. The sample covers 64 stars with masses between those of the most massive Taurus members at ∼3 M {sub ☉} and low-mass stars at ∼0.2 M {sub ☉}. We detected 74 companion candidates, 34 of these reported for the first time. Twenty-five companions are likely physically bound, partly confirmed by follow-up observations. Four candidate companions are likely unrelated field stars. Assuming physical association with their host star, estimated companion masses are as low as ∼2 M {sub Jup}. The inferred multiplicity frequency within our sensitivity limits between ∼10-1500 AU is 26.3{sub −4.9}{sup +6.6}%. Applying a completeness correction, 62% ± 14% of all Taurus stars between 0.7 and 1.4 M {sub ☉} appear to be multiple. Higher order multiples were found in 1.8{sub −1.5}{sup +4.2}% of the cases, in agreement with previous observations of the field. We estimate a sub-stellar companion frequency of ∼3.5%-8.8% within our sensitivity limits from the discovery of two likely bound and three other tentative very low-mass companions. This frequency appears to be in agreement with what is expected from the tail of the stellar companion mass ratio distribution, suggesting that stellar and brown dwarf companions share the same dominant formation mechanism. Further, we find evidence for possible evolution of binary parameters between two identified sub-populations in Taurus with ages of ∼2 Myr and ∼20 Myr, respectively.

  3. MULTIPLICITY, DISKS, AND JETS IN THE NGC 2071 STAR-FORMING REGION

    SciTech Connect

    Carrasco-Gonzalez, Carlos; Osorio, Mayra; Anglada, Guillem; Gomez, Jose F.; D'Alessio, Paola; Rodriguez, Luis F.; Torrelles, Jose M.

    2012-02-10

    We present centimeter (cm) and millimeter (mm) observations of the NGC 2071 star-forming region performed with the Very Large Array (VLA) and Combined Array for Research in Millimeter-wave Astronomy (CARMA). We detected counterparts at 3.6 cm and 3 mm for the previously known sources IRS 1, IRS 2, IRS 3, and VLA 1. All these sources show spectral energy distributions (SEDs) dominated by free-free thermal emission at cm wavelengths and thermal dust emission at mm wavelengths, suggesting that all of them are associated with young stellar objects (YSOs). IRS 1 shows a complex morphology at 3.6 cm, with changes in the direction of its elongation. We discuss two possible explanations to this morphology: the result of changes in the direction of a jet due to interactions with a dense ambient medium, or that we are actually observing the superposition of two jets arising from two components of a binary system. Higher angular resolution observations at 1.3 cm support the second possibility, since a double source is inferred at this wavelength. IRS 3 shows a clear jet-like morphology at 3.6 cm. Over a timespan of four years, we observed changes in the morphology of this source that we interpret as due to ejection of ionized material in a jet. The emission at 3 mm of IRS 3 is angularly resolved, with a deconvolved size (FWHM) of {approx}120 AU, and seems to be tracing a dusty circumstellar disk perpendicular to the radio jet. An irradiated accretion disk model around an intermediate-mass YSO can account for the observed SED and spatial intensity profile at 3 mm, supporting this interpretation.

  4. The Physical Environment of the Massive Star-forming Region W42

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Luna, A.; Ojha, D. K.; Anandarao, B. G.; Mallick, K. K.; Mayya, Y. D.

    2015-10-01

    We present an analysis of multi-wavelength observations from various data sets and Galactic plane surveys to study the star-formation process in the W42 complex. A bipolar appearance of the W42 complex is evident due to the ionizing feedback from the O5-O6 type star in a medium that is highly inhomogeneous. The Very Large Telescope/NACO adaptive-optics K and L‧ images (resolutions ˜0.″2-0.″1) resolved this ionizing source into multiple point-like sources below ˜5000 AU scale. The position angle ˜15° of the W42 molecular cloud is consistent with the H-band starlight mean polarization angle, which in turn is close to the Galactic magnetic field, suggesting the influence of the Galactic field on the evolution of the W42 molecular cloud. Herschel sub-millimeter data analysis reveals three clumps located along the waist axis of the bipolar nebula, with the peak column densities of ˜(3-5) × 1022 cm-2 corresponding to visual extinctions of AV ˜ 32-53.5 mag. The Herschel temperature map traces a temperature gradient in W42, revealing regions of 20 K, 25 K, and 30-36 K. Herschel maps reveal embedded filaments (length ˜1-3 pc) that appear to be radially pointed to the denser clump associated with the O5-O6 star, forming a hub-filament system. A total of 512 candidate young stellar objects (YSOs) are identified in the complex, ˜40% of which are present in clusters distributed mainly within the molecular cloud, including the Herschel filaments. Our data sets suggest that the YSO clusters, including the massive stars, are located at the junction of the filaments, similar to those seen in the Rosette Molecular Cloud.

  5. A Multi-line Study of Atomic Carbon and Carbon Monoxide in the Galactic Star- forming Region W3

    NASA Astrophysics Data System (ADS)

    Jakob, H.; Kramer, C.; Mookerjea, B.; Jeyakumar, S.; Stutzki, J.

    We present results from simultaneous observations of the fine structure line emissions of neutral carbon (C I) at 492 and 809 GHz from selected Galactic star forming regions. These observations include the first results using the the newly installed SMART (SubmilliMeter Array Receiver at Two wavelengths) on KOSMA. The regions observed were selected in order to cover a range of strengths of the incident UV radiation from the exciting star/stars and also densities of the interstellar medium. Extended maps of C I emission from massive star forming regions including W3, S106 and Orion BN/KL have been observed. Simultaneous observation of the two C I lines ensures better relative calibration. The results from these observations will be combined with observed intensities of low-J and mid-J CO and C+ lines and analyzed using radiation transfer based models for Photon Dominated Regions (PDRs).

  6. A search for companions to brown dwarfs in the Taurus and Chamaeleon star-forming regions

    SciTech Connect

    Todorov, K. O.; Luhman, K. L.; Konopacky, Q. M.; McLeod, K. K.; Apai, D.; Pascucci, I.; Ghez, A. M.; Robberto, M.

    2014-06-10

    We have used WFPC2 on board the Hubble Space Telescope to obtain images of 47 members of the Taurus and Chamaeleon I star-forming regions that have spectral types of M6-L0 (M ∼ 0.01-0.1 M {sub ☉}). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. In these images, we have identified promising candidate companions to 2MASS J04414489+2301513 (ρ = 0.''105/15 AU), 2MASS J04221332+1934392 (ρ = 0.''05/7 AU), and ISO 217 (ρ = 0.''03/5 AU). We reported the first candidate in a previous study, showing that it has a similar proper motion as the primary in images from WFPC2 and Gemini adaptive optics. We have collected an additional epoch of data with Gemini that further supports that result. By combining our survey with previous high-resolution imaging in Taurus, Chamaeleon I, and Upper Sco (τ ∼ 10 Myr), we measure binary fractions of 14/93 = 0.15{sub −0.03}{sup +0.05} for M4-M6 (M ∼ 0.1-0.3 M {sub ☉}) and 4/108 = 0.04{sub −0.01}{sup +0.03} for >M6 (M ≲ 0.1 M {sub ☉}) at separations of >10 AU. Given the youth and low density of these regions, the lower binary fraction at later types is probably primordial rather than due to dynamical interactions among association members. The widest low-mass binaries (>100 AU) also appear to be more common in Taurus and Chamaeleon I than in the field, which suggests that the widest low-mass binaries are disrupted by dynamical interactions at >10 Myr, or that field brown dwarfs have been born predominantly in denser clusters where wide systems are disrupted or inhibited from forming.

  7. Spectacular Spitzer images of the Trifid Nebula: Protostars in a young, massive-star-forming region

    NASA Astrophysics Data System (ADS)

    Rho, Jeonghee; Reach, W. T.; Lefloch, B.; Fazio, G.

    2005-07-01

    competing for materials and the clustering is consistent with competitive accretion. We also compare statistics and characteristics of the sources detected at infrared wavelengths by Spitzer with the discrete X-ray sources detected by Chandra in the Trifid Nebula. By generating spectral energy distributions of these discrete X-ray sources using data from Spitzer observations (as well as complementary near-infrared and millimeter data), we can classify the detected young stellar objects into their evolutionary stages. We demonstrate the advantage of our multi-wavelength complementary study in understanding a complete population of young stars in a star-forming region and the evolution of protostars and disks.

  8. An x-ray study of massive star forming regions with CHANDRA

    NASA Astrophysics Data System (ADS)

    Wang, Junfeng

    2007-08-01

    Massive stars are characterized by powerful stellar winds, strong ultraviolet (UV) radiation, and consequently devastating supernovae explosions, which have a profound influence on their natal clouds and galaxy evolution. However, the formation and evolution of massive stars themselves and how their low-mass siblings are affected in the wind-swept and UV-radiation-dominated environment are not well understood. Much of the stellar populations inside of the massive star forming regions (MSFRs) are poorly studied in the optical and IR wavelengths because of observational challenges caused by large distance, high extinction, and heavy contamination from unrelated sources. Although it has long been recognized that X-rays open a new window to sample the young stellar populations residing in the MSFRs, the low angular resolution of previous generation X-ray telescopes has limited the outcome from such studies. The sensitive high spatial resolution X-ray observations enabled by the Chandra X- ray Observatory and the Advanced CCD Imaging Spectrometer (ACIS) have significantly improved our ability to study the X-ray-emitting populations in the MSFRs in the last few years. In this thesis, I analyzed seven high spatial resolution Chandra /ACIS images of two massive star forming complexes, namely the NGC 6357 region hosting the 1 Myr old Pismis 24 cluster (Chapter 3) and the Rosette Complex including the 2 Myr old NGC 2244 cluster immersed in the Rosette Nebula (Chapter 4), embedded clusters in the Rosette Molecular Cloud (RMC; Chapter 5), and a triggered cluster NGC 2237 (Chapter 6). The X-ray sampled stars were studied in great details. The unique power of X-ray selection of young stellar cluster members yielded new knowledge in the stellar populations, the cluster structures, and the star formation histories. The census of cluster members is greatly improved in each region. A large fraction of the X-ray detections have optical or near-infrared (NIR) stellar counterparts

  9. RADIO JETS AND DISKS IN THE INTERMEDIATE-MASS STAR-FORMING REGION NGC2071IR

    SciTech Connect

    Trinidad, M. A.; Rodriguez, T.; Rodriguez, L. F.

    2009-11-20

    We report the results of simultaneous radio continuum and water maser observations toward the NGC 2071IR star-forming region, carried out with the VLA in its A configuration. We detect continuum emission toward the infrared sources IRS 1 and IRS 3 at 1.3 and 3.6 cm. In addition, a new continuum source, VLA 1, is also detected at both wavelengths, which is located between IRS 1 and IRS 3. IRS 1 breaks up into three continuum peaks (IRS 1E, 1C, and 1W), aligned in the east-west direction (P.A. = 100{sup 0}). IRS 1 is the central source, while the sources E and W seem to be condensations ejected by IRS 1. In the same way, IRS 3 is also forming a triple system (IRS 3N, 3C and 3S), which is elongated in the northeast-southwest direction and the condensations, IRS 3N and IRS 3S, are symmetrically located along the major axis. Based on the morphology and the continuum emission, we suggest that both IRS 1 and IRS 3 are radio jets, which have ejected condensations into the interstellar medium. Moreover, IRS 1 and IRS 3 seem to be the driving sources of the large-scale outflows observed in H{sub 2} and CO, respectively. In addition, we also detected water emission toward the systems IRS 1, IRS 3, and the new source VLA 1. Based on the spatial-kinematic distribution of the water masers, we find evidence that the water masers are tracing part of circumstellar disks around IRS 1C and IRS 3C. Moreover, we estimate that the sources IRS 1C and IRS 3C have central masses of approx5 and approx1 M {sub sun}, respectively. We conclude that the radio continuum and water maser emission are tracing disk-YSO-outflow systems toward IRS 1 and IRS 3, which are low- and intermediate-mass young stellar objects, respectively.

  10. Trigonometric parallaxes of high mass star forming regions: the structure and kinematics of the Milky Way

    SciTech Connect

    Reid, M. J.; Dame, T. M.; Menten, K. M.; Brunthaler, A.; Wu, Y.; Zhang, B.; Sanna, A.; Sato, M.; Choi, Y. K.; Immer, K.; Zheng, X. W.; Xu, Y.; Hachisuka, K.; Moscadelli, L.; Rygl, K. L. J.; Bartkiewicz, A.

    2014-03-10

    Over 100 trigonometric parallaxes and proper motions for masers associated with young, high-mass stars have been measured with the Bar and Spiral Structure Legacy Survey, a Very Long Baseline Array key science project, the European VLBI Network, and the Japanese VLBI Exploration of Radio Astrometry project. These measurements provide strong evidence for the existence of spiral arms in the Milky Way, accurately locating many arm segments and yielding spiral pitch angles ranging from about 7° to 20°. The widths of spiral arms increase with distance from the Galactic center. Fitting axially symmetric models of the Milky Way with the three-dimensional position and velocity information and conservative priors for the solar and average source peculiar motions, we estimate the distance to the Galactic center, R {sub 0}, to be 8.34 ± 0.16 kpc, a circular rotation speed at the Sun, Θ{sub 0}, to be 240 ± 8 km s{sup –1}, and a rotation curve that is nearly flat (i.e., a slope of –0.2 ± 0.4 km s{sup –1} kpc{sup –1}) between Galactocentric radii of ≈5 and 16 kpc. Assuming a 'universal' spiral galaxy form for the rotation curve, we estimate the thin disk scale length to be 2.44 ± 0.16 kpc. With this large data set, the parameters R {sub 0} and Θ{sub 0} are no longer highly correlated and are relatively insensitive to different forms of the rotation curve. If one adopts a theoretically motivated prior that high-mass star forming regions are in nearly circular Galactic orbits, we estimate a global solar motion component in the direction of Galactic rotation, V {sub ☉} = 14.6 ± 5.0 km s{sup –1}. While Θ{sub 0} and V {sub ☉} are significantly correlated, the sum of these parameters is well constrained, Θ{sub 0} + V {sub ☉} = 255.2 ± 5.1 km s{sup –1}, as is the angular speed of the Sun in its orbit about the Galactic center, (Θ{sub 0} + V {sub ☉})/R {sub 0} = 30.57 ± 0.43 km s{sup –1} kpc{sup –1}. These parameters improve the accuracy of

  11. An Unbiased Census of Weak Herbig-Haro Flows in the R Corona Australis Star Forming Region

    NASA Astrophysics Data System (ADS)

    Quick, Lynnae C.; Roberge, A.; Weinberger, A. J.

    2007-12-01

    Bipolar outflows are produced by protostars as they draw gas from surrounding accretion disks. As these outflows collide with the interstellar medium, bow shocks are produced, giving rise to Herbig-Haro knots. A Herbig-Haro flow is a sign that active accretion is occurring in a protostellar system. In an effort to constrain the time available for giant planet formation in gas- rich disks, we seek to find weak Herbig-Haro flows by sensitively mapping the entire R Corona Australis star forming region. Between ≤ 1 and 6 Myrs old (Neuhäuser et al. 2000), and located approximately 129±11pc away (Casey et al. 1998), the R Corona Australis region is home to approximately 50 young stars (Neuhäuser et al. 2000). We have imaged this region in the near-IR using a narrow band H2 S(1) filter that isolates emission from the ν=1, J=3 level of H2 at 2.12 μm. We will present preliminary results of this analysis.

  12. THE BLAST VIEW OF THE STAR-FORMING REGION IN AQUILA (l = 45{sup 0}, b = 0{sup 0})

    SciTech Connect

    Rivera-Ingraham, Alana; Martin, Peter G.; Netterfield, Calvin B.; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Bock, James J.; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Scott, Douglas; Devlin, Mark J.; Dicker, Simon R.; Klein, Jeff; Rex, Marie; Gundersen, Joshua O.; Hughes, David H.; Olmi, Luca; Patanchon, Guillaume

    2010-11-01

    We have carried out the first general submillimeter analysis of the field toward GRSMC 45.46+0.05, a massive star-forming region in Aquila. The deconvolved 6 deg{sup 2} (3{sup 0} x 2{sup 0}) maps provided by BLAST in 2005 at 250, 350, and 500 {mu}m were used to perform a preliminary characterization of the clump population previously investigated in the infrared, radio, and molecular maps. Interferometric CORNISH data at 4.8 GHz have also been used to characterize the Ultracompact H II regions (UCHIIRs) within the main clumps. By means of the BLAST maps, we have produced an initial census of the submillimeter structures that will be observed by Herschel, several of which are known Infrared Dark Clouds. Our spectral energy distributions of the main clumps in the field, located at {approx}7 kpc, reveal an active population with temperatures of T{approx} 35-40 K and masses of {approx}10{sup 3} M{sub sun} for a dust emissivity index {beta} = 1.5. The clump evolutionary stages range from evolved sources, with extended H II regions and prominent IR stellar population, to massive young stellar objects, prior to the formation of an UCHIIR. The CORNISH data have revealed the details of the stellar content and structure of the UCHIIRs. In most cases, the ionizing stars corresponding to the brightest radio detections are capable of accounting for the clump bolometric luminosity, in most cases powered by embedded OB stellar clusters.

  13. H{sub 2}D{sup +} IN THE HIGH-MASS STAR-FORMING REGION CYGNUS X

    SciTech Connect

    Pillai, T.; Lis, D. C.; Caselli, P.; Kauffmann, J.; Zhang, Q.; Thompson, M. A.

    2012-06-01

    H{sub 2}D{sup +} is a primary ion that dominates the gas-phase chemistry of cold dense gas. Therefore, it is hailed as a unique tool in probing the earliest, prestellar phase of star formation. Observationally, its abundance and distribution is, however, just beginning to be understood in low-mass prestellar and cluster-forming cores. In high-mass star-forming regions, H{sub 2}D{sup +} has been detected only in two cores, and its spatial distribution remains unknown. Here, we present the first map of the ortho-H{sub 2}D{sup +} J{sub k{sup +},k{sup -}} = 1{sub 1,0} {yields} 1{sub 1,1} and N{sub 2}H{sup +} 4-3 transition in the DR21 filament of Cygnus X with the James Clerk Maxwell Telescope, and N{sub 2}D{sup +} 3-2 and dust continuum with the Submillimeter Array. We have discovered five very extended ({<=}34, 000 AU diameter) weak structures in H{sub 2}D{sup +} in the vicinity of, but distinctly offset from, embedded protostars. More surprisingly, the H{sub 2}D{sup +} peak is not associated with either a dust continuum or N{sub 2}D{sup +} peak. We have therefore uncovered extended massive cold dense gas that was undetected with previous molecular line and dust continuum surveys of the region. This work also shows that our picture of the structure of cores is too simplistic for cluster-forming cores and needs to be refined: neither dust continuum with existing capabilities nor emission in tracers like N{sub 2}D{sup +} can provide a complete census of the total prestellar gas in such regions. Sensitive H{sub 2}D{sup +} mapping of the entire DR21 filament is likely to discover more of such cold quiescent gas reservoirs in an otherwise active high-mass star-forming region.

  14. 15N Fractionation in Star-Forming Regions and Solar System Objects

    NASA Technical Reports Server (NTRS)

    Wirstrom, Eva; Milam, Stefanie; Adande, GIlles; Charnley, Steven; Cordiner, Martin

    2015-01-01

    A central issue for understanding the formation and evolution of matter in the early Solar System is the relationship between the chemical composition of star-forming interstellar clouds and that of primitive Solar System materials. The pristinemolecular content of comets, interplanetary dust particles and carbonaceous chondrites show significant bulk nitrogen isotopic fractionation relative to the solar value, 14N15N 440. In addition, high spatial resolution measurements in primitive materials locally show even more extreme enhancements of 14N15N 100.

  15. The Effects of Episodic Star Formation on the FUV-NUV Colors of Star Forming Regions in Outer Disks

    NASA Astrophysics Data System (ADS)

    Barnes, Kate L.; van Zee, Liese; Dowell, Jayce D.

    2013-09-01

    We run stellar population synthesis models to examine the effects of a recently episodic star formation history (SFH) on UV and Hα colors of star forming regions. Specifically, the SFHs we use are an episodic sampling of an exponentially declining star formation rate (SFR; τ model) and are intended to simulate the SFHs in the outer disks of spiral galaxies. To enable comparison between our models and observational studies of star forming regions in outer disks, we include in our models sensitivity limits that are based on recent deep UV and Hα observations in the literature. We find significant dispersion in the FUV-NUV colors of simulated star forming regions with frequencies of star formation episodes of 1 × 10-8 to 4 × 10-9 yr-1. The dispersion in UV colors is similar to that found in the outer disk of nearby spiral galaxies. As expected, we also find large variations in L_{H_{\\alpha }}/L_{FUV}. We interpret our models within the context of inside-out disk growth, and find that a radially increasing τ and decreasing metallicity with an increasing radius will only produce modest FUV-NUV color gradients, which are significantly smaller than what is found for some nearby spiral galaxies. However, including moderate extinction gradients with our models can better match the observations with steeper UV color gradients. We estimate that the SFR at which the number of stars emitting FUV light becomes stochastic is ~2 × 10-6 M ⊙ yr-1, which is substantially lower than the SFR of many star forming regions in outer disks. Therefore, we conclude that stochasticity in the upper end of the initial mass function is not likely to be the dominant cause of dispersion in the FUV-NUV colors of star forming regions in outer disks. Finally, we note that if outer disks have had an episodic SFH similar to that used in this study, this should be taken into account when estimating gas depletion timescales and modeling chemical evolution of spiral galaxies.

  16. THE EFFECTS OF EPISODIC STAR FORMATION ON THE FUV-NUV COLORS OF STAR FORMING REGIONS IN OUTER DISKS

    SciTech Connect

    Barnes, Kate L.; Van Zee, Liese; Dowell, Jayce D. E-mail: vanzee@astro.indiana.edu

    2013-09-20

    We run stellar population synthesis models to examine the effects of a recently episodic star formation history (SFH) on UV and Hα colors of star forming regions. Specifically, the SFHs we use are an episodic sampling of an exponentially declining star formation rate (SFR; τ model) and are intended to simulate the SFHs in the outer disks of spiral galaxies. To enable comparison between our models and observational studies of star forming regions in outer disks, we include in our models sensitivity limits that are based on recent deep UV and Hα observations in the literature. We find significant dispersion in the FUV-NUV colors of simulated star forming regions with frequencies of star formation episodes of 1 × 10{sup –8} to 4 × 10{sup –9} yr{sup –1}. The dispersion in UV colors is similar to that found in the outer disk of nearby spiral galaxies. As expected, we also find large variations in L{sub H{sub α}}/L{sub FUV}. We interpret our models within the context of inside-out disk growth, and find that a radially increasing τ and decreasing metallicity with an increasing radius will only produce modest FUV-NUV color gradients, which are significantly smaller than what is found for some nearby spiral galaxies. However, including moderate extinction gradients with our models can better match the observations with steeper UV color gradients. We estimate that the SFR at which the number of stars emitting FUV light becomes stochastic is ∼2 × 10{sup –6} M{sub ☉} yr{sup –1}, which is substantially lower than the SFR of many star forming regions in outer disks. Therefore, we conclude that stochasticity in the upper end of the initial mass function is not likely to be the dominant cause of dispersion in the FUV-NUV colors of star forming regions in outer disks. Finally, we note that if outer disks have had an episodic SFH similar to that used in this study, this should be taken into account when estimating gas depletion timescales and modeling chemical

  17. Narrow-band Imaging of Massive Star-Forming Regions: Tracing Outflows and the Rate of Star-Formation

    NASA Astrophysics Data System (ADS)

    Hall, Kendall; Willis, Sarah; Hora, Joseph L.

    2016-01-01

    Narrowband images targeting ionized hydrogen (Brackett gamma, 2.17 microns) and molecular hydrogen (2.12 microns) were obtained for six massive star-forming regions within the Milky Way, NGC 6334, G305, G3333, G3264, G3266, and G351. These regions are within 1-4 kpc from our solar system. The narrowband flux in Brackett gamma was used as a star-formation tracer to calculate a star-formation rate for each region. This is compared with other star-formation rates found using other methods such as the count of young stars and YSOs, and rates calculated from using other tracers (e.g. 70 micron monochromatic luminosity). The molecular hydrogen narrowband images were manually searched to locate outflows from young stars. Once these outflows are identified, it may help to get a better survey of the young stellar population. A better understanding of the stellar population distribution can lead to more accurate star-formation rates to compare to those calculated from star-formation tracers. We found the regions NGC 6334 and G3266 to have the highest levels of ongoing star formation activity as indicated by the number of molecular hydrogen objects (MHOs) detected. There are a total of 279 cataloged MHOs in 181 categorized systems for the six regions. There are a total of 150 identified potential driving sources.This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  18. WIDESPREAD AND HIDDEN ACTIVE GALACTIC NUCLEI IN STAR-FORMING GALAXIES AT REDSHIFT >0.3

    SciTech Connect

    Juneau, Stephanie; Bournaud, Frederic; Daddi, Emanuele; Elbaz, David; Alexander, David M.; Mullaney, James R.; Magnelli, Benjamin; Hwang, Ho Seong; Willner, S. P.; Coil, Alison L.; Rosario, David J.; Trump, Jonathan R.; Faber, S. M.; Kocevski, Dale D.; Cooper, Michael C.; Frayer, David T.; and others

    2013-02-20

    We characterize the incidence of active galactic nuclei (AGNs) in 0.3 < z < 1 star-forming galaxies by applying multi-wavelength AGN diagnostics (X-ray, optical, mid-infrared, radio) to a sample of galaxies selected at 70 {mu}m from the Far-Infrared Deep Extragalactic Legacy survey (FIDEL). Given the depth of FIDEL, we detect 'normal' galaxies on the specific star formation rate (sSFR) sequence as well as starbursting systems with elevated sSFR. We find an overall high occurrence of AGN of 37% {+-} 3%, more than twice as high as in previous studies of galaxies with comparable infrared luminosities and redshifts but in good agreement with the AGN fraction of nearby (0.05 < z < 0.1) galaxies of similar infrared luminosities. The more complete census of AGNs comes from using the recently developed Mass-Excitation (MEx) diagnostic diagram. This optical diagnostic is also sensitive to X-ray weak AGNs and X-ray absorbed AGNs, and reveals that absorbed active nuclei reside almost exclusively in infrared-luminous hosts. The fraction of galaxies hosting an AGN appears to be independent of sSFR and remains elevated both on the sSFR sequence and above. In contrast, the fraction of AGNs that are X-ray absorbed increases substantially with increasing sSFR, possibly due to an increased gas fraction and/or gas density in the host galaxies.

  19. The structure and early evolution of massive star forming regions. Substructure in the infrared dark cloud SDC13

    NASA Astrophysics Data System (ADS)

    McGuire, C.; Fuller, G. A.; Peretto, N.; Zhang, Q.; Traficante, A.; Avison, A.; Jimenez-Serra, I.

    2016-10-01

    Context. Investigations into the substructure of massive star forming regions are essential for understanding the observed relationships between core mass distributions and mass distributions in stellar clusters, differentiating between proposed mechanisms of massive star formation. Aims: We study the substructure in the two largest fragments (i.e. cores) MM1 and MM2, in the infrared dark cloud complex SDC13. As MM1 appears to be in a later stage of evolution than MM2, comparing their substructure provides an insight in to the early evolution of massive clumps. Methods: We report the results of high resolution SMA dust continuum observations towards MM1 and MM2. Combining these data with Herschel observations, we carry out RADMC-3D radiative transfer modelling to characterise the observed substructure. Results: SMA continuum data indicates 4 sub-fragments in the SDC13 region. The nature of the second brightest sub-fragment (B) is uncertain as it does not appear as prominent at the lower MAMBO resolution or at radio wavelengths. Statistical analysis indicates that it is unlikely to be a background source, an AGB star, or the free-free emission of a HII region. It is plausible that B is a runaway object ejected from MM1. MM1, which is actively forming stars, consists of two sub-fragments A and C. This is confirmed by 70 μmHerschel data. While MM1 and MM2 appear quite similar in previous low resolution observations, at high resolution, the sub-fragment at the centre of MM2 (D) is much fainter than sub-fragment at the centre of MM1 (A). RADMC-3D models of MM1 and MM2 are able to reproduce these results, modelling MM2 with a steeper density profile and higher mass than is required for MM1. The relatively steep density profile of MM2 depends on a significant temperature decrease in its centre, justified by the lack of star formation in MM2. A final stellar population for MM1 was extrapolated, indicating a star formation efficiency typical of regions of core and cluster

  20. A multi-wavelength study of pre-main sequence stars in the Taurus-Auriga star-forming region

    NASA Astrophysics Data System (ADS)

    Guenther, E. W.; Stelzer, B.; Neuhäuser, R.; Hillwig, T. C.; Durisen, R. H.; Menten, K. M.; Greimel, R.; Barwig, H.; Englhauser, J.; Robb, R. M.

    2000-05-01

    Although many lowmass pre-main sequence stars are strong X-ray sources, the origin of the X-ray emission is not well known. Since these objects are variable at all frequencies, simultaneous observations in X-rays and in other wavelengths are able to constrain the properties of the X-ray emitting regions. In this paper, we report quasi-simultaneous observations in X-rays, the optical, and the radio regime for classical and weak-line T Tauri stars from the Taurus-Auriga star-forming region. We find that all detected T Tauri stars show significant night-to-night variations of the X-ray emission. For three of the stars, FM Tau and CW Tau, both classical T Tauri stars, and V773 Tau, a weak-line T Tauri star, the variations are especially large. From observations taken simultaneously, we also find that there is some correspondence between the strength of Hα and the X-ray brightness in V773 Tau. The lack of a strong correlation leads us to conclude that the X-ray emission of V773 Tau is not a superposition of flares. However, we suggest that a weak correlation occurs because chromospherically active regions and regions of strong X-ray emission are generally related. V773 Tau was detected at 8.46 GHz as a weakly circularly polarised but highly variable source. We also find that the X-ray emission and the equivalent width of Hα remained unchanged, while large variations of the flux density in the radio regime were observed. This clearly indicates that the emitting regions are different. Using optical spectroscopy we detected a flare in Hα and event which showed a flare-like light-curve of the continuum brightness in FM Tau. However, ROSAT did not observe the field at the times of these flares. Nevertheless, an interesting X-ray event was observed in V773 Tau, during which the flux increased for about 8 hours and then decreased back to the same level in 5 hours. We interpret this as a long-duration event similar to those seen on the sun and other active stars. In the

  1. X-Ray and Radio Observations of the Massive Star-forming Region IRAS 20126+4104

    NASA Astrophysics Data System (ADS)

    Montes, V. A.; Hofner, P.; Anderson, C.; Rosero, V.

    2015-08-01

    We present results from Chandra ACIS-I and Karl G. Jansky Very Large Array 6 cm continuum observations of the IRAS 20126+4104 massive star-forming region. We detect 150 X-ray sources within the 17‧ × 17‧ ACIS-I field, and a total of 13 radio sources within the 9.‧2 primary beam at 4.9 GHz. Among these observtions are the first 6 cm detections of the central sources reported by Hofner et al., namely, I20N1, I20S, and I20var. A new variable radio source is also reported. Searching the 2MASS archive, we identified 88 near-infrared (NIR) counterparts to the X-ray sources. Only four of the X-ray sources had 6 cm counterparts. Based on an NIR color-color analysis and on the Besançon simulation of Galactic stellar populations, we estimate that approximately 80 X-ray sources are associated with this massive star-forming region. We detect an increasing surface density of X-ray sources toward the massive protostar and infer the presence of a cluster of at least 43 young stellar objects within a distance of 1.2 pc from the massive protostar.

  2. Water maser variability over 20 years in a large sample of star-forming regions: the complete database

    NASA Astrophysics Data System (ADS)

    Felli, M.; Brand, J.; Cesaroni, R.; Codella, C.; Comoretto, G.; Di Franco, S.; Massi, F.; Moscadelli, L.; Nesti, R.; Olmi, L.; Palagi, F.; Panella, D.; Valdettaro, R.

    2007-12-01

    Context: Water vapor emission at 22 GHz from masers associated with star-forming regions is highly variable. Aims: We present a database of up to 20 years of monitoring of a sample of 43 masers within star-forming regions. The sample covers a large range of luminosities of the associated IRAS source and is representative of the entire population of H2O masers of this type. The database forms a good starting point for any further study of H2O maser variability. Methods: The observations were obtained with the Medicina 32-m radiotelescope, at a rate of 4-5 observations per year. Results: To provide a database that can be easily accessed through the web, we give for each source: plots of the calibrated spectra, the velocity-time-flux density plot, the light curve of the integrated flux, the lower and upper envelopes of the maser emission, the mean spectrum, and the rate of the maser occurrence as a function of velocity. Figures for just one source are given in the text for representative purposes. Figures for all the sources are given in electronic form the appendix. A discussion of the main properties of the H2O variability in our sample will be presented in a forthcoming paper. Based on observations with the Medicina radiotelescope operated by INAF - Istituto di Radioastronomia.

  3. X-RAY AND RADIO OBSERVATIONS OF THE MASSIVE STAR-FORMING REGION IRAS 20126+4104

    SciTech Connect

    Montes, V. A.; Hofner, P.; Anderson, C.; Rosero, V.

    2015-08-15

    We present results from Chandra ACIS-I and Karl G. Jansky Very Large Array 6 cm continuum observations of the IRAS 20126+4104 massive star-forming region. We detect 150 X-ray sources within the 17′ × 17′ ACIS-I field, and a total of 13 radio sources within the 9.′2 primary beam at 4.9 GHz. Among these observtions are the first 6 cm detections of the central sources reported by Hofner et al., namely, I20N1, I20S, and I20var. A new variable radio source is also reported. Searching the 2MASS archive, we identified 88 near-infrared (NIR) counterparts to the X-ray sources. Only four of the X-ray sources had 6 cm counterparts. Based on an NIR color–color analysis and on the Besançon simulation of Galactic stellar populations, we estimate that approximately 80 X-ray sources are associated with this massive star-forming region. We detect an increasing surface density of X-ray sources toward the massive protostar and infer the presence of a cluster of at least 43 young stellar objects within a distance of 1.2 pc from the massive protostar.

  4. Probing the Low-Mass End of the IMF in Star-Forming Regions: AWIRCam/CFHT Survey

    NASA Astrophysics Data System (ADS)

    Alves de Oliveira, Catarina; Moraux, Estelle; Bouvier, Jerôme; Burgess, Andrew; Bouy, Hervé; Marmo, Chiara; Hudelot, Patrick

    One of the most attempted goals of star formation theories is to determine the dominant process by which brown dwarfs form and the implications of the environment on its outcome. Current theories must be able to reproduce not only the observed shape of the IMF, but predict observable properties of clusters such as multiplicity, mass segregation, frequency and sizes of discs, accretion, etc. The new observational frontier is therefore the detection and characterization of very low mass objects in star forming regions, to confront model predictions from numerical simulations of the collapse of molecular clouds to the observed properties of YSOs. This is the main driver behind a WIRCam large program that has been conducted at CFHT to detect BD with masses between 1 and 30 Jupiter masses in a sample of 6 young clusters. I will present the main results obtained so far for the ρ Ophiuchi molecular cloud and IC 348, where a spectroscopic follow-up of many of these candidates is being conducted using several facilities (TNG, GTC, NTT, VLT, Gemini) to ascertain their spectral types and masses, and ultimately, to construct the low-mass end of the IMF for those star forming regions.

  5. Ice Mapping Observations in Galactic Star-Forming Regions: the AKARI Legacy

    NASA Astrophysics Data System (ADS)

    Fraser, Helen Jane; Suutarinnen, Aleksi; Noble, Jennifer

    2015-08-01

    It is becoming increasingly clear that explaining the small-scale distribution of many gas-phase molecules relies on our interpretation of the complex inter-connectivity between gas- and solid-phase interstellar chemistries. Inputs to proto-stellar astrochemical models are required that exploit ice compositions reflecting the historical physical conditions in pre-stellar environments when the ices first formed. Such data are required to translate the near-universe picture of ice-composition to our understanding of the role of extra-galactic ices in star-formation at higher redshifts.Here we present the first attempts at multi-object ice detections, and the subsequent ice column density mapping. The AKARI space telescope was uniquely capable of observing all the ice features between 2 and 5 microns, thereby detecting H2O, CO and CO2 ices concurrently, through their stretching vibrational features. Our group has successfully extracted an unprecedented volume of ice spectra from AKARI, including sources with not more than 2 mJy flux at 3 microns, showing:(a) H2O CO and CO2 ices on 30 lines of sight towards pre-stellar and star-forming cores, which when combined with laboratory experiments indicate how the chemistries of these three ices are interlinked (Noble et al (2013)),(b) ice maps showing the spatial distribution of water ice across 12 pre-stellar cores, in different molecular clouds (Suutarinnen et al (2015)), and the distribution of ice components within these cores on 1000 AU scales (Noble et al (2015)),(c) over 200 new detections of water ice, mostly on lines of sight towards background sources (> 145), indicating that water ice column density has a minimum value as a function of Av, but on a cloud-by-cloud basis typically correlates with Av, and dust emissivity at 250 microns (Suutarinnen et al (2015)),(d) the first detections of HDO ice towards background stars (Fraser et al (2015)).We discuss whether these results support the picture of a generic chemical

  6. TESTING 24 {mu}m AND INFRARED LUMINOSITY AS STAR FORMATION TRACERS FOR GALACTIC STAR-FORMING REGIONS

    SciTech Connect

    Vutisalchavakul, Nalin; Evans, Neal J. II

    2013-03-10

    We have tested some relations for star formation rates used in extragalactic studies for regions within the Galaxy. In nearby molecular clouds, where the initial mass function is not fully sampled, the dust emission at 24 {mu}m greatly underestimates star formation rates (by a factor of 100 on average) when compared to star formation rates determined from counting young stellar objects. The total infrared emission does no better. In contrast, the total far-infrared method agrees within a factor of two on average with star formation rates based on radio continuum emission for massive, dense clumps that are forming enough massive stars to have L{sub TIR} exceed 10{sup 4.5} L{sub Sun }. The total infrared and 24 {mu}m also agree well with each other for both nearby, low-mass star-forming regions and the massive, dense clump regions.

  7. Uncovering the monster stars in W49: the most luminous star-forming region in the Milky Way

    NASA Astrophysics Data System (ADS)

    Wu, Shiwei; Bik, Arjan; Henning, Thomas; Pasquali, Anna; Brandner, Wolfgang; Stolte, Andrea

    2015-08-01

    As a part of the LOBSTAR project (Luci OBservations of STARburst regions), which aims at understanding the stellar content of some of the most massive star-forming regions, we present our result on the high-mass stellar content of W49. K-band spectra of the candidate massive stars from VLT/ISAAC and LBT/LUCI provide us with reliable spectral types of dozens of massive stars in this HII region.The first results show that this region hosts several of the most massive stars in our galaxy. Two most brightest stars, one in the core of the central cluster and one in W49 South, were identified as very massive stars (M > 100 M⊙). Their K-band spectra exhibit strong stellar wind features, and they are classified as O2-3.5If* supergiant stars. After comparison to the Geneva evolutionary models, the mass range of W49nr1 was estimated to be between 100 M⊙ and 180 M⊙. Additionally we find 12 O stars with spectral types between O7V and O3V and masses from 25 M⊙ to 125 M⊙, respectively.These results allow us to derive the fundamental parameters of the cluster (mass, age) as well as the total energy output in the form of ionising photons. This will enable us to study the feedback effects of this extreme star forming region in great detail. To our surprise, two young stellar objects with infrared excess feature showing CO emission lines in their spectra are identified. This suggests that circumstellar disks can survive even in this extreme environment. Finally the spatial distribution of the massive stars is analysed to discuss the star formation history and identify potential runaway stars. The extreme properties of this region makes it a good template for more extreme star formation outside our galaxy.

  8. SMA Observations of the Massive Star-forming Regions NGC 6334 I & I(N)

    NASA Astrophysics Data System (ADS)

    Hunter, Todd R.; Beuther, Henrik; Megeath, Tom; Menten, Karl; Thorwirth, Sven; Zhang, Qizhou

    We present high-resolution observations of the massive star-formation regions NGC 6334 I and I(N) in the 230 GHz band. Data were obtained during Spring 2004 and 2005 in the compact and extended configurations of the Submillimeter Array (SMA), a joint venture of the Smithsonian Astrophysical Observatory and the Academica Sinica Institute of Astronomy and Astrophysics. Various pieces of evidence, including a molecular line survey by Thorwirth et al. (2003), have suggested that these two fields exist in different evolutionary stages, with field I(N) being younger. Our new observations will help to explore this hypothesis. We have detected and imaged a number of molecular lines that trace the outflow activity and dense gas in both fields. In field I, we have begun to resolve the strong dust continuum emission into multiple sources. In a separate work, these new sources were found to coincide with strong thermal centimeter lines of ammonia and methanol (Beuther et al. 2005).

  9. VLBA Determination of the Distance to Nearby Star-forming Regions. VII. Monoceros R2

    NASA Astrophysics Data System (ADS)

    Dzib, Sergio A.; Ortiz-León, Gisela N.; Loinard, Laurent; Mioduszewski, Amy J.; Rodríguez, Luis F.; Torres, Rosa M.; Deller, Adam

    2016-08-01

    We present a series of 16 Very Long Baseline Array high angular resolution observations of a cluster of suspected low-mass young stars in the Monoceros R2 region. Four compact and highly variable radio sources are detected; three of them in only one epoch, the fourth one a total of seven times. This latter source is seen in the direction of the previously known UC H ii region VLA 1, and has radio properties that resemble those of magnetically active stars; we shall call it VLA 1⋆. We model its displacement on the celestial sphere as a combination of proper motion and trigonometric parallax. The fit obtained using a uniform proper motion yields a parallax ϖ = 1.10 ± 0.18 mas, but with a fairly high post-fit dispersion. If acceleration terms (probably due to an undetected companion) are included, the quality of the fit improves dramatically, and the best estimate of the parallax becomes ϖ = 1.12 ± 0.05 mas. The magnitude of the fitted acceleration suggests an orbital period of the order of a decade. The measured parallax corresponds to a distance d = {893}-40+44 {pc} , in very good agreement with previous, indirect determinations.

  10. The Role of Grain Surface Reactions in the Chemistry of Star Forming Regions

    NASA Technical Reports Server (NTRS)

    Kress, M. E.; Tielens, A. G. G. M.; Roberge, W. G.

    1998-01-01

    The importance of reactions at the surfaces of dust grains has long been recognized to be one of the two main chemical processes that form molecules in cold, dark interstellar clouds where simple, saturated (fully-hydrogenated) molecules such as H2 water, methanol, H2CO, H2S, ammonia and CH4 are present in quantities far too high to be consistent with their extremely low gas phase formation rates. In cold dark regions of interstellar space, dust grains provide a substrate onto which gas-phase species can accrete and react. Grains provide a "third body" or a sink for the energy released in the exothermic reactions that form chemical bonds. In essence, the surfaces of dust grains open up alternative reaction pathways to form observed molecules whose abundances cannot be explained with gas-phase chemistry alone. This concept is taken one step further in this work: instead of merely acting as a substrate onto which radicals and molecules may physically adsorb, some grains may actively participate in the reaction itself, forming chemical bonds with the accreting species. Until recently, surface chemical reactions had not been thought to be important in warm circumstellar media because adspecies rapidly desorb from grains at very low temperatures; thus, the residence times of molecules and radicals on the surface of grains at all but the lowest temperatures are far too short to allow these reactions to occur. However, if the adspecies could adsorb more strongly, via a true chemical bond with surfaces of some dust grains, then grain surface reactions will play an important role in warm circumstellar regions as well. In this work, the surface-catalyzed reaction CO + 3 H2 yields CH4 + H2O is studied in the context that it may be very effective at converting the inorganic molecule CO into the simplest organic compound, methane. H2 and CO are the most abundant molecules in space, and the reaction converting them to methane, while kinetically inhibited in the gas phase under

  11. The Formation of Glycine in Hot Cores: New Gas-grain Chemical Simulations of Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Garrod, Robin

    2012-07-01

    Organic molecules of increasing complexity have been detected in the warm envelopes of star-forming cores, commonly referred to as "hot cores". Spectroscopic searches at mm/sub-mm wavelengths have uncovered both amines and carboxylic acids in these regions, as well as a range of other compounds including alcohols, ethers, esters, and nitriles. However, the simplest amino acid, glycine (NH2CH2COOH), has not yet been reliably detected in the ISM. There has been much interest in this molecule, due to its importance to the formation of proteins, and to life, while the positive identification of interstellar molecules of similar or greater complexity suggests that its existence in star-forming regions is plausible. I will present the results of recent models of hot-core chemistry that simulate the formation of both simple and complex molecules on the surfaces or within the ice mantles of dust grains. I will also present results from the first gas-grain astrochemical model to approach the question of amino-acid formation in hot cores. The formation of glycine in moderate abundance is found to be as efficient as that for similarly complex species, while its sublimation from the grains occurs at somewhat higher temperatures. However, simulated emission spectra based on the model results show that the degree of compactness of high-abundance regions, and the density and temperature profiles of the cores may be the key variables affecting the future detection of glycine, as well as other amino acids, and may explain its non-detection to date.

  12. Nebular excitation in z ∼ 2 star-forming galaxies from the SINS and LUCI surveys: The influence of shocks and active galactic nuclei

    SciTech Connect

    Newman, Sarah F.; Genzel, Reinhard; Buschkamp, Peter; Förster Schreiber, Natascha M.; Kurk, Jaron; Rosario, David; Davies, Ric; Eisenhauer, Frank; Lutz, Dieter; Sternberg, Amiel; Gnat, Orly; Mancini, Chiara; Renzini, Alvio; Lilly, Simon J.; Carollo, C. Marcella; Burkert, Andreas; Cresci, Giovanni; Genel, Shy; Shapiro Griffin, Kristen; Hicks, Erin K. S.; and others

    2014-01-20

    Based on high-resolution, spatially resolved data of 10 z ∼ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the 'composite' region of the z ∼ 0 [N II]/Hα versus [O III]/Hβ diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with H II regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [O III]/Hβ versus stellar mass plane, does not properly separate z ∼ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ∼ 2 mass-metallicity relation (i.e., to the mass they would have at z ∼ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [N II]/Hα are more biased by shocks and AGNs at high-z than the [O III]/Hβ/[N II]/Hα calibration.

  13. Observations of Galactic star-forming regions with the Cosmic Background Imager at 31 GHz

    NASA Astrophysics Data System (ADS)

    Demetroullas, C.; Dickinson, C.; Stamadianos, D.; Harper, S. E.; Cleary, K.; Jones, Michael E.; Pearson, T. J.; Readhead, A. C. S.; Taylor, Angela C.

    2015-10-01

    Studies of the diffuse Galactic radio emission are interesting both for better understanding the physical conditions in our Galaxy and for minimizing the contamination in cosmological measurements. Motivated by this, we present Cosmic Background Imager 31 GHz observations of the Galactic regions NGC 6357, NGC 6334, W51 and W40 at ˜4.5 arcmin resolution and conduct an investigation of the spectral emission process in the regions at 4.5 arcmin and 1° resolution. We find that most of the emission in the regions is due to optically thin free-free. For two sub-regions of NGC 6334 and for a sub-region of W51 though, at 4.5 arcmin resolution and at 31 GHz we detect less emission than expected from extrapolation of radio data at lower frequencies assuming a spectral index of -0.12 for optically thin free-free emission, at 3.3σ, 3.7σ and 6.5σ, respectively. We also detect excess emission in a sub-region of NCG 6334 at 6.4σ, after ruling out any possible contribution from ultra-compact H II regions. At 1° resolution, we detect a spinning dust component in the spectral energy distribution of W40 that accounts for 18 ± 7 per cent of the total flux density in the region at the peak frequency of 37 GHz. Comparison with 100 μm data indicates an average dust emissivity for the sub-regions of 0.5 ± 4.4 μK(MJy sr-1)-1. Finally, we translate the excess emission in the regions to an anomalous microwave emission (AME) emissivity relative to the optical depth at 250 μm. We find that this form of emissivity is independent of the AME significance and has a value somewhere in the order of 104 Jy.

  14. Age gradients in the stellar populations of massive star forming regions based on a new stellar chronometer

    SciTech Connect

    Getman, Konstantin V.; Feigelson, Eric D.; Kuhn, Michael A.; Broos, Patrick S.; Townsley, Leisa K.; Luhman, Kevin L.; Naylor, Tim; Povich, Matthew S.; Garmire, Gordon P.

    2014-06-01

    A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age {sub JX} . Stellar masses are derived from X-ray luminosities using the L{sub X} -M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age {sub JX} is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age {sub JX} method has been applied to 5525 out of 31,784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age {sub JX} ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J – H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.

  15. On the onset of secondary stellar generations in giant star-forming regions and massive star clusters

    SciTech Connect

    Palouš, J.; Wünsch, R.; Tenorio-Tagle, G.

    2014-09-10

    Here we consider the strong evolution experienced by the matter reinserted by massive stars, both in giant star-forming regions driven by a constant star formation rate and in massive and coeval superstar clusters. In both cases we take into consideration the changes induced by stellar evolution on the number of massive stars, the number of ionizing photons, and the integrated mechanical luminosity of the star-forming regions. The latter is at all times compared with the critical luminosity that defines, for a given size, the lower mechanical luminosity limit above which the matter reinserted via strong winds and supernova explosions suffers frequent and recurrent thermal instabilities that reduce its temperature and pressure and inhibit its exit as part of a global wind. Instead, the unstable reinserted matter is compressed by the pervasive hot gas, and photoionization maintains its temperature at T ∼ 10{sup 4} K. As the evolution proceeds, more unstable matter accumulates and the unstable clumps grow in size. Here we evaluate the possible self-shielding of thermally unstable clumps against the UV radiation field. Self-shielding allows for a further compression of the reinserted matter, which rapidly develops a high-density neutral core able to absorb in its outer skin the incoming UV radiation. Under such conditions the cold (T ∼ 10 K) neutral cores soon surpass the Jeans limit and become gravitationally unstable, creating a new stellar generation with the matter reinserted by former massive stars. We present the results of several calculations of this positive star formation feedback scenario promoted by strong radiative cooling and mass loading.

  16. On the Onset of Secondary Stellar Generations in Giant Star-forming Regions and Massive Star Clusters

    NASA Astrophysics Data System (ADS)

    Palouš, J.; Wünsch, R.; Tenorio-Tagle, G.

    2014-09-01

    Here we consider the strong evolution experienced by the matter reinserted by massive stars, both in giant star-forming regions driven by a constant star formation rate and in massive and coeval superstar clusters. In both cases we take into consideration the changes induced by stellar evolution on the number of massive stars, the number of ionizing photons, and the integrated mechanical luminosity of the star-forming regions. The latter is at all times compared with the critical luminosity that defines, for a given size, the lower mechanical luminosity limit above which the matter reinserted via strong winds and supernova explosions suffers frequent and recurrent thermal instabilities that reduce its temperature and pressure and inhibit its exit as part of a global wind. Instead, the unstable reinserted matter is compressed by the pervasive hot gas, and photoionization maintains its temperature at T ~ 104 K. As the evolution proceeds, more unstable matter accumulates and the unstable clumps grow in size. Here we evaluate the possible self-shielding of thermally unstable clumps against the UV radiation field. Self-shielding allows for a further compression of the reinserted matter, which rapidly develops a high-density neutral core able to absorb in its outer skin the incoming UV radiation. Under such conditions the cold (T ~ 10 K) neutral cores soon surpass the Jeans limit and become gravitationally unstable, creating a new stellar generation with the matter reinserted by former massive stars. We present the results of several calculations of this positive star formation feedback scenario promoted by strong radiative cooling and mass loading.

  17. Multi-wavelength, Multi-scale Observations of Outflows in Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Plunkett, Adele Laurie Dennis

    ratio of outflow energy to gravitational binding energy; further, if gas escapes from NGC 1333, then outflow energy and gravitational energy may become comparable within the next N ~ 0.5 Myr, possibly disrupting the cluster. Finally, we investigate the properties of a particular Class 0 molecular outflow in Serpens South, providing evidence for episodic outflow events and corresponding accretion at a very early stage. This remarkable outflow remains intact even within the active, central hub region of Serpens South.

  18. TADPOL: A 1.3 mm SURVEY OF DUST POLARIZATION IN STAR-FORMING CORES AND REGIONS

    SciTech Connect

    Hull, Charles L. H.; Plambeck, Richard L.; Bower, Geoffrey C.; Heiles, Carl; Kwon, Woojin; Carpenter, John M.; Lamb, James W.; Pillai, Thushara; Crutcher, Richard M.; Hakobian, Nicholas S.; Looney, Leslie W.; Fiege, Jason D.; Franzmann, Erica; Houde, Martin; Hughes, A. Meredith; Marrone, Daniel P.; Matthews, Brenda C.; Pound, Marc W.; Rahman, Nurur; Sandell, Göran; and others

    2014-07-01

    We present λ 1.3 mm Combined Array for Research in Millimeter-wave Astronomy observations of dust polarization toward 30 star-forming cores and eight star-forming regions from the TADPOL survey. We show maps of all sources, and compare the ∼2.''5 resolution TADPOL maps with ∼20'' resolution polarization maps from single-dish submillimeter telescopes. Here we do not attempt to interpret the detailed B-field morphology of each object. Rather, we use average B-field orientations to derive conclusions in a statistical sense from the ensemble of sources, bearing in mind that these average orientations can be quite uncertain. We discuss three main findings. (1) A subset of the sources have consistent magnetic field (B-field) orientations between large (∼20'') and small (∼2.''5) scales. Those same sources also tend to have higher fractional polarizations than the sources with inconsistent large-to-small-scale fields. We interpret this to mean that in at least some cases B-fields play a role in regulating the infall of material all the way down to the ∼1000 AU scales of protostellar envelopes. (2) Outflows appear to be randomly aligned with B-fields; although, in sources with low polarization fractions there is a hint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fields have been wrapped up by envelope rotation. (3) Finally, even at ∼2.''5 resolution we see the so-called polarization hole effect, where the fractional polarization drops significantly near the total intensity peak. All data are publicly available in the electronic edition of this article.

  19. Star forming regions towards Gum 31: distribution of the molecular gas

    NASA Astrophysics Data System (ADS)

    Vazzano, M. M.; Cappa, C. E.; Vasquez, J.; Rubio, M.

    2015-08-01

    We analyze the distribution of the molecular gas associated with IRAS and 2MASS sources, young stellar objects linked to the Hii region Gum31. We based our studies on observations obtained with the APEX telescope, located in the north of Chile. We used observations of different CO isotopologues, CS(7-6) and HCO(4-3) lines. The sources are located on the edge of the Gum31 Hii region, whose shock front substantially affects the morphology of their molecular environs. The observations revealed that in the surroundings of the sources there is molecular gas associated with the nebula, which is shown by the CO(3-2) emission, with small high density clumps detected in CO(3-2).

  20. SPITZER IRAC COLOR DIAGNOSTICS FOR EXTENDED EMISSION IN STAR-FORMING REGIONS

    SciTech Connect

    Ybarra, Jason E.; Tapia, Mauricio; Román-Zúñiga, Carlos G.; Lada, Elizabeth A.

    2014-10-20

    The infrared data from the Spitzer Space Telescope are an invaluable tool for identifying physical processes in star formation. In this study, we calculate the Infrared Array Camera (IRAC) color space of UV fluorescent H{sub 2} and polycyclic aromatic hydrocarbon (PAH) emission in photodissociation regions (PDRs) using the Cloudy code with PAH opacities from Draine and Li. We create a set of color diagnostics that can be applied to study the structure of PDRs and to distinguish between FUV-excited and shock-excited H{sub 2} emission. To test this method, we apply these diagnostics to Spitzer IRAC data of NGC 2316. Our analysis of the structure of the PDR is consistent with previous studies of the region. In addition to UV excited emission, we identify shocked gas that may be part of an outflow originating from the cluster.

  1. Bridging the gap: A Spitzer Census of Intermediate-Mass Star Forming Regions from Galactic Surveys.

    NASA Astrophysics Data System (ADS)

    Kerton, Charles; Kobulnicky, Chip

    2008-03-01

    High-mass star formation (M>10 Msun) appears to proceed through different channels than low-mass star formation (M<2 Msun). The differences between these two regimes are thought to include not only the timescales and masses involved but also the initial conditions and operative physics within the parent molecular clouds. We propose an archival analysis of ~50 *intermediate-mass* star formation (SF) regions that straddle the boundary between these two regimes---regions forming stars up to 4-8 Msun. These, relatively unknown and unstudied IR sources are selected by their IRAS colors and lie within the Spitzer GLIMPSE+MIPSGAL legacy survey fields. Compared to their more famous high-mass SF cousins (e.g., the Westerhout 'W' HII objects), these regions are radio-quiet, relatively nearby, and structurally less complex. We will use complementary public-domain 13CO, 21-cm, and radio continuum Galactic surveys to 1) confirm the intermediate-mass SF nature of these objects, 2) compile a catalog and an atlas of mid-IR morphologies, 3) estimate distances, 4) calculate total luminosities and gas masses of affiliated molecular and atomic material, and 5) identify associated young stellar objects using IRAC+[24] colors. This work will provide a benchmark useful for contrasting the star formation process in both lower-mass and higher-mass SF environments.

  2. First results from a NIR survey of High Mass Star Forming Regions on the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Nuernberger, Dieter; Bronfman, Leonardo

    In spite of the lower formation rate and shorter evolutionary time scale of high mass stars (M > 8 M_{\\odot}) in comparison to low mass stars (M < 3 M_{\\odot}) there is no doubt that young OB stars have a more severe impact on their parental environment. On the one hand they are associated both with high energetic winds and massive molecular outflows, on the other hand they emit a large amount of Lyman-Continuum photons, which ionize the circumstellar material resulting in the formation of ultracompact H ii regions (UCHIIs). Here we present first results from a JHK^{'} survey of 42 regions of high mass star formation, showing FIR colour characteristics of UCHIIs (Wood & Churchwell 1989) and strong emission in the CS(2--1) rotational transition (Bronfman etal.\\ 1996). As all regions are mapped at mm wavelengths we are able to study the interplay between the young (deeply embedded) high mass stars and their ambient medium of gas and dust. Furthermore, we investigate the multiplicity of the sources as well as the spatial shape and spectral (NIR) characteristic of the UCHIIs.

  3. Molecular gas in the star-forming region IRAS 08589-4714

    NASA Astrophysics Data System (ADS)

    Saldaño, Hugo P.; Vásquez, J.; Cappa, C. E.; Gómez, M.; Duronea, N.; Rubio, M.

    2016-10-01

    Aims: We present an analysis of the region IRAS 08589-4714 with the aim of characterizing the molecular environment. Methods: We observed the 12CO(3 -2), 13CO(3 -2), C18O(3 -2), HCO+(3 -2), and HCN(3 -2) molecular lines in a region of 150''× 150'', centered on the IRAS source, to analyze the distribution and characteristics of the molecular gas linked to the IRAS source. Results: The molecular gas distribution reveals a molecular clump that is coincident with IRAS 08589-4714 and with a dust clump detected at 1.2 mm. The molecular clump is 0.45 pc in radius and its mass and H2 volume density are 310 M⊙ and 1.2 × 104 cm-3, respectively. Two overdensities were identified within the clump in HCN(3-2) and HCO+(3-2) lines. A comparison of the LTE and virial masses suggests that the clump is collapsing in regions that harbor young stellar objects. An analysis of the molecular lines suggests that they are driving molecular outflows. Final reduced APEX data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A115

  4. THE FRACTAL DIMENSION OF STAR-FORMING REGIONS AT DIFFERENT SPATIAL SCALES IN M33

    SciTech Connect

    Sanchez, Nestor; Alfaro, Emilio J.; Anez, Neyda; Odekon, Mary Crone

    2010-09-01

    We study the distribution of stars, H II regions, molecular gas, and individual giant molecular clouds in M33 over a wide range of spatial scales. The clustering strength of these components is systematically estimated through the fractal dimension. We find scale-free behavior at small spatial scales and a transition to a larger correlation dimension (consistent with a nearly uniform distribution) at larger scales. The transition region lies in the range {approx}500-1000 pc. This transition defines a characteristic size that separates the regime of small-scale turbulent motion from that of large-scale galactic dynamics. At small spatial scales, bright young stars and molecular gas are distributed with nearly the same three-dimensional fractal dimension (D {sub f,3D} {approx}< 1.9), whereas fainter stars and H II regions exhibit higher values, D {sub f,3D} {approx_equal} 2.2-2.5. Our results indicate that the interstellar medium in M33 is on average more fragmented and irregular than in the Milky Way.

  5. Revealing spectacular, young and sequential star forming regions of the Trifid Nebula with Spitzer

    NASA Astrophysics Data System (ADS)

    Rho, J.; Reach, W. T.; Lefloch, B.; Fazio, G.

    2004-12-01

    Spitzer IRAC and MIPS images of a young HII region, the Trifid Nebula (M20), reveal its spectacular appearance in infrared light, with recently formed massive protostars and numerous young stars illuminating the surrounding molecular clouds from which they formed and unveiling large scale filamentary dark clouds, which demonstrate a special evolutionary stage of HII regions. The hot dust grains show contrasting infrared colors in shells, arcs, bow-shocks and dark cores. Infrared emission is detected from the central O star complex, including the protoplanetary disks. Large populations of young stars including three dozen protostars (Classes I and 0) and over one hundred Class II pre-main sequence stars, are identified. The protostars are clustered along the filamentary dark lanes on western side of M20, which include the reflection nebula in the northern portion of the Trifid. Class II stars are distributed along the ionization front at the circular shape of HII regions. We suggest that the distribution of the protostars revealed by Spitzer is a result of sequential star formation triggered by the expansion of the young HII region of the Trifid Nebula along the filamentary dark clouds, where the massive stars tend to form in groups. The Spitzer images revealed clusters of protostars within the Class 0 objects, which were previously believed to be "starless" cores. These Spitzer images, with unprecedented sensitivity, now uncover the Class 0 protostars in infrared that are powering the SiO and CO outflows. Clusters of protostars are also detected from each of the continuum peaks TC3 and TC4, and some of these sources feature silicate absorption lines in their spectral energy distribution. The driving infrared source of a SiO outflow and submillimeter core TC1, near the exciting O star, is detected within a heated, infrared shell surrounding a dark, cold envelope. Lastly, the images also unveil three infrared sources lying along axis of the photoionized jet HH399 and

  6. Near-Infrared Variability Among YSOs in the Star Forming Region Cygnus OB7

    NASA Astrophysics Data System (ADS)

    Rice, Thomas; Wolk, S. J.; Aspin, C.

    2013-01-01

    We present an analysis of near-infrared time-series photometry in J, H, and K bands for about 100 epochs of a 1 deg x 1 deg region of the Lynds 1003/1004 dark cloud in the Cygnus OB7 region. From the 7 bands of near and mid-infrared photometry we identify 92 candidate disk bearing young stellar objects (YSOs). Of these, 27 are clearly Class I or earlier. Using the Wide-Field imaging CAMera (WFCAM) on the United Kingdom InfraRed Telescope (UKIRT), we were able to obtain photometry over three observing seasons, with photometric uncertainty better than 0.05 mag down to J=17. We study in detail the light curves and color trajectories of 50 of these sources in the monitored field. We investigate the variability and periodicity of the YSOs and find the data are consistent with all YSOs being variable in these wavelengths on time scales of a few years. We divide the variability into four observational classes: 1) stars with periodic variability stable over long timescales, 2) variables which exhibit short-lived periodicity, 3) long-term eruptive variables, and 4) stochastic variables. Some YSO variability defies simple classification. We can explain much of the observed variability as being due to dynamic and rotational changes in the disk, including an asymmetric or changing blocking fraction, changes to the inner disk hole size as well as the accretion rate.

  7. Far-infrared observations of a star-forming region in the Corona Australis dark cloud

    NASA Technical Reports Server (NTRS)

    Cruz-Gonzalez, I.; Mcbreen, B.; Fazio, G. G.

    1984-01-01

    A high-resolution far-IR (40-250-micron) survey of a 0.9-sq-deg section of the core region of the Corona Australis dark cloud (containing very young stellar objects such as T Tauri stars, Herbig Ae and Be stars, Herbig-Haro objects, and compact H II regions) is presented. Two extended far-IR sources were found, one associated with the Herbig emission-line star R CrA and the other with the irregular emission-line variable star TY CrA. The two sources have substantially more far-IR radiation than could be expected from a blackbody extrapolation of their near-IR fluxes. The total luminosities of these sources are 145 and 58 solar luminosity, respectively, implying that the embedded objects are of intermediate or low mass. The infrared observations of the sources associated with R CrA and TY CrA are consistent with models of the evolution of protostellar envelopes of intermediate mass. However, the TY CrA source appears to have passed the evolutionary stage of expelling most of the hot dust near the central source, yielding an age of about 1 Myr.

  8. Deuterated H3+ as a probe of isotope fractionation in star-forming regions

    NASA Astrophysics Data System (ADS)

    Roberts, Helen; Millar, T. J.

    2006-11-01

    A new 'semi-direct' method for solving viscous-inviscid interaction problems for high-Reynolds-number separated flows is developed. Both supersonic and subsonic flow separation may be studied using this technique. The method is based upon the vorticity and streamfunction formulation. It is fully implicit with respect to the vorticity equation and 'interaction law', which describes the mutual interdependence of the viscous layer near the body surface and the rest of the flow. The main idea of this approach consists of taking advantage of the particular structure of the governing equations, which allows the entire flow field to be solved simultaneously by using the Thomas matrix technique. The method had better numerical stability characteristics than most of the traditional techniques and was also faster than many other techniques developed before. In this paper the method is used for solving the classical problem of the boundarylayer separation in compression ramp flow. Supersonic and subsonic versions of the problem have been studied. In both cases the semi-direct method allows calculation of flow regimes with extended separation regions corresponding to large ramp angles that could not be analysed using other methods. Full Text Access Full Text Available The full text of this article is available. You may view the article as (a): PDF Although it may be a lengthier download, this is the most authoritative online format. Open: Entire document One page at a time

  9. Far-ultraviolet Imaging Rocket Experiment (FIRE) and the imaging of star-forming regions in galaxies

    NASA Astrophysics Data System (ADS)

    Gantner, Brennan L.

    2012-01-01

    I designed, built, tested and launched a sounding rocket payload to study the far-ultraviolet radiation of M51 (the Whirlpool Galaxy). This instrument, the Far-ultraviolet Imaging Rocket Experiment (FIRE, all acronyms are listed in Appendix), produced the first ever astronomical image of 900-1000 A light. It was designed to look at star forming regions in nearby galaxies by imaging the youngest, hottest O-type stars. Quantifying and locating the star forming regions within galaxies will directly aid galactic formation models. In addition, with the combination of the GALEX two-color images, FIRE was designed to investigate the intervening dust that significantly obscures these wavelengths. Since the accurate correction for dust is vital to measurements across the ultraviolet regime, improving dust extinction models aids a wide variety of both galactic and extra-galactic observations. Finally, FIRE demonstrated the successful use of two novel technologies, a silicon carbide imaging mirror and a pure indium filter. In addition to FIRE, I also examined the absorption of neutral hydrogen in the intergalactic medium (IGM) along quasi-stellar objects (QSO) sightlines. The IGM is expected to contain a significant fraction of baryons at all epochs, but is difficult to detect and map since it diffuse and emits radiation weakly. An ongoing IGM debate is whether clouds of gas detected through their Lyα absorption to QSOs are truly intergalactic or are extended halos of galaxies. A definitive answer would constrain estimates of baryonic density in the local universe and enhance our understanding of the formation of its structure. The CfA Great Wall of galaxies at redshifts of 0:015 < z < 0:03 offers an excellent locale to probe this question. This region is over-dense in galaxies and is surrounded by under-dense galactic voids, enabling us to compare absorbers' nearest galactic neighbors in highly contrasting density regions. I found 167 Lyα absorbers along

  10. Spectacular Spitzer Images of the Trifid Nebula: Protostars in a Young, Massive-Star-forming Region

    NASA Astrophysics Data System (ADS)

    Rho, Jeonghee; Reach, William T.; Lefloch, Bertrand; Fazio, Giovanni G.

    2006-06-01

    Spitzer IRAC and MIPS images of the Trifid Nebula (M20) reveal its spectacular appearance in infrared light, highlighting the nebula's special evolutionary stage. The images feature recently formed massive protostars and numerous young stellar objects, and a single O star that illuminates the surrounding molecular cloud from which it formed, and unveil large-scale, filamentary dark clouds. Multiple protostars are detected in the infrared, within the cold dust cores of TC3 and TC4, which were previously defined as Class 0. The cold dust continuum cores of TC1 and TC2 contain only one protostar each. The Spitzer color-color diagram allowed us to identify ~160 young stellar objects (YSOs) and classify them into different evolutionary stages. The diagram also revealed a unique group of YSOs that are bright at 24 μm but have the spectral energy distribution peaking at 5-8 μm. Despite expectation that Class 0 sources would be ``starless'' cores, the Spitzer images, with unprecedented sensitivity, uncover mid-infrared emission from these Class 0 protostars. The mid-infrared detections of Class 0 protostars show that the emission escapes the dense, cold envelope of young protostars. The mid-infrared emission of the protostars can be fit by two temperatures of 150 and 400 K; the hot core region is probably optically thin in the mid-infrared regime, and the size of hot core is much smaller than that of the cold envelope. The presence of multiple protostars within the cold cores of Class 0 objects implies that clustering occurs at this early stage of star formation. The most massive star in the TC3 cluster is located at the center of the cluster and at the bottom of the gravitational potential well.

  11. DIRECT SPECTROSCOPIC IDENTIFICATION OF THE ORIGIN OF 'GREEN FUZZY' EMISSION IN STAR-FORMING REGIONS

    SciTech Connect

    De Buizer, James M.; Vacca, William D.

    2010-07-15

    'Green fuzzies' or 'extended green objects' were discovered in the recent Spitzer GLIMPSE survey data. These extended sources have enhanced emission in the 4.5 {mu}m IRAC channel images (which are generally assigned to be green when making three-color RGB images from Spitzer data). Green fuzzies are frequently found in the vicinities of massive young stellar objects (MYSO), and it has been established that they are in some cases associated with outflows. Nevertheless, the spectral carrier(s) of this enhanced emission is (are) still uncertain. Although it has been suggested that Br {alpha}, H{sub 2}, [Fe II], and/or broad CO emission may be contributing to and enhancing the 4.5 {mu}m flux from these objects, to date there have been no direct observations of the 4-5 {mu}m spectra of these objects. Here we report on the first direct spectroscopic identification of the origin of the green fuzzy emission. We obtained spatially resolved L- and M-band spectra for two green fuzzy sources using NIRI on the Gemini North telescope. In the case of one source, G19.88 - 0.53, we detect three individual knots of green fuzzy emission around the source. The knots exhibit a pure molecular hydrogen line emission spectrum, with the 4.695 {mu}m {nu} = 0-0 S(9) line dominating the emission in the 4-5 {mu}m wavelength range, and no detected continuum component. Our data for G19.88 - 0.53 prove that green fuzzy emission can be due primarily to emission lines of molecular hydrogen within the bandpass of the IRAC 4.5 {mu}m channel. However, the other target observed, G49.27 - 0.34, does not exhibit any line emission and appears to be an embedded MYSO with a cometary UC H II region. We suggest that the effects of extinction in the 3-8 {mu}m wavelength range and an exaggeration in the color stretch of the 4.5 {mu}m filter in IRAC RGB images could lead to embedded sources such as this one falsely appearing 'green'.

  12. Spectacular Spitzer images of the Trifid Nebula: Protostars in a young, massive-star-forming region

    NASA Astrophysics Data System (ADS)

    Rho, J.; Reach, W. T.; Lefloch, B.; Fazio, G.

    Spitzer IRAC and MIPS images of the Trifid Nebula (M20; see Figure 1) reveal its spectacular appearance in infrared light, demonstrating its special evolutionary stage: recently-formed massive protostars and numerous young stars, including a single O star that illuminates the surrounding molecular cloud from which it formed and unveiling large-scale, filamentary dark clouds. The hot dust grains show contrasting infrared colors in shells, arcs, bow-shocks and dark cores. Multiple protostars, previously defined as Class 0 from dust continuum and molecular outflow observations, are revealed in the infrared within the cold dust continuum peaks TC3 and TC4. The cold dust continuum cores of TC1 and TC2 contain only one protostar each; the newly-discovered infrared protostar in TC2 is the driving source of the HH399 jet. The Spitzer color-color diagram allowed us to identify ~150 young stellar objects (YSO) and classify them into different evolutionary stages, and also revealed a new class of YSO which are bright at 24μm but with spectral energy distribution peaking at 5-8μm; we name these sources "Hot excess" YSO. Despite of expectation that Class 0 sources would be "starless" cores, the Spitzer images, with unprecedented sensitivity, uncover mid-infrared emission from these Class 0 protostars. The mid-infrared detections of Class 0 protostars show that the emission escapes the dense, cold envelope of young protostars; the mid-infrared emission cannot arise from the same location as the mm-wave emission, and instead must arise from a much smaller region with less intervening extinction to the central accretion. The presence of multiple protostars within the cold cores of Class 0 objects implies that clustering occurs at this early stage of star formation. The most massive stars are located at the center of the cluster and are formed simultaneously with low-mass stars. The angular and mass distributions of protostars within the dust cores imply that these early

  13. Evolutionary status of dense cores in the NGC 1333 IRAS 4 star-forming region

    NASA Astrophysics Data System (ADS)

    Koumpia, E.; van der Tak, F. F. S.; Kwon, W.; Tobin, J. J.; Fuller, G. A.; Plume, R.

    2016-10-01

    Context. Protostellar evolution after the formation of the protostar is becoming reasonably well characterized, but the evolution from a prestellar core to a protostar is not well known, although the first hydrostatic core (FHSC) must be a pivotal step. Aims: NGC 1333 - IRAS 4C is a potentially very young object that we can directly compare with the nearby Class 0 objects IRAS 4A and IRAS 4B. Observational constraints are provided by spectral imaging from the JCMT Spectral Legacy Survey (330-373 GHz). We present integrated intensity and velocity maps of several species, including CO, H2CO and CH3OH. CARMA observations provide additional information with which we can distinguish IRAS 4C from other evolutionary stages. Methods: We present the observational signatures of the velocity of an observed outflow, the degree of CO depletion, the deuterium fractionation of [DCO+]/[HCO+], and gas kinetic temperatures. Results: We report differences between the three sources in four aspects: a) the kinetic temperature as probed using the H2CO lines is much lower toward IRAS 4C than the other two sources; b) the line profiles of the detected species show strong outflow activity toward IRAS 4A and IRAS 4B, but not toward IRAS 4C; c) the HCN/HNC is <1 toward IRAS 4C, which confirms the cold nature of the source; d) the degree of CO depletion and the deuteration are lowest toward the warmest of the sources, IRAS 4B. Conclusions: IRAS 4C seems to be in a different evolutionary state than the sources IRAS 4A and IRAS 4B. We can probably exclude the FHSC stage becaues of the relatively low Lsmm/Lbol ( 6%), and we investigate the earliest accretion phase of Class 0 stage and the transition between Class 0 to Class I. Our results do not show a consistent scenario for either case; the main problem is the absence of outflow activity and the cold nature of IRAS 4C. The number of FHSC candidates in Perseus is 10 times higher than current models predict, which suggests that the lifespan of

  14. Effects of external radiation fields on line emission—application to star-forming regions

    SciTech Connect

    Chatzikos, Marios; Ferland, G. J.; Williams, R. J. R.; Porter, Ryan; Van Hoof, P. A. M.

    2013-12-20

    A variety of astronomical environments contain clouds irradiated by a combination of isotropic and beamed radiation fields. For example, molecular clouds may be irradiated by the isotropic cosmic microwave background, as well as by a nearby active galactic nucleus. These radiation fields excite atoms and molecules and produce emission in different ways. We revisit the escape probability theorem and derive a novel expression that accounts for the presence of external radiation fields. We show that when the field is isotropic the escape probability is reduced relative to that in the absence of external radiation. This is in agreement with previous results obtained under ad hoc assumptions or with the two-level system, but can be applied to complex many-level models of atoms or molecules. This treatment is in the development version of the spectral synthesis code CLOUDY. We examine the spectrum of a Spitzer cloud embedded in the local interstellar radiation field and show that about 60% of its emission lines are sensitive to background subtraction. We argue that this geometric approach could provide an additional tool toward understanding the complex radiation fields of starburst galaxies.

  15. Direct imaging of extra-solar planets in star forming regions. Lessons learned from a false positive around IM Lupi

    NASA Astrophysics Data System (ADS)

    Mawet, D.; Absil, O.; Montagnier, G.; Riaud, P.; Surdej, J.; Ducourant, C.; Augereau, J.-C.; Röttinger, S.; Girard, J.; Krist, J.; Stapelfeldt, K.

    2012-08-01

    Context. Most exoplanet imagers consist of ground-based adaptive optics coronagraphic cameras which are currently limited in contrast, sensitivity and astrometric precision, but advantageously observe in the near-infrared window (1-5 μm). Because of these practical limitations, our current observational aim at detecting and characterizing planets puts heavy constraints on target selection, observing strategies, data reduction, and follow-up. Most surveys so far have thus targeted young systems (1-100 Myr) to catch the putative remnant thermal radiation of giant planets, which peaks in the near-infrared. They also favor systems in the solar neighborhood (d < 80 pc), which eases angular resolution requirements but also ensures a good knowledge of the distance and proper motion, which are critical to secure the planet status, and enable subsequent characterization. Aims: Because of their youth, it is very tempting to target the nearby star forming regions, which are typically twice as far as the bulk of objects usually combed for planets by direct imaging. Probing these interesting reservoirs sets additional constraints that we review in this paper by presenting the planet search that we initiated in 2008 around the disk-bearing T Tauri star IM Lup, which is part of the Lupus star forming region (140-190 pc). Methods: We show and discuss why age determination, the choice of evolutionary model for both the central star and the planet, precise knowledge of the host star proper motion, relative or absolute (between different instruments) astrometric accuracy (including plate scale calibration), and patience are the key ingredients for exoplanet searches around more distant young stars. Results: Unfortunately, most of the time, precision and perseverance are not paying off: we discovered a candidate companion around IM Lup in 2008, which we report here to be an unbound background object. We nevertheless review in details the lessons learned from our endeavor, and

  16. a Search for Interstellar Carbon-Chain Alcohol HC4OH in the Star Forming Region L1527

    NASA Astrophysics Data System (ADS)

    Araki, Mitsunori; Takano, Shuro; Koshikawa, Hiromichi Yamabe Naohiro; Tsukiyama, Koichi; Nakane, Aya; Okabatyashi, Toshiaki; Kunimatsu, Arisa; Kuze, Nobuhiko

    2011-06-01

    We have made a sensitive search for the rotational transitions of carbon-chain alcohol HC_4OH with the frequency ragne from 21.2 to 46.7 GHz in the star forming region L1527 in Taurus with rich carbon-chain chemistry. The incentive of this observation was a laboratory detection of HC_4OH by the microwave spectroscopy. Despite achieving an rms of several mK in antenna temperature by the 45m telescope at Nobeyama Radio Observatory, the searche for HC_4OH was negative, leading to a 5 sigma upper limit corresponding to the column density of 4 × 1012 Cm-2 based on the excitation temperature of 12.3 K. The upper limit indicates that the [HC_4-OH]/[HC_4-CN] ratio is less than 1.0. The ratio suggests that the cyanide species with carbon-chain structure is dominant in comparison with the hydroxyl one in L1527, which can be the opposite case of saturated compounds, e.g. CH_3OH and CH_3CN, in hot cores and dark clouds.

  17. Observations of the 6 Centimeter Lines of OH in OH/IR Stars and Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Zschaechner, Laura K.; Fish, V. L.; Sjouwerman, L. O.; Pihlstrom, Y. M.; Claussen, M. J.

    2006-12-01

    Recent observational and theoretical advances have given rise to ambiguities regarding the model for OH maser pumping in OH/IR stars. While ground-state OH lines have already been observed, the detection of excited-state OH lines would provide additional constraints on theoretical pumping models. To date, the only positive detections of excited-state OH emission in OH/IR stars have been a 4750 MHz maser in AU Gem and 6035 MHz maser emission in NML Cyg. We report on Very Large Array observations of the 4750 and 4765 MHz OH lines toward 45 sources, most of which are OH/IR stars. All of the sources have previously exhibited ground-state maser emission. We do not detect excited-state emission in any evolved star at the 100 mJy level (5 σ). However, masers in the 4765 MHz transition are detected toward two star forming regions: Mon R2 and LDN 1084. Masers in each of these sources have been previously detected and have shown significant variability in the past. the 4765 MHz maser in Mon R2, which had exhibited two distinct flares, one of which surpassed 75 Jy before disappearing in 1998 December, appears to be undergoing a new flaring event. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. L. K. Z. acknowledges support from the NSF Research Experiences for Undergraduates program.

  18. "X-Ray Transients in Star-Forming Regions" and "Hard X-Ray Emission from X-Ray Bursters"

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.; Kaaret, Philip

    1999-01-01

    This grant funded work on the analysis of data obtained with the Burst and Transient Experiment (BATSE) on the Compton Gamma-Ray Observatory. The goal of the work was to search for hard x-ray transients in star forming regions using the all-sky hard x-ray monitoring capability of BATSE. Our initial work lead to the discovery of a hard x-ray transient, GRO J1849-03. Follow-up observations of this source made with the Wide Field Camera on BeppoSAX showed that the source should be identified with the previously known x-ray pulsar GS 1843-02 which itself is identified with the x-ray source X1845-024 originally discovered with the SAS-3 satellite. Our identification of the source and measurement of the outburst recurrence time, lead to the identification of the source as a Be/X-ray binary with a spin period of 94.8 s and an orbital period of 241 days. The funding was used primarily for partial salary and travel support for John Tomsick, then a graduate student at Columbia University. John Tomsick, now Dr. Tomsick, received his Ph.D. from Columbia University in July 1999, based partially on results obtained under this investigation. He is now a postdoctoral research scientist at the University of California, San Diego.

  19. EVIDENCE FOR LOW EXTINCTION IN ACTIVELY STAR-FORMING GALAXIES AT z > 6.5

    SciTech Connect

    Walter, F.; Decarli, R.; Carilli, C.; Riechers, D.; Bertoldi, F.; Weiss, A.; Cox, P.; Neri, R.; Maiolino, R.; Ouchi, M.; Egami, E.

    2012-06-20

    We present a search for the [C II] 158 {mu}m fine structure line (a main cooling line of the interstellar medium) and the underlying far-infrared (FIR) continuum in three high-redshift (6.6 < z < 8.2) star-forming galaxies using the IRAM Plateau de Bure Interferometer. We targeted two Ly{alpha}-selected galaxies (Ly{alpha} emitters, LAEs) with moderate UV-based star formation rates (SFRs {approx} 20 M{sub Sun} yr{sup -1}; Himiko at z = 6.6 and IOK-1 at z = 7.0) and a gamma-ray burst (GRB) host galaxy (GRB 090423 at z {approx} 8.2). Based on our 3{sigma} rest-frame FIR continuum limits, previous (rest-frame) UV continuum measurements and spectral energy distribution (SED) fitting, we rule out SED shapes similar to highly obscured galaxies (e.g., Arp 220, M 82) and less extreme dust-rich nearby spiral galaxies (e.g., M 51) for the LAEs. Conservatively assuming an SED shape typical of local spiral galaxies we derive upper limits for the FIR-based star formation rates (SFRs) of {approx}70 M{sub Sun} yr{sup -1}, {approx}50 M{sub Sun} yr{sup -1}, and {approx}40 M{sub Sun} yr{sup -1} for Himiko, IOK-1, and GRB 090423, respectively. For the LAEs these limits are only a factor {approx}3 higher than the published UV-based SFRs (uncorrected for extinction). This indicates that the dust obscuration in the z > 6 LAEs studied here is lower by a factor of a few than what has recently been found in some LAEs at lower redshift (2 < z < 3.5) with similar UV-based SFRs. A low obscuration in our z > 6 LAE sample is consistent with recent rest-frame UV studies of z {approx} 7 Lyman break galaxies.

  20. A GALEX-BASED SEARCH FOR THE SPARSE YOUNG STELLAR POPULATION IN THE TAURUS-AURIGAE STAR FORMING REGION

    SciTech Connect

    Gómez de Castro, Ana I.; Lopez-Santiago, Javier; López-Martínez, Fatima; Sánchez, Néstor; Sestito, Paola; Gestoso, Javier Yañez; De Castro, Elisa; Cornide, Manuel

    2015-02-01

    In this work, we identify 63 bona fide new candidates to T Tauri stars (TTSs) in the Taurus-Auriga region, using its ultraviolet excess as our baseline. The initial data set was defined from the GALEX all sky survey (AIS). The GALEX satellite obtained images in the near-ultraviolet (NUV) and far-ultraviolet (FUV) bands where TTSs show a prominent excess compared with main-sequence or giants stars. GALEX AIS surveyed the Taurus-Auriga molecular complex, as well as a fraction of the California Nebula and the Perseus complex; bright sources and dark clouds were avoided. The properties of TTSs in the ultraviolet (GALEX), optical (UCAC4), and infrared (2MASS) have been defined using the TTSs observed with the International Ultraviolet Explorer reference sample. The candidates were identified by means of a mixed ultraviolet-optical-infrared excess set of colors; we found that the FUV-NUV versus J–K color-color diagram is ideally suited for this purpose. From an initial sample of 163,313 bona fide NUV sources, a final list of 63 new candidates to TTSs in the region was produced. The search procedure has been validated by its ability to detect all known TTSs in the area surveyed: 31 TTSs. Also, we show that the weak-lined TTSs are located in a well-defined stripe in the FUV-NUV versus J–K diagram. Moreover, in this work, we provide a list of TTSs photometric standards for future GALEX-based studies of the young stellar population in star forming regions.

  1. THE INTEGRATED DIFFUSE X-RAY EMISSION OF THE CARINA NEBULA COMPARED TO OTHER MASSIVE STAR-FORMING REGIONS

    SciTech Connect

    Townsley, Leisa K.; Broos, Patrick S.; Chu, You-Hua; Gruendl, Robert A.; Oey, M. S.; Pittard, Julian M.

    2011-05-01

    The Chandra Carina Complex Project (CCCP) has shown that the Carina Nebula displays bright, spatially-complex soft diffuse X-ray emission. Here, we 'sum up' the CCCP diffuse emission work by comparing the global morphology and spectrum of Carina's diffuse X-ray emission to other famous sites of massive star formation with pronounced diffuse X-ray emission: M17, NGC 3576, NGC 3603, and 30 Doradus. All spectral models require at least two diffuse thermal plasma components to achieve adequate spectral fits, a softer component with kT = 0.2-0.6 keV and a harder component with kT = 0.5-0.9 keV. In several cases these hot plasmas appear to be in a state of non-equilibrium ionization that may indicate recent and current strong shocks. A cavity north of the embedded giant H II region NGC 3576 is the only region studied here that exhibits hard diffuse X-ray emission; this emission appears to be nonthermal and is likely due to a recent cavity supernova, as evidenced by a previously-known pulsar and a newly-discovered pulsar wind nebula also seen in this cavity. All of these targets exhibit X-ray emission lines that are not well modeled by variable-abundance thermal plasmas and that might be attributed to charge exchange at the shock between the hot, tenuous, X-ray-emitting plasma and cold, dense molecular material; this is likely evidence for dust destruction at the many hot/cold interfaces that characterize massive star-forming regions.

  2. Spectroscopically resolved far-IR observations of the massive star-forming region G5.89-0.39

    NASA Astrophysics Data System (ADS)

    Leurini, S.; Wyrowski, F.; Wiesemeyer, H.; Gusdorf, A.; Güsten, R.; Menten, K. M.; Gerin, M.; Levrier, F.; Hübers, H. W.; Jacobs, K.; Ricken, O.; Richter, H.

    2015-12-01

    Context. The fine-structure line of atomic oxygen at 63 μm ([OI]63μm) is an important diagnostic tool in different fields of astrophysics: it is for example predicted to be the main coolant in several environments of star-forming regions (SFRs). However, our knowledge of this line relies on observations with low spectral resolution, and the real contribution of each component (photon-dominated region, jet) in the complex environment of SFRs to its total flux is poorly understood. Aims: We investigate the contribution of jet and photon-dominated region emission, and of absorption to the [OI]63μm line towards the hot gas around the ultra-compact Hii region G5.89-0.39 and study the far-IR line luminosity of the source in different velocity regimes through spectroscopically resolved spectra of atomic oxygen, [CII], CO, OH, and H2O. Methods: We mapped G5.89-0.39 in [OI]63μm and in CO(16-15) with the GREAT receiver onboard SOFIA. We also observed the central position of the source in the ground-state OH 2Π3/2 J = 5/2 → J = 3/2 triplet and in the excited OH 2Π1/2 J = 3/2 → J = 1/2 triplets with SOFIA. These data were complemented with APEX CO(6-5) and CO(7-6) maps and with Herschel/HIFI maps and single-pointing observations in lines of [CII], H2O, and HF. Results: The [OI] spectra in G5.89-0.39 are severely contaminated by absorptions from the source envelope and from different clouds along the line of sight. Emission is detected only at high velocities, and it is clearly associated with the compact north-south outflows traced by extremely high-velocity emission in low-J CO lines. The mass-loss rate and the energetics of the jet system derived from the [OI]63μm line agree well with previous estimates from CO, thus suggesting that the molecular outflows in G5.89-0.39 are driven by the jet system seen in [OI]. The far-IR line luminosity of G5.89-0.39 is dominated by [OI] at high-velocities; the second coolant in this velocity regime is CO, while [CII], OH and H2O

  3. The Dust Content and Opacity of Actively Star-Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Calzetti, Daniela; Armus, Lee; Bohlin, Ralph C.; Kinney, Anne L.; Koornneef, Jan; Storchi-Bergmann, Thaisa

    2000-01-01

    ), UV - bright star-forming galaxies, these galaxies' FIR emission will be generally undetected in submillimeter surveys, unless: (1) their bolometric luminosity is comparable to or larger than that of ultraluminous FIR galaxies and (2) their FIR SED contains a cool dust component.

  4. FOUR HIGHLY LUMINOUS MASSIVE STAR-FORMING REGIONS IN THE NORMA SPIRAL ARM. I. MOLECULAR GAS AND DUST OBSERVATIONS

    SciTech Connect

    Garay, Guido; Mardones, Diego; Bronfman, Leonardo; May, Jorge; Chavarria, Luis; Nyman, Lars-Ake

    2010-02-10

    We report molecular line and dust continuum observations, made with the Swedish-ESO Submillimeter Telescope, toward four young high-mass star-forming regions associated with highly luminous (L>6x10{sup 5}L{sub odot}) Infrared Astronomical Satellite sources (15290-5546, 15502-5302, 15567-5236, and 16060-5146). Molecular emission was mapped in three lines of CS (J = 2 -> 1, 3 -> 2, and 5 -> 4), two lines of SiO (J = 2 -> 1 and 3 -> 2), two rotational transitions of CH{sub 3}OH (J{sub k} = 3{sub k} -> 2{sub k} and 2{sub k} -> 1{sub k}), and in the C{sup 34}S(J = 3 -> 2) line. In addition, single spectra at the peak position were taken in the CO(J = 1 -> 0), {sup 13}CO(J = 1 -> 0), and C{sup 18}O(J = 1 -> 0) lines. We find that the luminous star-forming regions are associated with molecular gas and dust structures with radii of typically 0.5 pc, masses of {approx}5 x 10{sup 3} M{sub sun}, column densities of {approx}5 x 10{sup 23} cm{sup -2}, molecular hydrogen densities of typically {approx}2 x 10{sup 5} cm{sup -3}, and dust temperatures of {approx}40 K. The 1.2 mm dust continuum observations further indicate that the cores are centrally condensed, having radial density profiles with power-law indices in the range 1.9-2.3. We find that under these conditions dynamical friction by the gas plays an important role in the migration of high-mass stars toward the central core region, providing an explanation for the observed stellar mass segregation within the cores. The CS profiles show two distinct emission components: a bright component, with line widths of typically 5 km s{sup -1} (FWHM), and a weaker and wider velocity component, which typically extends up to +-13 km s{sup -1} from the ambient cloud velocity. The SiO profiles also show emission from both components, but the intensity of the pedestal feature relative to that of the bright component is stronger than for CS. The narrow SiO component is likely to trace warm ambient gas close to the recently formed massive

  5. A lunar occultation and direct imaging survey of multiplicity in the Ophiuchus and Taurus star-forming regions

    NASA Technical Reports Server (NTRS)

    Simon, M.; Ghez, A. M.; Leinert, CH.; Cassar, L.; Chen, W. P.; Howell, R. R.; Jameson, R. F.; Matthews, K.; Neugebauer, G.; Richichi, A.

    1995-01-01

    We present an IR lunar occultation and direct imaging search for companions in the Ophiuchus star-forming region and update a similar search of the Taurus region. The search is sensitive to companions in the angular separation range 0.005-10 sec. In Ophiuchus, we surveyed 35 young star targets; this sample contains at least 10 binaries, two triples, and one quadruple. Ten of the companion stars are newly discovered. In Taurus, the survey now includes 47 systems among which there are at least 22 binaries and four triples. Only two companion stars are newly identified because there is strong overlap with prior work. All the triples and quadruple are hierarchical. The observed binary frequency in Ophiuchus, in the 3-1400 AU range of separations, is at least 1.1 +/- 0.3 that of the nearby solar-like stars. This value is a lower bound because we make no corrections for incompleteness. In Taurus, in the same range of separations, the observed binary frequency is at least 1.6 +/- 0.3 that of the nearby solar-like stars. This value extends Ghez et al.'s (1993) and Leinert's et al.'s (1993) determination of an excess binary frequency to 3 AU separation. We used the weak-line T Tauri star/T Tauri star (WT/TT) type and the K-L color index to distinguish between systems with and without inner disks. We find no convincing difference in the binary frequency or distribution of separations of the systems with and without inner disks. The 1.3 mm continuum emission of the single systems exceeds that of the multiples suggesting that their extensive outer disks are more massive. The specific angular momenta of the binaries overlap those of molecular cloud cores measured by Goodman et al. (1993).

  6. Far-infrared molecular lines from low- to high-mass star forming regions observed with Herschel

    NASA Astrophysics Data System (ADS)

    Karska, A.; Herpin, F.; Bruderer, S.; Goicoechea, J. R.; Herczeg, G. J.; van Dishoeck, E. F.; San José-García, I.; Contursi, A.; Feuchtgruber, H.; Fedele, D.; Baudry, A.; Braine, J.; Chavarría, L.; Cernicharo, J.; van der Tak, F. F. S.; Wyrowski, F.

    2014-02-01

    Aims: Our aim is to study the response of the gas-to-energetic processes associated with high-mass star formation and compare it with previously published studies on low- and intermediate-mass young stellar objects (YSOs) using the same methods. The quantified far-IR line emission and absorption of CO, H2O, OH, and [O i] reveals the excitation and the relative contribution of different atomic and molecular species to the gas cooling budget. Methods: Herschel/PACS spectra covering 55-190 μm are analyzed for ten high-mass star forming regions of luminosities Lbol ~ 104-106 L⊙ and various evolutionary stages on spatial scales of ~104 AU. Radiative transfer models are used to determine the contribution of the quiescent envelope to the far-IR CO emission. Results: The close environments of high-mass protostars show strong far-IR emission from molecules, atoms, and ions. Water is detected in all 10 objects even up to high excitation lines, often in absorption at the shorter wavelengths and in emission at the longer wavelengths. CO transitions from J = 14 - 13 up to typically 29 - 28 (Eu/kB ~ 580-2400 K) show a single temperature component with a rotational temperature of Trot ~ 300 K. Typical H2O excitation temperatures are Trot ~250 K, while OH has Trot ~ 80 K. Far-IR line cooling is dominated by CO (~75%) and, to a smaller extent, by [O i] (~20%), which becomes more important for the most evolved sources. H2O is less important as a coolant for high-mass sources because many lines are in absorption. Conclusions: Emission from the quiescent envelope is responsible for ~45-85% of the total CO luminosity in high-mass sources compared with only ~10% for low-mass YSOs. The highest- J lines (Jup ≥ 20) originate most likely in shocks, based on the strong correlation of CO and H2O with physical parameters (Lbol, Menv) of the sources from low- to high-mass YSOs. The excitation of warm CO described by Trot ~ 300 K is very similar for all mass regimes, whereas H2O

  7. Nebular Excitation in z ~ 2 Star-forming Galaxies from the SINS and LUCI Surveys: The Influence of Shocks and Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Newman, Sarah F.; Buschkamp, Peter; Genzel, Reinhard; Förster Schreiber, Natascha M.; Kurk, Jaron; Sternberg, Amiel; Gnat, Orly; Rosario, David; Mancini, Chiara; Lilly, Simon J.; Renzini, Alvio; Burkert, Andreas; Carollo, C. Marcella; Cresci, Giovanni; Davies, Ric; Eisenhauer, Frank; Genel, Shy; Shapiro Griffin, Kristen; Hicks, Erin K. S.; Lutz, Dieter; Naab, Thorsten; Peng, Yingjie; Tacconi, Linda J.; Wuyts, Stijn; Zamorani, Gianni; Vergani, Daniela; Weiner, Benjamin J.

    2014-01-01

    Based on high-resolution, spatially resolved data of 10 z ~ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the "composite" region of the z ~ 0 [N II]/Hα versus [O III]/Hβ diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with H II regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [O III]/Hβ versus stellar mass plane, does not properly separate z ~ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ~ 2 mass-metallicity relation (i.e., to the mass they would have at z ~ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [N II]/Hα are more biased by shocks and AGNs at high-z than the [O III]/Hβ/[N II]/Hα calibration. Based on observations at the Very Large Telescope (VLT) of the European Southern Observatory (ESO), Paranal, Chile (ESO program IDs 073.B-9018, 076.A-0527, 079.A-0341, 080.A-0330, 080.A-0339, 080.A-0635, 083.A-0781,084.A-0853, 087.A-0081, 091.A.-0126) and at the Large Binocular Telescope (LBT) on Mt. Graham in Arizona.

  8. An HST Imaging Survey of Low-mass Stars in the Chamaeleon I Star-forming Region

    NASA Astrophysics Data System (ADS)

    Robberto, M.; Spina, L.; Da Rio, N.; Apai, D.; Pascucci, I.; Ricci, L.; Goddi, C.; Testi, L.; Palla, F.; Bacciotti, F.

    2012-09-01

    We present new Hubble Space Telescope/WFPC2 observations of 20 fields centered around T Tauri stars in the Chamaeleon I star-forming region. Images have been obtained in the F631N ([O I] λ6300), F656N (Hα), and F673N ([S II] λλ6716, 6731) narrow-band filters, plus the Johnson V-band equivalent F547M filter. We detect 31 T Tauri stars falling within our fields. We discuss the optical morphology of 10 sources showing evidence of either binarity, circumstellar material, or mass loss. We supplement our photometry with a compilation of optical, infrared, and submillimeter (sub-mm) data from the literature, together with new sub-mm data for three objects, to build the spectral energy distributions (SEDs) of 19 single sources. Using an SED model fitting tool, we self-consistently estimate a number of stellar and disk parameters, while mass accretion rates are directly derived from our Hα photometry. We find that bolometric luminosities derived from dereddened optical data tend to be underestimated in systems with high α2-24 IR spectral index, suggesting that disks seen nearly edge-on may occasionally be interpreted as low-luminosity (and therefore more evolved) sources. On the other hand, the same α2-24 IR spectral index, a tracer of the amount of dust in the warmer layers of the circumstellar disks, and the mass accretion rate appear to decay with the isochronal stellar age, suggesting that the observed age spread (sime 0.5-5 Myr) within the cluster is real. Our sample contains a few outliers that may have dissipated their circumstellar disks on a shorter timescale.

  9. Fundamental stellar parameters for selected T-Tauri stars in the Chamaeleon and Rho Ophiuchus star-forming regions

    NASA Astrophysics Data System (ADS)

    James, D. J.; Aarnio, A. N.; Richert, A. J. W.; Cargile, P. A.; Santos, N. C.; Melo, C. H. F.; Bouvier, J.

    2016-06-01

    We present the results of an optical photometry and high-resolution spectroscopy campaign for a modest sample of X-ray selected stars in the Chamaeleon and Rho Ophiuchus star-forming regions. With R˜ 50 000 optical spectra, we establish kinematic membership of the parent association and confirm stellar youth for each star in our sample. With the acquisition of new standardized BVIc photometry, in concert with near-infrared data from the literature, we derive age and mass from stellar positions in model-dependent Hertzsprung-Russell diagrams. We compare isochronal ages derived using colour-dependent extinction values finding that, within error bars, ages are the same irrespective of whether E(B - V), E(V - Ic), E(J - H) or E(H - K) is used to establish extinction, although model ages tend to be marginally younger for redder Ecolour values. For Cham I and η Cham members, we derive ages of ≲5-6 Myr, whereas our three η Cha candidates are more consistent with a ≳25 Myr post-T Tauri star population. In Rho Ophiuchus, most stars in our sample have isochronal ages <10 Myr. Five objects show evidence of strong infrared excess (Av > 5) in the Two Micron All Sky Survey colour-colour diagram, however in terms of Hα emission, all stars except RXJ1625.6-2613 are consistent with being weak-lined T-Tauri stars. Spectral energy distributions (SEDs) over the range ≃4000 Å <λ < 1000 μm, show that only one Chamaeleon star (RXJ1112.7 -7637) and three Rho Ophiuchus stars (ROXR1 13, RXJ1625.6-2613 & RXJ1627.1-2419) reveal substantial departures from a bare photosphere.

  10. DECONVOLUTION OF IMAGES FROM BLAST 2005: INSIGHT INTO THE K3-50 AND IC 5146 STAR-FORMING REGIONS

    SciTech Connect

    Roy, Arabindo; Netterfield, Calvin B.; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Bock, James J.; Brunt, Christopher M.; Chapin, Edward L.; Gibb, Andrew G.; Halpern, Mark; Marsden, Gaelen; Devlin, Mark J.; Dicker, Simon R.; Klein, Jeff; France, Kevin; Gundersen, Joshua O.; Hughes, David H.; Martin, Peter G.; Olmi, Luca

    2011-04-01

    We present an implementation of the iterative flux-conserving Lucy-Richardson (L-R) deconvolution method of image restoration for maps produced by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST). Compared to the direct Fourier transform method of deconvolution, the L-R operation restores images with better-controlled background noise and increases source detectability. Intermediate iterated images are useful for studying extended diffuse structures, while the later iterations truly enhance point sources to near the designed diffraction limit of the telescope. The L-R method of deconvolution is efficient in resolving compact sources in crowded regions while simultaneously conserving their respective flux densities. We have analyzed its performance and convergence extensively through simulations and cross-correlations of the deconvolved images with available high-resolution maps. We present new science results from two BLAST surveys, in the Galactic regions K3-50 and IC 5146, further demonstrating the benefits of performing this deconvolution. We have resolved three clumps within a radius of 4.'5 inside the star-forming molecular cloud containing K3-50. Combining the well-resolved dust emission map with available multi-wavelength data, we have constrained the spectral energy distributions (SEDs) of five clumps to obtain masses (M), bolometric luminosities (L), and dust temperatures (T). The L-M diagram has been used as a diagnostic tool to estimate the evolutionary stages of the clumps. There are close relationships between dust continuum emission and both 21 cm radio continuum and {sup 12}CO molecular line emission. The restored extended large-scale structures in the Northern Streamer of IC 5146 have a strong spatial correlation with both SCUBA and high-resolution extinction images. A dust temperature of 12 K has been obtained for the central filament. We report physical properties of ten compact sources, including six associated protostars, by

  11. Challenging shock models with SOFIA OH observations in the high-mass star-forming region Cepheus A

    NASA Astrophysics Data System (ADS)

    Gusdorf, A.; Güsten, R.; Menten, K. M.; Flower, D. R.; Pineau des Forêts, G.; Codella, C.; Csengeri, T.; Gómez-Ruiz, A. I.; Heyminck, S.; Jacobs, K.; Kristensen, L. E.; Leurini, S.; Requena-Torres, M. A.; Wampfler, S. F.; Wiesemeyer, H.; Wyrowski, F.

    2016-01-01

    Context. OH is a key molecule in H2O chemistry, a valuable tool for probing physical conditions, and an important contributor to the cooling of shock regions around high-mass protostars. OH participates in the re-distribution of energy from the protostar towards the surrounding Interstellar Medium. Aims: Our aim is to assess the origin of the OH emission from the Cepheus A massive star-forming region and to constrain the physical conditions prevailing in the emitting gas. We thus want to probe the processes at work during the formation of massive stars. Methods: We present spectrally resolved observations of OH towards the protostellar outflows region of Cepheus A with the GREAT spectrometer onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) telescope. Three triplets were observed at 1834.7 GHz, 1837.8 GHz, and 2514.3 GHz (163.4 μm, 163.1 μm between the 2Π1/2 J = 1/2 states, and 119.2 μm, a ground transition between the 2Π3/2 J = 3/2 states), at angular resolutions of 16.̋3, 16.̋3, and 11.̋9, respectively. We also present the CO (16-15) spectrum at the same position. We compared the integrated intensities in the redshifted wings to the results of shock models. Results: The two OH triplets near 163 μm are detected in emission, but with blending hyperfine structure unresolved. Their profiles and that of CO (16-15) can be fitted by a combination of two or three Gaussians. The observed 119.2 μm triplet is seen in absorption, since its blending hyperfine structure is unresolved, but with three line-of-sight components and a blueshifted emission wing consistent with that of the other lines. The OH line wings are similar to those of CO, suggesting that they emanate from the same shocked structure. Conclusions: Under this common origin assumption, the observations fall within the model predictions and within the range of use of our model only if we consider that four shock structures are caught in our beam. Overall, our comparisons suggest that

  12. THE IMPORTANCE OF THE MAGNETIC FIELD FROM AN SMA-CSO-COMBINED SAMPLE OF STAR-FORMING REGIONS

    SciTech Connect

    Koch, Patrick M.; Tang, Ya-Wen; Ho, Paul T. P.; Chen, Huei-Ru Vivien; Liu, Hau-Yu Baobab; Yen, Hsi-Wei; Lai, Shih-Ping; Zhang, Qizhou; Chen, How-Huan; Ching, Tao-Chung; Girart, Josep M.; Frau, Pau; Li, Hua-Bai; Li, Zhi-Yun; Padovani, Marco; Qiu, Keping; Rao, Ramprasad

    2014-12-20

    Submillimeter dust polarization measurements of a sample of 50 star-forming regions, observed with the Submillimeter Array (SMA) and the Caltech Submillimeter Observatory (CSO) covering parsec-scale clouds to milliparsec-scale cores, are analyzed in order to quantify the magnetic field importance. The magnetic field misalignment δ—the local angle between magnetic field and dust emission gradient—is found to be a prime observable, revealing distinct distributions for sources where the magnetic field is preferentially aligned with or perpendicular to the source minor axis. Source-averaged misalignment angles (|δ|) fall into systematically different ranges, reflecting the different source-magnetic field configurations. Possible bimodal (|δ|) distributions are found for the separate SMA and CSO samples. Combining both samples broadens the distribution with a wide maximum peak at small (|δ|) values. Assuming the 50 sources to be representative, the prevailing source-magnetic field configuration is one that statistically prefers small magnetic field misalignments |δ|. When interpreting |δ| together with a magnetohydrodynamics force equation, as developed in the framework of the polarization-intensity gradient method, a sample-based log-linear scaling fits the magnetic field tension-to-gravity force ratio (Σ {sub B}) versus (|δ|) with (Σ {sub B}) = 0.116 · exp (0.047 · (|δ|)) ± 0.20 (mean error), providing a way to estimate the relative importance of the magnetic field, only based on measurable field misalignments |δ|. The force ratio Σ {sub B} discriminates systems that are collapsible on average ((Σ {sub B}) < 1) from other molecular clouds where the magnetic field still provides enough resistance against gravitational collapse ((Σ {sub B}) > 1). The sample-wide trend shows a transition around (|δ|) ≈ 45°. Defining an effective gravitational force ∼1 – (Σ {sub B}), the average magnetic-field-reduced star formation efficiency is at least a

  13. Sulfur-bearing molecules observed in the massive star-forming regions, DR21(OH) and G33.92+0.11

    NASA Astrophysics Data System (ADS)

    Minh, Y. C.

    2016-07-01

    Recent high sensitive and high angular resolution observations are providing unprecedented amount of chemical data, especially, on the massive star-forming regions. It will greatly extend our understandings on the complicated star formation process, if we can digest those huge amount of information. We discuss here on the properties of the sulfurbearing species observed with high angular resolutions toward two massive star-forming regions, DR21(OH) and G33.92+0.11. H2S may not exist as a solid form in the grain mantles, but OCS is believed to be one of major solid sulfur species, as suggested before. In addition, the bipolar-like outflow of the H2CS emission observed in DR21(OH) may suggest that H2CS is also one of solid sulfur species on the grain mantles. Depending on the chemical environment, the competition between hydrogenation and oxidization on the grain surface may lead to formation of specific solid forms to dominate, which could be either H2CS or OCS. SO and SO2 are often observed to be associated with ionized gas, such as the UC HII regions. These species seem to be formed in the high temperature turbulent gas in a later stage of star formation after the hot core phase. Fractional abundances of these sulfur-bearing species appear to be consistent to a certain extent in several star-forming regions. The physical and chemical evolution of massive star formation seems to pass through very similar stages in most star-forming regions. Consequently, it may indicate that there exists a consistent and coherent pattern of processes experienced by the massive star formation, in spite of the large variations in small scale locational differences.

  14. SULFUR-BEARING MOLECULES IN MASSIVE STAR-FORMING REGIONS: OBSERVATIONS OF OCS, CS, H{sub 2}S, AND SO

    SciTech Connect

    Li, Juan; Wang, Junzhi; Zhu, Qingfeng; Zhang, Jiangshui; Li, Di

    2015-03-20

    We studied the sulfur chemistry of massive star-forming regions through single-dish submillimeter spectroscopy. OCS, O{sup 13}CS, {sup 13}CS, H{sub 2}S, and SO transitions were observed toward a sample of massive star-forming regions with embedded UCH ii or CH ii regions. These sources could be divided into H ii-hot core and H ii-only sources based on their CH{sub 3}CN emission. Our results show that the OCS line of thirteen sources is optically thick, with optical depth ranging from 5 to 16. Column densities of these molecules were computed under LTE conditions. CS column densities were also derived using its optically thin isotopologue {sup 13}CS. H{sub 2}S is likely to be the most abundant gas-phase sulfuretted molecule in hot massive cores. Both the column density and abundance of sulfur-bearing molecules decrease significantly from H ii-hot core to H ii-only sources. Ages derived from hot core models appear to be consistent with star formation theories, suggesting that abundance ratios of [CS]/[SO], [SO]/[OCS], and [OCS]/[CS] could be used as chemical clocks in massive star-forming regions.

  15. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crighton, Devin; Das, Sudeep; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, Erik D.; Schmitt, Benjamin; Sehgal, Neelima; Sievers, Johnathan; Staggs, Suzanne; Swetz, Daniel; Thornton, Robert; Wollack, Edward

    2014-01-01

    We present a catalogue of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 -1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97 per cent of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogues. When combined with flux densities from the Australia Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, A(sub 148-218), of 3.7 (+0.62 or -0.86), and includes both local galaxies and sources with redshift around 6. Dusty sources with no counterpart in existing catalogues likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  16. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Duenner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, EriK D.; Wollack, Edward

    2013-01-01

    We present a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 GHz and/or 218GHz in the 2008 Southern survey. Flux densities span 14-1700mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two sub-populations: 167 radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogs. When combined with flux densities from the Australian Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148GHz, with the trend continuing to 218GHz. The ACT dust-dominated source population has a median spectral index, alpha(sub 148-218), of 3.7+0.62 or -0.86, and includes both local galaxies and sources with redshifts as great as 5.6. Dusty sources with no counterpart in existing catalogs likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  17. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, Erik D.; Wollack, Edward

    2014-01-01

    We present a catalogue of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 - 1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97 per cent of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogues. When combined with flux densities from the Australia Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, alpha(sub 148-218), of 3.7 +0.62/-0.86), and includes both local galaxies and sources with redshift around 6. Dusty sources with no counterpart in existing catalogues likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  18. Variability of young stars: Determination of rotational periods of weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region

    NASA Astrophysics Data System (ADS)

    Koeltzsch, A.; Mugrauer, M.; Raetz, St.; Schmidt, T. O. B.; Roell, T.; Eisenbeiss, T.; Hohle, M. M.; Vaňko, M.; Ginski, Ch.; Marka, C.; Moualla, M.; Schreyer, K.; Broeg, Ch.; Neuhäuser, R.

    2009-05-01

    We report on observation and determination of rotational periods of ten weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region. Observations were carried out with the Cassegrain-Teleskop-Kamera (CTK) at University Observatory Jena between 2007 June and 2008 May. The periods obtained range between 0.49 d and 5.7 d, typical for weak-line and post T Tauri stars. Based on observations obtained with telescopes of the University Observatory Jena, which is operated by the Astrophysical Institute of the Friedrich-Schiller-University.

  19. Extended High Circular Polarization in the Orion Massive Star Forming Region: Implications for the Origin of Homochirality in the Solar System

    PubMed Central

    Tamura, Motohide; Kandori, Ryo; Kusakabe, Nobuhiko; Hough, James H.; Bailey, Jeremy; Whittet, Douglas C. B.; Lucas, Philip W.; Nakajima, Yasushi; Hashimoto, Jun

    2010-01-01

    We present a wide-field (∼6′ × 6′) and deep near-infrared (Ks band: 2.14 μm) circular polarization image in the Orion nebula, where massive stars and many low-mass stars are forming. Our results reveal that a high circular polarization region is spatially extended (∼0.4 pc) around the massive star-forming region, the BN/KL nebula. However, other regions, including the linearly polarized Orion bar, show no significant circular polarization. Most of the low-mass young stars do not show detectable extended structure in either linear or circular polarization, in contrast to the BN/KL nebula. If our solar system formed in a massive star-forming region and was irradiated by net circularly polarized radiation, then enantiomeric excesses could have been induced, through asymmetric photochemistry, in the parent bodies of the meteorites and subsequently delivered to Earth. These could then have played a role in the development of biological homochirality on Earth. PMID:20213160

  20. Extended high circular polarization in the Orion massive star forming region: implications for the origin of homochirality in the solar system.

    PubMed

    Fukue, Tsubasa; Tamura, Motohide; Kandori, Ryo; Kusakabe, Nobuhiko; Hough, James H; Bailey, Jeremy; Whittet, Douglas C B; Lucas, Philip W; Nakajima, Yasushi; Hashimoto, Jun

    2010-06-01

    We present a wide-field (approximately 6' x 6') and deep near-infrared (K(s) band: 2.14 mum) circular polarization image in the Orion nebula, where massive stars and many low-mass stars are forming. Our results reveal that a high circular polarization region is spatially extended (approximately 0.4 pc) around the massive star-forming region, the BN/KL nebula. However, other regions, including the linearly polarized Orion bar, show no significant circular polarization. Most of the low-mass young stars do not show detectable extended structure in either linear or circular polarization, in contrast to the BN/KL nebula. If our solar system formed in a massive star-forming region and was irradiated by net circularly polarized radiation, then enantiomeric excesses could have been induced, through asymmetric photochemistry, in the parent bodies of the meteorites and subsequently delivered to Earth. These could then have played a role in the development of biological homochirality on Earth. PMID:20213160

  1. New SIO Masers in Star Forming Regions W:51 IRS:2 and SAGITTARIUS-B2 MD:5

    NASA Astrophysics Data System (ADS)

    Hasegawa, T.; Morita, K.; Okumura, S.; Kaifu, N.; Suzuki, H.; Ohishi, M.; Hayashi, M.; Ukita, N.

    The maser emission of the 43 GHz SiO J = 1-0 transitions in two regions of active star formation, W51 IRS2 and Sgr B2 MD5, have been detected using the 45 m telescope at Nobeyama. The SiO masers coincide in position with strong H2O masers in each region within a positional uncertainty of 5arcsec. If the masers radiate isotropically, the power radiated from W51 IRS2 and Sgr B2 MD5 in the masing 43 GHz SiO lines are comparable to that from the maser in Orion-KL.

  2. THE CLUSTERED NATURE OF STAR FORMATION. PRE-MAIN-SEQUENCE CLUSTERS IN THE STAR-FORMING REGION NGC 602/N90 IN THE SMALL MAGELLANIC CLOUD

    SciTech Connect

    Gouliermis, Dimitrios A.; Gennaro, Mario; Schmeja, Stefan; Dolphin, Andrew E.; Tognelli, Emanuele; Prada Moroni, Pier Giorgio

    2012-03-20

    Located at the tip of the wing of the Small Magellanic Cloud (SMC), the star-forming region NGC 602/N90 is characterized by the H II nebular ring N90 and the young cluster of pre-main-sequence (PMS) and early-type main-sequence stars NGC 602, located in the central area of the ring. We present a thorough cluster analysis of the stellar sample identified with Hubble Space Telescope/Advanced Camera for Surveys in the region. We show that apart from the central cluster low-mass PMS stars are congregated in 13 additional small, compact sub-clusters at the periphery of NGC 602, identified in terms of their higher stellar density with respect to the average background density derived from star counts. We find that the spatial distribution of the PMS stars is bimodal, with an unusually large fraction ({approx}60%) of the total population being clustered, while the remaining is diffusely distributed in the intercluster area, covering the whole central part of the region. From the corresponding color-magnitude diagrams we disentangle an age difference of {approx}2.5 Myr between NGC 602 and the compact sub-clusters, which appear younger, on the basis of comparison of the brighter PMS stars with evolutionary models, which we accurately calculated for the metal abundance of the SMC. The diffuse PMS population appears to host stars as old as those in NGC 602. Almost all detected PMS sub-clusters appear to be centrally concentrated. When the complete PMS stellar sample, including both clustered and diffused stars, is considered in our cluster analysis, it appears as a single centrally concentrated stellar agglomeration, covering the whole central area of the region. Considering also the hot massive stars of the system, we find evidence that this agglomeration is hierarchically structured. Based on our findings, we propose a scenario according to which the region NGC 602/N90 experiences an active clustered star formation for the last {approx}5 Myr. The central cluster NGC 602 was

  3. GRB 060505: A Possible Short-Duration Gamma-Ray Burst in a Star Forming Region at Redshift of 0.09

    NASA Technical Reports Server (NTRS)

    Ofek, E. O.; Cenko, S. B.; Gal-Yam, A.; Fox, D. B.; Nakar, E.; Rau, A.; Frail, D. A.; Kullkarni, S. R.; Price, P. A.; Schmidt, B. P.; Soderberg, A. M.; Peterson, B.; Berger, E.; Sharon, K.; Shemmer, O.; Penprase, B. E.; Chevalier, R. A.; Brown, P. J.; Burrows, D. N.; Gehrels, N.; Harrison, F.; Holland, S. T.

    2007-01-01

    On May 5, 2006 a four-second duration, low-energy, approximately 10(exp 59) erg, Gamma-Ray Burst (GRB) was observed, spatially associated with a z=0.0894 galaxy. Here, we report the discovery of the GRB optical afterglow and observations of its environment using gemini-south, Hubble Space Telescope (HST), Chandra, Swift and the Very Large Array. The optical afterglow of this GRB is spatially associated with a prominent star forming region in the Sc-type galaxy 2dFGRS S173Z112. Its proximity to a star forming region suggests that the progenitor delay time, from birth to explosion, is smaller than about 10 Myr. Our HST deep imaging rules out the presence of a supernova brighter than an absolute magnitude of about -11 (or -126 in case of 'maximal' extinction) at about two weeks after the burst, and limits the ejected mass of radioactive Nickel 56 to be less than about 2x10(exp -4) solar mass (assuming no extinction). Although it was suggested that GRB 060505 may belong to a new class of long-duration GRBs with no supernova, we argue that the simplest interpretation is that the physical mechanism for this burst is the same as for short-duration GRBs.

  4. INTER- AND INTRA-CLUSTER AGE GRADIENTS IN MASSIVE STAR FORMING REGIONS AND INDIVIDUAL NEARBY STELLAR CLUSTERS REVEALED BY MYStIX

    NASA Astrophysics Data System (ADS)

    Getman, Konstantin V.; Feigelson, Eric; Kuhn, Michael A.; Broos, Patrick S; Townsley, Leisa K.; Naylor, Tim; Povich, Matthew S.; Luhman, Kevin; Garmire, Gordon

    2014-08-01

    The MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray) project seeks to characterize 20 OB-dominated young star forming regions (SFRs) at distances <4 kpc using photometric catalogs from the Chandra X-ray Observatory, Spitzer Space Telescope, UKIRT and 2MASS surveys. As part of the MYStIX project, we developed a new stellar chronometer that employs near-infrared and X-ray photometry data, AgeJX. Computing AgeJX averaged over MYStIX (sub)clusters reveals previously unknown age gradients across most of the MYStIX regions as well as within some individual rich clusters. Within the SFRs, the inferred AgeJX ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed stellar populations. Noticeable intra-cluster gradients are seen in the NGC 2024 (Flame Nebula) star cluster and the Orion Nebula Cluster (ONC): stars in cluster cores appear younger and thus were formed later than stars in cluster halos. The latter result has two important implications for the formation of young stellar clusters. Clusters likely form slowly: they do not arise from a single nearly-instantaneous burst of star formation. The simple models where clusters form inside-out are likely incorrect, and more complex models are needed. We provide several star formation scenarios that alone or in combination may lead to the observed core-halo age gradients.

  5. Physical and chemical differentiation of the luminous star-forming region W49A. Results from the JCMT Spectral Legacy Survey

    NASA Astrophysics Data System (ADS)

    Nagy, Z.; van der Tak, F. F. S.; Fuller, G. A.; Plume, R.

    2015-05-01

    Context. The massive and luminous star-forming region W49A is a well-known Galactic candidate to probe the physical conditions and chemistry similar to those expected in external starburst galaxies. Aims: We aim to probe the physical and chemical structure of W49A on a spatial scale of ~0.8 pc based on the JCMT Spectral Legacy Survey, which covers the frequency range between 330 and 373 GHz. Methods: The wide 2 × 2 arcmin field and the high spectral resolution of the HARP instrument on JCMT provides information on the spatial structure and kinematics of the cloud traced by the observed molecular lines. For species where multiple transitions are available, we estimate excitation temperatures and column densities using a population diagram method that takes beam dilution and optical depth corrections into account. Results: We detected 255 transitions corresponding to 63 species in the 330-373 GHz range at the center position of W49A. Excitation conditions can be probed for 14 molecules, including the complex organic molecules CH3CCH, CH3CN, and CH3OH. The chemical composition suggests the importance of shock, photon-dominated region (PDR), and hot core chemistry. Many molecular lines show a significant spatial extent across the maps including CO and its isotopologues, high density tracers (e.g., HCN, HNC, CS, HCO+), and tracers of UV irradiation (e.g., CN and C2H). The spatially extended species reveal a complex velocity-structure of W49A with possible infall and outflow motions. Large variations are seen between the subregions with mostly blue-shifted emission toward the eastern tail, mostly red-shifted emission toward the northern clump, and emission peaking around the expected source velocity toward the southwest clump. Conclusions: A comparison of column density ratios of characteristic species observed toward W49A to Galactic PDRs suggests that while the chemistry toward the W49A center is driven by a combination of UV irradiation and shocks, UV irradiation

  6. SIMBA survey of southern high-mass star forming regions. I. Physical parameters of the 1.2 mm/IRAS sources

    NASA Astrophysics Data System (ADS)

    Faúndez, S.; Bronfman, L.; Garay, G.; Chini, R.; Nyman, L.-Å.; May, J.

    2004-10-01

    We report the results of a 1.2 mm continuum emission survey toward 146 IRAS sources thought to harbour high-mass star forming regions. The sources have FIR colors typical of UCHII regions and were detected in the CS(2->1) line survey of Bronfman et al. (\\cite{bnm}). Regions of 15 arcmin × 10 arcmin, centered on each IRAS source, were mapped with an angular resolution of ˜24 arcsec, using the SIMBA array on the SEST telescope. 1.2 mm emission was detected toward all IRAS sources. We find that the dust cores associated with these sources have typical sizes of 0.4 pc and masses of 5× 103 M⊙. Dust temperatures and luminosities, derived from the SED, are typically 32 K and 2.3 × 105 L⊙. Table 1 and Figs. 6 to 23 are only available in electronic form at http://www.edpsciences.org

  7. A study on subarcsecond scales of the ammonia and continuum emission toward the G16.59-0.05 high-mass star-forming region

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Cesaroni, R.; Sánchez-Monge, Á.; Goddi, C.; Furuya, R. S.; Sanna, A.; Pestalozzi, M.

    2013-10-01

    Aims: We wish to investigate the structure, velocity field, and stellar content of the G16.59-0.05 high-mass star-forming region, where previous studies have established the presence of two almost perpendicular (NE-SW and SE-NW), massive outflows, and a rotating disk traced by methanol maser emission. Methods: We performed Very Large Array observations of the radio continuum and ammonia line emission, complemented by COMICS/Subaru and Hi-GAL/Herschel images in the mid- and far-infrared. Results: Our centimeter continuum maps reveal a collimated radio jet that is oriented E-W and centered on the methanol maser disk, placed at the SE border of a compact molecular core. The spectral index of the jet is negative, indicating non-thermal emission over most of the jet, except the peak close to the maser disk, where thermal free-free emission is observed. We find that the ammonia emission presents a bipolar structure consistent (on a smaller scale) in direction and velocity with that of the NE-SW bipolar outflow detected in previous CO observations. After analyzing our previous N2H+(1-0) observations again, we conclude that two scenarios are possible. In one case both the radio jet and the ammonia emission would trace the root of the large-scale CO bipolar outflow. The different orientation of the jet and the ammonia flow could be explained by precession and/or a non-isotropic density distribution around the star. In the other case, the N2H+(1-0) and ammonia bipolarity is interpreted as two overlapping clumps moving with different velocities along the line of sight. The ammonia gas also seems to undergo rotation consistent with the maser disk. Our infrared images complemented by archival data allow us to derive a bolometric luminosity of ~104 L⊙ and to conclude that most of the luminosity is due to the young stellar object associated with the maser disk. Conclusions: The new data suggest a scenario where the luminosity and the outflow activity of the whole region could

  8. Investigation of OH and H2O masers in the star-forming region G 188.946+0.886

    NASA Astrophysics Data System (ADS)

    Ashimbaeva, N. T.; Colom, P.; Lekht, E. E.; Pashchenko, M. I.; Rudnitskii, G. M.; Tolmachev, A. M.

    2016-10-01

    We present the results of our observations of the maser radio emission source G188.946+0.886 in hydroxyl (OH) molecular lines with the radio telescope of the Nançay Observatory (France) and in the H2O line at λ = 1.35 cm with the RT-22 radio telescope at the Pushchino Observatory (Russia). An emission feature in the 1720-MHz satellite line of the OH ground state has been detected for the first time. The radial velocity of the feature, V LSR = 3.6 km s-1, has a "blue" shift relative to the range of emission velocities in the main 1665- and 1667-MHz OH lines, which is 8-11 km s-1. This suggests a probable connection of the observed feature in the 1720-MHz line with the "blue" wing of the bipolar outflow observed in this region in the CO line. We have estimated the magnetic field strength for three features (0.90 and 0.8 mG for 1665 MHz and 0.25 mG for 1720 MHz) from the Zeeman splitting in the 1665- and 1720-MHz lines. No emission and (or) absorption has been detected in the other 1612-MHz satellite OH line. Three cycles of H2O maser activity have been revealed. The variability is quasi-periodic in pattern. There is a general tendency for the maser activity to decrease. Some clusters of H2O maser spots can form organized structures, for example, chains and other forms.

  9. Identification of protostellar clusters in the inner part of the milky way : Interaction between the ISM and star forming regions.

    NASA Astrophysics Data System (ADS)

    Beuret, M.; Billot, N.; Cambrésy, L.; Elia, D.; Molinari, S.; Pezzuto, S.; Pestalozzi, M.; Schisano, E.

    2014-12-01

    Interactions between the interstellar medium (ISM) and young stellar objects (YSO) need to be investigated to better understand star formation. We used the Minimum Spanning Tree (MST) method to identify protostellar clusters in the inner part of galactic plane. Using heliocentric distance estimates, we obtained about 230 clusters over a 140 × 2 square degree region. Most of these clusters are correlated with Infrared Dark Cloud (IRDC) or H II regions. We conclude that clustering is more important for protostars than for prestellar clumps and that a strong correlation can be established between the distribution of H II regions, known star formation complexes and the YSOs identified in the Hi-GAL data.

  10. Scaling stellar feedback: A study of the physical processes involved in star-forming regions of vastly different sizes

    NASA Astrophysics Data System (ADS)

    Pellegrini, Eric W.

    2009-09-01

    Regions of recent or ongoing star formation often contain massive stars capable of ionizing the surfaces of nearby molecular clouds. These layers of ionized gas, called H II regions, produce emission lines that serve as beacons of star formation as we look out into distant parts of our Galaxy and the universe. The complex physical processes of star formation are responsible for the chemical and structural evolution of galaxies throughout the history of the universe on many size scales. Light and winds from massive stars heat and compress nearby clouds, acting to simultaneously inhibit and enhance further star formation. To disentangle the importance of competing processes such as photoionization, supernovae, stellar winds, magnetic fields, radiation pressure, I have studied the dominant physical processes in nearby H II regions to determine the relative contribution of each feedback mechanism as a function of star formation intensity. The Orion Nebula is an H II region that is visible to the naked eye. Due to its proximity to the Sun and brightness, it has been studied extensively in all wavelengths. It is dominated by a single O star and offers the least complex environment to compare with models of H II regions. The most complex site of star formation in the local universe is 30 Doradus in the Large Magellanic Cloud. Hundreds of O stars dominated a region thousands of times larger than the Orion Nebula. Together these two examples provide the constraints necessary to quantify stellar feedback on different scales.

  11. Where massive stars form - Associated radio H II regions and CO clouds in the northern Milky Way

    NASA Technical Reports Server (NTRS)

    Waller, W. H.; Clemens, D. P.; Sanders, D. B.; Scoville, N. Z.

    1987-01-01

    The sites of massive star formation in molecular clouds are investigated by comparing high-resolution radio surveys of molecular and ionized gas emission in the Milky Way. CO emission maps from the Massachusetts-Stony Brook survey of the first Galactic quadrant are used to locate, in l, b, and v, the molecular clouds associated with radio recombination-line H II regions. It is found that the radio H II regions are typically associated with giant molecular clouds (GMCs) with diameters of 20-60 pc and virial masses of 100,000 to a million solar masses. The radio H II regions appear preferentially concentrated toward the centers of the GMCs, contrary to the 'blister' picture of massive star formation on cloud surfaces.

  12. Modeling the physical structure of star-forming regions with LIME, a 3D radiative transfer code

    NASA Astrophysics Data System (ADS)

    Quénard, D.; Bottinelli, S.; Caux, E.

    2016-05-01

    The ability to predict line emission is crucial in order to make a comparison with observations. From LTE to full radiative transfer codes, the goal is always to derive the most accurately possible the physical properties of the source. Non-LTE calculations can be very time consuming but are needed in most of the cases since many studied regions are far from LTE.

  13. IRX-β Relation of Star-forming Regions in NGC 628 Based on Integral Field Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ye, Chengyun; Zou, Hu; Lin, Lin; Lian, Jianhui; Hu, Ning; Kong, Xu

    2016-08-01

    It has been found that the infrared-to-ultraviolet luminosity ratio (IRX) and ultraviolet spectral slope (β) have a tight correlation in starburst galaxies, while in normal galaxies the relation is deviated and has a much larger scatter. Star formation regions are much simpler in both morphology and physical properties than galaxies, so their photometric and spectroscopic properties are more easily and accurately determined. We have used the integral field spectroscopy and multiband photometric images to study the IRX–β relation of H ii regions in a nearby galaxy, NGC 628. There are obvious correlations between the Dn (4000), stellar population age, star formation rate, especially Hα equivalent width EW(Hα), and deviation distance d p from the starburst IRX–β relation. However, there is little correlation between the Balmer decrement, metallicity, and d p. It is much more complicated than expected, so that we cannot introduce a single second parameter to describe the scatter and deviation of the H ii region IRX–β relation.

  14. A BRIGHT RADIO HH OBJECT WITH LARGE PROPER MOTIONS IN THE MASSIVE STAR-FORMING REGION W75N

    SciTech Connect

    Carrasco-Gonzalez, Carlos; Anglada, Guillem; Rodriguez, Luis F.; Torrelles, Jose M.; Gonzalez-Martin, Omaira

    2010-06-15

    We analyze radio continuum and line observations from the archives of the Very Large Array (VLA), as well as X-ray observations from the Chandra archive of the region of massive star formation W75N. Five radio continuum sources are detected: VLA 1, VLA 2, VLA 3, Bc, and VLA 4. VLA 3 appears to be a radio jet; we detect J = 1-0, v = 0 SiO emission toward it, probably tracing the inner parts of a molecular outflow. The radio continuum source Bc, previously believed to be tracing an independent star, is found to exhibit important changes in total flux density, morphology, and position. These results suggest that source Bc is actually a radio Herbig-Haro object, one of the brightest known, powered by the VLA 3 jet source. VLA 4 is a new radio continuum component, located a few arcsec to the south of the group of previously known radio sources. Strong and broad (1,1) and (2,2) ammonia emission is detected from the region containing the radio sources VLA 1, VLA 2, and VLA 3. Finally, the 2-10 keV emission seen in the Chandra/ACIS image shows two regions that could be the termination shocks of the outflows from the multiple sources observed in W75N.

  15. IRX-β Relation of Star-forming Regions in NGC 628 Based on Integral Field Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ye, Chengyun; Zou, Hu; Lin, Lin; Lian, Jianhui; Hu, Ning; Kong, Xu

    2016-08-01

    It has been found that the infrared-to-ultraviolet luminosity ratio (IRX) and ultraviolet spectral slope (β) have a tight correlation in starburst galaxies, while in normal galaxies the relation is deviated and has a much larger scatter. Star formation regions are much simpler in both morphology and physical properties than galaxies, so their photometric and spectroscopic properties are more easily and accurately determined. We have used the integral field spectroscopy and multiband photometric images to study the IRX-β relation of H ii regions in a nearby galaxy, NGC 628. There are obvious correlations between the Dn (4000), stellar population age, star formation rate, especially Hα equivalent width EW(Hα), and deviation distance d p from the starburst IRX-β relation. However, there is little correlation between the Balmer decrement, metallicity, and d p. It is much more complicated than expected, so that we cannot introduce a single second parameter to describe the scatter and deviation of the H ii region IRX-β relation.

  16. On the Identification of High-Mass Star Forming Regions Using IRAS: Contamination by Low-Mass Protostars

    NASA Astrophysics Data System (ADS)

    Bourke, Tyler L.; Hyland, A. R.; Robinson, Garry

    2005-06-01

    We present the results of a survey of a small sample (14) of low-mass protostars (LIR<103 Lsolar) for 6.7 GHz methanol maser emission performed using the ATNF Parkes radio telescope. No new masers were discovered. We find that the lower luminosity limit for maser emission is near 103 Lsolar by comparison of the sources in our sample with previously detected methanol maser sources. We examine the IRAS properties of our sample and compare them with sources previously observed for methanol maser emission, almost all of which satisfy the Wood & Churchwell criterion for selecting candidate UC H II regions. We find that about half of our sample satisfy this criterion, and in addition, almost all of this subgroup have integrated fluxes between 25 and 60 μm that are similar to sources with detectable methanol maser emission. By identifying a number of low-mass protostars in this work and from the literature that satisfy the Wood & Churchwell criterion for candidate UC H II regions, we show conclusively for the first time that the fainter flux end of their sample is contaminated by lower mass nonionizing sources, confirming the suggestion by van der Walt and Ramesh & Sridharan.

  17. The Precise Radio Observation of the 13C Isotopic Fractionation for Carbon Chain Molecule HC3N in the Low-Mass Star Forming Region L1527

    NASA Astrophysics Data System (ADS)

    Araki, Mitsunori; Takano, Shuro; Sakai, Nami; Yamamoto, Satoshi; Oyama, Takahiro; Kuze, Nobuhiko; Tsukiyama, Koichi

    2016-06-01

    We observed the three 13C isotopic species of HC3N with the high signal-to-noise ratios in L1527 using Green Bank 100 m telescope and Nobeyama 45 m telescope to explore the production scheme of HC3N, where L1527 is the low-mass star forming region in the phase of a warm carbon chain chemistry region. The spectral lines of the J = 5--4, 9--8, 10--9, and 12--11 transitions in the 44-109 GHz region were used to measure isotopic ratios. The abundance of HCCCN was determined from the line intensities of the two weak hyperfine components of the J = 5-4 transition. The isotopic ratios were precisely determined to be 1.00 : 1.01 : 1.35 : 86.4 for [H13CCCN] : [HC13CCN] : [HCC13CN] : [HCCCN]. It was found that the abundance of H13CCCN is equal to that of HC13CCN, and it was implied that HC3N is mainly formed by the reaction schemes via C2H2 and C2H2+ in L1527. This would suggest a universality of dicarbide chemistry producing HC3N irrespective of evolutional phases from a starless dark cloud to a warm carbon chain chemistry region. Sakai, N., Sakai, T., Hirota, T., & Yamamoto, S. 2008, ApJ, 672, 371 Takano, S., Masuda, A., Hirahara, Y., et al. 1998, A&A, 329, 1156

  18. Analysis of MOST light curves of five young stars in Taurus-Auriga and Lupus 3 star-forming regions

    NASA Astrophysics Data System (ADS)

    Siwak, Michal; Rucinski, Slavek M.; Matthews, Jaymie M.; Kuschnig, Rainer; Guenther, David B.; Moffat, Anthony F. J.; Sasselov, Dimitar; Weiss, Werner W.

    2011-08-01

    Continuous photometric observations of five young stars obtained by the MOST satellite in 2009 and 2010 in the Taurus and Lupus star formation regions are presented. Using light-curve modelling under the assumption of internal invariability of spots, we obtained small values of the solar-type differential-rotation parameter (k = 0.0005-0.009) for three spotted weak-line T Tauri stars, V410 Tau, V987 Tau and Lupus 3-14; for another spotted weak-line T Tauri star (WTTS), Lupus 3-48, the data are consistent with a rigidly rotating surface (k = 0). Three flares of similar rise (4 min and 30 s) and decay (1 h and 45 min) times were detected in the light curve of Lupus 3-14. The brightness of the classical T Tauri star RY Tau continuously decreased over 3 weeks of its observations with a variable modulation not showing any obvious periodic signal. Based on data from the MOST satellite, a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute of Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna.

  19. Cannibalization and rebirth in the NGC 5387 system. I. The stellar stream and star-forming region

    SciTech Connect

    Beaton, Rachael L.; Majewski, Steven R.; Johnson, Kelsey E.; Verbiscer, Anne; Martínez-Delgado, David; D'Onghia, Elena; Zibetti, Stefano; Gabany, R. Jay; Blanton, Michael

    2014-08-01

    We have identified a low surface brightness stellar stream from visual inspection of Sloan Digital Sky Survey (SDSS) imaging for the edge-on, spiral galaxy NGC 5387. An optically blue overdensity coincident with the stream intersection with the NGC 5387 disk was also identified in SDSS and in the Galaxy Evolution Explorer Deep Imaging Survey contributing 38% of the total far-UV integrated flux from NGC 5387. Deeper optical imaging was acquired with the Vatican Advanced Technology Telescope that confirmed the presence of both features. The stellar stream is red in color, (B – V) = 0.7, has a stellar mass of 6 × 10{sup 8} M{sub ☉}, which implies a 1:50 merger ratio, has a circular radius, R{sub circ} ∼ 11.7 kpc, formed in ∼240 Myr, and the progenitor had a total mass of ∼4 × 10{sup 10} M{sub ☉}. Spectroscopy from LBT+MODS1 was used to determine that the blue overdensity is at the same redshift as NGC 5387, consists of young stellar populations (∼10 Myr), is metal-poor (12 + log (O/H) = 8.03), and is forming stars at an enhanced rate (∼1-3 M{sub ☉} yr{sup –1}). The most likely interpretations are that the blue overdensity is (1) a region of enhanced star formation in the outer disk of NGC 5387 induced by the minor accretion event or (2) the progenitor of the stellar stream experiencing enhanced star formation. Additional exploration of these scenarios is presented in a companion paper.

  20. Cannibalization and Rebirth in the NGC 5387 System. I. The Stellar Stream and Star-forming Region

    NASA Astrophysics Data System (ADS)

    Beaton, Rachael L.; Martínez-Delgado, David; Majewski, Steven R.; D'Onghia, Elena; Zibetti, Stefano; Gabany, R. Jay; Johnson, Kelsey E.; Blanton, Michael; Verbiscer, Anne

    2014-08-01

    We have identified a low surface brightness stellar stream from visual inspection of Sloan Digital Sky Survey (SDSS) imaging for the edge-on, spiral galaxy NGC 5387. An optically blue overdensity coincident with the stream intersection with the NGC 5387 disk was also identified in SDSS and in the Galaxy Evolution Explorer Deep Imaging Survey contributing 38% of the total far-UV integrated flux from NGC 5387. Deeper optical imaging was acquired with the Vatican Advanced Technology Telescope that confirmed the presence of both features. The stellar stream is red in color, (B - V) = 0.7, has a stellar mass of 6 × 108 M ⊙, which implies a 1:50 merger ratio, has a circular radius, R circ ~ 11.7 kpc, formed in ~240 Myr, and the progenitor had a total mass of ~4 × 1010 M ⊙. Spectroscopy from LBT+MODS1 was used to determine that the blue overdensity is at the same redshift as NGC 5387, consists of young stellar populations (~10 Myr), is metal-poor (12 + log (O/H) = 8.03), and is forming stars at an enhanced rate (~1-3 M ⊙ yr-1). The most likely interpretations are that the blue overdensity is (1) a region of enhanced star formation in the outer disk of NGC 5387 induced by the minor accretion event or (2) the progenitor of the stellar stream experiencing enhanced star formation. Additional exploration of these scenarios is presented in a companion paper. Based on observations with the VATT: the Alice P. Lennon Telescope and the Thomas J. Bannan Astrophysics Facility.

  1. Trigonometric distance and proper motion of IRAS 20056+3350: a massive star-forming region on the solar circle

    SciTech Connect

    Burns, Ross A.; Handa, Toshihiro; Omodaka, Toshihiro; Nakagawa, Akiharu; Nakanishi, Hiroyuki; Nagayama, Takumi; Hayashi, Masahiko; Shizugami, Makoto

    2014-12-10

    We report our measurement of the trigonometric distance and proper motion of IRAS 20056+3350, obtained from the annual parallax of H{sub 2}O masers. Our distance of D=4.69{sub −0.51}{sup +0.65} kpc, which is 2.8 times larger than the near kinematic distance adopted in the literature, places IRAS 20056+3350 at the leading tip of the Local arm and proximal to the solar circle. Using our distance, we reevaluate past observations to reveal IRAS 20056+3350 as a site of massive star formation at a young stage of evolution. This result is consistent with the spectral energy distribution of the source evaluated with published photometric data from UKIDSS, WISE, AKARI, IRAS, and the submillimeter continuum. Both analytical approaches reveal the luminosity of the region to be 2.4 × 10{sup 4} L {sub ☉}, and suggest that IRAS 20056+3350 is forming an embedded star of ≥16 M {sub ☉}. We estimated the proper motion of IRAS 20056+3350 to be (μ{sub α}cos δ, μ{sub δ}) = (–2.62 ± 0.33, –5.65 ± 0.52) mas yr{sup –1} from the group motion of H{sub 2}O masers, and use our results to estimate the angular velocity of Galactic rotation at the Galactocentric distance of the Sun, Ω{sub 0} = 29.75 ± 2.29 km s{sup –1} kpc{sup –1}, which is consistent with the values obtained for other tangent point and solar circle objects.

  2. On the accretion process in a high-mass star forming region. A multitransitional THz Herschel-HIFI study of ammonia toward G34.26+0.15

    NASA Astrophysics Data System (ADS)

    Hajigholi, M.; Persson, C. M.; Wirström, E. S.; Black, J. H.; Bergman, P.; Olofsson, A. O. H.; Olberg, M.; Wyrowski, F.; Coutens, A.; Hjalmarson, Å.; Menten, K. M.

    2016-01-01

    Aims: Our aim is to explore the gas dynamics and the accretion process in the early phase of high-mass star formation. Methods: The inward motion of molecular gas in the massive star forming region G34.26+0.15 is investigated by using high-resolution profiles of seven transitions of ammonia at THz frequencies observed with Herschel-HIFI. The shapes and intensities of these lines are interpreted in terms of radiative transfer models of a spherical, collapsing molecular envelope. An accelerated Lambda Iteration (ALI) method is used to compute the models. Results: The seven ammonia lines show mixed absorption and emission with inverse P-Cygni-type profiles that suggest infall onto the central source. A trend toward absorption at increasingly higher velocities for higher excitation transitions is clearly seen in the line profiles. The J = 3 ← 2 lines show only very weak emission, so these absorption profiles can be used directly to analyze the inward motion of the gas. This is the first time a multitransitional study of spectrally resolved rotational ammonia lines has been used for this purpose. Broad emission is, in addition, mixed with the absorption in the 10-00 ortho-NH3 line, possibly tracing a molecular outflow from the star forming region. The best-fitting ALI model reproduces the continuum fluxes and line profiles, but slightly underpredicts the emission and absorption depth in the ground-state ortho line 10-00. An ammonia abundance on the order of 10-9 relative to H2 is needed to fit the profiles. The derived ortho-to-para ratio is approximately 0.5 throughout the infalling cloud core similar to recent findings for translucent clouds in sight lines toward W31C and W49N. We find evidence of two gas components moving inwards toward the central region with constant velocities: 2.7 and 5.3 km s-1, relative to the source systemic velocity. Attempts to model the inward motion with a single gas cloud in free-fall collapse did not succeed. Herschel is an ESA space

  3. {sup 13}C-METHYL FORMATE: OBSERVATIONS OF A SAMPLE OF HIGH-MASS STAR-FORMING REGIONS INCLUDING ORION-KL AND SPECTROSCOPIC CHARACTERIZATION

    SciTech Connect

    Favre, Cécile; Bergin, Edwin A.; Crockett, Nathan R.; Neill, Justin L.; Carvajal, Miguel; Field, David; Jørgensen, Jes K.; Bisschop, Suzanne E.; Brouillet, Nathalie; Despois, Didier; Baudry, Alain; Kleiner, Isabelle; Margulès, Laurent; Huet, Thérèse R.; Demaison, Jean E-mail: miguel.carvajal@dfa.uhu.es

    2015-01-01

    We have surveyed a sample of massive star-forming regions located over a range of distances from the Galactic center for methyl formate, HCOOCH{sub 3}, and its isotopologues H{sup 13}COOCH{sub 3} and HCOO{sup 13}CH{sub 3}. The observations were carried out with the APEX telescope in the frequency range 283.4-287.4 GHz. Based on the APEX observations, we report tentative detections of the {sup 13}C-methyl formate isotopologue HCOO{sup 13}CH{sub 3} toward the following four massive star-forming regions: Sgr B2(N-LMH), NGC 6334 IRS 1, W51 e2, and G19.61-0.23. In addition, we have used the 1 mm ALMA science verification observations of Orion-KL and confirm the detection of the {sup 13}C-methyl formate species in Orion-KL and image its spatial distribution. Our analysis shows that the {sup 12}C/{sup 13}C isotope ratio in methyl formate toward the Orion-KL Compact Ridge and Hot Core-SW components (68.4 ± 10.1 and 71.4 ± 7.8, respectively) are, for both the {sup 13}C-methyl formate isotopologues, commensurate with the average {sup 12}C/{sup 13}C ratio of CO derived toward Orion-KL. Likewise, regarding the other sources, our results are consistent with the {sup 12}C/{sup 13}C in CO. We also report the spectroscopic characterization, which includes a complete partition function, of the complex H{sup 13}COOCH{sub 3} and HCOO{sup 13}CH{sub 3} species. New spectroscopic data for both isotopomers H{sup 13}COOCH{sub 3} and HCOO{sup 13}CH{sub 3}, presented in this study, have made it possible to measure this fundamentally important isotope ratio in a large organic molecule for the first time.

  4. Molecular line survey of the high-mass star-forming region NGC 6334I with Herschel/HIFI and the Submillimeter Array

    NASA Astrophysics Data System (ADS)

    Zernickel, A.; Schilke, P.; Schmiedeke, A.; Lis, D. C.; Brogan, C. L.; Ceccarelli, C.; Comito, C.; Emprechtinger, M.; Hunter, T. R.; Möller, T.

    2012-10-01

    Aims: We aim at deriving the molecular abundances and temperatures of the hot molecular cores in the high-mass star-forming region NGC 6334I and consequently deriving their physical and astrochemical conditions. Methods: In the framework of the Herschel guaranteed time key program CHESS (Chemical HErschel Surveys of Star forming regions), NGC 6334I is investigated by using the Heterodyne Instrument for the Far-Infrared (HIFI) aboard the Herschel Space Observatory. A spectral line survey is carried out in the frequency range 480-1907 GHz, and further auxiliary interferometric data from the Submillimeter Array (SMA) in the 230 GHz band provide spatial information for disentangling the different physical components contributing to the HIFI spectrum. The spectral lines in the processed Herschel data are identified with the aid of former surveys and spectral line catalogs. The observed spectrum is then compared to a simulated synthetic spectrum, assuming local thermal equilibrium, and best fit parameters are derived using a model optimization package. Results: A total of 46 molecules are identified, with 31 isotopologues, resulting in about 4300 emission and absorption lines. High-energy levels (Eu > 1000 K) of the dominant emitter methanol and vibrationally excited HCN (ν2 = 1) are detected. The number of unidentified lines remains low with 75, or <2% of the lines detected. The modeling suggests that several spectral features need two or more components to be fitted properly. Other components could be assigned to cold foreground clouds or to outflows, most visible in the SiO and H2O emission. A chemical variation between the two embedded hot cores is found, with more N-bearing molecules identified in SMA1 and O-bearing molecules in SMA2. Conclusions: Spectral line surveys give powerful insights into the study of the interstellar medium. Different molecules trace different physical conditions like the inner hot core, the envelope, the outflows or the cold foreground

  5. Velocity resolved [C ii], [C i], and CO observations of the N159 star-forming region in the Large Magellanic Cloud: a complex velocity structure and variation of the column densities

    NASA Astrophysics Data System (ADS)

    Okada, Yoko; Requena-Torres, Miguel Angel; Güsten, Rolf; Stutzki, Jürgen; Wiesemeyer, Helmut; Pütz, Patrick; Ricken, Oliver

    2015-08-01

    Context. The [C ii] 158 μm fine structure line is one of the dominant cooling lines in star-forming active regions. Together with models of photon-dominated regions, the data is used to constrain the physical properties of the emitting regions, such as the density and the radiation field strength. According to the modeling, the [C ii] 158 μm line integrated intensity compared to the CO emission is expected to be stronger in lower metallicity environments owing to lower dust shielding of the UV radiation, a trend that is also shown by spectral-unresolved observations. In the commonly assumed clumpy UV-penetrated cloud scenario, the models predict a [C ii] line profile similar to that of CO. However, recent spectral-resolved observations by Herschel/HIFI and SOFIA/GREAT (as well as the observations presented here) show that the velocity resolved line profile of the [C ii] emission is often very different from that of CO lines, indicating a more complex origin of the line emission including the dynamics of the source region. Aims: The Large Magellanic Cloud (LMC) provides an excellent opportunity to study in great detail the physics of the interstellar medium (ISM) in a low-metallicity environment by spatially resolving individual star-forming regions. The aim of our study is to investigate the physical properties of the star-forming ISM in the LMC by separating the origin of the emission lines spatially and spectrally. In this paper, we focus on the spectral characteristics and the origin of the emission lines, and the phases of carbon-bearing species in the N159 star-forming region in the LMC. Methods: We mapped a 4' × (3'-4') region in N159 in [C ii] 158 μm and [N ii] 205 μm with the GREAT instrument on board SOFIA. We also observed CO(3-2), (4-3), (6-5), 13CO(3-2), and [C i] 3P1-3P0 and 3P2-3P1 with APEX. All spectra are velocity resolved. Results: The emission of all transitions observed shows a large variation in the line profiles across the map and in

  6. A SAMPLE OF INTERMEDIATE-MASS STAR-FORMING REGIONS: MAKING STARS AT MASS COLUMN DENSITIES <1 g cm{sup -2}

    SciTech Connect

    Arvidsson, K.; Kerton, C. R.; Alexander, M. J.; Kobulnicky, H. A.; Uzpen, B. E-mail: kerton@iastate.ed E-mail: chipk@uwyo.ed E-mail: buzpen@itt-tech.ed

    2010-08-15

    In an effort to understand the factors that govern the transition from low- to high-mass star formation, for the first time we identify a sample of intermediate-mass star-forming regions (IM SFRs) where stars up to (but not exceeding) {approx}8 M{sub sun} are being produced. We use IRAS colors and Spitzer Space Telescope mid-IR images, in conjunction with millimeter continuum and {sup 13}CO maps, to compile a sample of 50 IM SFRs in the inner Galaxy. These are likely to be precursors to Herbig AeBe stars and their associated clusters of low-mass stars. IM SFRs constitute embedded clusters at an early evolutionary stage akin to compact H II regions, but they lack the massive ionizing central star(s). The photodissociation regions that demarcate IM SFRs have typical diameters of {approx}1 pc and luminosities of {approx}10{sup 4} L{sub sun}, making them an order of magnitude less luminous than (ultra-)compact H II regions. IM SFRs coincide with molecular clumps of mass {approx}10{sup 3} M{sub sun} which, in turn, lie within larger molecular clouds spanning the lower end of the giant molecular cloud mass range, 10{sup 4}-10{sup 5} M{sub sun}. The IR luminosity and associated molecular mass of IM SFRs are correlated, consistent with the known luminosity-mass relationship of compact H II regions. Peak mass column densities within IM SFRs are {approx}0.1-0.5 g cm{sup -2}, a factor of several lower than ultra-compact H II regions, supporting the proposition that there is a threshold for massive star formation at {approx}1 g cm{sup -2}.

  7. WFCAM, Spitzer/IRAC and SCUBA observations of the massive star-forming region DR21/W75 - II. Stellar content and star formation

    NASA Astrophysics Data System (ADS)

    Kumar, M. S. N.; Davis, C. J.; Grave, J. M. C.; Ferreira, B.; Froebrich, D.

    2007-01-01

    Wide-field near-infrared observations and Spitzer Space Telescope Infrared Array Camera (IRAC) observations of the DR21/W75 star formation regions are presented. The photometric data are used to analyse the extinction, stellar content and clustering in the entire region by using standard methods. A young stellar population is identified all over the observed field, which is found to be distributed in embedded clusters that are surrounded by a distributed halo population extending over a larger projected area. The Spitzer/IRAC data are used to compute a spectral index value, α, for each young stellar object in the field. We use these data to separate pure photospheres from disc excess sources. We find a small fraction of sources with α in excess of 2 to 3 (plus a handful with α ~ 4), which is much higher than the values found in the low-mass star-forming region IC348 (α <= 2). The sources with high values of α spatially coincide with the densest regions of the filaments and also with the sites of massive star formation. Star formation is found to be occurring in long filaments stretching to few parsecs that are fragmented over a scale of ~1pc. The spatial distribution of young stars are found to be correlated with the filamentary nebulae that are prominently revealed by 8- and 850-μm observations. Five filaments are identified that appear to converge on a centre that includes the DR21/DR21(OH) regions. The morphological pattern of filaments and clustering compare well with numerical simulations of star cluster formation by Bate et al.

  8. A Search for Interstellar Carbon-chain Alcohol HC4OH in Star-forming Region l1527 and Dark Cloud TMC-1

    NASA Astrophysics Data System (ADS)

    Araki, Mitsunori; Takano, Shuro; Yamabe, Hiromichi; Koshikawa, Naohiro; Tsukiyama, Koichi; Nakane, Aya; Okabayashi, Toshiaki; Kunimatsu, Arisa; Kuze, Nobuhiko

    2012-01-01

    We report a sensitive search for the rotational transitions of the carbon-chain alcohol HC4OH in the frequency range 21.2-46.7 GHz in the star-forming region L1527 and the dark cloud TMC-1. The motivation was laboratory detection of HC4OH by microwave spectroscopy. Despite achieving rms noise levels of several millikelvin in the antenna temperature using the 45 m telescope at Nobeyama Radio Observatory, the detection was not successful, leading to 3σ upper limits corresponding to the column densities of 2.0 × 1012 and 5.6 × 1012 cm-2 in L1527 and TMC-1, respectively. These upper limits indicate that [HC4OH]/[HC5N] ratios are less than 0.3 and 0.1 in L1527 and TMC-1, respectively, where HC5N is an HC4-chain cyanide and HC4OH is a hydroxide. These ratios suggest that the cyano carbon-chain molecule dominates the hydroxyl carbon-chain molecule in L1527 and TMC-1. This is contrary to the case of saturated compounds in hot cores, e.g., CH3OH and CH3CN, and can be a chemical feature of carbon-chain molecules in L1527 and TMC-1. In addition, the column densities of the "unsubstituted" carbon-chain molecule C4H and the sulfur-bearing molecules SO and HCS+ were determined from detected lines in L1527.

  9. APEX CO (9-8) MAPPING OF AN EXTREMELY HIGH VELOCITY AND JET-LIKE OUTFLOW IN A HIGH-MASS STAR-FORMING REGION

    SciTech Connect

    Qiu Keping; Wyrowski, Friedrich; Menten, Karl M.; Guesten, Rolf; Leurini, Silvia; Leinz, Christian

    2011-12-10

    Atacama Pathfinder Experiment (APEX) mapping observations in CO (9-8) and (4-3) toward a high-mass star-forming region, NGC 6334 I, are presented. The CO (9-8) map has a 6.''4 resolution, revealing a {approx}0.5 pc, jet-like, and bipolar outflow. This is the first map of a molecular outflow in a THz line. The CO (9-8) and (4-3) lines arising from the outflow lobes both show extremely high velocity line wings, and their ratios indicate a gas temperature greater than 100 K and a density higher than 10{sup 4} cm{sup -3}. The spatial-velocity structure of the CO (9-8) data is typical of a bow-shock-driven flow, which is consistent with the association between the bipolar outflow and the infrared bow-shaped tips. In short, the observations unveil a highly excited and collimated component in a bipolar outflow that is powered by a high-mass protostar, and provide insights into the driving mechanism of the outflow. Meanwhile, the observations demonstrate that high-quality mapping observations can be performed with the new THz receiver on APEX.

  10. NEAR-INFRARED PERIODIC AND OTHER VARIABLE FIELD STARS IN THE FIELD OF THE CYGNUS OB7 STAR-FORMING REGION

    SciTech Connect

    Wolk, Scott J.; Rice, Thomas S.; Aspin, Colin A.

    2013-04-15

    We present a subset of the results of a three-season, 124 night, near-infrared monitoring campaign of the dark clouds Lynds 1003 and Lynds 1004 in the Cygnus OB7 star-forming region. In this paper, we focus on the field star population. Using three seasons of UKIRT J, H, and K-band observations spanning 1.5 years, we obtained high-quality photometry on 9200 stars down to J = 17 mag, with photometric uncertainty better than 0.04 mag. After excluding known disk-bearing stars we identify 149 variables-1.6% of the sample. Of these, about 60 are strictly periodic, with periods predominantly <2 days. We conclude this group is dominated by eclipsing binaries. A few stars have long period signals of between 20 and 60 days. About 25 stars have weak modulated signals, but it was not clear if these were periodic. Some of the stars in this group may be diskless young stellar objects with relatively large variability due to cool starspots. The remaining {approx}60 stars showed variations which appear to be purely stochastic.

  11. ANNUAL PARALLAX DETERMINATION TOWARD A NEW X-RAY-EMITTING CLASS 0 CANDIDATE WITH THE WATER MASER IN THE NGC 2264 STAR-FORMING REGION

    SciTech Connect

    Kamezaki, Tatsuya; Imura, Kenji; Omodaka, Toshihiro; Handa, Toshihiro; Tsuboi, Yohko; Nagayama, Takumi; Hirota, Tomoya; Sunada, Kazuyoshi; Kobayashi, Hideyuki; Chibueze, James O.; Kawai, Eiji; Nakano, Makoto

    2014-04-01

    In our multi-epoch observation of the star-forming region NGC 2264 with the VLBI Exploration of Radio Astrometry, we detected two water maser features. We have measured the annual parallax of the maser sources for the first time in NGC 2264 and derived 1.356 ± 0.098 mas, corresponding to the distance of 738{sub −50}{sup +57} pc, which is consistent with its previously reported photometric observations. One of the maser features is located near a dust continuum core, CMM4S, positionally corresponding to the X-ray source FMS2-1269 listed in Flaccomio et al. Re-analyzing Chandra X-ray data, we found that FMS2-1269 is still surrounded by a dense envelope of a H{sub 2} column density, 5.4 × 10{sup 23} cm{sup –2}. We suggest that the maser detected near the CMM4S core is most likely associated with the X-ray-emitting Class 0 candidate FMS2-1269. The other maser feature is found to emerge from a high-velocity outflow of 150 km s{sup –1} and is associated with the 3.6 cm radio continuum source NGC 2264 VLA 3 located close to IRS1.

  12. Astrometry and spatio-kinematics of H{sub 2}O masers in the massive star-forming region NGC 6334I(North) with VERA

    SciTech Connect

    Chibueze, James O.; Omodaka, Toshihiro; Handa, Toshihiro; Imai, Hiroshi; Kurayama, Tomoharu; Nagayama, Takumi; Sunada, Kazuyoshi; Hirota, Tomoya; Honma, Mareki; Nakano, Makoto

    2014-04-01

    We measured the trigonometric parallax of an H{sub 2}O maser source associated with the massive star-forming region NGC 6334I(North), hereafter as NGC 6334I(N), with the VLBI Exploration of Radio Astrometry. The derived annual parallax is 0.789 ± 0.161 mas, corresponding to a distance of 1.26{sub −0.21}{sup +0.33} kpc. Using the new distance, we recalculated the physical parameters (masses and luminosities) of the dust continuum cores in the region, and the revised parameters are only ∼50% of their originally reported values. We also traced 23 relative proper motions of the H{sub 2}O masers associated with SMA1 (central millimeter source in the region) between epochs, which exhibit an average amplitude of maser proper motion of ∼2.03 mas yr{sup –1} (∼12.22 km s{sup –1}), tracing a bipolar outflow. The bipolar outflow structure extends through ∼600 mas (∼720 AU), with a dynamical timescale of ∼295 yr. Using an expanding flow model, we derived the most plausible dynamical center of the outflow, pointing to SMA1b (1.3 cm and 7 mm continuum source) as the outflow driving source. Based on our results and other existing parallax results, we derive the pitch angles of the Sagittarius arm as 6.°2 ± 5.°4 along the Galactic longitude range of ∼0.°7 – ∼40.°1 assuming a perfect logarithmic spiral. We derived the peculiar motion of NGC 6334I(N) to be –4 ± 1 km s{sup –1} toward the Galactic center, 8 ± 2 km s{sup –1} in the direction of the Galactic rotation, and 25 ± 2 km s{sup –1} toward the Galactic north pole.

  13. The Mid-infrared High-ionization Lines from Active Galactic Nuclei and Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Pereira-Santaella, Miguel; Diamond-Stanic, Aleksandar M.; Alonso-Herrero, Almudena; Rieke, George H.

    2010-12-01

    We used Spitzer/Infrared Spectrograph spectroscopic data on 426 galaxies including quasars, Seyferts, LINERs, and H II galaxies to investigate the relationship among the mid-IR emission lines. There is a tight linear correlation between the [Ne V]14.3 μm and 24.3 μm (97.1 eV) and the [O IV]25.9 μm (54.9 eV) high-ionization emission lines. The correlation also holds for these high-ionization emission lines and the [Ne III]15.56 μm (41 eV) emission line, although only for active galaxies. We used these correlations to calculate the [Ne III] excess due to star formation in Seyfert galaxies. We also estimated the [O IV] luminosity due to star formation in active galaxies and determined that it dominates the [O IV] emission only if the contribution of the active nucleus to the total luminosity is below 5%. We find that the active galactic nucleus dominates the [O IV] emission in most Seyfert galaxies, whereas star formation adequately explains the observed [O IV] emission in optically classified H II galaxies. Finally, we computed photoionization models to determine the physical conditions of the narrow-line region where these high-ionization lines originate. The estimated ionization parameter range is -2.8 < log U < -2.5 and the total hydrogen column density range is 20 < log n H (cm-2) < 21. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407.

  14. Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA

    NASA Astrophysics Data System (ADS)

    Beltrán, M. T.; Sánchez-Monge, Á.; Cesaroni, R.; Kumar, M. S. N.; Galli, D.; Walmsley, C. M.; Etoka, S.; Furuya, R. S.; Moscadelli, L.; Stanke, T.; van der Tak, F. F. S.; Vig, S.; Wang, K.-S.; Zinnecker, H.; Elia, D.; Schisano, E.

    2014-11-01

    Context. Theoretical scenarios propose that high-mass stars are formed by disk-mediated accretion. Aims: To test the theoretical predictions on the formation of massive stars, we wish to make a thorough study at high-angular resolution of the structure and kinematics of the dust and gas emission toward the high-mass star-forming region G35.03+0.35, which harbors a disk candidate around a B-type (proto)star. Methods: We carried out ALMA Cycle 0 observations at 870 μm of dust of typical high-density, molecular outflow, and cloud tracers with resolutions of < 0''&dotbelow;5. Complementary Subaru COMICS 25 μm observations were carried out to trace the mid-infrared emission toward this star-forming region. Results: The submillimeter continuum emission has revealed a filamentary structure fragmented into six cores, called A-F. The filament could be in quasi-equilibrium taking into account that the mass per unit length of the filament, 200-375 M⊙/pc, is similar to the critical mass of a thermally and turbulently supported infinite cylinder, ~335 M⊙/pc. The cores, which are on average separated by ~0.02 pc, have deconvolved sizes of 1300-3400 AU, temperatures of 35-240 K, H2 densities >107 cm -3, and masses in the range 1-5 M⊙, and they are subcritical. Core A, which is associated with a hypercompact Hii region and could be the driving source of the molecular outflow observed in the region, is the most chemically rich source in G35.03+0.35 with strong emission of typical hot core tracers such as CH3CN. Tracers of high density and excitation show a clear velocity gradient along the major axis of the core, which is consistent with a disk rotating about the axis of the associated outflow. The PV plots along the SE-NW direction of the velocity gradient show clear signatures of Keplerian rotation, although infall could also be present, and they are consistent with the pattern of an edge-on Keplerian disk rotating about a star with a mass in the range 5-13 M⊙. The high

  15. B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid nebula, one of the youngest star forming regions

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; Fossati, L.; Carroll, T. A.; Castro, N.; González, J. F.; Ilyin, I.; Przybilla, N.; Schöller, M.; Oskinova, L. M.; Morel, T.; Langer, N.; Scholz, R. D.; Kharchenko, N. V.; Nieva, M.-F.

    2014-04-01

    Aims: Recent magnetic field surveys in O- and B-type stars revealed that about 10% of the core-hydrogen-burning massive stars host large-scale magnetic fields. The physical origin of these fields is highly debated. To identify and model the physical processes responsible for the generation of magnetic fields in massive stars, it is important to establish whether magnetic massive stars are found in very young star-forming regions or whether they are formed in close interacting binary systems. Methods: In the framework of our ESO Large Program, we carried out low-resolution spectropolarimetric observations with FORS 2 in 2013 April of the three most massive central stars in the Trifid nebula, HD 164492A, HD 164492C, and HD 164492D. These observations indicated a strong longitudinal magnetic field of about 500-600 G in the poorly studied component HD 164492C. To confirm this detection, we used HARPS in spectropolarimetric mode on two consecutive nights in 2013 June. Results: Our HARPS observations confirmed the longitudinal magnetic field in HD 164492C. Furthermore, the HARPS observations revealed that HD 164492C cannot be considered as a single star as it possesses one or two companions. The spectral appearance indicates that the primary is most likely of spectral type B1-B1.5 V. Since in both observing nights most spectral lines appear blended, it is currently unclear which components are magnetic. Long-term monitoring using high-resolution spectropolarimetry is necessary to separate the contribution of each component to the magnetic signal. Given the location of the system HD 164492C in one of the youngest star formation regions, this system can be considered as a Rosetta Stone for our understanding of the origin of magnetic fields in massive stars. Based on observations obtained in the framework of the ESO Prg. 191.D-0255(A,B).

  16. A SEARCH FOR INTERSTELLAR CARBON-CHAIN ALCOHOL HC{sub 4}OH IN STAR-FORMING REGION L1527 AND DARK CLOUD TMC-1

    SciTech Connect

    Araki, Mitsunori; Yamabe, Hiromichi; Koshikawa, Naohiro; Tsukiyama, Koichi; Takano, Shuro; Nakane, Aya; Okabayashi, Toshiaki; Kunimatsu, Arisa; Kuze, Nobuhiko

    2012-01-10

    We report a sensitive search for the rotational transitions of the carbon-chain alcohol HC{sub 4}OH in the frequency range 21.2-46.7 GHz in the star-forming region L1527 and the dark cloud TMC-1. The motivation was laboratory detection of HC{sub 4}OH by microwave spectroscopy. Despite achieving rms noise levels of several millikelvin in the antenna temperature using the 45 m telescope at Nobeyama Radio Observatory, the detection was not successful, leading to 3{sigma} upper limits corresponding to the column densities of 2.0 Multiplication-Sign 10{sup 12} and 5.6 Multiplication-Sign 10{sup 12} cm{sup -2} in L1527 and TMC-1, respectively. These upper limits indicate that [HC{sub 4}OH]/[HC{sub 5}N] ratios are less than 0.3 and 0.1 in L1527 and TMC-1, respectively, where HC{sub 5}N is an HC{sub 4}-chain cyanide and HC{sub 4}OH is a hydroxide. These ratios suggest that the cyano carbon-chain molecule dominates the hydroxyl carbon-chain molecule in L1527 and TMC-1. This is contrary to the case of saturated compounds in hot cores, e.g., CH{sub 3}OH and CH{sub 3}CN, and can be a chemical feature of carbon-chain molecules in L1527 and TMC-1. In addition, the column densities of the 'unsubstituted' carbon-chain molecule C{sub 4}H and the sulfur-bearing molecules SO and HCS{sup +} were determined from detected lines in L1527.

  17. Water in star-forming regions with Herschel (WISH). IV. A survey of low-J H2O line profiles toward high-mass protostars

    NASA Astrophysics Data System (ADS)

    van der Tak, F. F. S.; Chavarría, L.; Herpin, F.; Wyrowski, F.; Walmsley, C. M.; van Dishoeck, E. F.; Benz, A. O.; Bergin, E. A.; Caselli, P.; Hogerheijde, M. R.; Johnstone, D.; Kristensen, L. E.; Liseau, R.; Nisini, B.; Tafalla, M.

    2013-06-01

    Context. Water is a key constituent of star-forming matter, but the origin of its line emission and absorption during high-mass star formation is not well understood. Aims: We study the velocity profiles of low-excitation H2O lines toward 19 high-mass star-forming regions and search for trends with luminosity, mass, and evolutionary stage. Methods: We decompose high-resolution Herschel-HIFI line spectra near 990, 1110 and 1670 GHz into three distinct physical components. Dense cores (protostellar envelopes) are usually seen as narrow absorptions in the H2O 1113 and 1669 GHz ground-state lines, the H2O 987 GHz excited-state line, and the H218O 1102 GHz ground-state line. In a few sources, the envelopes appear in emission in some or all studied lines, indicating higher temperatures or densities. Broader features due to outflows are usually seen in absorption in the H2O 1113 and 1669 GHz lines, in 987 GHz emission, and not seen in H218O, indicating a lower column density and a higher excitation temperature than the envelope component. A few outflows are detected in H218O, indicating higher column densities of shocked gas. In addition, the H2O 1113 and 1669 GHz spectra show narrow absorptions by foreground clouds along the line of sight. The lack of corresponding features in the 987 GHz and H218O lines indicates a low column density and a low excitation temperature for these clouds, although their derived H2O ortho/para ratios are close to 3. Results: The intensity of the ground state lines of H2O at 1113 and 1669 GHz does not show significant trends with source luminosity, envelope mass, or evolutionary state. In contrast, the flux in the excited-state 987 GHz line appears correlated with luminosity and the H218O line flux appears correlated with the envelope mass. Furthermore, appearance of the envelope in absorption in the 987 GHz and H218O lines seems to be a sign of an early evolutionary stage, as probed by the mid-infrared brightness and the Lbol/Menv ratio of

  18. A panchromatic view of star-forming regions in the Magellanic clouds: Characterizing physical and evolutionary parameters of young stellar objects

    NASA Astrophysics Data System (ADS)

    Carlson, Lynn Redding

    2010-07-01

    Many factors affect the formation of stars, and none of them is well-understood. Metal abundance, environment, turbulence, and multiplicity all have roles to play in how quickly Young Stellar Objects (YSOs) form and evolve, what masses they achieve, and the rate at which interstellar medium is converted into stars. The first step in understanding star formation must be to construct a representative catalog of YSOs, including a variety of evolutionary stages, masses, and environments. Here, we examine clustered star formation in 10 H II regions in the Large and Small Magellanic Clouds (LMC and SMC). These two galaxies have different sub-Solar metallicities, and we choose star-forming regions with different sizes, morphologies, locations, and surrounding environments. By combining photometric data across a range of wavelengths to characterize diverse stellar and proto-stellar populations, we refine a method to find and characterize YSO candidates, identifying ˜ 1200 new YSOs in the two Clouds. We construct initial lists of YSO candidates based on 10 new color-selection criteria and then leverage data from the SAGE Spitzer Space Telescope Legacy Programs along with ancillary data from ground-based surveys. We fit photometric measurements to Spectral Energy Distributions (SEDs) of model YSOs and select which are well-fit based on their reduced chi 2 values. Where deep Hubble Space Telescope (HST) observations are available, we note that most (˜ 70%) single infrared sources actually correspond to several optical sources in apparent compact proto-clusters. Preliminary imaging from the HERITAGE Herschel Space Telescope photometric survey of the Magellanic Clouds even affords us a qualitative glimpse of the earliest, most embedded stages of star formation, which we compare visually to our YSO candidates. We outline an entirely new technique to determine the lifetimes of YSO evolutionary stages, comparing the spatial locations of stellar populations, pre-main sequence

  19. Evidence for wide-spread active galactic nucleus-driven outflows in the most massive z ∼ 1-2 star-forming galaxies

    SciTech Connect

    Genzel, R.; Förster Schreiber, N. M.; Rosario, D.; Lang, P.; Lutz, D.; Wisnioski, E.; Wuyts, E.; Wuyts, S.; Bandara, K.; Bender, R.; Berta, S.; Kurk, J.; Mendel, J. T.; Tacconi, L. J.; Wilman, D.; Beifiori, A.; Burkert, A.; Buschkamp, P.; Chan, J.; Brammer, G. E-mail: genzel@mpe.mpg.de; and others

    2014-11-20

    In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M {sub *}/M {sub ☉}) ≥ 10.9) z ∼ 1-3 star-forming galaxies by increasing the sample size by a factor of six (to 44 galaxies above log(M {sub *}/M {sub ☉}) ≥ 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS{sup 3D}spectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Hα, [N II], and [S II] lines ∼450-5300 km s{sup –1}), with large [N II]/Hα ratios, above log(M {sub *}/M {sub ☉}) ∼ 10.9, with about two-thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z ∼ 1 and ∼2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGNs), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation.

  20. Using Cosmic Telescopes to Study Dusty, Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Walth, Gregory; Egami, Eiichi; Clément, Benjamin; Rujopakarn, Wiphu; Rawle, Tim; Rex, Marie; Richard, Johan; Dessauges, Miroslava; Perez-Gonzalez, Pablo; Stark, Daniel; Herschel Lensing Survey

    2016-06-01

    Dusty, star-forming galaxies (DSFGs), characterized by their far-infrared (far-IR) emission, undergo the largest starbursts in the Universe, contributing to the majority of the cosmic star formation rate density at z = 1 ‑ 4. These starbursts have important implications for galaxy evolution and feedback as these galaxies build up much of their stellar mass during this time and may experience strong stellar driven winds. For the first time the Herschel Space Observatory was able observe the full far-IR dust emission for a large population of high-redshift DSFGs. However, Herschel reaches the confusion limit quickly and only the brightest galaxies at redshifts z > 2 can be detected. With gravitational lensing, we are able to surpass the Herschel confusion limit and probe intrinsically less luminous and therefore more normal star-forming galaxies. With this goal in mind, we have conducted a large Herschel survey, the Herschel Lensing Survey, of the cores of almost 600 massive galaxy clusters, where the effects of gravitational lensing are the strongest. In this presentation I will discuss how using one of largest gravitational lenses enables the detailed study of star forming regions at high redshift by investigating a giant (D ~ 1 kpc) luminous star forming region in aDSFG at z=0.6. Next, I will discuss how using one of the brightest sources from our sample allows us to investigate the molecular gas and dust properties of a typical DSFG with a CO outflow at z~2. Finally, I will discuss ongoing work using the brightest DSFGs in our sample to detect rest-frame optical nebular emission lines, using near-infrared spectroscopy with Keck/MOSFIRE, LBT/LUCI, and Magellan/MMIRS, which reveal conditions of their ISM; specifically ionization, star formation, metallicity, AGN activity, and dust attenuation.

  1. Using Cosmic Telescopes to Study Dusty, Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Walth, Gregory; Egami, Eiichi; Clément, Benjamin; Rujopakarn, Wiphu; Rawle, Tim; Rex, Marie; Richard, Johan; Dessauges, Miroslava; Perez-Gonzalez, Pablo; Stark, Daniel; Herschel Lensing Survey

    2016-06-01

    Dusty, star-forming galaxies (DSFGs), characterized by their far-infrared (far-IR) emission, undergo the largest starbursts in the Universe, contributing to the majority of the cosmic star formation rate density at z = 1 - 4. These starbursts have important implications for galaxy evolution and feedback as these galaxies build up much of their stellar mass during this time and may experience strong stellar driven winds. For the first time the Herschel Space Observatory was able observe the full far-IR dust emission for a large population of high-redshift DSFGs. However, Herschel reaches the confusion limit quickly and only the brightest galaxies at redshifts z > 2 can be detected. With gravitational lensing, we are able to surpass the Herschel confusion limit and probe intrinsically less luminous and therefore more normal star-forming galaxies. With this goal in mind, we have conducted a large Herschel survey, the Herschel Lensing Survey, of the cores of almost 600 massive galaxy clusters, where the effects of gravitational lensing are the strongest. In this presentation I will discuss how using one of largest gravitational lenses enables the detailed study of star forming regions at high redshift by investigating a giant (D ~ 1 kpc) luminous star forming region in aDSFG at z=0.6. Next, I will discuss how using one of the brightest sources from our sample allows us to investigate the molecular gas and dust properties of a typical DSFG with a CO outflow at z~2. Finally, I will discuss ongoing work using the brightest DSFGs in our sample to detect rest-frame optical nebular emission lines, using near-infrared spectroscopy with Keck/MOSFIRE, LBT/LUCI, and Magellan/MMIRS, which reveal conditions of their ISM; specifically ionization, star formation, metallicity, AGN activity, and dust attenuation.

  2. The Intrinsic Eddington Ratio Distribution of Active Galactic Nuclei in Star-forming Galaxies from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Jones, Mackenzie L.; Hickox, Ryan C.; Black, Christine S.; Hainline, Kevin N.; DiPompeo, Michael A.; Goulding, Andy D.

    2016-07-01

    An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGNs). Based on observations at X-ray wavelengths, the observed Eddington ratio distribution appears as a power law, while optical studies have often yielded a lognormal distribution. There is increasing evidence that these observed discrepancies may be due to contamination by star formation and other selection effects. Using a sample of galaxies from the Sloan Digital Sky Survey Data Release 7, we test whether or not an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previous work suggesting that young galaxies in optical surveys have an observed lognormal Eddington ratio distribution. We simulate the optical emission line properties of a population of galaxies and AGNs using a broad, instantaneous luminosity distribution described by a Schechter function near the Eddington limit. This simulated AGN population is then compared to observed galaxies via their positions on an emission line excitation diagram and Eddington ratio distributions. We present an improved method for extracting the AGN distribution using BPT diagnostics that allows us to probe over one order of magnitude lower in Eddington ratio, counteracting the effects of dilution by star formation. We conclude that for optically selected AGNs in young galaxies, the intrinsic Eddington ratio distribution is consistent with a possibly universal, broad power law with an exponential cutoff, as this distribution is observed in old, optically selected galaxies and X-rays.

  3. PROBING THE BALANCE OF AGN AND STAR-FORMING ACTIVITY IN THE LOCAL UNIVERSE WITH ChaMP

    SciTech Connect

    Constantin, Anca; Green, Paul; Aldcroft, Tom; Kim, Dong-Woo; Haggard, Daryl; Anderson, Scott F.; Barkhouse, Wayne

    2009-11-10

    The combination of the Sloan Digital Sky Survey (SDSS) and the Chandra Multiwavelength Project (ChaMP) currently offers the largest and most homogeneously selected sample of nearby galaxies for investigating the relation between X-ray nuclear emission, nebular line emission, black hole masses, and properties of the associated stellar populations. We provide X-ray spectral fits and valid uncertainties for all the galaxies with counts ranging from 2 to 1325 (mean 76, median 19). We present here novel constraints that both X-ray luminosity L{sub X} and X-ray spectral energy distribution bring to the galaxy evolutionary sequence H II -> Seyfert/Transition Object -> LINER -> Passive suggested by optical data. In particular, we show that both L{sub X} and GAMMA, the slope of the power law that best fits the 0.5-8 keV spectra, are consistent with a clear decline in the accretion power along the sequence, corresponding to a softening of their spectra. This implies that, at z approx 0, or at low-luminosity active galactic nucleus (AGN) levels, there is an anticorrelation between GAMMA and L/L {sub edd}, opposite to the trend exhibited by high z AGN (quasars). The turning point in the GAMMA-L/L{sub edd} LLAGN + quasars relation occurs near GAMMA approx 1.5 and L/L{sub edd} approx 0.01. Interestingly, this is identical to what stellar mass X-ray binaries exhibit, indicating that we have probably found the first empirical evidence for an intrinsic switch in the accretion mode, from advection-dominated flows to standard (disk/corona) accretion modes in supermassive black hole accretors, similar to what has been seen and proposed to happen in stellar mass black hole systems. The anticorrelation we find between GAMMA and L/L{sub edd} may instead indicate that stronger accretion correlates with greater absorption. Therefore, the trend for softer spectra toward more luminous, high redshift, and strongly accreting (L/L{sub edd} approx> 0.01) AGNs/quasars could simply be the result

  4. Star-forming galaxy models: Blending star formation into TREESPH

    NASA Technical Reports Server (NTRS)

    Mihos, J. Christopher; Hernquist, Lars

    1994-01-01

    We have incorporated star-formation algorithms into a hybrid N-body/smoothed particle hydrodynamics code (TREESPH) in order to describe the star forming properties of disk galaxies over timescales of a few billion years. The models employ a Schmidt law of index n approximately 1.5 to calculate star-formation rates, and explicitly include the energy and metallicity feedback into the Interstellar Medium (ISM). Modeling the newly formed stellar population is achieved through the use of hybrid SPH/young star particles which gradually convert from gaseous to collisionless particles, avoiding the computational difficulties involved in creating new particles. The models are shown to reproduce well the star-forming properties of disk galaxies, such as the morphology, rate of star formation, and evolution of the global star-formation rate and disk gas content. As an example of the technique, we model an encounter between a disk galaxy and a small companion which gives rise to a ring galaxy reminiscent of the Cartwheel (AM 0035-35). The primary galaxy in this encounter experiences two phases of star forming activity: an initial period during the expansion of the ring, and a delayed phase as shocked material in the ring falls back into the central regions.

  5. Gas and dust in the star-forming region ρ Oph A. The dust opacity exponent β and the gas-to-dust mass ratio g2d

    NASA Astrophysics Data System (ADS)

    Liseau, R.; Larsson, B.; Lunttila, T.; Olberg, M.; Rydbeck, G.; Bergman, P.; Justtanont, K.; Olofsson, G.; de Vries, B. L.

    2015-06-01

    Aims: We aim at determining the spatial distribution of the gas and dust in star-forming regions and address their relative abundances in quantitative terms. We also examine the dust opacity exponent β for spatial and/or temporal variations. Methods: Using mapping observations of the very dense ρ Oph A core, we examined standard 1D and non-standard 3D methods to analyse data of far-infrared and submillimetre (submm) continuum radiation. The resulting dust surface density distribution can be compared to that of the gas. The latter was derived from the analysis of accompanying molecular line emission, observed with Herschel from space and with APEX from the ground. As a gas tracer we used N2H+, which is believed to be much less sensitive to freeze-out than CO and its isotopologues. Radiative transfer modelling of the N2H+ (J = 3-2) and (J = 6-5) lines with their hyperfine structure explicitly taken into account provides solutions for the spatial distribution of the column density N(H2), hence the surface density distribution of the gas. Results: The gas-to-dust mass ratio is varying across the map, with very low values in the central regions around the core SM 1. The global average, = 88, is not far from the canonical value of 100, however. In ρ Oph A, the exponent β of the power-law description for the dust opacity exhibits a clear dependence on time, with high values of 2 for the envelope-dominated emission in starless Class -1 sources to low values close to 0 for the disk-dominated emission in Class III objects. β assumes intermediate values for evolutionary classes in between. Conclusions: Since β is primarily controlled by grain size, grain growth mostly occurs in circumstellar disks. The spatial segregation of gas and dust, seen in projection toward the core centre, probably implies that, like C18O, also N2H+ is frozen onto the grains. Based on observations with APEX, which is a 12 m diameter submillimetre telescope at 5100 m altitude on Llano Chajnantor

  6. Evidence for Wide-spread Active Galactic Nucleus-driven Outflows in the Most Massive z ~ 1-2 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Genzel, R.; Förster Schreiber, N. M.; Rosario, D.; Lang, P.; Lutz, D.; Wisnioski, E.; Wuyts, E.; Wuyts, S.; Bandara, K.; Bender, R.; Berta, S.; Kurk, J.; Mendel, J. T.; Tacconi, L. J.; Wilman, D.; Beifiori, A.; Brammer, G.; Burkert, A.; Buschkamp, P.; Chan, J.; Carollo, C. M.; Davies, R.; Eisenhauer, F.; Fabricius, M.; Fossati, M.; Kriek, M.; Kulkarni, S.; Lilly, S. J.; Mancini, C.; Momcheva, I.; Naab, T.; Nelson, E. J.; Renzini, A.; Saglia, R.; Sharples, R. M.; Sternberg, A.; Tacchella, S.; van Dokkum, P.

    2014-11-01

    In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M */M ⊙) >= 10.9) z ~ 1-3 star-forming galaxies by increasing the sample size by a factor of six (to 44 galaxies above log(M */M ⊙) >= 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS3Dspectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Hα, [N II], and [S II] lines ~450-5300 km s-1), with large [N II]/Hα ratios, above log(M */M ⊙) ~ 10.9, with about two-thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z ~ 1 and ~2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGNs), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation. Based on observations obtained at the Very Large Telescope (VLT) of the European Southern Observatory (ESO), Paranal, Chile (ESO program IDs 073.B-9018, 074.A-9011, 075.A-0466, 076.A-0527, 078.A-0660, 079.A-0341, 080.A-0330, 080.A-0339, 080.A-0635, 081.A-0672, 082.A-0396, 183.A-0781, 087.A-0081, 088.A-0202, 088.A-0209, 091.A-0126, 092.A-0082, 092.A-0091, 093.A-0079). Also based on observations at the Large Binocular Telescope (LBT) on Mt. Graham in Arizona.

  7. CHARACTERISTIC STRUCTURE OF STAR-FORMING CLOUDS

    SciTech Connect

    Myers, Philip C.

    2015-06-20

    This paper presents a new method to diagnose the star-forming potential of a molecular cloud region from the probability density function of its column density (N-pdf). This method provides expressions for the column density and mass profiles of a symmetric filament having the same N-pdf as a filamentary region. The central concentration of this characteristic filament can distinguish regions and can quantify their fertility for star formation. Profiles are calculated for N-pdfs which are pure lognormal, pure power law, or a combination. In relation to models of singular polytropic cylinders, characteristic filaments can be unbound, bound, or collapsing depending on their central concentration. Such filamentary models of the dynamical state of N-pdf gas are more relevant to star-forming regions than are spherical collapse models. The star formation fertility of a bound or collapsing filament is quantified by its mean mass accretion rate when in radial free fall. For a given mass per length, the fertility increases with the filament mean column density and with its initial concentration. In selected regions the fertility of their characteristic filaments increases with the level of star formation.

  8. Characteristic Structure of Star-forming Clouds

    NASA Astrophysics Data System (ADS)

    Myers, Philip C.

    2015-06-01

    This paper presents a new method to diagnose the star-forming potential of a molecular cloud region from the probability density function of its column density (N-pdf). This method provides expressions for the column density and mass profiles of a symmetric filament having the same N-pdf as a filamentary region. The central concentration of this characteristic filament can distinguish regions and can quantify their fertility for star formation. Profiles are calculated for N-pdfs which are pure lognormal, pure power law, or a combination. In relation to models of singular polytropic cylinders, characteristic filaments can be unbound, bound, or collapsing depending on their central concentration. Such filamentary models of the dynamical state of N-pdf gas are more relevant to star-forming regions than are spherical collapse models. The star formation fertility of a bound or collapsing filament is quantified by its mean mass accretion rate when in radial free fall. For a given mass per length, the fertility increases with the filament mean column density and with its initial concentration. In selected regions the fertility of their characteristic filaments increases with the level of star formation.

  9. A PHOTON-DOMINATED REGION MODEL FOR THE FIR MID-J CO LADDER WITH UNIVERSAL ROTATIONAL TEMPERATURE IN STAR FORMING REGIONS

    SciTech Connect

    Lee, Seokho; Park, Yong-Sun; Lee, Jeong-Eun; Bergin, Edwin A.

    2014-08-01

    A photon-dominated region (PDR) is one of the leading candidate mechanisms for the origin of warm CO gas with near universal ∼300 K rotational temperature inferred from the CO emission detected toward embedded protostars by Herschel/PACS. We have developed a PDR model in general coordinates, where we can use the most adequate coordinate system for an embedded protostar having outflow cavity walls, to solve chemistry and gas energetics self-consistently for given UV radiation fields with different spectral shapes. Simple one-dimensional tests and applications show that FIR mid-J (14 ≤ J ≤ 24) CO lines are emitted from close to the surface of a dense region exposed to high UV fluxes. We apply our model to HH46 and find that the UV-heated outflow cavity wall can reproduce the mid-J CO transitions observed by Herschel/PACS. A model with UV radiation corresponding to a blackbody of 10,000 K results in a rotational temperature lower than 300 K, while models with the Draine interstellar radiation field and the 15,000 K blackbody radiation field predict a rotational temperature similar to the observed one.

  10. Characterising molecular gas in nearby star forming galaxies

    NASA Astrophysics Data System (ADS)

    Kelly, George; Viti, Serena; Garcia-Burillo, Santiago

    2015-08-01

    Regions of very dense, star-forming gas in the interstellar medium are necessary to maintain star formation activity in hostile conditions. Star-forming regions in these environments are able to resist winds and radiative forces from newly formed stars longer than gas in the surrounding ISM. Subject to a proper interpretation, observations of molecules can be used for many purposes: tracing the reservoir or leftover of the star formation process; tracing the process of star formation itself; and determining the galaxy energetics through influence of newly-formed stars or an AGN on their environments. We map the distribution of several tracer molecules over three nearby galaxies. We begin by mapping two starburst galaxies with single dish observations of the dense gas tracer CS. The formation of CS is modelled under different conditions with results fed into a molecular line radiative transfer model. From this we can obtain the physical conditions of the regions of the ISM where there is a high rate of star-formation, as well as compare how the conditions vary away from the galactic centre. Moving on from here, we use ALMA to map NGC 1068. Observations of several molecules across the AGN and starburst regions are used to determine conditions and processes with a spatial resolution of less than 35 parsecs.

  11. The ISO View of Star Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Helou, George

    1999-01-01

    ISO studies of normal galaxies in the local Universe have revealed basic new properties whose significant implications for the star formation process and cosmology are only starting to be understood. This review will touch on the general results of a statistical nature, and provide a quick summary of the profusion of exciting results on individual objects. In the mid-infrared, PHT-S has established that the spectra of star forming galaxies between 6 and-13microns are dominated by the Aromatic Features in Emission (AFE), and show little variation as a function of the heating intensity. The Carriers of the AFE (CAFE) are thus a universal component of dust with standard properties, and contribute between 10 and 25% of the total dust luminosity. In addition to AFE, the spectra show a low-level continuum detectable at wavelengths longer than 3.5microns whose origin is still under investigation. The mid-infrared colors formed as the ratio of flux densities in the 6.75micron and the 15micron bands of ISO-CAM remain essentially constant and near unity for quiescent and mildly active galaxies. As dust heating increases further, the 15micron flux increases steeply compared to 6.75microns, indicating that dust heated to 100Kregions. At the other end of the spectrum, photometry at 120-200microns using ISO-PHOT is starting to constrain the distribution of dust temperatures at the low end of the temperature scale. From LWS data, the far-infrared fine-structure lines of [CII] and [OI], which provide most of the cooling for warm atomic gas, show variations that have remained controversial in their interpretation. In particular, as the galaxy become more active in star formation, its [CII] flux weakens relative to total dust emission while the [OI] does not. This behavior has attracted much interest because it extrapolates to the most active galaxies, making them weaker in [CII

  12. ASSESSING RADIATION PRESSURE AS A FEEDBACK MECHANISM IN STAR-FORMING GALAXIES

    SciTech Connect

    Andrews, Brett H.; Thompson, Todd A.

    2011-02-01

    Radiation pressure from the absorption and scattering of starlight by dust grains may be an important feedback mechanism in regulating star-forming galaxies. We compile data from the literature on star clusters, star-forming subregions, normal star-forming galaxies, and starbursts to assess the importance of radiation pressure on dust as a feedback mechanism, by comparing the luminosity and flux of these systems to their dust Eddington limit. This exercise motivates a novel interpretation of the Schmidt law, the L{sub IR}-L'{sub CO} correlation, and the L{sub IR}-L'{sub HCN} correlation. In particular, the linear L{sub IR}-L'{sub HCN} correlation is a natural prediction of radiation pressure regulated star formation. Overall, we find that the Eddington limit sets a hard upper bound to the luminosity of any star-forming region. Importantly, however, many normal star-forming galaxies have luminosities significantly below the Eddington limit. We explore several explanations for this discrepancy, especially the role of 'intermittency' in normal spirals-the tendency for only a small number of subregions within a galaxy to be actively forming stars at any moment because of the time dependence of the feedback process and the luminosity evolution of the stellar population. If radiation pressure regulates star formation in dense gas, then the gas depletion timescale is 6 Myr, in good agreement with observations of the densest starbursts. Finally, we highlight the importance of observational uncertainties, namely, the dust-to-gas ratio and the CO-to-H{sub 2} and HCN-to-H{sub 2} conversion factors, that must be understood before a definitive assessment of radiation pressure as a feedback mechanism in star-forming galaxies.

  13. Assessing Radiation Pressure as a Feedback Mechanism in Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Andrews, Brett H.; Thompson, Todd A.

    2011-02-01

    Radiation pressure from the absorption and scattering of starlight by dust grains may be an important feedback mechanism in regulating star-forming galaxies. We compile data from the literature on star clusters, star-forming subregions, normal star-forming galaxies, and starbursts to assess the importance of radiation pressure on dust as a feedback mechanism, by comparing the luminosity and flux of these systems to their dust Eddington limit. This exercise motivates a novel interpretation of the Schmidt law, the L IR-L'CO correlation, and the L IR-L'HCN correlation. In particular, the linear L IR-L'HCN correlation is a natural prediction of radiation pressure regulated star formation. Overall, we find that the Eddington limit sets a hard upper bound to the luminosity of any star-forming region. Importantly, however, many normal star-forming galaxies have luminosities significantly below the Eddington limit. We explore several explanations for this discrepancy, especially the role of "intermittency" in normal spirals—the tendency for only a small number of subregions within a galaxy to be actively forming stars at any moment because of the time dependence of the feedback process and the luminosity evolution of the stellar population. If radiation pressure regulates star formation in dense gas, then the gas depletion timescale is 6 Myr, in good agreement with observations of the densest starbursts. Finally, we highlight the importance of observational uncertainties, namely, the dust-to-gas ratio and the CO-to-H2 and HCN-to-H2 conversion factors, that must be understood before a definitive assessment of radiation pressure as a feedback mechanism in star-forming galaxies.

  14. Water in star-forming regions with Herschel (WISH). V. The physical conditions in low-mass protostellar outflows revealed by multi-transition water observations

    NASA Astrophysics Data System (ADS)

    Mottram, J. C.; Kristensen, L. E.; van Dishoeck, E. F.; Bruderer, S.; San José-García, I.; Karska, A.; Visser, R.; Santangelo, G.; Benz, A. O.; Bergin, E. A.; Caselli, P.; Herpin, F.; Hogerheijde, M. R.; Johnstone, D.; van Kempen, T. A.; Liseau, R.; Nisini, B.; Tafalla, M.; van der Tak, F. F. S.; Wyrowski, F.

    2014-12-01

    Context. Outflows are an important part of the star formation process as both the result of ongoing active accretion and one of the main sources of mechanical feedback on small scales. Water is the ideal tracer of these effects because it is present in high abundance for the conditions expected in various parts of the protostar, particularly the outflow. Aims: We constrain and quantify the physical conditions probed by water in the outflow-jet system for Class 0 and I sources. Methods: We present velocity-resolved Herschel HIFI spectra of multiple water-transitions observed towards 29 nearby Class 0/I protostars as part of the WISH guaranteed time key programme. The lines are decomposed into different Gaussian components, with each component related to one of three parts of the protostellar system; quiescent envelope, cavity shock and spot shocks in the jet and at the base of the outflow. We then use non-LTE radex models to constrain the excitation conditions present in the two outflow-related components. Results: Water emission at the source position is optically thick but effectively thin, with line ratios that do not vary with velocity, in contrast to CO. The physical conditions of the cavity and spot shocks are similar, with post-shock H2 densities of order 105 - 108 cm-3 and H2O column densities of order 1016 - 1018 cm-2. H2O emission originates in compact emitting regions: for the spot shocks these correspond to point sources with radii of order 10-200 AU, while for the cavity shocks these come from a thin layer along the outflow cavity wall with thickness of order 1-30 AU. Conclusions: Water emission at the source position traces two distinct kinematic components in the outflow; J shocks at the base of the outflow or in the jet, and C shocks in a thin layer in the cavity wall. The similarity of the physical conditions is in contrast to off-source determinations which show similar densities but lower column densities and larger filling factors. We propose

  15. The SINS/zC-SINF survey of z ∼ 2 galaxy kinematics: Evidence for powerful active galactic nucleus-driven nuclear outflows in massive star-forming galaxies

    SciTech Connect

    Förster Schreiber, N. M.; Genzel, R.; Kurk, J. D.; Lutz, D.; Tacconi, L. J.; Wuyts, S.; Bandara, K.; Buschkamp, P.; Davies, R.; Eisenhauer, F.; Lang, P.; Newman, S. F.; Burkert, A.; Carollo, C. M.; Lilly, S. J.; Cresci, G.; Daddi, E.; Mainieri, V.; Mancini, C.; and others

    2014-05-20

    We report the detection of ubiquitous powerful nuclear outflows in massive (≥10{sup 11} M {sub ☉}) z ∼ 2 star-forming galaxies (SFGs), which are plausibly driven by an active galactic nucleus (AGN). The sample consists of the eight most massive SFGs from our SINS/zC-SINF survey of galaxy kinematics with the imaging spectrometer SINFONI, six of which have sensitive high-resolution adaptive optics-assisted observations. All of the objects are disks hosting a significant stellar bulge. The spectra in their central regions exhibit a broad component in Hα and forbidden [N II] and [S II] line emission, with typical velocity FWHM ∼ 1500 km s{sup –1}, [N II]/Hα ratio ≈ 0.6, and intrinsic extent of 2-3 kpc. These properties are consistent with warm ionized gas outflows associated with Type 2 AGN, the presence of which is confirmed via independent diagnostics in half the galaxies. The data imply a median ionized gas mass outflow rate of ∼60 M {sub ☉} yr{sup –1} and mass loading of ∼3. At larger radii, a weaker broad component is detected but with lower FWHM ∼485 km s{sup –1} and [N II]/Hα ≈ 0.35, characteristic for star formation-driven outflows as found in the lower-mass SINS/zC-SINF galaxies. The high inferred mass outflow rates and frequent occurrence suggest that the nuclear outflows efficiently expel gas out of the centers of the galaxies with high duty cycles and may thus contribute to the process of star formation quenching in massive galaxies. Larger samples at high masses will be crucial in confirming the importance and energetics of the nuclear outflow phenomenon and its connection to AGN activity and bulge growth.

  16. OH (1720 MHz) Masers: A Multiwavelength Study of the Interaction between the W51C Supernova Remnant and the W51B Star Forming Region

    NASA Astrophysics Data System (ADS)

    Brogan, C. L.; Goss, W. M.; Hunter, T. R.; Richards, A. M. S.; Chandler, C. J.; Lazendic, J. S.; Koo, B.-C.; Hoffman, I. M.; Claussen, M. J.

    2013-07-01

    We present a comprehensive view of the W51B H II region complex and the W51C supernova remnant (SNR) using new radio observations from the VLA, VLBA, MERLIN, JCMT, and CSO along with archival data from Spitzer, ROSAT, ASCA, and Chandra. Our VLA data include the first λ = 400 cm (74 MHz) continuum image of W51 at high resolution (88''). The 400 cm image shows non-thermal emission surrounding the G49.2-0.3 H II region, and a compact source of non-thermal emission (W51B_NT) coincident with the previously-identified OH (1720 MHz) maser spots, non-thermal 21 and 90 cm emission, and a hard X-ray source. W51B_NT falls within the region of high likelihood for the position of TeV γ-ray emission. Using the VLBA, three OH (1720 MHz) maser spots are detected in the vicinity of W51B_NT with sizes of 60-300 AU and Zeeman effect magnetic field strengths of 1.5-2.2 mG. The multiwavelength data demonstrate that the northern end of the W51B H II region complex has been partly enveloped by the advancing W51C SNR and this interaction explains the presence of W51B_NT and the OH masers. This interaction also appears in the thermal molecular gas which partially encircles W51B_NT and exhibits narrow pre-shock (Δv ~ 5 km s-1) and broad post-shock (Δv ~ 20 km s-1) velocity components. RADEX radiative transfer modeling of these two components yield physical conditions consistent with the passage of a non-dissociative C-type shock. Confirmation of the W51B/W51C interaction provides additional evidence in favor of this region being one of the best candidates for hadronic particle acceleration known thus far.

  17. The Herschel M 33 extended survey (HerM33es): PACS spectroscopy of the star-forming region BCLMP 302

    NASA Astrophysics Data System (ADS)

    Mookerjea, B.; Kramer, C.; Buchbender, C.; Boquien, M.; Verley, S.; Relaño, M.; Quintana-Lacaci, G.; Aalto, S.; Braine, J.; Calzetti, D.; Combes, F.; Garcia-Burillo, S.; Gratier, P.; Henkel, C.; Israel, F.; Lord, , S.; Nikola, T.; Röllig, M.; Stacey, G.; Tabatabaei, F. S.; van der Tak, F.; van der Werf, P.

    2011-08-01

    Context. The emission line of [C ii] at 158 μm is one of the strongest cooling lines of the interstellar medium (ISM) in galaxies. Aims: Distinguishing the relative contributions of the different ISM phases to [C ii] emission is a major objective of the HerM33es program, a Herschel key project to study the ISM in the nearby spiral galaxy M 33. Methods: Using PACS, we have mapped the emission of [C ii] 158 μm, [O i] 63 μm, and other FIR lines in a 2' × 2' region of the northern spiral arm of M 33, centered on the H ii region BCLMP 302. At the peak of Hα emission, we observed in addition a velocity-resolved [C ii] spectrum using HIFI. We use scatterplots to compare these data with PACS 160 μm continuum maps, and with maps of CO and H i data, at a common resolution of 12″ or 50 pc. Maps of Hα and 24 μm emission observed with Spitzer are used to estimate the SFR. We created maps of the [C ii] and [O i] 63 μm emission and detected [N ii] 122 μm and [N iii] 57 μm at individual positions. Results: The [C ii] line observed with HIFI is significantly broader than that of CO, and slightly blue-shifted. In addition, there is little spatial correlation between [C ii] observed with PACS and CO over the mapped region. There is even less spatial correlation between [C ii] and the atomic gas traced by H i. Detailed comparison of the observed intensities towards the H ii region with models of photo-ionization and photon-dominated regions, confirms that a significant fraction, 20-30%, of the observed [C ii] emission stems from the ionized gas and not from the molecular cloud. The gas heating efficiency, using the ratio of [C ii] to the TIR as a proxy, varies between 0.07 and 1.5%, with the largest variations found outside the H ii region. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  18. OH (1720 MHz) MASERS: A MULTIWAVELENGTH STUDY OF THE INTERACTION BETWEEN THE W51C SUPERNOVA REMNANT AND THE W51B STAR FORMING REGION

    SciTech Connect

    Brogan, C. L.; Hunter, T. R.; Goss, W. M.; Chandler, C. J.; Claussen, M. J.; Richards, A. M. S.; Lazendic, J. S.; Koo, B.-C.; Hoffman, I. M.

    2013-07-10

    We present a comprehensive view of the W51B H II region complex and the W51C supernova remnant (SNR) using new radio observations from the VLA, VLBA, MERLIN, JCMT, and CSO along with archival data from Spitzer, ROSAT, ASCA, and Chandra. Our VLA data include the first {lambda} = 400 cm (74 MHz) continuum image of W51 at high resolution (88''). The 400 cm image shows non-thermal emission surrounding the G49.2-0.3 H II region, and a compact source of non-thermal emission (W51B{sub N}T) coincident with the previously-identified OH (1720 MHz) maser spots, non-thermal 21 and 90 cm emission, and a hard X-ray source. W51B{sub N}T falls within the region of high likelihood for the position of TeV {gamma}-ray emission. Using the VLBA, three OH (1720 MHz) maser spots are detected in the vicinity of W51B{sub N}T with sizes of 60-300 AU and Zeeman effect magnetic field strengths of 1.5-2.2 mG. The multiwavelength data demonstrate that the northern end of the W51B H II region complex has been partly enveloped by the advancing W51C SNR and this interaction explains the presence of W51B{sub N}T and the OH masers. This interaction also appears in the thermal molecular gas which partially encircles W51B{sub N}T and exhibits narrow pre-shock ({Delta}v {approx} 5 km s{sup -1}) and broad post-shock ({Delta}v {approx} 20 km s{sup -1}) velocity components. RADEX radiative transfer modeling of these two components yield physical conditions consistent with the passage of a non-dissociative C-type shock. Confirmation of the W51B/W51C interaction provides additional evidence in favor of this region being one of the best candidates for hadronic particle acceleration known thus far.

  19. Structure, Motion, and Evolution of Star-Forming Dense Cores

    NASA Technical Reports Server (NTRS)

    Myers, Philip C.

    2003-01-01

    We have pursued spectral-line observations of star-forming regions over size scales from 0.01 pc to 0.5 pc. Our main goal has been to measure the systematic and turbulent motions of condensing and collapsing gas.

  20. Stellar populations in local star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Perez-Gonzalez, P. G.

    2003-11-01

    The main goal of this thesis work is studying the main properties of the stellar populations embedded in a statistically complete sample of local active star-forming galaxies: the Universidad Complutense de Madrid (UCM) Survey of emission-line galaxies. This sample contains 191 local star-forming galaxies at an average redshift of 0.026. The survey was carried out using an objective-prism technique centered at the wavelength of the Halpha nebular emission-line (a common tracer of recent star formation). (continues)

  1. A CHANDRA STUDY OF THE ROSETTE STAR-FORMING COMPLEX. III. THE NGC 2237 CLUSTER AND THE REGION'S STAR FORMATION HISTORY

    SciTech Connect

    Wang Junfeng; Feigelson, Eric D.; Townsley, Leisa K.; Broos, Patrick S.; Garmire, Gordon; Roman-Zuniga, Carlos G.; Lada, Elizabeth

    2010-06-10

    We present high spatial resolution Chandra X-ray images of the NGC 2237 young stellar cluster on the periphery of the Rosette Nebula. We detect 168 X-ray sources, 80% of which have stellar counterparts in USNO, Two Micron All Sky Survey, and deep FLAMINGOS images. These constitute the first census of the cluster members with 0.2 {approx}< M {approx}< 2 M {sub sun}. Star locations in near-infrared color-magnitude diagrams indicate a cluster age around 2 Myr with a visual extinction of 1 {approx}< A{sub V} {approx}< 3 at 1.4 kpc, the distance of the Rosette Nebula's main cluster NGC 2244. We derive the K-band luminosity function and the X-ray luminosity function of the cluster, which indicate a population {approx}400-600 stars. The X-ray-selected sample shows a K-excess disk frequency of 13%. The young Class II counterparts are aligned in an arc {approx}3 pc long suggestive of a triggered formation process induced by the O stars in NGC 2244. The diskless Class III sources are more dispersed. Several X-ray emitting stars are located inside the molecular cloud and around gaseous pillars projecting from the cloud. These stars, together with a previously unreported optical outflow originating inside the cloud, indicate that star formation is continuing at a low level and the cluster is still growing. This X-ray view of young stars on the western side of the Rosette Nebula complements our earlier studies of the central cluster NGC 2244 and the embedded clusters on the eastern side of the Nebula. The large-scale distribution of the clusters and molecular material is consistent with a scenario in which the rich central NGC 2244 cluster formed first, and its expanding H II region triggered the formation of the now-unobscured satellite clusters Rosette Molecular Cloud (RMC) XA and NGC 2237. A large swept-up shell material around the H II region is now in a second phase of collect-and-collapse fragmentation, leading to the recent formation of subclusters. Other clusters deeper

  2. A Chandra Study of the Rosette Star-forming Complex. III. The NGC 2237 Cluster and the Region's Star Formation History

    NASA Astrophysics Data System (ADS)

    Wang, Junfeng; Feigelson, Eric D.; Townsley, Leisa K.; Broos, Patrick S.; Román-Zúñiga, Carlos G.; Lada, Elizabeth; Garmire, Gordon

    2010-06-01

    We present high spatial resolution Chandra X-ray images of the NGC 2237 young stellar cluster on the periphery of the Rosette Nebula. We detect 168 X-ray sources, 80% of which have stellar counterparts in USNO, Two Micron All Sky Survey, and deep FLAMINGOS images. These constitute the first census of the cluster members with 0.2 <~ M <~ 2 M sun. Star locations in near-infrared color-magnitude diagrams indicate a cluster age around 2 Myr with a visual extinction of 1 <~ AV <~ 3 at 1.4 kpc, the distance of the Rosette Nebula's main cluster NGC 2244. We derive the K-band luminosity function and the X-ray luminosity function of the cluster, which indicate a population ~400-600 stars. The X-ray-selected sample shows a K-excess disk frequency of 13%. The young Class II counterparts are aligned in an arc ~3 pc long suggestive of a triggered formation process induced by the O stars in NGC 2244. The diskless Class III sources are more dispersed. Several X-ray emitting stars are located inside the molecular cloud and around gaseous pillars projecting from the cloud. These stars, together with a previously unreported optical outflow originating inside the cloud, indicate that star formation is continuing at a low level and the cluster is still growing. This X-ray view of young stars on the western side of the Rosette Nebula complements our earlier studies of the central cluster NGC 2244 and the embedded clusters on the eastern side of the Nebula. The large-scale distribution of the clusters and molecular material is consistent with a scenario in which the rich central NGC 2244 cluster formed first, and its expanding H II region triggered the formation of the now-unobscured satellite clusters Rosette Molecular Cloud (RMC) XA and NGC 2237. A large swept-up shell material around the H II region is now in a second phase of collect-and-collapse fragmentation, leading to the recent formation of subclusters. Other clusters deeper in the molecular cloud appear unaffected by the

  3. SCUBA-Diving In Nearby Molecular Clouds: Large-Area Mapping of Star-Forming Regions at Sub-millimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Johnstone, D.

    Wide area sub-millimeter mapping of nearby molecular clouds allows for the study of large scale structures such as the Integral Shaped Filament in the Orion A cloud. Examination of these regions suggests that they are not equilibrium isothermal structures but rather require significant, and radially dependent, non-thermal support such as produced by helical magnetic fields Also observed in the large area maps are dense condensations with masses typical for stars. The mass distribution of these clumps is similar to the stellar initial mass function; however, the clumps appear stable against collapse. The clumps are clustered within the cores of molecular clouds and restricted to those locations where the molecular cloud column density is high (A_v > 4). As well, the typical sub-millimeter clump reveals little or no emission from isotopes of CO, likely indicating that the combination of high density and low temperatures within the clumps provides an environment in which these molecules freeze-out onto dust grain surfaces.

  4. Coronal evolution of solar-like stars: X-ray spectroscopy of stars in star- forming regions and the solar neighborhood

    NASA Astrophysics Data System (ADS)

    Telleschi, Alessandra Silvia

    Solar-like stars are strong X-ray emitters in both their pre-main sequence (PMS) and main-sequence (MS) phases. In analogy to the Sun, X-rays are thought to originate in a corona. However, in the case of pre-main sequence stars, accretion processes might influence the X-ray properties of the stars. In this thesis, results from X-ray spectroscopy of main-sequence solar analogs, pre-main sequence solar-like stars and a Herbig Ae/Be star are presented and discussed. All X-ray spectra have been obtained by the Reflection Grating Spectrometers (RGS) and the European Photon Imaging Cameras (EPIC) on board the XMM-Newton satellite. In the first part of the thesis, high-resolution (RGS) X-ray spectra of a sample of six main-sequence G-type stars with ages between [approximate] 0.1 Gyr and [approximate] 1.6 Gyr have been analyzed. Using individual spectral lines, the Emission Measure Distributions (EMD) and the coronal abundances have been derived. As a solar analog evolves, its rotation rate decreases and its internal magnetic dynamo weakens, resulting in a decrease of magnetic activity and a decrease of the star's X-ray luminosity. The mean coronal temperatures derived from the EMDs decrease from [approximate] 10 MK for the youngest stars to [approximate] 4 MK for the oldest star in our stellar sample. These results have been interpreted with a model in which the coronal emission is produced by a superposition of stochastically occurring flares; more active stars are found to require a larger range of flare energies than less active stars. Abundances change from an inverse First Ionization Potential (FIP) effect, where abundances with high FIP are enhanced with respect to abundances with low FIP, to a solar-like FIP effect at ages >= 0.3 Gyr. The analysis has then been extended to pre-main sequence stars in the Taurus- Auriga complex. The results presented here are part of a large survey, the "XMM-Newton Extended Survey of the Taurus Molecular Cloud" (XEST). High- and

  5. Water in star-forming regions with Herschel (WISH). III. Far-infrared cooling lines in low-mass young stellar objects

    NASA Astrophysics Data System (ADS)

    Karska, A.; Herczeg, G. J.; van Dishoeck, E. F.; Wampfler, S. F.; Kristensen, L. E.; Goicoechea, J. R.; Visser, R.; Nisini, B.; San José-García, I.; Bruderer, S.; Śniady, P.; Doty, S.; Fedele, D.; Yıldız, U. A.; Benz, A. O.; Bergin, E.; Caselli, P.; Herpin, F.; Hogerheijde, M. R.; Johnstone, D.; Jørgensen, J. K.; Liseau, R.; Tafalla, M.; van der Tak, F.; Wyrowski, F.

    2013-04-01

    Context. Understanding the physical phenomena involved in the earlierst stages of protostellar evolution requires knowledge of the heating and cooling processes that occur in the surroundings of a young stellar object. Spatially resolved information from its constituent gas and dust provides the necessary constraints to distinguish between different theories of accretion energy dissipation into the envelope. Aims. Our aims are to quantify the far-infrared line emission from low-mass protostars and the contribution of different atomic and molecular species to the gas cooling budget, to determine the spatial extent of the emission, and to investigate the underlying excitation conditions. Analysis of the line cooling will help us characterize the evolution of the relevant physical processes as the protostar ages. Methods. Far-infrared Herschel-PACS spectra of 18 low-mass protostars of various luminosities and evolutionary stages are studied in the context of the WISH key program. For most targets, the spectra include many wavelength intervals selected to cover specific CO, H2O, OH, and atomic lines. For four targets the spectra span the entire 55-200 μm region. The PACS field-of-view covers ~47" with the resolution of 9.4". Results. Most of the protostars in our sample show strong atomic and molecular far-infrared emission. Water is detected in 17 out of 18 objects (except TMC1A), including 5 Class I sources. The high-excitation H2O 818-707 63.3 μm line (Eu/kB = 1071 K) is detected in 7 sources. CO transitions from J = 14-13 up to J = 49 - 48 are found and show two distinct temperature components on Boltzmann diagrams with rotational temperatures of ~350 K and ~700 K. H2O has typical excitation temperatures of ~150 K. Emission from both Class 0 and I sources is usually spatially extended along the outflow direction but with a pattern that depends on the species and the transition. In the extended sources, emission is stronger off source and extended on &≥10,000 AU

  6. Extragalactic stellar populations in the near and mid-infrared: 1-30 mum emission from evolved populations, young and dusty star forming regions and the earliest stellar populations

    NASA Astrophysics Data System (ADS)

    Mentuch, Erin

    2010-11-01

    The near- through mid-infrared offers a unique and, as this thesis aims to show, essential view of extragalactic stellar populations both nearby, at intermediate redshifts and at very high redshift. In chapter 2, I demonstrate that rest-frame near-IR photometry obtained by the Spitzer Space Telescope provides more robust stellar mass estimates for a spectroscopic sample of ˜ 100 galaxies in the redshift desert (0:5 < z < 2), and is crucial for modeling galaxies with young star-forming populations. From this analysis, a surprising result emerges in the data. Although the rest-frame light short of 2 mum improves stellar mass estimates, the models and observations disagree beyond 2 mum and emission from non-stellar sources becomes significant. At wavelengths from 1--30 mum, stellar and non-stellar emission contribute equally to a galaxy's global spectral energy distribution. This is unlike visible wavelengths where stellar emission dominates or the far-IR where dust emission provides the bulk of a galaxy's luminosity. Using the sample of high-z galaxies, in chapter 3, I quantify the statistical significance of the excess emission at 2-5 mum and find the emission to correlate with the O II luminosity, suggesting a link between the excess emission and star formation. The origin of the excess emission is not clear, although I explore a number of non-stellar candidates in this chapter. Nearby resolved observations provide a clearer picture of the excess by spatially resolving 68 nearby galaxies. By analyzing the pixel-by-pixel near-IR colours within each galaxy at ˜1-5 mum, increasingly red near-IR colors are mapped to spatial regions in chapter 4. For regions with red NIR colors and high star formation rates, I find the broad near- through mid-IR spectrum is constant, varying only in amplitude as a function of the intensity of star formation, suggesting the infrared emission of a young, dusty stellar populations can be added to stellar population synthesis models as an

  7. DDT_nnesvadb_4: C+ and H2 spectroscopy of a single star-forming region at z=2.599 recently discovered with Planck/SUCBA2/SPIRE

    NASA Astrophysics Data System (ADS)

    Nesvadba, N.

    2013-02-01

    We request DD time to observe a highly magnified starburst at z=2.599 recently discovered with Planck, which has CO line widths like those of giant molecular clouds in the Milky Way! The velocity gradient and narrowness of the CO lines indicates that we are observing small (a few 10s pc) star forming regions in a distant galaxy due to its extreme magnification and fortuitous alignment with the lensing mass. This is a UNIQUE opportunity to probe a starburst at z=2.5 AT THE SCALE OF SINGLE STAR-FORMING REGIONS. We will measure [CII]158, the main coolant of UV-heated gas and thus, a prime tracer of star formation, and the H2 0-0 S(1) line, the main coolant of shocked gas, a tracer of turbulence dissipation and the warm molecular mass. Only Herschel can observe these important lines. ALMA cannot, and SOFIA cannot. During the formation process of galaxies, strong turbulence is generated with potentially dramatic consequences for the nature of star formation in distant galaxies. For example, if the gas remains turbulent on scales <100 pc, then the global galaxy kinematics (i.e., Toomre stability) no longer stabilizes the gas. What are the consequences for the star formation in such an environment and how does this high level of turbulence during galaxy formation change the nature of galaxies? Through a unique synergy of the Planck all-sky survey, Herschel, and IRAM sub-arcsec DDT interferometry, we have just caught a unique source at z=2.599, G80.3+49.8, with bright FIR continuum akin to dusty high-z starbursts, and surprisingly narrow CO line widths like GMCs in the Milky Way! G80.3+49.8 is truly unique and will become a benchmark for studying the physics regulating intense star formation at high-z. Herschel "last-minute" observations are our only way to quantify the global budgets of UV and shock heating estimated from the main IR cooling lines, both of which are unobservable from the ground, and both critical in linking the details of star formation with the

  8. Organic compounds in star forming regions.

    PubMed

    Kochina, O; Wiebe, D

    2014-09-01

    The influence of complex dust composition on the general chemical evolution of a prestellar core and the content of complex organic compounds is studied. It is shown that various component groups respond differently to the presence of a small dust population. At early stages the difference is determined primarily by changes in the balance of photo processes due to effective absorption of ultraviolet photons by small dust grains of the second population and collisional reactions with dust particles. At later stages differences are also caused by the growing dominance of additional reaction channels related to surface organic synthesis. PMID:25515345

  9. Organic compounds in star forming regions.

    PubMed

    Kochina, O; Wiebe, D

    2014-09-01

    The influence of complex dust composition on the general chemical evolution of a prestellar core and the content of complex organic compounds is studied. It is shown that various component groups respond differently to the presence of a small dust population. At early stages the difference is determined primarily by changes in the balance of photo processes due to effective absorption of ultraviolet photons by small dust grains of the second population and collisional reactions with dust particles. At later stages differences are also caused by the growing dominance of additional reaction channels related to surface organic synthesis.

  10. The ISO View of Star Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Helou, George

    1999-01-01

    ISO studies of normal galaxies in the local Universe have revealed basic new properties whose significant implications for the star formation process and cosmology are only starting to be understood. This review will touch on the general results of a statistical nature, and provide a quick summary of the profusion of exciting results on individual objects. In the mid-infrared, PHT-S has established that the spectra of star forming galaxies between 6 and-13microns are dominated by the Aromatic Features in Emission (AFE), and show little variation as a function of the heating intensity. The Carriers of the AFE (CAFE) are thus a universal component of dust with standard properties, and contribute between 10 and 25% of the total dust luminosity. In addition to AFE, the spectra show a low-level continuum detectable at wavelengths longer than 3.5microns whose origin is still under investigation. The mid-infrared colors formed as the ratio of flux densities in the 6.75micron and the 15micron bands of ISO-CAM remain essentially constant and near unity for quiescent and mildly active galaxies. As dust heating increases further, the 15micron flux increases steeply compared to 6.75microns, indicating that dust heated to 100K

  11. Hubble Space Telescope Hx Imaging of Star-forming Galaxies at z approximately equal to 1-1.5: Evolution in the Size and Luminosity of Giant H II Regions

    NASA Technical Reports Server (NTRS)

    Livermore, R. C.; Jones, T.; Richard, J.; Bower, R. G.; Ellis, R. S.; Swinbank, A. M.; Rigby, J. R.; Smail, Ian; Arribas, S.; Rodriguez-Zaurin, J.; Colina, L.; Ebeling, H.; Crain, R. A.

    2013-01-01

    We present Hubble Space Telescope/Wide Field Camera 3 narrow-band imaging of the Ha emission in a sample of eight gravitationally lensed galaxies at z = 1-1.5. The magnification caused by the foreground clusters enables us to obtain a median source plane spatial resolution of 360 pc, as well as providing magnifications in flux ranging from approximately 10× to approximately 50×. This enables us to identify resolved star-forming HII regions at this epoch and therefore study their Ha luminosity distributions for comparisons with equivalent samples at z approximately 2 and in the local Universe. We find evolution in the both luminosity and surface brightness of HII regions with redshift. The distribution of clump properties can be quantified with an HII region luminosity function, which can be fit by a power law with an exponential break at some cut-off, and we find that the cut-off evolves with redshift. We therefore conclude that 'clumpy' galaxies are seen at high redshift because of the evolution of the cut-off mass; the galaxies themselves follow similar scaling relations to those at z = 0, but their HII regions are larger and brighter and thus appear as clumps which dominate the morphology of the galaxy. A simple theoretical argument based on gas collapsing on scales of the Jeans mass in a marginally unstable disc shows that the clumpy morphologies of high-z galaxies are driven by the competing effects of higher gas fractions causing perturbations on larger scales, partially compensated by higher epicyclic frequencies which stabilize the disc.

  12. Characterizing filaments in regions of high-mass star formation: High-resolution submilimeter imaging of the massive star-forming complex NGC 6334 with ArTéMiS

    NASA Astrophysics Data System (ADS)

    André, Ph.; Revéret, V.; Könyves, V.; Arzoumanian, D.; Tigé, J.; Gallais, P.; Roussel, H.; Le Pennec, J.; Rodriguez, L.; Doumayrou, E.; Dubreuil, D.; Lortholary, M.; Martignac, J.; Talvard, M.; Delisle, C.; Visticot, F.; Dumaye, L.; De Breuck, C.; Shimajiri, Y.; Motte, F.; Bontemps, S.; Hennemann, M.; Zavagno, A.; Russeil, D.; Schneider, N.; Palmeirim, P.; Peretto, N.; Hill, T.; Minier, V.; Roy, A.; Rygl, K. L. J.

    2016-07-01

    Context. Herschel observations of nearby molecular clouds suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. The observations support a picture of low-mass star formation according to which filaments of ~0.1 pc width form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and then prestellar cores arise from gravitational fragmentation of the densest filaments. Whether this scenario also applies to regions of high-mass star formation is an open question, in part because the resolution of Herschel is insufficient to resolve the inner width of filaments in the nearest regions of massive star formation. Aims: In an effort to characterize the inner width of filaments in high-mass star-forming regions, we imaged the central part of the NGC 6334 complex at a resolution higher by a factor of >3 than Herschel at 350 μm. Methods: We used the large-format bolometer camera ArTéMiS on the APEX telescope and combined the high-resolution ArTéMiS data at 350 μm with Herschel/HOBYS data at 70-500 μm to ensure good sensitivity to a broad range of spatial scales. This allowed us to study the structure of the main narrow filament of the complex with a resolution of 8″ or <0.07 pc at d ~ 1.7 kpc. Results: Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ~500 M⊙/pc to ~2000 M⊙/pc over nearly 10 pc. It also demonstrates for the first time that its inner width remains as narrow as W ~ 0.15 ± 0.05 pc all along the filament length, within a factor of <2 of the characteristic 0.1 pc value found with Herschel for lower-mass filaments in the Gould Belt. Conclusions: While it is not completely clear whether the NGC 6334 filament will form massive stars in the future, it is two to three orders of magnitude denser than the majority of filaments observed in Gould Belt

  13. STAR-FORMING GALAXY EVOLUTION IN NEARBY RICH CLUSTERS

    SciTech Connect

    Tyler, K. D.; Rieke, G. H.; Bai, L.

    2013-08-20

    Dense environments are known to quench star formation in galaxies, but it is still unknown what mechanism(s) are directly responsible. In this paper, we study the star formation of galaxies in A2029 and compare it to that of Coma, combining indicators at 24 {mu}m, H{alpha}, and UV down to rates of 0.03 M{sub Sun} yr{sup -1}. We show that A2029's star-forming galaxies follow the same mass-SFR relation as the field. The Coma cluster, on the other hand, has a population of galaxies with star formation rates (SFRs) significantly lower than the field mass-SFR relation, indicative of galaxies in the process of being quenched. Over half of these galaxies also host active galactic nuclei. Ram-pressure stripping and starvation/strangulation are the most likely mechanisms for suppressing the star formation in these galaxies, but we are unable to disentangle which is dominating. The differences we see between the two clusters' populations of star-forming galaxies may be related to their accretion histories, with A2029 having accreted its star-forming galaxies more recently than Coma. Additionally, many early-type galaxies in A2029 are detected at 24 {mu}m and/or in the far-UV, but this emission is not directly related to star formation. Similar galaxies have probably been classified as star forming in previous studies of dense clusters, possibly obscuring some of the effects of the cluster environment on true star-forming galaxies.

  14. Lithopanspermia in star-forming clusters.

    PubMed

    Adams, Fred C; Spergel, David N

    2005-08-01

    This paper considers the lithopanspermia hypothesis in star-forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to action in the field) because of the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses approximately 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed v (eject) and number N(.) of members in the birth aggregate. The odds of any given ejected meteoroid being recaptured by another solar system are relatively low, about 1:10(3)-10(6) over the expected range of ejection speeds and cluster sizes. Because the number of ejected rocks (with mass m > 10 kg) per system can be large, N (R) approximately 10(16), virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that N (B) approximately 10(7) rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life-bearing rocks is expected to occur N (bio) asymptotically equal to 10-16,000 times (per cluster), depending on the ejection speeds. Only a small fraction (f (imp) approximately 10(4)) of the captured rocks impact the surfaces of terrestrial planets, so that N (lps) asymptotically equal to 10(3)-1.6 lithopanspermia events are expected per cluster (under favorable conditions). Finally, we discuss the question of internal versus external seeding of clusters and the possibility of Earth seeding young clusters over its biologically active lifetime.

  15. Lithopanspermia in star-forming clusters.

    PubMed

    Adams, Fred C; Spergel, David N

    2005-08-01

    This paper considers the lithopanspermia hypothesis in star-forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to action in the field) because of the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses approximately 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed v (eject) and number N(.) of members in the birth aggregate. The odds of any given ejected meteoroid being recaptured by another solar system are relatively low, about 1:10(3)-10(6) over the expected range of ejection speeds and cluster sizes. Because the number of ejected rocks (with mass m > 10 kg) per system can be large, N (R) approximately 10(16), virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that N (B) approximately 10(7) rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life-bearing rocks is expected to occur N (bio) asymptotically equal to 10-16,000 times (per cluster), depending on the ejection speeds. Only a small fraction (f (imp) approximately 10(4)) of the captured rocks impact the surfaces of terrestrial planets, so that N (lps) asymptotically equal to 10(3)-1.6 lithopanspermia events are expected per cluster (under favorable conditions). Finally, we discuss the question of internal versus external seeding of clusters and the possibility of Earth seeding young clusters over its biologically active lifetime. PMID:16078868

  16. The Compact Star-forming Complex at the Heart of NGC 253

    NASA Astrophysics Data System (ADS)

    Davidge, T. J.

    2016-02-01

    We discuss integral field spectra of the compact star-forming complex that is the brightest near-infrared (NIR) source in the central regions of the starburst galaxy NGC 253. The spectra cover the H and K passbands and were recorded with the Gemini NIR Spectrograph during subarcsecond seeing conditions. Absorption features in the spectrum of the star-forming complex are weaker than in the surroundings. An absorption feature is found near 1.78 μm that coincides with the location of a C2 bandhead. If this feature is due to C2 then the star-forming complex has been in place for at least a few hundred Myr. Emission lines of Brγ, [Fe ii], and He i 2.06 μm do not track the NIR continuum light. Pockets of star-forming activity that do not have associated concentrations of red supergiants, and so likely have ages <8 Myr, are found along the western edge of the complex, and there is evidence that one such pocket contains a rich population of Wolf-Rayet stars. Unless the star-forming complex is significantly more metal-poor than the surroundings, then a significant fraction of its total mass is in stars with ages <8 Myr. If the present-day star formation rate is maintained then the timescale to double its stellar mass ranges from a few Myr to a few tens of Myr, depending on the contribution made by stars older than ˜8 Myr. If—as suggested by some studies—the star-forming complex is centered on the galaxy’s nucleus, which presumably contains a large population of old and intermediate-age stars, then the nucleus of NGC 253 is currently experiencing a phase of rapid growth in its stellar mass. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  17. The dependence of protostellar luminosity on environment in the Cygnus-X star-forming complex

    SciTech Connect

    Kryukova, E.; Megeath, S. T.; Hora, J. L.; Smith, Howard A.; Gutermuth, R. A.; Bontemps, S.; Schneider, N.; Kraemer, K.; Hennemann, M.; Motte, F.

    2014-07-01

    The Cygnus-X star-forming complex is one of the most active regions of low- and high-mass star formation within 2 kpc of the Sun. Using mid-infrared photometry from the IRAC and MIPS Spitzer Cygnus-X Legacy Survey, we have identified over 1800 protostar candidates. We compare the protostellar luminosity functions of two regions within Cygnus-X: CygX-South and CygX-North. These two clouds show distinctly different morphologies suggestive of dissimilar star-forming environments. We find the luminosity functions of these two regions are statistically different. Furthermore, we compare the luminosity functions of protostars found in regions of high and low stellar density within Cygnus-X and find that the luminosity function in regions of high stellar density is biased to higher luminosities. In total, these observations provide further evidence that the luminosities of protostars depend on their natal environment. We discuss the implications this dependence has for the star formation process.

  18. Water in star-forming regions with Herschel (WISH). VI. Constraints on UV and X-ray irradiation from a survey of hydrides in low- to high-mass young stellar objects

    NASA Astrophysics Data System (ADS)

    Benz, A. O.; Bruderer, S.; van Dishoeck, E. F.; Melchior, M.; Wampfler, S. F.; van der Tak, F.; Goicoechea, J. R.; Indriolo, N.; Kristensen, L. E.; Lis, D. C.; Mottram, J. C.; Bergin, E. A.; Caselli, P.; Herpin, F.; Hogerheijde, M. R.; Johnstone, D.; Liseau, R.; Nisini, B.; Tafalla, M.; Visser, R.; Wyrowski, F.

    2016-05-01

    Context. Hydrides are simple compounds containing one or a few hydrogen atoms bonded to a heavier atom. They are fundamental precursor molecules in cosmic chemistry and many hydride ions have become observable in high quality for the first time thanks to the Herschel Space Observatory. Ionized hydrides such as CH+ and OH+ (and also HCO+), which affect the chemistry of molecules such as water, provide complementary information on irradiation by far-UV (FUV) or X-rays and gas temperature. Aims: We explore hydrides of the most abundant heavier elements in an observational survey covering young stellar objects (YSOs) with different mass and evolutionary state. The focus is on hydrides associated with the dense protostellar envelope and outflows, contrary to previous work that focused on hydrides in diffuse foreground clouds. Methods: Twelve YSOs were observed with HIFI on Herschel in six spectral settings providing fully velocity-resolved line profiles as part of the Water in star-forming regions with Herschel (WISH) program. The YSOs include objects of low (Class 0 and I), intermediate, and high mass, with luminosities ranging from 4 L⊙ to 2 × 105 L⊙. Results: The targeted lines of CH+, OH+, H2O+, C+, and CH are detected mostly in blue-shifted absorption. H3O+ and SH+ are detected in emission and only toward some high-mass objects. The observed line parameters and correlations suggest two different origins related to gas entrained by the outflows and to the circumstellar envelope. The derived column densities correlate with bolometric luminosity and envelope mass for all molecules, best for CH, CH+, and HCO+. The column density ratios of CH+/OH+ are estimated from chemical slab models, assuming that the H2 density is given by the specific density model of each object at the beam radius. For the low-mass YSOs the observed ratio can be reproduced for an FUV flux of 2-400 times the interstellar radiation field (ISRF) at the location of the molecules. In two high

  19. Ammonia thermometry of star-forming galaxies

    SciTech Connect

    Mangum, Jeffrey G.; MacGregor, Meredith; Svoboda, Brian E.; Darling, Jeremy; Henkel, Christian; Menten, Karl M.; Schinnerer, Eva E-mail: mmacgreg@fas.harvard.edu E-mail: jdarling@origins.colorado.edu E-mail: kmenten@mpifr-bonn.mpg.de

    2013-12-10

    With a goal toward deriving the physical conditions in external galaxies, we present a study of the ammonia (NH{sub 3}) emission and absorption in a sample of star-forming systems. Using the unique sensitivities to kinetic temperature afforded by the excitation characteristics of several inversion transitions of NH{sub 3}, we have continued our characterization of the dense gas in star-forming galaxies by measuring the kinetic temperature in a sample of 23 galaxies and one galaxy offset position selected for their high infrared luminosity. We derive kinetic temperatures toward 13 galaxies, 9 of which possess multiple kinetic temperature and/or velocity components. Eight of these galaxies exhibit kinetic temperatures >100 K, which are in many cases at least a factor of two larger than kinetic temperatures derived previously. Furthermore, the derived kinetic temperatures in our galaxy sample, which are in many cases at least a factor of two larger than derived dust temperatures, point to a problem with the common assumption that dust and gas kinetic temperatures are equivalent. As previously suggested, the use of dust emission at wavelengths greater than 160 μm to derive dust temperatures, or dust heating from older stellar populations, may be skewing derived dust temperatures in these galaxies to lower values. We confirm the detection of high-excitation OH {sup 2}Π{sub 3/2} J = 9/2 absorption toward Arp 220. We also report the first detections of non-metastable NH{sub 3} inversion transitions toward external galaxies in the (2,1) (NGC 253, NGC 660, IC 342, and IC 860), (3,1), (3,2), (4,3), (5,4) (all in NGC 660), and (10,9) (Arp 220) transitions.

  20. After the Interaction: an Efficiently Star-forming Molecular Disk in NGC 5195

    NASA Astrophysics Data System (ADS)

    Alatalo, Katherine; Aladro, Rebeca; Nyland, Kristina; Aalto, Susanne; Bitsakis, Theodoros; Gallagher, John S.; Lanz, Lauranne

    2016-10-01

    We present new molecular gas maps of NGC 5195 (alternatively known as M51b) from the Combined Array for Research in Millimeter Astronomy, including 12CO(1–0), 13CO(1–0), CN(1{}{0,2}–{0}{0,1}), CS(2–1), and 3 mm continuum. We also detected HCN(1–0) and HCO+(1–0) using the Onsala Space Observatory. NGC 5195 has a 12CO/13CO ratio ({{ R }}12/13 = 11.4 ± 0.5) consistent with normal star-forming galaxies. The CN(1–0) intensity is higher than is seen in an average star-forming galaxy, possibly enhanced in the diffuse gas in photo-dissociation regions. Stellar template fitting of the nuclear spectrum of NGC 5195 shows two stellar populations: an 80% mass fraction of old (≳10 Gyr) and a 20% mass fraction of intermediate-aged (≈1 Gyr) stellar populations. This provides a constraint on the timescale over which NGC 5195 experienced enhanced star formation during its interaction with M51a. The average molecular gas depletion timescale in NGC 5195 is < {τ }{dep}> = 3.08 Gyr, a factor of ≈ 2 larger than the depletion timescales in nearby star-forming galaxies, but consistent with the depletion seen in CO-detected early-type galaxies. While radio continuum emission at centimeter and millimeter wavelengths is present in the vicinity of the nucleus of NGC 5195, we find it is most likely associated with nuclear star formation rather than radio-loud AGN activity. Thus, despite having a substantial interaction with M51a ∼1/2 Gyr ago, the molecular gas in NGC 5195 has resettled and is currently forming stars at an efficiency consistent with settled early-type galaxies.

  1. Motions and Initial Conditions in Star-Forming Dense Cores

    NASA Technical Reports Server (NTRS)

    Myers, Philip C.

    2004-01-01

    The main focus was the study of star-forming regions through high spectral- and spatial resolution observations of mm-wavelength lines, and through models of the observations. The main accomplishments were a) demonstration that more than 15 starless cores show substantial evidence of extended inward motion at about half the sound speed; b) observations of infall asymmetry in several cores, in lines of N2H(+) and DCO(+), low- depletion tracers of the "inner core"; c) observation of "infall asymmetry" of spectral lines over approx. 0.5 pc in the NGC1333 cluster-forming region; d) observations indicating that cores are nearly at rest with respect to their envelopes; and e) development of analytic, power-series solutions to the equations of motions for condensing 1-D systems (layers, cylinders and spheres).

  2. DISTRIBUTIONS OF LONG-LIVED RADIOACTIVE NUCLEI PROVIDED BY STAR-FORMING ENVIRONMENTS

    SciTech Connect

    Fatuzzo, Marco; Adams, Fred C.

    2015-11-01

    Radioactive nuclei play an important role in planetary evolution by providing an internal heat source, which affects planetary structure and helps facilitate plate tectonics. A minimum level of nuclear activity is thought to be necessary—but not sufficient—for planets to be habitable. Extending previous work that focused on short-lived nuclei, this paper considers the delivery of long-lived radioactive nuclei to circumstellar disks in star forming regions. Although the long-lived nuclear species are always present, their abundances can be enhanced through multiple mechanisms. Most stars form in embedded cluster environments, so that disks can be enriched directly by intercepting ejecta from supernovae within the birth clusters. In addition, molecular clouds often provide multiple episodes of star formation, so that nuclear abundances can accumulate within the cloud; subsequent generations of stars can thus receive elevated levels of radioactive nuclei through this distributed enrichment scenario. This paper calculates the distribution of additional enrichment for {sup 40}K, the most abundant of the long-lived radioactive nuclei. We find that distributed enrichment is more effective than direct enrichment. For the latter mechanism, ideal conditions lead to about 1 in 200 solar systems being directly enriched in {sup 40}K at the level inferred for the early solar nebula (thereby doubling the abundance). For distributed enrichment from adjacent clusters, about 1 in 80 solar systems are enriched at the same level. Distributed enrichment over the entire molecular cloud is more uncertain, but can be even more effective.

  3. An atlas of ultraviolet spectra of star-forming galaxies

    NASA Technical Reports Server (NTRS)

    Kinney, A. L.; Bohlin, R. C.; Calzetti, D.; Panagia, N.; Wyse, Rosemary F. G.

    1993-01-01

    A systematic study is presented of the UV spectra of star-forming galaxies of different morphological type and activity class using a sample drawn from a uniformly reduced IUE data set. The spectra for a wide variety of galaxies, including normal spiral, LINER, starburst, blue compact, blue compact dwarf, and Seyfert 2 galaxies, are presented in the form of spectral energy distributions to demonstrate the overall characteristics according to morphology and activity class and in the form of absolute flux distributions to better show the absorption and emission features of individual objects. The data support the picture based on UV spectra of the Orbiting Astronomical Observatory and of the Astronautical Netherlands Satellite that spiral galaxies of later Hubble class have more flux at the shortest UV wavelengths than do spiral galaxies of earlier Hubble class.

  4. Study of the Cygnus Star-Forming Field

    NASA Astrophysics Data System (ADS)

    Christopherson, Christopher; Kaltcheva, Nadia

    2016-01-01

    The star-forming complexes in Cygnus extend nearly 30 deg in Galactic longitude and 20 deg in latitude, and most probably include star-formation sites located between 600 and 4000 pc. We combine the catalog by Heiles (2000) with uvbyβ photometric data from the catalog of Paunzen (2015) to collate a sample of O and B-type stars with precise homogeneous distances, color excess and available polarimetry. This allows us to identify star-forming sites at different distances along the line of sight and to investigate their spatial correlation to the interstellar matter. Further, we use this sample to study the orientation of the polarization as revealed by the polarized light of the bright early-type stars and analyze the polarization-extinction correlation for this field. Since dust grains align in the presence of a magnetic field cause the observed polarization at optical wavelengths, the data contain information about the large-scale component of the Galactic magnetic field. In addition, wide-field astrophotography equipment was used to image the Cygnus field in Hydrogen-alpha, Hydrogen-beta and the [OIII] line at 500.7 nm. This allows us to map the overall distribution of ionized material and the interstellar dust and trace large-scale regions where the physical conditions change rapidly due to supernova shock fronts and strong stellar winds. Acknowledgments: This work was supported by NSF grant AST- 1516932 and the Wisconsin Space Grant Consortium, NASA Space Grant College and Fellowship Program, NASA Training Grant #NNX14AP22H.

  5. VizieR Online Data Catalog: Star-forming galaxies in near-IR (Martins+, 2013)

    NASA Astrophysics Data System (ADS)

    Martins, L. P.; Rodriguez-Ardila, A.; Diniz, S.; Riffel, R.; de Souza, R.

    2014-10-01

    The sample used here was presented in Martins et al. (2013MNRAS.431.1823M) and is a subset of the one presented in the magnitude-limited optical spectroscopic survey of nearby bright galaxies of Ho, Filippenko & Sargent (1995, Cat. J/ApJS/98/477, hereafter HO95). These galaxies are sources defined by Ho, Filippenko & Sargent (1997, Cat. J/ApJS/112/315, hereafter HO97) as those composed of 'nuclei dominated by emission lines from regions of active star formation (HII or starburst nuclei)'. In addition, five galaxies, classified as non-star forming in the optical, dominated by old stellar population and with no detected emission lines, were included as a control sample. All spectra were obtained at the NASA 3m Infrared Telescope Facility (IRTF) in two observing runs (2007 and 2008) - the same data from Martins et al. (2013MNRAS.431.1823M). (2 data files).

  6. The COMPLETE Survey of Nearby Star-Forming Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Di Francesco, J.; Goodman, A. A.; Alves, J.; Arce, H.; Caselli, P.; Heyer, M. H.; Johnstone, D.; Schnee, S.; Tafalla, M.; Wilson, T. L.

    2002-12-01

    We report on the preliminary data and ongoing progress of the COMPLETE* Survey of Nearby Star-Forming Molecular Clouds, an international effort to provide the astronomical community with uniform, wide-field observations of molecular line emission, dust continuum emission, and dust extinction across the Ophiuchus, Perseus, and Serpens molecular clouds. Such observations of ~10 square degrees are now only feasible with the recent simultaneous availability of multi-element mapping instruments at various facilities. Extensive data of 12CO and 13CO J = 1-0 rotational transition emission across the 3 clouds will be obtained this winter using the 32-element SEQUOIA array of the Five College Radio Astronomy Observatory (FCRAO). Complementary 850 micron thermal continuum emission from dust within these same regions may be obtained this winter using the 37-element Long-Wave SCUBA array of the James Clerk Maxwell Telescope (JCMT). Dust extinction maps of these regions are being compiled initially using Two-Micron All Sky Survey (2MASS) data. The resulting COMPLETE database, accessible freely to the public through a pilot program of the National Virtual Observatory, will allow for comprehensive studies of the relationships between star formation and the physical conditions within molecular clouds, especially in conjunction with sensitive near- to mid-infrared data of these regions expected from the SIRTF Legacy program ``Cores to Disks" (c2d). (* COMPLETE = CO-ordinated Molecular Probe Line, Thermal Emission, and Extinction)

  7. Metallicity gradients and newly created star-forming systems in interacting galaxies

    NASA Astrophysics Data System (ADS)

    Mendes de Oliveira, Claudia L.

    2015-08-01

    Interactions play an extremely important role in the evolution of galaxies, changing their morphologies and kinematics. Galaxy collisions may result in the formation of intergalactic star-forming objects, such as HII regions, young clusters and/or tidal dwarf galaxies. Several studies have found a wealth of newly created objects in interacting systems. We will exemplify the problems and challenges in this field and will describe observations of the interacting group NGC 6845, which contains four bright galaxies, two of which have extended tidal tails. We obtained Gemini/GMOS spectra for 28 of the regions located in the galaxies and in the tails. All regions in the latter are star-forming objects according to their line ratios, with ages younger than 10 Myr. A super luminous star forming complex is found in the brightest member of the group, NGC 6845A. Its luminosity reveals a star formation density of 0.19 solar masses, per year, per kpc^2, suggesting that this object is a localized starburst. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. We speculate that the observed metallicity gradient may be related to one or more of the following mechanisms: (1) interaction induced inflow of fresh gas to the galaxy center, as seen in simulations, which is expected to dilute the metallicity of the central burst, (2) the formation of young metal-rich star forming regions in the tidal tails, which were born out of enriched gas expelled from the central regions of the system during the interaction and (3) the incremental growth of metals accumulated over time, due to the successful generations of star forming regions along the tails. Finally we will describe our plans to do a search for such objects on Halpha images that will soon be available for 17.5k degrees of the sky, with the A-PLUS survey.

  8. Stars Form Surprisingly Close to Milky Way's Black Hole

    NASA Astrophysics Data System (ADS)

    2005-10-01

    million low mass, sun-like stars in and around the ring, whereas in the disk model, the number of low mass stars could be much less. Nayakshin and his coauthor, Rashid Sunyaev of the Max Plank Institute for Physics in Garching, Germany, used Chandra observations to compare the X-ray glow from the region around Sgr A* to the X-ray emission from thousands of young stars in the Orion Nebula star cluster. They found that the Sgr A* star cluster contains only about 10,000 low mass stars, thereby ruling out the migration model. "We can now say that the stars around Sgr A* were not deposited there by some passing star cluster, rather they were born there," said Sunyaev . "There have been theories that this was possible, but this is the first real evidence. Many scientists are going to be very surprised by these results." Because the Galactic Center is shrouded in dust and gas, it has not been possible to look for the low-mass stars in optical observations. In contrast, X-ray data have allowed astronomers to penetrate the veil of gas and dust and look for these low mass stars. Scenario Dismissed by Chandra Results Scenario Dismissed by Chandra Results "In one of the most inhospitable places in our Galaxy, stars have prevailed," said Nayakshin. "It appears that star formation is much more tenacious than we previously believed." The results suggest that the "rules" of star formation change when stars form in the disk of a giant black hole. Because this environment is very different from typical star formation regions, there is a change in the proportion of stars that form. For example, there is a much higher percentage of massive stars in the disks around black holes. And, when these massive stars explode as supernovae, they will "fertilize" the region with heavy elements such as oxygen. This may explain the large amounts of such elements observed in the disks of young supermassive black holes. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for

  9. Motions and Initial Conditions in Star-Forming Dense Cores

    NASA Technical Reports Server (NTRS)

    Myers, Philip C.

    2001-01-01

    Under this grant in the past year we have pursued spectral-line observations of star-forming regions over size scales from 0.01 pc to 0.5 pc. Our main goal has been to measure the systematic and turbulent motions of condensing and collapsing gas. In this area, our results include (1) in 67 starless dense cores, some 19 show clear evidence of spatially extended inward motions, with typical line-of-sight inward speed 0.05-0.09 km s(sup -1) and with typical plane-of-the-sky extent 0.1-0.3 pc, (2) In some 40 nearby regions with embedded groups and clusters, we see extended infall asymmetry in lines of CS and HCO(+) clearly in 4 regions and less clearly in 4 others, (3) Using finer resolution (15 arcsec or 0.01-0.02 pc) and lines tracing higher density, we see spatial concentration of infall asymmetry near the protostars in NGC 1333 IRS 4A and B, L483, and L1251B, and with still finer resolution (2 arcsec or 0.003 pc or 600 AU) we detect inverse P Cyg profiles, indicating absorption of continuum emission from the protostellar envelope by infalling gas in NGC 1333 IRS 4A and 4B. Further, at high resolution we identify regions of stellar mass and low turbulence ("kernels") which are good candidates to become the next generation of stars in embedded clusters. In addition we have completed a survey for the OH Zeeman effect in absorption against nearby H II regions, indicating that the large-scale magnetic field may be nearly critical if it typically threads a flattened structure. We have also developed a model of spatially extended infall motions based on dissipation of turbulence in a magnetized, selfgravitating layer. In the following we describe some of these results in more detail.

  10. Isolated Star-Forming Cloud Discovered in Intracluster Space

    NASA Astrophysics Data System (ADS)

    2003-01-01

    galaxies, Messier 86 and Messier 84, indicate the presence of other isolated HII regions, thus suggesting that isolated star formation may occur more generally in galaxies. If so, this process may provide a natural explanation to the current riddle why some young stars are found high up in the halo of our own Milky Way galaxy, far from the star-forming clouds in the main plane. The Virgo Cluster ESO PR Photo 04a/03 ESO PR Photo 04a/03 [Preview - JPEG: 400 x 428 pix - 74k [Normal - JPEG: 800 x 855 pix - 408k] [Hi-Res - JPEG: 4252 x 4544 pix - 10.3M] ESO PR Photo 04b/03 ESO PR Photo 04b/03 [Preview - JPEG: 433 x 400 pix - 60k [Normal - JPEG: 865 x 800 pix - 456k] [Hi-Res - JPEG: 3077 x 2847 pix - 4.2M] Captions: PR Photo 04a/03 displays a sky field near some of the brighter galaxies in the Virgo Cluster. It was obtained in April 2000 with the Wide Field Imager (WFI) at the La Silla Observatory (exposure 6 x 5 min; red R-band; seeing 1.3 arcsec). The large elliptical galaxy at the centre is Messier 84; the elongated image of NGC 4388 (an active spiral galaxy, seen from the side) is in the lower left corner. The field measures 16.9 x 15.7 arcmin2. PR Photo 04b/03 shows a larger region of the Virgo cluster, with the galaxies Messier 86 (at the upper edge of the field, to the left of the centre), as well as Messier 84 (upper right) and NGC 4388 (just below the centre) that are also seen in PR Photo 04a/03. It is reproduced from a long-exposure Subaru Suprime-Cam image, obtained in the red light of ionized hydrogen (the H-alpha spectral line at wavelength 656.2 nm). In order to show the faintest possible hydrogen emitting objects embedded in the outskirts of bright galaxies, their smooth envelopes have been "subtracted" during the image processing. The field measures 34 x 27 arcmin2. Part of this sky field is shown in colour in PR Photo 04c/03. Captions: PR Photo 04a/03 displays a sky field near some of the brighter galaxies in the Virgo Cluster. It was obtained in April 2000

  11. Far-ultraviolet morphology of star-forming filaments in cool core brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Tremblay, G. R.; O'Dea, C. P.; Baum, S. A.; Mittal, R.; McDonald, M. A.; Combes, F.; Li, Y.; McNamara, B. R.; Bremer, M. N.; Clarke, T. E.; Donahue, M.; Edge, A. C.; Fabian, A. C.; Hamer, S. L.; Hogan, M. T.; Oonk, J. B. R.; Quillen, A. C.; Sanders, J. S.; Salomé, P.; Voit, G. M.

    2015-08-01

    We present a multiwavelength morphological analysis of star-forming clouds and filaments in the central (≲50 kpc) regions of 16 low-redshift (z < 0.3) cool core brightest cluster galaxies. New Hubble Space Telescope imaging of far-ultraviolet continuum emission from young (≲10 Myr), massive (≳5 M⊙) stars reveals filamentary and clumpy morphologies, which we quantify by means of structural indices. The FUV data are compared with X-ray, Lyα, narrow-band Hα, broad-band optical/IR, and radio maps, providing a high spatial resolution atlas of star formation locales relative to the ambient hot (˜107-8 K) and warm ionized (˜104 K) gas phases, as well as the old stellar population and radio-bright active galactic nucleus (AGN) outflows. Nearly half of the sample possesses kpc-scale filaments that, in projection, extend towards and around radio lobes and/or X-ray cavities. These filaments may have been uplifted by the propagating jet or buoyant X-ray bubble, or may have formed in situ by cloud collapse at the interface of a radio lobe or rapid cooling in a cavity's compressed shell. The morphological diversity of nearly the entire FUV sample is reproduced by recent hydrodynamical simulations in which the AGN powers a self-regulating rain of thermally unstable star-forming clouds that precipitate from the hot atmosphere. In this model, precipitation triggers where the cooling-to-free-fall time ratio is tcool/tff ˜ 10. This condition is roughly met at the maximal projected FUV radius for more than half of our sample, and clustering about this ratio is stronger for sources with higher star formation rates.

  12. Submillimeter Array Observations Toward the Massive Star-forming Core MM1 of W75N

    NASA Astrophysics Data System (ADS)

    Minh, Y. C.; Su, Y.-N.; Chen, H.-R.; Liu, S.-Y.; Yan, C.-H.; Kim, S.-J.

    2010-11-01

    The massive star-forming core MM1 of W75N was observed using the Submillimeter Array with ~1'' and 2'' spatial resolutions at 217 and 347 GHz, respectively. From the 217 GHz continuum we found that the MM1 core consists of two sources, separated by about 1'': MM1a (~0.6 M sun) and MM1b (~1.4 M sun), located near the radio continuum sources VLA 2/VLA 3 and VLA 1, respectively. Within MM1b, two gas clumps were found to be expanding away from VLA 1 at about ±3 km s-1, as a result of the most recent star formation activity in the region. Observed molecular lines show emission peaks at two positions, MM1a and MM1b: sulfur-bearing species have emission peaks toward MM1a, but methanol and saturated species at MM1b. We identified high-temperature (~200 K) gas toward MM1a and the hot core in MM1b. This segregation may result from the evolution of the massive star-forming core. In the very early phase of star formation, the hot core is seen through the evaporation of dust ice-mantle species. As the mantle species are consumed via evaporation the high-temperature gas species (such as the sulfur-bearing molecules) become bright. The SiO molecule is unique in having an emission peak exactly at the VLA 2 position, probably tracing a shock powered by VLA 2. The observed sulfur-bearing species show similar abundances both in MM1a and MM1b, whereas the methanol and saturated species show significant abundance enhancement toward MM1b, by about an order of magnitude, compared to MM1a.

  13. Merger Signatures in the Dynamics of Star-forming Gas

    NASA Astrophysics Data System (ADS)

    Hung, Chao-Ling; Hayward, Christopher C.; Smith, Howard A.; Ashby, Matthew L. N.; Lanz, Lauranne; Martínez-Galarza, Juan R.; Sanders, D. B.; Zezas, Andreas

    2016-01-01

    The recent advent of integral field spectrographs and millimeter interferometers has revealed the internal dynamics of many hundreds of star-forming galaxies. Spatially resolved kinematics have been used to determine the dynamical status of star-forming galaxies with ambiguous morphologies, and constrain the importance of galaxy interactions during the assembly of galaxies. However, measuring the importance of interactions or galaxy merger rates requires knowledge of the systematics in kinematic diagnostics and the visible time with merger indicators. We analyze the dynamics of star-forming gas in a set of binary merger hydrodynamic simulations with stellar mass ratios of 1:1 and 1:4. We find that the evolution of kinematic asymmetries traced by star-forming gas mirrors morphological asymmetries derived from mock optical images, in which both merger indicators show the largest deviation from isolated disks during strong interaction phases. Based on a series of simulations with various initial disk orientations, orbital parameters, gas fractions, and mass ratios, we find that the merger signatures are visible for ˜0.2-0.4 Gyr with kinematic merger indicators but can be approximately twice as long for equal-mass mergers of massive gas-rich disk galaxies designed to be analogs of z ˜ 2-3 submillimeter galaxies. Merger signatures are most apparent after the second passage and before the black holes coalescence, but in some cases they persist up to several hundred Myr after coalescence. About 20%-60% of the simulated galaxies are not identified as mergers during the strong interaction phase, implying that galaxies undergoing violent merging process do not necessarily exhibit highly asymmetric kinematics in their star-forming gas. The lack of identifiable merger signatures in this population can lead to an underestimation of merger abundances in star-forming galaxies, and including them in samples of star-forming disks may bias the measurements of disk properties such

  14. Boxy Hα emission profiles in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Chen, Yan-Mei; Gu, Qiu-Sheng; Tremonti, Christy A.; Shi, Yong; Jin, Yifei

    2016-07-01

    We assemble a sample of disc star-forming galaxies from the Sloan Digital Sky Survey Data Release 7, studying the structure of Hα emission lines, finding a large fraction of this sample contains boxy Hα line profiles. This fraction depends on galaxy physical and geometric parameters in the following way: (1) it increases monotonically with star formation rate per unit area (ΣSFR), and stellar mass (M*), with the trend being much stronger with M*, from ˜0 per cent at M* = 1010 M⊙ to about 50 per cent at M* = 1011 M⊙; (2) the fraction is much smaller in face-on systems than in edge-on systems. It increases with galaxy inclination (i) while i < 60° and is roughly a constant of 25 per cent beyond this range; (3) for the sources which can be modelled well with two velocity components, blueshifted and redshifted from the systemic velocity, these is a positive correlation between the velocity difference of these two components and the stellar mass, with a slope similar to the Tully-Fisher relation; (4) the two components are very symmetric in the mean, both in velocity and in amplitude. The four findings listed above can be understood as a natural result of a rotating galaxy disc with a kpc-scale ring-like Hα emission region.

  15. Herschel Dust Temperatures of High-Mass Star Forming Cores

    NASA Astrophysics Data System (ADS)

    Jackson, James

    We request NASA ADAP support to infer the evolutionary state, luminosities, and masses of 3,000 star-forming dense molecular cores using Herschel Hi-GAL data. The target cores are selected from the 870 μm ATLASGAL survey to host the early stages of high-mass star formation and to span the complete range of their early evolutionary stages. All 3,000 of these cores will be mapped in the Millimeter Astronomy Legacy Team 90 GHz Survey (MALT90), a new project designed to simultaneously image 16 molecular lines near 90 GHz. The dust temperatures derived from the Hi-GAL data will provide the key diagnostic of the evolutionary phase, as the cores evolve due to heating by the embedded young stars from the earliest cold "starless cores," to intermediate temperature "protostellar cores," and finally on to "hot cores" and H II regions. We will correlate the evolutionary state indicated by the Hi-GAL dust temperatures with the chemical and kinematic information supplied by the MALT 90 molecular line survey. Moreover, since MALT 90 data provides kinematic distances, the Hi-GAL submm/FIR spectral energy distributions will also provide the luminosity and mass distributions of dense cores. This project will allow for the first time a complete and robust characterization of the physical evolution of dense cores. Since this project studies the formation of high-mass stars, it bears directly on NASA's Origins theme.

  16. Star-forming regions at the periphery of the supershell surrounding the Cyg OB1 association - I. The star cluster vdB 130 and its ambient gas and dust medium

    NASA Astrophysics Data System (ADS)

    Sitnik, T. G.; Egorov, O. V.; Lozinskaya, T. A.; Moiseev, A. V.; Rastorguev, A. S.; Tatarnikov, A. M.; Tatarnikova, A. A.; Wiebe, D. S.; Zabolotskikh, M. V.

    2015-12-01

    Stellar population and the interstellar gas-dust medium in the vicinity of the open star cluster vdB 130 are analysed using optical observations taken with the 6 m telescope of the Special Astrophysical Observatory of Russian Academy of Sciences and the 125 cm telescope of the Sternberg Astronomical Institute, Lomonosov Moscow State University along with the data of Spitzer and Herschel. Based on proper motions and BV and JHKs Two Micron All Sky Survey photometric data, we select additional 36 stars as probable cluster members. Some stars in vdB 130 are classified as B stars. Our estimates of minimum colour excess, apparent distance modulus and the distance are consistent with young age (from 5 to 10 Myr) of the cluster vdB 130. We suppose the large deviations from the conventional extinction law in the cluster direction, with RV ˜ 4-5. The cluster vdB 130 appears to be physically related to the supershell around Cyg OB1, a cometary CO cloud, ionized gas and regions of infrared emission. There are a few regions of bright mid-infrared emission in the vicinity of vdB 130. The largest of them is also visible on Hα and [S II] emission maps. We suggest that the infrared blobs that coincide in projection with the head of the molecular cloud are H II regions, excited by the cluster B stars. Some signatures of a shock front are identified between these IR-bright regions.

  17. HUBBLE SPIES HUGE CLUSTERS OF STARS FORMED

    NASA Technical Reports Server (NTRS)

    2002-01-01

    BY ANCIENT ENCOUNTER This stunningly beautiful image [right] taken with the NASA Hubble Space Telescope shows the heart of the prototypical starburst galaxy M82. The ongoing violent star formation due to an ancient encounter with its large galactic neighbor, M81, gives this galaxy its disturbed appearance. The smaller picture at upper left shows the entire galaxy. The image was taken in December 1994 by the Kitt Peak National Observatory's 0.9-meter telescope. Hubble's view is represented by the white outline in the center. In the Hubble image, taken by the Wide Field and Planetary Camera 2, the huge lanes of dust that crisscross M82's disk are another telltale sign of the flurry of star formation. Below the center and to the right, a strong galactic wind is spewing knotty filaments of hydrogen and nitrogen gas. More than 100 super star clusters -- very bright, compact groupings of about 100,000 stars -- are seen in this detailed Hubble picture as white dots sprinkled throughout M82's central region. The dark region just above the center of the picture is a huge dust cloud. A collaboration of European and American scientists used these clusters to date the ancient interaction between M82 and M81. About 600 million years ago, a region called 'M82 B' (the bright area just below and to the left of the central dust cloud) exploded with new stars. Scientists have discovered that this ancient starburst was triggered by the violent encounter with M81. M82 is a bright (eighth magnitude), nearby (12 million light-years from Earth) galaxy in the constellation Ursa Major (the Great Bear). The Hubble picture was taken Sept. 15, 1997. The natural-color composite was constructed from three Wide Field and Planetary Camera 2 exposures, which were combined in chromatic order: 4,250 seconds through a blue filter (428 nm); 2,800 seconds through a green filter (520 nm); and 2,200 seconds through a red (820 nm) filter. Credits for Hubble image: NASA, ESA, R. de Grijs (Institute of

  18. Modeling abundances in star forming galaxies

    NASA Astrophysics Data System (ADS)

    Kobayashi, Chiaki

    2015-08-01

    Heavy elements are produced from various types of supernovae (and AGB stars). I first show that elemental abundances of extremely metal-poor stars are consistent not with pair-instability supernovae but with faint supernovae. Then I introduce subclasses of Type Ia supernovae such as SN 2002cx-like objects and sub-Chandrasekhar mass explosions. These "minor" supernovae are important in the early Universe or metal-poor systems such as dwarf spheroidal galaxies. With "major" chemical enrichment sources, I show cosmic chemical enrichment in our cosmological, hydrodynamical simulations. The feedback from active galactic nuclei (AGN) is also included with a new model for the formation of black holes motivated by the first star formation. AGN-driven outflows transport metals into the circumgalactic medium and the intergalactic medium. Nonetheless, the metallicity changes of galaxies are negligible, and the mass-metallicity relations, which are mainly generated by supernova feedback at the first star burst, are preserved. Within galaxies, metallicity radial gradients are produced, which can be affected by AGN feedback but are more sensitive to the merging histories. We find a weak correlation between the gradients and galaxy mass, which is consistent with available observations. These simulations also provide predictions of supernova/hypernova/GRB rates and the properties of their host galaxies.

  19. The global chemical properties of high-mass star forming clumps at different evolutionary stages

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-Jun; Zhou, Jian-Jun; Esimbek, Jarken; He, Yu-Xin; Li, Da-Lei; Tang, Xin-Di; Ji, Wei-Guang; Yuan, Ye; Guo, Wei-Hua

    2016-06-01

    A total of 197 relatively isolated high-mass star-forming clumps were selected from the Millimeter Astronomy Legacy Team 90 GHz (MALT90) survey data and their global chemical evolution investigated using four molecular lines, N2H+ (1--0), HCO+ (1--0), HCN (1-0), and HNC (1-0). The results suggest that the global averaged integrated intensity ratios I(HCO+)/I(HNC), I(HCN)/I(HNC), I(N2H+)/I(HCO+), and I(N2H+)/ I(HCN) are promising tracers for evolution of high-mass star-forming clumps. The global averaged column densities and abundances of N2H+, HCO+, HCN, and HNC increase as clumps evolve. The global averaged abundance ratios X(HCN)/X(HNC) could be used to trace evolution of high-mass star forming clumps, X(HCO+)/X(HNC) is more suitable for distinguishing high-mass star-forming clumps in prestellar (stage A) from those in protostellar (stage B) and HII/PDR region (stage C). These results suggest that the global averaged integrated intensity ratios between HCN (1-0), HNC (1-0), HCO+ (1--0) and N2H+ (1--0) are more suitable for tracing the evolution of high-mass star forming clumps. We also studied the chemical properties of the target high-mass star-forming clumps in each spiral arm of the Galaxy, and got results very different from those above. This is probably due to the relatively small sample in each spiral arm. For high-mass star-forming clumps in Sagittarius arm and Norma-Outer arm, comparing two groups located on one arm with different Galactocentric distances, the clumps near the Galactic Center appear to be younger than those far from the Galactic center, which may be due to more dense gas concentrated near the Galactic Center, and hence more massive stars being formed there.

  20. Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Izotov, Y. I.; Schaerer, D.; Thuan, T. X.; Worseck, G.; Guseva, N. G.; Orlitová, I.; Verhamme, A.

    2016-10-01

    Following our first detection reported in Izotov et al., we present the detection of Lyman continuum (LyC) radiation of four other compact star-forming galaxies observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope. These galaxies, at redshifts of z ˜ 0.3, are characterized by high emission-line flux ratios [O III] λ5007/[O II] λ3727 ≳ 5. The escape fractions of the LyC radiation fesc(LyC) in these galaxies are in the range of ˜6-13 per cent, the highest values found so far in low-redshift star-forming galaxies. Narrow double-peaked Ly α emission lines are detected in the spectra of all four galaxies, compatible with predictions for LyC leakers. We find escape fractions of Ly α, fesc(Ly α) ˜ 20-40 per cent, among the highest known for Ly α emitting galaxies. Surface brightness profiles produced from the COS acquisition images reveal bright star-forming regions in the centre and exponential discs in the outskirts with disc scalelengths α in the range ˜0.6-1.4 kpc. Our galaxies are characterized by low metallicity, ˜1/8-1/5 solar, low stellar mass ˜(0.2-4) × 109 M⊙, high star formation rates, SFR ˜ 14-36 M⊙ yr-1, and high SFR densities, Σ ˜ 2-35 M⊙ yr-1 kpc-2. These properties are comparable to those of high-redshift star-forming galaxies. Finally, our observations, combined with our first detection reported in Izotov et al., reveal that a selection for compact star-forming galaxies showing high [O III] λ5007/[O II] λ3727 ratios appears to pick up very efficiently sources with escaping LyC radiation: all five of our selected galaxies are LyC leakers.

  1. THE TWO STATES OF STAR-FORMING CLOUDS

    SciTech Connect

    Collins, David C.; Kritsuk, Alexei G.; Norman, Michael L.; Padoan, Paolo; Li Hui; Xu Hao; Ustyugov, Sergey D.

    2012-05-01

    We examine the effects of self-gravity and magnetic fields on supersonic turbulence in isothermal molecular clouds with high-resolution simulations and adaptive mesh refinement. These simulations use large root grids (512{sup 3}) to capture turbulence and four levels of refinement to follow the collapse to high densities, for an effective resolution of 8192{sup 3}. Three Mach 9 simulations are performed, two super-Alfvenic and one trans-Alfvenic. We find that gravity splits the clouds into two populations, one low-density turbulent state and one high-density collapsing state. The low-density state exhibits properties similar to non-self-gravitating in this regime, and we examine the effects of varied magnetic field strength on statistical properties: the density probability distribution function is approximately lognormal, the velocity power spectral slopes decrease with decreasing mean field strength, the alignment between velocity and magnetic field increases with the field, and the magnetic field probability distribution can be fitted to a stretched exponential. The high-density state is well characterized by self-similar spheres: the density probability distribution is a power law, collapse rate decreases with increasing mean field, density power spectra have positive slopes, P({rho}, k){proportional_to}k, thermal-to-magnetic pressure ratios are roughly unity for all mean field strengths, dynamic-to-magnetic pressure ratios are larger than unity for all mean field strengths, the magnetic field distribution follows a power-law distribution. The high Alfven Mach numbers in collapsing regions explain the recent observations of magnetic influence decreasing with density. We also find that the high-density state is typically found in filaments formed by converging flows, consistent with recent Herschel observations. Possible modifications to existing star formation theories are explored. The overall trans-Alfvenic nature of star-forming clouds is discussed.

  2. Extreme Dust Heating in Optically Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    O'Connor, Jessica

    A complete census of supermassive black holes in the local universe is important, especially in low mass (log(stellar mass/solar masses) < 10) galaxies. It provides observational constraints on the black hole occupation fractions of low mass galaxies and broadens our understanding of the co-evolution of active galactic nuclei (AGN) and their host galaxies. Infrared selection criteria including [3.4]-[4.6] micron (W1-W2) color provides a useful method for detecting obscured AGN which may be missed in X-ray or optical surveys. Recent work has found that not only are there more AGN in low mass galaxies than would be predicted using optical selection criteria, but that the fraction of high W1-W2 (>0.5) galaxies is actually highest in the lowest mass galaxies. This could be evidence of a significant population of obscured AGN in low mass galaxies, but it is still unclear whether the dust heating that causes high W1-W2 color can only be caused by AGN or if stars alone are sufficient. This dissertation is a study of the demographics of high W1-W2 galaxies in the local universe and the AGN or star-forming nature of their nuclear activity. First, the number density of z0.3, 0.5 and 0.8 are calculated as a function of r-band luminosity and stellar mass. Not only does the number density of high W1-W2 galaxies rise toward the lowest host mass regime in stark contrast to the mass distribution of optical AGN, but the red WISE population displays a bimodality in its luminosity and stellar mass functions. They are a combination of a high mass optical AGN and a low mass optically star-forming component. One optically normal, IR-red (W1-W2>1) galaxy (SDSS J1224+5555) was included in a pilot study of bulgeless, high W1-W2 galaxies which found that its X-ray flux is much lower than would be expected if it hosted an AGN. Decomposing its photometry with multiwavelength spectral energy distribution (SED) modeling revealed that it is impossible to reproduce the galaxy's mid

  3. Acceptance of Ideas of Others [Number Form and Star Form].

    ERIC Educational Resources Information Center

    Masters, James R.; Laverty, Grace E.

    As part of the instrumentation to assess the effectiveness of the Schools Without Failure (SWF) program in 10 elementary schools in the New Castle, Pa. School District, the Acceptance of Ideas of Others (Number and Star Forms) were developed to determine pupils' attitudes toward classmates. Given a list of all class members, pupils are asked to…

  4. The Circumstellar Environment of Low Mass Star Forming Regions

    NASA Technical Reports Server (NTRS)

    Butner, Harold M.

    1999-01-01

    The final technical report of the NASA grant project is presented. The goals of the grant were to: (1) analyze the data from the Far-Infrared (FIR) Camera on board the Kuiper Airborne Observatory (KAO); (2) acquire additional data at other wavelengths for models and (4) to develop source models for the Young stellar objects (YSOs)under study. The complete Spectral Energy Distribution (SED) from 10 microns out to 1.3 mm for all sources being studied have been obtained. The FIR imaging data was processed to reveal the maximum angular resolution possible, which allows us to model the disk. To model the disk we have the high resolution millimeter interferometry data. In summary the results to date are: (1) the vast majority of embedded YSOs in Taurus are compact at 100 microns. The models mos consistent with our data and other observations are either dominated by disk emissions, or envelopes that have relatively steep density gradients; (2) the submillimeter/millimeter photometer suggests that models are very successful. Disk emission plays an important role and must be considered when predicting the overall emission. (3) in the two cases, where we seem to have extended emission, we have to investigate other possible source models than a Shu collapse.

  5. HYDROGEN FLUORIDE IN HIGH-MASS STAR-FORMING REGIONS

    SciTech Connect

    Emprechtinger, M.; Monje, R. R.; Lis, D. C.; Phillips, T. G.; Van der Tak, F. F. S.; Van der Wiel, M. H. D.; Neufeld, D.; Ceccarelli, C.

    2012-09-10

    Hydrogen fluoride (HF) has been established to be an excellent tracer of molecular hydrogen in diffuse clouds. In denser environments, however, the HF abundance has been shown to be approximately two orders of magnitude lower. We present Herschel/HIFI observations of HF J = 1-0 toward two high-mass star formation sites, NGC 6334 I and AFGL 2591. In NGC 6334 I the HF line is seen in absorption in foreground clouds and the source itself, while in AFGL 2591 HF is partially in emission. We find an HF abundance with respect to H{sub 2} of 1.5 Multiplication-Sign 10{sup -8} in the diffuse foreground clouds, whereas in the denser parts of NGC 6334 I we derive a lower limit on the HF abundance of 5 Multiplication-Sign 10{sup -10}. Lower HF abundances in dense clouds are most likely caused by freezeout of HF molecules onto dust grains in high-density gas. In AFGL 2591, the view of the hot core is obstructed by absorption in the massive outflow, in which HF is also very abundant (3.6 Multiplication-Sign 10{sup -8}) due to the desorption by sputtering. These observations provide further evidence that the chemistry of interstellar fluorine is controlled by freezeout onto gas grains.

  6. Formation of the nucleobases around the star forming region

    NASA Astrophysics Data System (ADS)

    Saha, Rajdeep; Majumdar, Liton; Das, Ankan; Chakrabarti, Sandip K.; Chakrabarti, Sonali

    2013-06-01

    Chemistry of the dense and cold interstellar clouds are mainly dominated by the ion-molecular and radical-radical interactions though some neutral-neutral reactions are also barrierless and feasible at this condition. The base pairs of RNA are guanine (G) & uracil (U) (G-U pair) and adenine (A) & cytosine (C) (A-C pair). We perform quantum chemical calculations to predict the energetically most economical as well as favorable root for the formation of major bases of the nucleic acids. The outcome of this quantum chemical calculations could be used into our hydro-chemical model to obtain the abundances of some of the important bases of RNA during the formation of a proto star. It is well known that the thymine (T) and uracil (U) are the two nucleobases which are not common in DNA and RNA. Our quantum chemical calculation suggests that uracil could be produced prior to thymine in our chemical network. These findings could be used to support the RNA world hypothesis.

  7. The Circumstellar Environment of Low Mass Star Forming Regions

    NASA Technical Reports Server (NTRS)

    Butner, Harold M.

    1997-01-01

    We have obtained the complete SED from 10 microns out to 1.3 mm for all of our sources. We have the FIR imaging data, processed to reveal the maximum angular resolution possible, which allows us to model the disk. To model the disk, we have high resolution millimeter interferometry data.

  8. SHOCKED SUPERWINDS FROM THE z {approx} 2 CLUMPY STAR-FORMING GALAXY, ZC406690

    SciTech Connect

    Newman, Sarah F.; Genzel, Reinhard; Shapiro Griffin, Kristen; Davies, Ric; Foerster-Schreiber, Natascha M.; Tacconi, Linda J.; Kurk, Jaron; Wuyts, Stijn; Genel, Shy; Buschkamp, Peter; Eisenhauer, Frank; Lutz, Dieter; Lilly, Simon J.; Carollo, C. Marcella; Renzini, Alvio; Mancini, Chiara; Bouche, Nicolas; Burkert, Andreas; Cresci, Giovanni; Hicks, Erin; and others

    2012-06-20

    We have obtained high-resolution data of the z {approx} 2 ring-like, clumpy star-forming galaxy (SFG) ZC406690 using the VLT/SINFONI with adaptive optics (in K band) and in seeing-limited mode (in H and J bands). Our data include all of the main strong optical emission lines: [O II], [O III], H{alpha}, H{beta}, [N II], and [S II]. We find broad, blueshifted H{alpha} and [O III] emission line wings in the spectra of the galaxy's massive, star-forming clumps ({sigma} {approx} 85 km s{sup -1}) and even broader wings (up to 70% of the total H{alpha} flux, with {sigma} {approx} 290 km s{sup -1}) in regions spatially offset from the clumps by {approx}2 kpc. The broad emission likely originates from large-scale outflows with mass outflow rates from individual clumps that are 1-8 Multiplication-Sign the star formation rate (SFR) of the clumps. Based on emission line ratio diagnostics ([N II]/H{alpha} and [S II]/H{alpha}) and photoionization and shock models, we find that the emission from the clumps is due to a combination of photoionization from the star-forming regions and shocks generated in the outflowing component, with 5%-30% of the emission deriving from shocks. In terms of the ionization parameter (6 Multiplication-Sign 10{sup 7} to 10{sup 8} cm s{sup -1}, based on both the SFR and the O{sub 32} ratio), density (local electron densities of 300-1800 cm{sup -3} in and around the clumps, and ionized gas column densities of 1200-8000 M{sub Sun }pc{sup -2}), and SFR (10-40 M{sub Sun} yr{sup -1}), these clumps more closely resemble nuclear starburst regions of local ultraluminous infrared galaxies and dwarf irregulars than H II regions in local galaxies. However, the star-forming clumps are not located in the nucleus as in local starburst galaxies but instead are situated in a ring several kpc from the center of their high-redshift host galaxy, and have an overall disk-like morphology. The two brightest clumps are quite different in terms of their internal properties

  9. Searching for star-forming dwarf galaxies in the Antlia cluster

    NASA Astrophysics Data System (ADS)

    Vaduvescu, O.; Kehrig, C.; Bassino, L. P.; Smith Castelli, A. V.; Calderón, J. P.

    2014-03-01

    Context. The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. Aims: In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Methods: Using the Gemini South and GMOS camera, we acquired the Hα imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived KS magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. Results: FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, KS surface photometry, oxygen abundance, and velocity redshift. FS90-155 and FS90-319 did not show any Hα emission, and they could not be confirmed as dwarf cluster star-forming galaxies. Based on our data, we studied some fundamental relations to compare star forming dwarfs (BCDs and dIs) in the LV and in the Virgo, Fornax, Hydra, and Antlia clusters. Conclusions: Star-forming dwarfs in nearby clusters appear to follow same fundamental relations in the near infrared with similar objects in the LV, specifically the size-luminosity and the metallicity-luminosity, while other more fundamental relations could not be checked in Antlia due to lack of data. Based on observations acquired at Gemini South (GS-2010A-Q-51 and GS-2012A-Q-59) and ESO VISTA Hemisphere Survey (VHS).

  10. Hubble Imaging of the Ionizing Radiation from a Star-forming Galaxy at Z=3.2 with fesc>50%

    NASA Astrophysics Data System (ADS)

    Vanzella, E.; de Barros, S.; Vasei, K.; Alavi, A.; Giavalisco, M.; Siana, B.; Grazian, A.; Hasinger, G.; Suh, H.; Cappelluti, N.; Vito, F.; Amorin, R.; Balestra, I.; Brusa, M.; Calura, F.; Castellano, M.; Comastri, A.; Fontana, A.; Gilli, R.; Mignoli, M.; Pentericci, L.; Vignali, C.; Zamorani, G.

    2016-07-01

    Star-forming galaxies are considered to be the leading candidate sources dominating cosmic reionization at z\\gt 7: the search for analogs at moderate redshift showing Lyman continuum (LyC) leakage is currently an active line of research. We have observed a star-forming galaxy at z = 3.2 with Hubble/WFC3 in the F336W filter, corresponding to the 730-890 Å rest-frame, and detected LyC emission. This galaxy is very compact and also has a large Oxygen ratio [{{O}} {{III}}]λ 5007/[{{O}} {{II}}]λ 3727 (≳ 10). No nuclear activity is revealed from optical/near-infrared spectroscopy and deep multi-band photometry (including the 6 Ms X-ray Chandra observations). The measured escape fraction of ionizing radiation spans the range 50%-100%, depending on the intergalactic medium (IGM) attenuation. The LyC emission is measured at {m}{{F}336{{W}}}=27.57+/- 0.11 (with signal-to-noise ratio (S/N) = 10) and is spatially unresolved, with an effective radius of {R}e\\lt 200 pc. Predictions from photoionization and radiative transfer models are in line with the properties reported here, indicating that stellar winds and supernova explosions in a nucleated star-forming region can blow cavities generating density-bounded conditions compatible to optically thin media. Irrespective of the nature of the ionizing radiation, spectral signatures of these sources over the entire electromagnetic spectrum are of central importance for their identification during the epoch of reionization when the LyC is unobservable. Intriguingly, the Spitzer/IRAC photometric signature of intense rest-frame optical emissions ([O iii]λλ4959,5007 + Hβ) recently observed at z≃ 7.5{--}8.5 is similar to what is observed in this galaxy. Only the James Webb Space Telescope will measure optical line ratios at z\\gt 7, allowing a direct comparison with the lower-redshift LyC emitters, such as that reported here. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope

  11. Hubble Imaging of the Ionizing Radiation from a Star-forming Galaxy at Z=3.2 with fesc>50%

    NASA Astrophysics Data System (ADS)

    Vanzella, E.; de Barros, S.; Vasei, K.; Alavi, A.; Giavalisco, M.; Siana, B.; Grazian, A.; Hasinger, G.; Suh, H.; Cappelluti, N.; Vito, F.; Amorin, R.; Balestra, I.; Brusa, M.; Calura, F.; Castellano, M.; Comastri, A.; Fontana, A.; Gilli, R.; Mignoli, M.; Pentericci, L.; Vignali, C.; Zamorani, G.

    2016-07-01

    Star-forming galaxies are considered to be the leading candidate sources dominating cosmic reionization at z\\gt 7: the search for analogs at moderate redshift showing Lyman continuum (LyC) leakage is currently an active line of research. We have observed a star-forming galaxy at z = 3.2 with Hubble/WFC3 in the F336W filter, corresponding to the 730–890 Å rest-frame, and detected LyC emission. This galaxy is very compact and also has a large Oxygen ratio [{{O}} {{III}}]λ 5007/[{{O}} {{II}}]λ 3727 (≳ 10). No nuclear activity is revealed from optical/near-infrared spectroscopy and deep multi-band photometry (including the 6 Ms X-ray Chandra observations). The measured escape fraction of ionizing radiation spans the range 50%–100%, depending on the intergalactic medium (IGM) attenuation. The LyC emission is measured at {m}{{F}336{{W}}}=27.57+/- 0.11 (with signal-to-noise ratio (S/N) = 10) and is spatially unresolved, with an effective radius of {R}e\\lt 200 pc. Predictions from photoionization and radiative transfer models are in line with the properties reported here, indicating that stellar winds and supernova explosions in a nucleated star-forming region can blow cavities generating density-bounded conditions compatible to optically thin media. Irrespective of the nature of the ionizing radiation, spectral signatures of these sources over the entire electromagnetic spectrum are of central importance for their identification during the epoch of reionization when the LyC is unobservable. Intriguingly, the Spitzer/IRAC photometric signature of intense rest-frame optical emissions ([O iii]λλ4959,5007 + Hβ) recently observed at z≃ 7.5{--}8.5 is similar to what is observed in this galaxy. Only the James Webb Space Telescope will measure optical line ratios at z\\gt 7, allowing a direct comparison with the lower-redshift LyC emitters, such as that reported here. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space

  12. ON THE DENSITY DISTRIBUTION IN STAR-FORMING INTERSTELLAR CLOUDS

    SciTech Connect

    Kritsuk, Alexei G.; Norman, Michael L.; Wagner, Rick

    2011-01-20

    We use deep adaptive mesh refinement simulations of isothermal self-gravitating supersonic turbulence to study the imprints of gravity on the mass density distribution in molecular clouds. The simulations show that the density distribution in self-gravitating clouds develops an extended power-law tail at high densities on top of the usual lognormal. We associate the origin of the tail with self-similar collapse solutions and predict the power index values in the range from -7/4 to -3/2 that agree with both simulations and observations of star-forming molecular clouds.

  13. Modelling the chemical evolution of star forming filaments

    NASA Astrophysics Data System (ADS)

    Seifried, D.; Walch, S.

    2016-05-01

    We present simulations of star forming filaments incorporating - to our knowledge - the largest chemical network used to date on-the-fly in a 3D-MHD simulation. The network contains 37 chemical species and about 300 selected reaction rates. For this we use the newly developed package KROME (Grassi et al. [4]). Our results demonstrate the feasibility of using such a complex chemical network in 3D-MHD simulations on modern supercomputers. We perform simulations with different strengths of the interstellar radiation field and the cosmic ray ionisation rate and find chemical and physical results in accordance with observations and other recent numerical work.

  14. THE CLUSTERING AND HALO MASSES OF STAR-FORMING GALAXIES AT z < 1

    SciTech Connect

    Dolley, Tim; Brown, Michael J. I.; Pimbblet, Kevin A.; Palamara, David P.; Beare, Richard; Weiner, Benjamin J.; Jannuzi, Buell T.; Brodwin, Mark; Kochanek, C. S.; Dey, Arjun; Atlee, David W.

    2014-12-20

    We present clustering measurements and halo masses of star-forming galaxies at 0.2 < z < 1.0. After excluding active galactic nuclei (AGNs), we construct a sample of 22,553 24 μm sources selected from 8.42 deg{sup 2} of the Spitzer MIPS AGN and Galaxy Evolution Survey of Boötes. Mid-infrared imaging allows us to observe galaxies with the highest star formation rates (SFRs), less biased by dust obscuration afflicting the optical bands. We find that the galaxies with the highest SFRs have optical colors that are redder than typical blue cloud galaxies, with many residing within the green valley. At z > 0.4 our sample is dominated by luminous infrared galaxies (LIRGs, L {sub TIR} > 10{sup 11} L {sub ☉}) and is composed entirely of LIRGs and ultraluminous infrared galaxies (ULIRGs, L {sub TIR} > 10{sup 12} L {sub ☉}) at z > 0.6. We observe weak clustering of r {sub 0} ≈ 3-6 h {sup –1} Mpc for almost all of our star-forming samples. We find that the clustering and halo mass depend on L {sub TIR} at all redshifts, where galaxies with higher L {sub TIR} (hence higher SFRs) have stronger clustering. Galaxies with the highest SFRs at each redshift typically reside within dark matter halos of M {sub halo} ≈ 10{sup 12.9} h {sup –1} M {sub ☉}. This is consistent with a transitional halo mass, above which star formation is largely truncated, although we cannot exclude that ULIRGs reside within higher mass halos. By modeling the clustering evolution of halos, we connect our star-forming galaxy samples to their local descendants. Most star-forming galaxies at z < 1.0 are the progenitors of L ≲ 2.5 L {sub *} blue galaxies in the local universe, but star-forming galaxies with the highest SFRs (L {sub TIR} ≳ 10{sup 11.7} L {sub ☉}) at 0.6 < z < 1.0 are the progenitors of early-type galaxies in denser group environments.

  15. Optical Color Gradients in Star-forming Ring Galaxies

    NASA Astrophysics Data System (ADS)

    Korchagin, Vladimir; Mayya, Y. D.; Vorobyov, Eduard

    2001-06-01

    We compute radial color gradients produced by an outwardly propagating circular wave of star formation and compare our results with color gradients observed in the classical ring galaxy, the ``Cartwheel.'' We invoke two independent models of star formation in the ring galaxies. The first one is the conventional density wave scenario, in which an intruder galaxy creates a radially propagating density wave accompanied by an enhanced star formation following the Schmidt's law. The second scenario is a pure self-propagating star formation model, in which the intruder sets off only the first burst of stars at the point of impact. Both models give essentially the same results. Systematic reddening of B-V, V-K colors toward the center, such as that observed in the Cartwheel, can be obtained only if the abundance of heavy elements in the star-forming gas is a few times below solar. The B-V and V-K color gradients observed in the Cartwheel can be explained as a result of mixing of stellar populations born in a star-forming wave propagating through a low-metallicity gaseous disk, and a preexisting stellar disk of the size of the gaseous disk with color properties typical to those observed in nearby disk galaxies.

  16. Gas inflow and metallicity drops in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Ceverino, Daniel; Sánchez Almeida, Jorge; Muñoz Tuñón, Casiana; Dekel, Avishai; Elmegreen, Bruce G.; Elmegreen, Debra M.; Primack, Joel

    2016-04-01

    Gas inflow feeds galaxies with low-metallicity gas from the cosmic web, sustaining star formation across the Hubble time. We make a connection between these inflows and metallicity inhomogeneities in star-forming galaxies, by using synthetic narrow-band images of the Hα emission line from zoom-in AMR cosmological simulations of galaxies with stellar masses of M* ≃ 109 M⊙ at redshifts z = 2-7. In ˜50 per cent of the cases at redshifts lower than 4, the gas inflow gives rise to star-forming, Hα-bright, off-centre clumps. Most of these clumps have gas metallicities, weighted by Hα luminosity, lower than the metallicity in the surrounding interstellar medium by ˜0.3 dex, consistent with observations of chemical inhomogeneities at high and low redshifts. Due to metal mixing by shear and turbulence, these metallicity drops are dissolved in a few disc dynamical times. Therefore, they can be considered as evidence for rapid gas accretion coming from cosmological inflow of pristine gas.

  17. THE SINS SURVEY OF z {approx} 2 GALAXY KINEMATICS: PROPERTIES OF THE GIANT STAR-FORMING CLUMPS

    SciTech Connect

    Genzel, R.; Foerster Schreiber, N. M.; Genel, S.; Tacconi, L. J.; Buschkamp, P.; Davies, R.; Eisenhauer, F.; Kurk, J.; Newman, S.; Jones, T.; Shapiro, K.; Lilly, S. J.; Carollo, C. M.; Renzini, A.; Bouche, N.; Burkert, A.; Cresci, G.; Ceverino, D.; Dekel, A.; Hicks, E.

    2011-06-01

    We have studied the properties of giant star-forming clumps in five z {approx} 2 star-forming disks with deep SINFONI AO spectroscopy at the ESO VLT. The clumps reside in disk regions where the Toomre Q-parameter is below unity, consistent with their being bound and having formed from gravitational instability. Broad H{alpha}/[N II] line wings demonstrate that the clumps are launching sites of powerful outflows. The inferred outflow rates are comparable to or exceed the star formation rates, in one case by a factor of eight. Typical clumps may lose a fraction of their original gas by feedback in a few hundred million years, allowing them to migrate into the center. The most active clumps may lose much of their mass and disrupt in the disk. The clumps leave a modest imprint on the gas kinematics. Velocity gradients across the clumps are 10-40 km s{sup -1} kpc{sup -1}, similar to the galactic rotation gradients. Given beam smearing and clump sizes, these gradients may be consistent with significant rotational support in typical clumps. Extreme clumps may not be rotationally supported; either they are not virialized or they are predominantly pressure supported. The velocity dispersion is spatially rather constant and increases only weakly with star formation surface density. The large velocity dispersions may be driven by the release of gravitational energy, either at the outer disk/accreting streams interface, and/or by the clump migration within the disk. Spatial variations in the inferred gas phase oxygen abundance are broadly consistent with inside-out growing disks, and/or with inward migration of the clumps.

  18. Chemical Pollution and Evolution of Massive Starbursts: Cleaning up the Environment in Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Kobulnicky, C.

    1996-12-01

    I present the results of a research program seeking to characterize the impact of massive star-clusters on the chemical and dynamical evolution of metal-poor, irregular and blue compact galaxies. The evolution of high mass stars is thought to contribute the bulk of heavy element enrichment in the interstellar medium, especially alpha -process elements like O, Si, etc. Yet, in actively star-forming galaxies, localized chemical inhomogeneities are seldom observed. Spatially-resolved optical and ultraviolet spectroscopy from the Hubble Space Telescope and ground-based observatories is used to search for chemical enrichment in the vicinity of young star clusters in nearby galaxies. VLA aperture synthesis maps are used to examine the neutral hydrogen content, dynamics, and local environment of the sample galaxies. Despite the spread in evolutionary state of the starbursts determined by the EW of Balmer emission lines and the radio continuum spectral index, few instances of localized enrichment are found. In light of these data, the ``instantaneous enrichment'' scenario for extragalactic HII regions appears less probable than one which operates on long timescales and global spatial scales. The results are consistent with the idea that starburst driven winds expel freshly synthesized metals in a hot 10(6) K phase into the halos of galaxies where they cool, condense into globules, and mix homogeneously with the rest of the galaxy on long (dynamical) timescales. The C/O and N/O ratios of the galaxies are used as new tools for measuring the recent star formation history. Implications for chemical evolution of galaxies both locally and cosmologically are developed.

  19. A deep Chandra observation of the interacting star-forming galaxy Arp 299

    NASA Astrophysics Data System (ADS)

    Anastasopoulou, K.; Zezas, A.; Ballo, L.; Della Ceca, R.

    2016-08-01

    We present results from a 90 ks Chandra ACIS-S observation of the X-ray luminous interacting galaxy system Arp 299 (NGC 3690/IC 694). We detect 25 discrete X-ray sources with luminosities above ˜4.0 × 1038 erg s-1 covering the entire Ultra Luminous X-ray source (ULX) regime. Based on the hard X-ray spectra of the non-nuclear discrete sources identified in Arp 299, and their association with young, actively star-forming region of Arp 299 we identify them as HMXBs. We find in total 20 off-nuclear sources with luminosities above the ULX limit, 14 of which are point-like sources. Furthermore we observe a marginally significant deficit in the number of ULXs, with respect to the number expected from scaling relations of X-ray binaries with the star formation rate (SFR). Although the high metallicity of the galaxy could result in lower ULX numbers, the good agreement between the observed total X-ray luminosity of ULXs, and that expected from the relevant scaling relation indicates that this deficit could be the result of confusion effects. The integrated spectrum of the galaxy shows the presence of a hot gaseous component with kT = 0.72 ± 0.03 keV, contributing ˜20 per cent of the soft (0.1-2.0 keV) unabsorbed luminosity of the galaxy. A plume of soft X-ray emission in the west of the galaxy indicates a large scale outflow. We find that the AGN in NGC 3690 contributes only 22 per cent of the observed broad-band X-ray luminosity of Arp 299.

  20. The SCUBA-2 cosmology legacy survey: Ultraluminous star-forming galaxies in a z = 1.6 cluster

    SciTech Connect

    Smail, Ian; Swinbank, A. M.; Danielson, A. L. R.; Edge, A. C.; Simpson, J. M.; Geach, J. E.; Tadaki, K.; Arumugam, V.; Dunlop, J. S.; Ivison, R. J.; Hartley, W.; Almaini, O.; Conselice, C.; Bremer, M. N.; Chapin, E.; Chapman, S. C.; Scott, D.; Simpson, C. J.; Karim, A.; Kodama, T.; and others

    2014-02-10

    We analyze new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z = 1.62 cluster, Cl 0218.3–0510, which lies in the UKIRT Infrared Deep Sky Survey/Ultra-Deep Survey field of the SCUBA-2 Cosmology Legacy Survey. Combining these tracers of obscured star-formation activity with the extensive photometric and spectroscopic information available for this field, we identify 31 far-infrared/submillimeter-detected probable cluster members with bolometric luminosities ≳10{sup 12} L {sub ☉} and show that by virtue of their dust content and activity, these represent some of the reddest and brightest galaxies in this structure. We exploit ALMA submillimeter continuum observations, which cover one of these sources, to confirm the identification of a SCUBA-2-detected ultraluminous star-forming galaxy in this structure. Integrating the total star-formation activity in the central region of the structure, we estimate that it is an order of magnitude higher (in a mass-normalized sense) than clusters at z ∼ 0.5-1. However, we also find that the most active cluster members do not reside in the densest regions of the structure, which instead host a population of passive and massive, red galaxies. We suggest that while the passive and active populations have comparable near-infrared luminosities at z = 1.6, M{sub H} ∼ –23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present day that are less luminous than the descendants of those galaxies that were already passive at z ∼ 1.6 (M{sub H} ∼ –20.5 and M{sub H} ∼ –21.5, respectively, at z ∼ 0). We conclude that the massive galaxy population in the dense cores of present-day clusters were already in place at z = 1.6 and that in Cl 0218.3–0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure.

  1. Star Formation in the Perseus Molecular Cloud: A Detailed Look at Star-Forming Clumps with Herschel

    NASA Astrophysics Data System (ADS)

    Sadavoy, Sarah I.

    2013-08-01

    This dissertation presents new Herschel observations at 70 micron, 160 micron, 250 micron, 350 micron, and 500 micron of the Perseus molecular cloud from the Herschel Gould Belt Survey. The Perseus molecular cloud is a nearby star-forming region consisting of seven main star-forming clumps. The Herschel observations are used to characterize and contrast the properties of these clumps, and to study their embedded core populations. First, we probed the exceptionally young clump, B1-E. Using complementary molecular line data, we demonstrate that B1-E is likely fragmenting into a first generation of dense cores in relative isolation. Such a core formation region has never been observed before. Second, we use complementary long wavelength observations at 850 micron to study the dust properties in the larger, more active B1 clump. We find that Herschel data alone cannot constrain well the dust properties of cold dust emission and that long wavelength observations are needed. Additionally, we find evidence of dust grain growth towards the dense cores in B1, where the dust emissivity index, beta, varies from the often assumed value of beta = 2. In the absence of long wavelength observations, however, assuming beta = 2 is preferable over measuring beta with the Herschel-only bands. Finally, we use the source extraction code, getsources, to identify the core populations within each clump from the Herschel data. In addition, we use complementary archival infrared observations to study their populations of young stellar objects (YSOs). We find that the more massive clumps have an excess of older stage YSOs, suggesting that these regions contracted first. Starless cores are typically associated with peaks in the column density, where those found towards regions of higher column density also have higher average densities and colder temperatures. Starless cores associated with a strong, local interstellar radiation field, however, have higher temperatures. We find that the clumps

  2. ALMA observation of high-z extreme star-forming environments discovered by Planck/Herschel

    NASA Astrophysics Data System (ADS)

    Kneissl, R.

    2016-05-01

    The Comic Microwave Background satellite Planck with its High Frequency Instrument has surveyed the mm/sub-mm sky in six frequency channels from 100 to 900 GHz. A sample of 228 cold sources of the Cosmic Infrared Background was observed in follow-up with Herschel SPIRE. The majority of sources appear to be over-densities of star-forming galaxies matching the size of high-z proto-cluster regions, while a 3% fraction are individual bright, lensed galaxies. A large observing program is underway with the aim of resolving the regions into the constituent members of the Planck sources. First ALMA data have been received on one Planck/Herschel proto-cluster candidate, showing the expected large over-abundance of bright mm/sub-mm sources within the cluster region. ALMA long baseline data of the brightest lensed galaxy in the sample with > 1 Jy at 350 μm are also forthcoming.

  3. Active region seismology

    NASA Technical Reports Server (NTRS)

    Bogdan, Tom; Braun, D. C.

    1995-01-01

    Active region seismology is concerned with the determination and interpretation of the interaction of the solar acoustic oscillations with near-surface target structures, such as magnetic flux concentration, sunspots, and plage. Recent observations made with a high spatial resolution and a long temporal duration enabled measurements of the scattering matrix for sunspots and solar active regions to be carried out as a function of the mode properties. Based on this information, the amount of p-mode absorption, partial-wave phase shift, and mode mixing introduced by the sunspot, could be determined. In addition, the possibility of detecting the presence of completely submerged magnetic fields was raised, and new procedures for performing acoustic holography of the solar interior are being developed. The accumulating evidence points to the mode conversion of p-modes to various magneto-atmospheric waves within the magnetic flux concentration as being the unifying physical mechanism responsible for these diverse phenomena.

  4. The Intergalactic and Circumgalactic Medium surrounding Star-Forming Galaxies at Redshifts 2 < z < 3

    NASA Astrophysics Data System (ADS)

    Rudie, Gwen C.

    We present measurements of the spatial distribution, kinematics, and physical properties of gas in the circumgalactic medium (CGM) of 2.0 < z < 2.8 UV color-selected galaxies as well as within the 2 < z < 3 intergalactic medium (IGM). These measurements are derived from Voigt profile decomposition of the full Lyalpha and Lybeta forest in 15 high-resolution, high signal-to-noise ratio QSO spectra resulting in a catalog of ˜ 6000 H I absorbers. Chapter 2 of this thesis focuses on H I surrounding high-z star-forming galaxies drawn from the Keck Baryonic Structure Survey (KBSS). The KBSS is a unique spectroscopic survey of the distant universe designed to explore the details of the connection between galaxies and intergalactic baryons within the same survey volumes. The KBSS combines high-quality background QSO spectroscopy with large densely-sampled galaxy redshift surveys to probe the CGM at scales of ˜ 50 kpc to a few Mpc. Based on these data, Chapter 2 presents the first quantitative measurements of the distribution, column density, kinematics, and absorber line widths of neutral hydrogen surrounding high-z star-forming galaxies. Chapter 3 focuses on the thermal properties of the diffuse IGM. This analysis relies on measurements of the ˜ 6000 absorber line widths to constrain the thermal and turbulent velocities of absorbing "clouds." A positive correlation between the column density of H I and the minimum line width is recovered and implies a temperature-density relation within the low-density IGM for which higher-density regions are hotter, as is predicted by simple theoretical arguments. Chapter 4 presents new measurements of the opacity of the IGM and CGM to hydrogen-ionizing photons. The chapter begins with a revised measurement of the H I column density distribution based on this new absorption line catalog that, due to the inclusion of high-order Lyman lines, provides the first statistically robust measurement of the frequency of absorbers with H I column

  5. The JCMT Gould Belt Survey: Evidence for Dust Grain Evolution in Perseus Star-forming Clumps

    NASA Astrophysics Data System (ADS)

    Chen, Michael Chun-Yuan; Di Francesco, J.; Johnstone, D.; Sadavoy, S.; Hatchell, J.; Mottram, J. C.; Kirk, H.; Buckle, J.; Berry, D. S.; Broekhoven-Fiene, H.; Currie, M. J.; Fich, M.; Jenness, T.; Nutter, D.; Pattle, K.; Pineda, J. E.; Quinn, C.; Salji, C.; Tisi, S.; Hogerheijde, M. R.; Ward-Thompson, D.; Bastien, P.; Bresnahan, D.; Butner, H.; Chrysostomou, A.; Coude, S.; Davis, C. J.; Drabek-Maunder, E.; Duarte-Cabral, A.; Fiege, J.; Friberg, P.; Friesen, R.; Fuller, G. A.; Graves, S.; Greaves, J.; Gregson, J.; Holland, W.; Joncas, G.; Kirk, J. M.; Knee, L. B. G.; Mairs, S.; Marsh, K.; Matthews, B. C.; Moriarty-Schieven, G.; Mowat, C.; Pezzuto, S.; Rawlings, J.; Richer, J.; Robertson, D.; Rosolowsky, E.; Rumble, D.; Schneider-Bontemps, N.; Thomas, H.; Tothill, N.; Viti, S.; White, G. J.; Wouterloot, J.; Yates, J.; Zhu, M.

    2016-07-01

    The dust emissivity spectral index, β, is a critical parameter for deriving the mass and temperature of star-forming structures and, consequently, their gravitational stability. The β value is dependent on various dust grain properties, such as size, porosity, and surface composition, and is expected to vary as dust grains evolve. Here we present β, dust temperature, and optical depth maps of the star-forming clumps in the Perseus Molecular Cloud determined from fitting spectral energy distributions to combined Herschel and JCMT observations in the 160, 250, 350, 500, and 850 μm bands. Most of the derived β and dust temperature values fall within the ranges of 1.0-2.7 and 8-20 K, respectively. In Perseus, we find the β distribution differs significantly from clump to clump, indicative of grain growth. Furthermore, we also see significant localized β variations within individual clumps and find low-β regions correlate with local temperature peaks, hinting at the possible origins of low-β grains. Throughout Perseus, we also see indications of heating from B stars and embedded protostars, as well evidence of outflows shaping the local landscape.

  6. YOUNG, ULTRAVIOLET-BRIGHT STARS DOMINATE DUST HEATING IN STAR-FORMING GALAXIES

    SciTech Connect

    Law, Ka-Hei; Gordon, Karl D.; Misselt, K. A. E-mail: kgordon@stsci.edu

    2011-09-10

    In star-forming galaxies, dust plays a significant role in shaping the ultraviolet (UV) through infrared (IR) spectrum. Dust attenuates the radiation from stars, and re-radiates the energy through equilibrium and non-equilibrium emission. Polycyclic aromatic hydrocarbons (PAHs), graphite, and silicates contribute to different features in the spectral energy distribution; however, they are all highly opaque in the same spectral region-the UV. Compared to old stellar populations, young populations release a higher fraction of their total luminosity in the UV, making them a good source of the energetic UV photons that can power dust emission. However, given their relative abundance, the question of whether young or old stellar populations provide most of these photons that power the IR emission is an interesting question. Using three samples of galaxies observed with the Spitzer Space Telescope and our dusty radiative transfer model, we find that young stellar populations (on the order of 100 million years old) dominate the dust heating in star-forming galaxies, and old stellar populations (13 billion years old) generally contribute less than 20% of the far-IR luminosity.

  7. A CORRELATION BETWEEN STAR FORMATION RATE AND AVERAGE BLACK HOLE ACCRETION IN STAR-FORMING GALAXIES

    SciTech Connect

    Chen, Chien-Ting J.; Hickox, Ryan C.; Alberts, Stacey; Pope, Alexandra; Brodwin, Mark; Jones, Christine; Forman, William R.; Goulding, Andrew D.; Murray, Stephen S.; Alexander, David M.; Mullaney, James R.; Assef, Roberto J.; Gorjian, Varoujan; Brown, Michael J. I.; Dey, Arjun; Jannuzi, Buell T.; Le Floc'h, Emeric

    2013-08-10

    We present a measurement of the average supermassive black hole accretion rate (BHAR) as a function of the star formation rate (SFR) for galaxies in the redshift range 0.25 < z < 0.8. We study a sample of 1767 far-IR-selected star-forming galaxies in the 9 deg{sup 2} Booetes multi-wavelength survey field. The SFR is estimated using 250 {mu}m observations from the Herschel Space Observatory, for which the contribution from the active galactic nucleus (AGN) is minimal. In this sample, 121 AGNs are directly identified using X-ray or mid-IR selection criteria. We combined these detected AGNs and an X-ray stacking analysis for undetected sources to study the average BHAR for all of the star-forming galaxies in our sample. We find an almost linear relation between the average BHAR (in M{sub Sun} yr{sup -1}) and the SFR (in M{sub Sun} yr{sup -1}) for galaxies across a wide SFR range 0.85 < log SFR < 2.56: log BHAR = (- 3.72 {+-} 0.52) + (1.05 {+-} 0.33)log SFR. This global correlation between SFR and average BHAR is consistent with a simple picture in which SFR and AGN activity are tightly linked over galaxy evolution timescales.

  8. Kinematic evolution of simulated star-forming galaxies

    SciTech Connect

    Kassin, Susan A.; Brooks, Alyson; Governato, Fabio; Weiner, Benjamin J.; Gardner, Jonathan P.

    2014-08-01

    Recent observations have shown that star-forming galaxies like our own Milky Way evolve kinematically into ordered thin disks over the last ∼8 billion years since z = 1.2, undergoing a process of 'disk settling'. For the first time, we study the kinematic evolution of a suite of four state of the art 'zoom in' hydrodynamic simulations of galaxy formation and evolution in a fully cosmological context and compare with these observations. Until now, robust measurements of the internal kinematics of simulated galaxies were lacking because the simulations suffered from low resolution, overproduction of stars, and overly massive bulges. The current generation of simulations has made great progress in overcoming these difficulties and is ready for a kinematic analysis. We show that simulated galaxies follow the same kinematic trends as real galaxies: they progressively decrease in disordered motions (σ{sub g}) and increase in ordered rotation (V{sub rot}) with time. The slopes of the relations between both σ{sub g} and V{sub rot} with redshift are consistent between the simulations and the observations. In addition, the morphologies of the simulated galaxies become less disturbed with time, also consistent with observations. This match between the simulated and observed trends is a significant success for the current generation of simulations, and a first step in determining the physical processes behind disk settling'.

  9. Kinematic Evolution of Simulated Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Kassin, Susan A.; Brooks, Alyson; Governato, Fabio; Weiner, Benjamin J.; Gardner, Jonathan P.

    2014-08-01

    Recent observations have shown that star-forming galaxies like our own Milky Way evolve kinematically into ordered thin disks over the last ~8 billion years since z = 1.2, undergoing a process of "disk settling." For the first time, we study the kinematic evolution of a suite of four state of the art "zoom in" hydrodynamic simulations of galaxy formation and evolution in a fully cosmological context and compare with these observations. Until now, robust measurements of the internal kinematics of simulated galaxies were lacking because the simulations suffered from low resolution, overproduction of stars, and overly massive bulges. The current generation of simulations has made great progress in overcoming these difficulties and is ready for a kinematic analysis. We show that simulated galaxies follow the same kinematic trends as real galaxies: they progressively decrease in disordered motions (σ g ) and increase in ordered rotation (V rot) with time. The slopes of the relations between both σ g and V rot with redshift are consistent between the simulations and the observations. In addition, the morphologies of the simulated galaxies become less disturbed with time, also consistent with observations. This match between the simulated and observed trends is a significant success for the current generation of simulations, and a first step in determining the physical processes behind disk settling.

  10. Kinematic Evolution of Simulated Star-Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Kassin, Susan A.; Brooks, Alyson; Governato, Fabio; Weiner, Benjamin J.; Gardner, Jonathan P.

    2014-01-01

    Recent observations have shown that star-forming galaxies like our own Milky Way evolve kinematically into ordered thin disks over the last approximately 8 billion years since z = 1.2, undergoing a process of "disk settling." For the first time, we study the kinematic evolution of a suite of four state of the art "zoom in" hydrodynamic simulations of galaxy formation and evolution in a fully cosmological context and compare with these observations. Until now, robust measurements of the internal kinematics of simulated galaxies were lacking as the simulations suffered from low resolution, overproduction of stars, and overly massive bulges. The current generation of simulations has made great progress in overcoming these difficulties and is ready for a kinematic analysis. We show that simulated galaxies follow the same kinematic trends as real galaxies: they progressively decrease in disordered motions (sigma(sub g)) and increase in ordered rotation (V(sub rot)) with time. The slopes of the relations between both sigma(sub g) and V(sub rot) with redshift are consistent between the simulations and the observations. In addition, the morphologies of the simulated galaxies become less disturbed with time, also consistent with observations. This match between the simulated and observed trends is a significant success for the current generation of simulations, and a first step in determining the physical processes behind disk settling.

  11. Overview of the Massive Young Star-Forming Complex Study in Infrared and X-Ray (MYStIX) Project

    NASA Astrophysics Data System (ADS)

    Feigelson, Eric D.; Townsley, Leisa K.; Broos, Patrick S.; Busk, Heather A.; Getman, Konstantin V.; King, Robert R.; Kuhn, Michael A.; Naylor, Tim; Povich, Matthew S.; Baddeley, Adrian; Bate, Matthew R.; Indebetouw, Remy; Luhman, Kevin L.; McCaughrean, Mark J.; Pittard, Julian M.; Pudritz, Ralph E.; Sills, Alison; Song, Yong; Wadsley, James

    2013-12-01

    The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) seeks to characterize 20 OB-dominated young clusters and their environs at distances d <= 4 kpc using imaging detectors on the Chandra X-ray Observatory, Spitzer Space Telescope, and the United Kingdom InfraRed Telescope. The observational goals are to construct catalogs of star-forming complex stellar members with well-defined criteria and maps of nebular gas (particularly of hot X-ray-emitting plasma) and dust. A catalog of MYStIX Probable Complex Members with several hundred OB stars and 31,784 low-mass pre-main sequence stars is assembled. This sample and related data products will be used to seek new empirical constraints on theoretical models of cluster formation and dynamics, mass segregation, OB star formation, star formation triggering on the periphery of H II regions, and the survivability of protoplanetary disks in H II regions. This paper gives an introduction and overview of the project, covering the data analysis methodology and application to two star-forming regions: NGC 2264 and the Trifid Nebula.

  12. Stellar Clusters in the NGC 6334 Star-Forming Complex

    NASA Astrophysics Data System (ADS)

    Feigelson, Eric D.; Martin, Amanda L.; McNeill, Collin J.; Broos, Patrick S.; Garmire, Gordon P.

    2009-07-01

    The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, has not been well sampled in past studies. We analyze here a mosaic of two Chandra X-ray Observatory images of the region using sensitive data analysis methods, giving a list of 1607 faint X-ray sources with arcsecond positions and approximate line-of-sight absorption. About 95% of these are expected to be cluster members, most lower mass pre-main-sequence stars. Extrapolating to low X-ray levels, the total stellar population is estimated to be 20,000-30,000 pre-main-sequence stars. The X-ray sources show a complicated spatial pattern with ~10 distinct star clusters. The heavily obscured clusters are mostly associated with previously known far-infrared sources and radio H II regions. The lightly obscured clusters are mostly newly identified in the X-ray images. Dozens of likely OB stars are found, both in clusters and dispersed throughout the region, suggesting that star formation in the complex has proceeded over millions of years. A number of extraordinarily heavily absorbed X-ray sources are associated with the active regions of star formation.

  13. STELLAR CLUSTERS IN THE NGC 6334 STAR-FORMING COMPLEX

    SciTech Connect

    Feigelson, Eric D.; Martin, Amanda L.; McNeill, Collin J.; Broos, Patrick S.; Garmire, Gordon P.

    2009-07-15

    The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, has not been well sampled in past studies. We analyze here a mosaic of two Chandra X-ray Observatory images of the region using sensitive data analysis methods, giving a list of 1607 faint X-ray sources with arcsecond positions and approximate line-of-sight absorption. About 95% of these are expected to be cluster members, most lower mass pre-main-sequence stars. Extrapolating to low X-ray levels, the total stellar population is estimated to be 20,000-30,000 pre-main-sequence stars. The X-ray sources show a complicated spatial pattern with {approx}10 distinct star clusters. The heavily obscured clusters are mostly associated with previously known far-infrared sources and radio H II regions. The lightly obscured clusters are mostly newly identified in the X-ray images. Dozens of likely OB stars are found, both in clusters and dispersed throughout the region, suggesting that star formation in the complex has proceeded over millions of years. A number of extraordinarily heavily absorbed X-ray sources are associated with the active regions of star formation.

  14. Spectral synthesis of star-forming galaxies in the near-infrared

    NASA Astrophysics Data System (ADS)

    Martins, Lucimara P.; Rodríguez-Ardila, Alberto; Diniz, Suzi; Riffel, Rogério; de Souza, Ronaldo

    2013-11-01

    The near-infrared spectral region is becoming a very useful wavelength range to detect and quantify the stellar population of galaxies. Models are developing to predict the contribution of the thermally pulsating stars on the asymptotic giant branch stars that should dominate the near-infrared region (NIR) spectra of populations 0.3 to 2 Gyr old. When present in a given stellar population, these stars leave unique signatures that can be used to detect them unambiguously. However, these models have to be tested in a homogeneous data base of star-forming galaxies, to check if the results are consistent with what is found from different wavelength ranges. In this work, we performed stellar population synthesis on the nuclear and extended regions of 23 star-forming galaxies to understand how the star formation tracers in the NIR can be used in practice. The stellar population synthesis shows that for the galaxies with strong emission in the NIR, there is an important fraction of young/intermediate population contributing to the spectra, which is probably the ionization source in these galaxies. Galaxies that had no emission lines measured in the NIR were found to have older average ages and less contribution of young populations. Although the stellar population synthesis method proved to be very effective to find the young ionizing population in these galaxies, no clear correlation between these results and the NIR spectral indexes were found. Thus, we believe that, in practice, the use of these indexes is still very limited due to observational limitations.

  15. Mass-metallicity relation for local star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Zhong; Zhang, Shuang-Nan; Zhao, Yong-Heng; Zhang, Wei

    2016-04-01

    We investigate the evolution of the mass-metallicity (M-Z) relation with a large sample of 53 444 star-forming galaxies (SFGs) at 0.04 < z < 0.12, selected from the catalogue of Max-Planck-Institute for Astrophysics-John Hopkins University (MPA-JHU) emission-line measurements for the Sloan Digital Sky Survey Data Release 7. Regarding the sample of SFGs, we correct the observational bias and raise the aperture covering fractions to check the reliability of the metallicity evolution. (i) We show that the redshift evolution of the log (Hα) and log([O III]) luminosities is displayed in our sample. (ii) We find the metallicity evolution of ˜0.15 dex at log (M*/M⊙) ˜ 9.3 in SFGs at 0.04 < z < 0.12. (iii) After applying the luminosity thresholds of log (LHα) > 41.0 and log (L_[O III])>39.7, we find that the metallicity evolution is shown well, and that the evolution of the star formation rate (SFR) is still shown well under the latter luminosity threshold, but the evolution is not observed under the former. (iv) The evolution of the M-Z relation seems to disappear at about log (M*/M⊙) > 10.0 after applying the luminosity threshold of log (LHα) > 41.0 or log (L_[O III])>39.7. (v) We find α = 0.09 and α = 0.07 in the equation, μ = log M* - αlog (SFR), for log (LHα) > 41.0 and log (L_[O III])>39.7 samples, respectively, and these imply that the evolution of the M-Z relation might have a weaker dependence on the SFR in our sample.

  16. Metallicity inhomogeneities in local star-forming galaxies as a sign of recent metal-poor gas accretion

    SciTech Connect

    Sánchez Almeida, J.; Morales-Luis, A. B.; Muñoz-Tuñón, C.; Méndez-Abreu, J.; Elmegreen, D. M.; Elmegreen, B. G. E-mail: abml@iac.es E-mail: elmegreen@vassar.edu E-mail: jma20@st-andrews.ac.uk

    2014-03-01

    We measure the oxygen metallicity of the ionized gas along the major axis of seven dwarf star-forming galaxies. Two of them, SDSSJ1647+21 and SDSSJ2238+14, show ≅0.5 dex metallicity decrements in inner regions with enhanced star formation activity. This behavior is similar to the metallicity drop observed in a number of local tadpole galaxies by Sánchez Almeida et al., and was interpreted as showing early stages of assembling in disk galaxies, with the star formation sustained by external metal-poor gas accretion. The agreement with tadpoles has several implications. (1) It proves that galaxies other than the local tadpoles present the same unusual metallicity pattern. (2) Our metallicity inhomogeneities were inferred using the direct method, thus discarding systematic errors usually attributed to other methods. (3) Taken together with the tadpole data, our findings suggest a threshold around one-tenth the solar value for the metallicity drops to show up. Although galaxies with clear metallicity drops are rare, the physical mechanism responsible for them may sustain a significant part of the star formation activity in the local universe. We argue that the star formation dependence of the mass-metallicity relationship, as well as other general properties followed by most local disk galaxies, is naturally interpreted as side effects of pristine gas infall. Alternatives to the metal-poor gas accretion are examined as well.

  17. IROCKS: Spatially Resolved Kinematics of z ∼ 1 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Mieda, Etsuko; Wright, Shelley A.; Larkin, James E.; Armus, Lee; Juneau, Stéphanie; Salim, Samir; Murray, Norman

    2016-11-01

    We present results from the Intermediate Redshift OSIRIS Chemo-Kinematic Survey (IROCKS) for sixteen z ∼ 1 and one z ∼ 1.4 star-forming galaxies. All galaxies were observed with OSIRIS with the laser guide star adaptive optics system at Keck Observatory. We use rest-frame nebular Hα emission lines to trace morphologies and kinematics of ionized gas in star-forming galaxies on sub-kiloparsec physical scales. We observe elevated velocity dispersions (σ ≳ 50 km s‑1) seen in z > 1.5 galaxies persist at z ∼ 1 in the integrated galaxies. Using an inclined disk model and the ratio of v/σ , we find that 1/3 of the z ∼ 1 sample are disk candidates while the other 2/3 of the sample are dominated by merger-like and irregular sources. We find that including extra attenuation toward H ii regions derived from stellar population synthesis modeling brings star formation rates (SFRs) using Hα and stellar population fit into a better agreement. We explore the properties of the compact Hα sub-component, or “clump,” at z ∼ 1 and find that they follow a similar size–luminosity relation as local H ii regions but are scaled-up by an order of magnitude with higher luminosities and sizes. Comparing the z ∼ 1 clumps to other high-redshift clump studies, we determine that the clump SFR surface density evolves as a function of redshift. This suggests clump formation is directly related to the gas fraction in these systems and may support disk fragmentation as their formation mechanism since gas fraction scales with redshift.

  18. Directed Panspermia. 3. strategies and Motivation for Seeding Star-Forming Clouds

    NASA Astrophysics Data System (ADS)

    Mautner, Michael N.

    1997-11-01

    Microbial swarms aimed at star-forming regions of interstellar clouds can seed stellar associations of 10 - 100 young planetary systems. Swarms of millimeter size, milligram packets can be launched by 35 cm solar sails at 5E-4 c, to penetrate interstellar clouds. Selective capture in high-density planetary accretion zones of densities > 1E-17 kg m-3 is achieved by viscous drag. Strategies are evaluated to seed dense cloud cores, or individual protostellar condensations, accretion disks or young planets therein. Targeting the Ophiuchus cloud is described as a model system. The biological content, dispersed in 30 μm, 1E-10 kg capsules of 1E6 freeze-dried microorganisms each, may be captured by new planets or delivered to planets after incorporation first into carbonaceous asteroids and comets. These objects, as modeled by meteorite materials, contain biologically available organic and mineral nutrients that are shown to sustain microbial growth. The program may be driven by panbiotic ethics, predicated on: 1. The unique position of complex organic life amongst the structures of Nature; 2. Self-propagation as the basic propensity of the living pattern; 3. The biophysical unity humans with of the organic, DNA/protein family of life; and 4. Consequently, the primary human purpose to safeguard and propagate our organic life form. To promote this purpose, panspermia missions with diverse biological payloads will maximize survival at the targets and induce evolutionary pressures. In particular, eukaryotes and simple multicellular organisms in the payload will accelerate higher evolution. Based on the geometries and masses of star-forming regions, the 1E24 kg carbon resources of one solar system, applied during its 5E9 yr lifespan, can seed all newly forming planetary systems in the galaxy.

  19. Fragmentation in Dusty Low-metallicity Star-forming Halos

    NASA Astrophysics Data System (ADS)

    Meece, Gregory R.; Smith, Britton D.; O'Shea, Brian W.

    2014-03-01

    The first stars in the universe, termed Population III, are thought to have been very massive compared to the stars that form in the present epoch. As feedback from the first generation of stars altered the contents of the interstellar medium, the universe switched to a low-mass mode of star formation, which continues in the high-metallicity stars formed in the present era. Several studies have investigated the transition between metal-free and metal-enriched star formation, with tentative evidence being found for a metallicity threshold near 10-3.5 Z ⊙ due to atomic and molecular transitions and another threshold near 10-5.5 Z ⊙ due to dust. In this work, we simulate the fragmentation of cooling gas in idealized, low-metallicity halos using the adaptive mesh refinement code Enzo. We conduct several simulations of 106 M ⊙ and 107 M ⊙ halos at z = 20 in which the metal content, initial rotation, and degree of turbulence are varied in order to study the effect of these properties on gas fragmentation over a range of densities. We find tentative support for the idea of a critical metallicity, but the effect of varying metallicity on the gas we observe is not as dramatic as what has been reported in earlier studies. It is theorized that at lower redshifts with a lower cosmic microwave background temperature, variations in metallicity might have a larger effect on cooling and fragmentation. We find no clear relation between the initial spin or the initial level of turbulence in the halo and the final properties of the gas contained therein. Additionally, we find that the degree to which the Jeans length is refined, the initial density profile of the gas, and the inclusion of deuterium chemistry each have a significant effect on the evolution and fragmentation of the gas in the halo—in particular, we find that at least 64 grid cells are needed to cover the Jeans length in order to properly resolve the fragmentation.

  20. Fragmentation in dusty low-metallicity star-forming halos

    SciTech Connect

    Meece, Gregory R.; Smith, Britton D.; O'Shea, Brian W.

    2014-03-10

    The first stars in the universe, termed Population III, are thought to have been very massive compared to the stars that form in the present epoch. As feedback from the first generation of stars altered the contents of the interstellar medium, the universe switched to a low-mass mode of star formation, which continues in the high-metallicity stars formed in the present era. Several studies have investigated the transition between metal-free and metal-enriched star formation, with tentative evidence being found for a metallicity threshold near 10{sup –3.5} Z {sub ☉} due to atomic and molecular transitions and another threshold near 10{sup –5.5} Z {sub ☉} due to dust. In this work, we simulate the fragmentation of cooling gas in idealized, low-metallicity halos using the adaptive mesh refinement code Enzo. We conduct several simulations of 10{sup 6} M {sub ☉} and 10{sup 7} M {sub ☉} halos at z = 20 in which the metal content, initial rotation, and degree of turbulence are varied in order to study the effect of these properties on gas fragmentation over a range of densities. We find tentative support for the idea of a critical metallicity, but the effect of varying metallicity on the gas we observe is not as dramatic as what has been reported in earlier studies. It is theorized that at lower redshifts with a lower cosmic microwave background temperature, variations in metallicity might have a larger effect on cooling and fragmentation. We find no clear relation between the initial spin or the initial level of turbulence in the halo and the final properties of the gas contained therein. Additionally, we find that the degree to which the Jeans length is refined, the initial density profile of the gas, and the inclusion of deuterium chemistry each have a significant effect on the evolution and fragmentation of the gas in the halo—in particular, we find that at least 64 grid cells are needed to cover the Jeans length in order to properly resolve the

  1. The nature of Hα-selected galaxies at z > 2. II. Clumpy galaxies and compact star-forming galaxies

    SciTech Connect

    Tadaki, Ken-ichi; Kodama, Tadayuki; Koyama, Yusei; Tanaka, Ichi; Hayashi, Masao; Shimakawa, Rhythm

    2014-01-01

    We present the morphological properties of Hα-selected galaxies at z > 2 in SXDF-UDS-CANDELS field. With high-resolution optical/near-infrared images obtained by the Hubble Space Telescope, we identify giant clumps within the Hα emitters (HAEs). We find that at least 41% of our sample shows clumpy structures in the underlying disks. The color gradient of clumps is commonly seen in the sense that the clumps near the galactic center tend to be redder than those in the outer regions. The mid-infrared detection in galaxies with red clumps and the spatial distribution of Hα emission suggest that dusty star-formation activity is probably occurring in the nuclear red clumps. A gas supply to a bulge component through clump migration is one of the most potent physical processes for producing such dusty star-forming clumps and forming massive bulges in local early-type galaxies. They would become large quiescent galaxies at later times just by consumption or blowout of remaining gas. Also, while most of the HAEs have extended disks, we observe two massive, compact HAEs whose stellar surface densities are significantly higher. They are likely to be the direct progenitors of massive, compact quiescent galaxies at z = 1.5-2.0. Two evolutionary paths to massive quiescent galaxies are devised to account for both the size growth of quiescent galaxies and their increased number density from z ∼ 2 to z = 0.

  2. Expanded Very Large Array Observations of the Barnard 5 Star-forming Core: Embedded Filaments Revealed

    NASA Astrophysics Data System (ADS)

    Pineda, Jaime E.; Goodman, Alyssa A.; Arce, Héctor G.; Caselli, Paola; Longmore, Steven; Corder, Stuartt

    2011-09-01

    We present ~6farcm5 × 8' Expanded Very Large Array (EVLA) mosaic observations of the NH3 (1,1) emission in the Barnard 5 region in Perseus, with an angular resolution of 6''. This map covers the coherent region, where the dense gas presents subsonic non-thermal motions (as seen from single dish observations with the Green Bank Telescope, GBT). The combined EVLA and GBT observations reveal, for the first time, a striking filamentary structure (20'' wide or 5000 AU at the distance of Perseus) in this low-mass star-forming region. The integrated intensity profile of this structure is consistent with models of an isothermal filament in hydrostatic equilibrium. The observed separation between the B5-IRS1 young stellar object (YSO), in the central region of the core, and the northern starless condensation matches the Jeans length of the dense gas. This suggests that the dense gas in the coherent region is fragmenting. The observed region displays a narrow velocity dispersion, where most of the gas shows evidence for subsonic turbulence and where little spatial variations are present. It is only close to the YSO where an increase in the velocity dispersion is found, but still displaying subsonic non-thermal motions.

  3. Different Evolutionary Stages in the Massive Star-forming Complex W3 Main

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Beuther, Henrik; Zhang, Qizhou; Bik, Arjan; Rodón, Javier A.; Jiang, Zhibo; Fallscheer, Cassandra

    2013-03-01

    We observed with the Submillimeter Array and IRAM 30 m telescope three high-mass star-forming regions in different evolutionary stages in the W3 high-mass star formation complex. These regions, i.e. W3 SMS1 (W3 IRS5), SMS2 (W3 IRS4) and SMS3, are located within the same large-scale environment, which allows us to study rotation and outflows as well as chemical properties in an evolutionary sense. While we find multiple mm continuum sources toward all regions, these three subregions exhibit different dynamical and chemical properties, which indicates that they are in different evolutionary stages. Even within each sub-region, massive cores of different ages are found, e.g. in SMS2, sub-sources from the most evolved UCHii region to potential starless cores exist within 30 000 AU (left panel, Fig. 1). Outflows and rotational structures are found in SMS1 and SMS2. Evidence for interactions between the molecular cloud and the HII regions is found in the 13CO channel maps (right panel, Fig. 1), which may indicate triggered star formation.

  4. Active region flows

    NASA Technical Reports Server (NTRS)

    Foukal, Peter

    1987-01-01

    A wide range of observations has shown that active region phenomena in the photospheric, chromospheric and coronal temperature regimes are dynamical in nature. At the photosphere, recent observations of full line profiles place an upper limit of about + or - 20/msec on any downflows at supergranule cell edges. Observations of the full Stokes 5 profiles in the network show no evidence for downflows in magnetic flux tubes. In the area of chromospheric dynamics, several models were put forward recently to reproduce the observed behavior of spicules. However, it is pointed out that these adiabatic models do not include the powerful radiative dissipation which tend to damp out the large amplitude disturbances that produce the spicular acceleration in the models. In the corona, loop flows along field lines clearly transport mass and energy at rates important for the dynamics of these structures. However, advances in understanding the heating and mass balance of the loop structures seem to require new kinds of observations. Some results are presented using a remote sensing diagnostic of the intensity and orientation of macroscopic plasma electric fields predicted by models of reconnective heating and also wave heating.

  5. KMOS3D: Dynamical Constraints on the Mass Budget in Early Star-forming Disks

    NASA Astrophysics Data System (ADS)

    Wuyts, Stijn; Förster Schreiber, Natascha M.; Wisnioski, Emily; Genzel, Reinhard; Burkert, Andreas; Bandara, Kaushala; Beifiori, Alessandra; Belli, Sirio; Bender, Ralf; Brammer, Gabriel B.; Chan, Jeffrey; Davies, Ric; Fossati, Matteo; Galametz, Audrey; Kulkarni, Sandesh K.; Lang, Philipp; Lutz, Dieter; Mendel, J. Trevor; Momcheva, Ivelina G.; Naab, Thorsten; Nelson, Erica J.; Saglia, Roberto P.; Seitz, Stella; Tacconi, Linda J.; Tadaki, Ken-ichi; Übler, Hannah; van Dokkum, Pieter G.; Wilman, David J.; Wuyts, Eva

    2016-11-01

    We exploit deep integral-field spectroscopic observations with KMOS/Very Large Telescope of 240 star-forming disks at 0.6\\lt z\\lt 2.6 to dynamically constrain their mass budget. Our sample consists of massive (≳ {10}9.8 {M}ȯ ) galaxies with sizes {R}e≳ 2 {kpc}. By contrasting the observed velocity and dispersion profiles with dynamical models, we find that on average the stellar content contributes {32}-7+8 % of the total dynamical mass, with a significant spread among galaxies (68th percentile range {f}{star}∼ 18 % {--}62 % ). Including molecular gas as inferred from CO- and dust-based scaling relations, the estimated baryonic mass adds up to {56}-12+17 % of the total for the typical galaxy in our sample, reaching ∼ 90 % at z\\gt 2. We conclude that baryons make up most of the mass within the disk regions of high-redshift star-forming disk galaxies, with typical disks at z\\gt 2 being strongly baryon-dominated within R e . Substantial object-to-object variations in both stellar and baryonic mass fractions are observed among the galaxies in our sample, larger than what can be accounted for by the formal uncertainties in their respective measurements. In both cases, the mass fractions correlate most strongly with measures of surface density. High-{{{Σ }}}{star} galaxies feature stellar mass fractions closer to unity, and systems with high inferred gas or baryonic surface densities leave less room for additional mass components other than stars and molecular gas. Our findings can be interpreted as more extended disks probing further (and more compact disks probing less far) into the dark matter halos that host them. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 092.A-0091, 093.A-0079, 094.A-0217, 095.A-0047, and 096.A-0025.

  6. Physical properties of low-mass star-forming galaxies at intermediate redshifts (z <1)

    NASA Astrophysics Data System (ADS)

    Gallego, J.; Rodríguez-Muñoz, L.; Pacifici, C.; Tresse, L.; Charlot, S.; Gil de Paz, A.; Barro, G.; Villar, V.

    2015-05-01

    In this poster we present the physical properties of a sample of low-mass star-forming galaxies at intermediate redshifts (z<1). We selected a population of dwarf galaxies because dwarf galaxies play a key role in galaxy formation and evolution: (1) they resemble the first structures that hierarchical models predict to form first in the Universe (Dekel & Silk 1986) and that are responsible for the reionization process (Bouwens et al. 2012); and (2) the way or epoch they form and how they evolve are still open questions of modern astrophysics. We selected the sample on the CDFS field. Photometry (40 bands, from UV to far-IR) and preliminary photometric redshifts and stellar masses were obtained from RAINBOW database (Pérez-González et al. 2008). Morphology fom Griffith et al. (2012). Main selection was done by stellar mass, selecting those galaxies with stellar mass M_*<10^8 {M}_⊙. Spectroscopic redshifts were obtained from deep (4 h) MOS spectroscopy with the VIMOS spectrograph at VLT. The average spectrum is characterized by a faint, blue and flat continuum and strong emission lines, revealing that the systems are dominated by an undergoing star formation burst. SFRs and stellar masses are consistent with the SF main-squence over a 2 dex range. More massive objects show higher SFRs than low-mass objects, following the SF main sequence. Distant dwarfs and BCDs follow the overall star-forming sequence in the excitation-luminosity diagram, populating the high excitation, low metallicity and high strength region.

  7. Astronomers Gain Important Insight on How Massive Stars Form

    NASA Astrophysics Data System (ADS)

    2006-09-01

    Astronomers using the National Science Foundation's Very Large Array (VLA) radio telescope have discovered key evidence that may help them figure out how very massive stars can form. Young Star Graphic Artist's Conception of Young Star Showing Motions Detected in G24 A1: (1) Infall toward torus, (2) Rotation and (3) outflow. CREDIT: Bill Saxton, NRAO/AUI/NSF Click on image for larger graphic file (JPEG, 129K) "We think we know how stars like the Sun are formed, but there are major problems in determining how a star 10 times more massive than the Sun can accumulate that much mass. The new observations with the VLA have provided important clues to resolving that mystery," said Maria Teresa Beltran, of the University of Barcelona in Spain. Beltran and other astronomers from Italy and Hawaii studied a young, massive star called G24 A1 about 25,000 light-years from Earth. This object is about 20 times more massive than the Sun. The scientists reported their findings in the September 28 issue of the journal Nature. Stars form when giant interstellar clouds of gas and dust collapse gravitationally, compacting the material into what becomes the star. While astronomers believe they understand this process reasonably well for smaller stars, the theoretical framework ran into a hitch with larger stars. "When a star gets up to about eight times the mass of the Sun, it pours out enough light and other radiation to stop the further infall of material," Beltran explained. "We know there are many stars bigger than that, so the question is, how do they get that much mass?" One idea is that infalling matter forms a disk whirling around the star. With most of the radiation escaping without hitting the disk, material can continue to fall into the star from the disk. According to this model, some material will be flung outward along the rotation axis of the disk into powerful outflows. "If this model is correct, there should be material falling inward, rushing outward and rotating

  8. Kinematics in the Interacting, Star-Forming Galaxies NGC 3395/3396 and NGC 3991/3994/3995

    NASA Technical Reports Server (NTRS)

    Weistrop, Donna; Nelson, Charles H.

    1999-01-01

    It has been suggested that induced star formation is more sensitive to galaxy dynamics than to local phenomena and that enhanced star formation is found in galaxies with disturbed velocity structures. We are studying the stellar populations of several UV-bright, interacting galaxies to try to understand the detailed star formation process in these systems. We present preliminary results of an investigation of the kinematics of star-forming regions in the interacting systems NGC 3395/3396 and NGC 3991/3994/3995. Regions of powerful star formation are observed throughout these galaxies. The observatation will be used to investigate rotation curves in the galaxies and motion in the tidal tails.

  9. Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core

    NASA Technical Reports Server (NTRS)

    Hamaguchi, Ken-Ji; Corcoran, Michael F.; Petre, Rob; White, Nicholas E.; Stelzer, Beate; Nedachi, Ko; Kobayashi, Naoto

    2004-01-01

    We detected three extremely embedded X-ray sources in the R Corona Australis (R CrA) star forming core, IRS 7 region. Two weak X-ray sources are associated with the VLA centimeter radio sources 10E & W, whereas the third brightest source detected in the two XMM-Newton observations on March 2003 has no counterpart at any wavelengths. The large K-band upper-limit (19.4m) measured with the University of Hawaii 88-inch Telescope and strong absorption derived in X-rays (N(sub H) approx. 2.8 x 10(exp 23)/sq cm equivalent to A(sub v) approx. 180 m) indicate that the source is younger than typical Class I protostars, i.e. a Class 0 protostar or an intermittent phase between Class 0 and Class I protostars. The X-ray luminosity was less than one thirtieth (log L(sub x) less than or approx. equals 29.3 ergs/s) in the former Chandra observation in October 2000, which suggests that the X-ray activity, probably generated by magnetic activity, is triggered by an intermittent mass accretion episode such as FU Ori type outbursts. Because the source was detected at high significance in the XMM-Newton observations (approx. 2,000 cnts), X-ray properties of such young protostars can be well investigated for the first time. The light curves were constant in the 1st observation and increased linearly by a factor of two during 30 ksec in the 2nd observation. Both spectra showed iron K lines originated in hot thin-thermal plasma and fluorescence by cold gas. They can be reproduced by an absorbed thin-thermal plasma model with a Gaussian component at 6.4 keV (kT approx. 3-4 keV, L(sub x) approx. 7-20 x 10(exp 30) ergs/s). The rising timescale of the light curves in the 2nd observation was too slow for magnetically generated X-ray flares, whereas large equivalent width of the fluorescence iron K line in the 1st observation (approx. 810 eV) requires strong partial covering of the X-ray source. These results suggest that a confined hot (perhaps accretion) spot on the protostellar core was

  10. The Fragmentation of Magnetized, Massive Star-forming Cores with Radiative Feedback

    NASA Astrophysics Data System (ADS)

    Myers, Andrew T.; McKee, Christopher F.; Cunningham, Andrew J.; Klein, Richard I.; Krumholz, Mark R.

    2013-04-01

    We present a set of three-dimensional, radiation-magnetohydrodynamic calculations of the gravitational collapse of massive (300 M ⊙), star-forming molecular cloud cores. We show that the combined effects of magnetic fields and radiative feedback strongly suppress core fragmentation, leading to the production of single-star systems rather than small clusters. We find that the two processes are efficient at suppressing fragmentation in different regimes, with the feedback most effective in the dense, central region and the magnetic field most effective in more diffuse, outer regions. Thus, the combination of the two is much more effective at suppressing fragmentation than either one considered in isolation. Our work suggests that typical massive cores, which have mass-to-flux ratios of about 2 relative to critical, likely form a single-star system, but that cores with weaker fields may form a small star cluster. This result helps us understand why the observed relationship between the core mass function and the stellar initial mass function holds even for ~100 M ⊙ cores with many thermal Jeans masses of material. We also demonstrate that a ~40 AU Keplerian disk is able to form in our simulations, despite the braking effect caused by the strong magnetic field.

  11. Spiral-like star-forming patterns in CALIFA early-type galaxies

    NASA Astrophysics Data System (ADS)

    Gomes, J. M.; Papaderos, P.; Vílchez, J. M.; Kehrig, C.; Iglesias-Páramo, J.; Breda, I.; Lehnert, M. D.; Sánchez, S. F.; Ziegler, B.; Dos Reis, S. N.; Bland-Hawthorn, J.; Galbany, L.; Bomans, D. J.; Rosales-Ortega, F. F.; Walcher, C. J.; García-Benito, R.; Márquez, I.; Del Olmo, A.; Mollá, M.; Marino, R. A.; Catalán-Torrecilla, C.; González Delgado, R. M.; López-Sánchez, Á. R.; Califa Collaboration

    2016-01-01

    Based on a combined analysis of SDSS imaging and CALIFA integral field spectroscopy data, we report on the detection of faint (24 <μr mag/□″< 26) star-forming spiral-arm-like features in the periphery of three nearby early-type galaxies (ETGs). These features are of considerable interest because they document the still ongoing inside-out growth of some local ETGs and may add valuable observational insight into the origin and evolution of spiral structure in triaxial stellar systems. A characteristic property of the nebular component in the studied ETGs, classified i+, is a two-radial-zone structure, with the inner zone that displays faint (EW(Hα) ≃ 1 Å) low-ionization nuclear emission-line region (LINER) properties, and the outer one (3 Å region characteristics. This spatial segregation of nebular emission in two physically distinct concentric zones calls for an examination of aperture effects in studies of type i+ ETGs with single-fiber spectroscopic data. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie (MPIA) and the Instituto de Astrofísica de Andalucía (CSIC).

  12. Regional Activities Division. Papers.

    ERIC Educational Resources Information Center

    International Federation of Library Associations, The Hague (Netherlands).

    Papers on library network activities in Canada, the Third World, Japan, Malaysia, Brazil, and Sweden which were presented at the 1982 International Federation of Library Associations (IFLA) conference include: (1) "Canada: A Voluntary and Flexible Network," a review by Guy Sylvestre of the political, social, and economic structures affecting…

  13. Spitzer Observations of the Massive Star-forming Complex S254-S258: Structure and Evolution

    NASA Astrophysics Data System (ADS)

    Chavarría, Luis A.; Allen, Lori E.; Hora, Joseph L.; Brunt, Christopher M.; Fazio, Giovanni G.

    2008-07-01

    We present Spitzer IRAC, NOAO 2.1 m Flamingos, Keck NIRC, and FCRAO SEQUOIA observations of the massive star-forming complex S254-S258, covering an area of 25' × 20'. Using a combination of the IRAC and NIR data, we identify and classify the young stellar objects (YSOs) in the complex. We detect 510 sources with near- or mid-IR excess, and we classify 87 Class I and 165 Class II sources. The YSOs are found in clusters surrounded by isolated YSOs in a low-density distributed population. The ratio of clustered to total YSOs is 0.8. We identify six new clusters in the complex. One of them, G192.63-00, is located around the ionizing star of the H II region S255. We hypothesize that the ionizing star of S255 was formed in this cluster. We also detect a southern component of the cluster in H II region S256. The cluster G192.54-0.15, located inside H II region S254 has a VLSR of 17 km s-1 with respect to the main cloud, and we conclude that it is located in the background of the complex. The structure of the molecular cloud is examined using 12CO and 13CO , as well as a near-IR extinction map. The main body of the molecular cloud has VLSR between 5 and 9 km s-1. The arc-shaped structure of the molecular cloud following the border of the H II regions and the high column density in the border of the H II regions support the idea that the material has been swept up by the expansion of the H II regions.

  14. Galactic Winds and Structure of z ~ 2 Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Newman, Sarah F.

    Galactic-scale outflows are a key driver of galaxy evolution through their feedback effect on star-formation and their ejection of metals and energy into the inter-galactic medium (IGM). While it is known that outflows likely play an important role in the quenching of star-formation - transforming actively star-forming, blue galaxies into their 'red and dead' counterparts - this role is currently not well understood. In particular, at z ˜ 2, during the most active epoch of star-formation, the mass and energy in these outflows is poorly constrained, as is the mechanism for launching them. Furthermore, active-galactic nuclei (AGN) in the centers of massive star-forming galaxies (SFGs) likely play an important role in star-formation quenching, but we do not have a clear understanding of how this AGN feedback compares with that of star-formation driven feedback, and it is not known how many of these massive SFGs at z ˜ 2 even have AGN. This issue is complicated by the fact that many high-z AGN are likely highly obscured, and have strong nebular emission line contributions from both star-formation and the AGN. In this dissertation, I explore these issues using high-spatial and spectral resolution integral field unit spectroscopic data of z ˜ 2 SFGs. The observations are obtained with the instrument SINFONI on the European Southern Observatory (ESO) Very Large Telescope (VLT) at Cerro Paranal. These high-quality data allow spatially-resolved studies of the gas-phase kinematics of these galaxies, as well dynamical information on their outflows. In this work, I explore outflow properties in one galaxy with exceptionally deep data, allowing detailed examination of the outflow energetics, spatial extent and underlying ISM properties, as well those from a larger sample of galaxies. I also probe the fraction of SFGs in our sample which contain (possibly obscured) AGN, and study how this affects our determination of galaxy properties, such as gas-phase metallicity. Finally

  15. [C II] LINE EMISSION IN MASSIVE STAR-FORMING GALAXIES AT z = 4.7

    SciTech Connect

    Wagg, J.; Aravena, M.; Martin, S.; Wiklind, T.; Peck, A.; Barkats, D.; Cortes, J. R.; Hills, R.; Hodge, J.; Impellizzeri, C. M V.; Rawlings, M. G.; Carilli, C. L.; Espada, D.; Iono, D.; Riechers, D.; Walter, F.; Wootten, A.; Leroy, A.; Maiolino, R.; McMahon, R. G.; and others

    2012-06-20

    We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C II] 157.7 {mu}m fine structure line and thermal dust continuum emission from a pair of gas-rich galaxies at z = 4.7, BR1202-0725. This system consists of a luminous quasar host galaxy and a bright submillimeter galaxy (SMG), while a fainter star-forming galaxy is also spatially coincident within a 4'' (25 kpc) region. All three galaxies are detected in the submillimeter continuum, indicating FIR luminosities in excess of 10{sup 13} L{sub Sun} for the two most luminous objects. The SMG and the quasar host galaxy are both detected in [C II] line emission with luminosities L{sub [CII]} = (10.0 {+-} 1.5) Multiplication-Sign 10{sup 9} L{sub Sun} and L{sub [CII]} = (6.5 {+-} 1.0) Multiplication-Sign 10{sup 9} L{sub Sun }, respectively. We estimate a luminosity ratio L{sub [CII]}/L{sub FIR} = (8.3 {+-} 1.2) Multiplication-Sign 10{sup -4} for the starburst SMG to the north and L{sub [CII]}/L{sub FIR} = (2.5 {+-} 0.4) Multiplication-Sign 10{sup -4} for the quasar host galaxy, in agreement with previous high-redshift studies that suggest lower [C II]-to-FIR luminosity ratios in quasars than in starburst galaxies. The third fainter object with a flux density S{sub 340GHz} = 1.9 {+-} 0.3 mJy is coincident with a Ly{alpha} emitter and is detected in HST ACS F775W and F814W images but has no clear counterpart in the H band. Even if this third companion does not lie at a redshift similar to BR1202-0725, the quasar and the SMG represent an overdensity of massive, infrared luminous star-forming galaxies within 1.3 Gyr of the big bang.

  16. The Herschel Virgo Cluster Survey. XVIII. Star-forming dwarf galaxies in a cluster environment

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Hunt, L. K.; Madden, S. C.; Hughes, T. M.; Auld, R.; Baes, M.; Bendo, G. J.; Bianchi, S.; Bizzocchi, L.; Boquien, M.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Davies, J.; De Looze, I.; di Serego Alighieri, S.; Fritz, J.; Pappalardo, C.; Pierini, D.; Rémy-Ruyer, A.; Smith, M. W. L.; Verstappen, J.; Viaene, S.; Vlahakis, C.

    2015-02-01

    To assess the effects of the cluster environment on the different components of the interstellar medium, we analyse the far-infrared (FIR) and submillimetre (submm) properties of a sample of star-forming dwarf galaxies detected by the Herschel Virgo Cluster Survey (HeViCS). We determine dust masses and dust temperatures by fitting a modified black body function to the spectral energy distributions (SEDs). Stellar and gas masses, star formation rates (SFRs), and metallicities are obtained from the analysis of a set of ancillary data. Dust is detected in 49 out of a total 140 optically identified dwarfs covered by the HeViCS field; considering only dwarfs brighter than mB = 18 mag, this gives a detection rate of 43%. After evaluating different emissivity indices, we find that the FIR-submm SEDs are best-fit by β = 1.5, with a median dust temperature Td = 22.4 K. Assuming β = 1.5, 67% of the 23 galaxies detected in all five Herschel bands show emission at 500 μm in excess of the modified black-body model. The fraction of galaxies with a submillimetre excess decreases for lower values of β, while a similarly high fraction (54%) is found if a β-free SED modelling is applied. The excess is inversely correlated with SFR and stellar masses. To study the variations in the global properties of our sample that come from environmental effects, we compare the Virgo dwarfs to other Herschel surveys,such as the Key Insights into Nearby Galaxies: Far-Infrared Survey with Herschel (KINGFISH), the Dwarf Galaxy Survey (DGS), and the HeViCS Bright Galaxy Catalogue (BGC). We explore the relations between stellar mass and Hi fraction, specific star formation rate, dust fraction, gas-to-dust ratio over a wide range of stellar masses (from 107 to 1011 M⊙) for both dwarfs and spirals. Highly Hi-deficient Virgo dwarf galaxies are mostly characterised by quenched star formation activity and lower dust fractions giving hints for dust stripping in cluster dwarfs. However, to explain the

  17. Reconciling the Observed Star-forming Sequence with the Observed Stellar Mass Function

    NASA Astrophysics Data System (ADS)

    Leja, Joel; van Dokkum, Pieter G.; Franx, Marijn; Whitaker, Katherine E.

    2015-01-01

    We examine the connection between the observed star-forming sequence (SFR vprop M α) and the observed evolution of the stellar mass function in the range 0.2 < z < 2.5. We find that the star-forming sequence cannot have a slope α <~ 0.9 at all masses and redshifts because this would result in a much higher number density at 10 < log (M/M ⊙) < 11 by z = 1 than is observed. We show that a transition in the slope of the star-forming sequence, such that α = 1 at log (M/M ⊙) < 10.5 and α = 0.7-0.13z (Whitaker et al.) at log (M/M ⊙) > 10.5, greatly improves agreement with the evolution of the stellar mass function. We then derive a star-forming sequence that reproduces the evolution of the mass function by design. This star-forming sequence is also well described by a broken power law, with a shallow slope at high masses and a steep slope at low masses. At z = 2, it is offset by ~0.3 dex from the observed star-forming sequence, consistent with the mild disagreement between the cosmic star formation rate (SFR) and recent observations of the growth of the stellar mass density. It is unclear whether this problem stems from errors in stellar mass estimates, errors in SFRs, or other effects. We show that a mass-dependent slope is also seen in other self-consistent models of galaxy evolution, including semianalytical, hydrodynamical, and abundance-matching models. As part of the analysis, we demonstrate that neither mergers nor hidden low-mass quiescent galaxies are likely to reconcile the evolution of the mass function and the star-forming sequence. These results are supported by observations from Whitaker et al.

  18. RECONCILING THE OBSERVED STAR-FORMING SEQUENCE WITH THE OBSERVED STELLAR MASS FUNCTION

    SciTech Connect

    Leja, Joel; Van Dokkum, Pieter G.; Franx, Marijn; Whitaker, Katherine E.

    2015-01-10

    We examine the connection between the observed star-forming sequence (SFR ∝ M {sup α}) and the observed evolution of the stellar mass function in the range 0.2 < z < 2.5. We find that the star-forming sequence cannot have a slope α ≲ 0.9 at all masses and redshifts because this would result in a much higher number density at 10 < log (M/M {sub ☉}) < 11 by z = 1 than is observed. We show that a transition in the slope of the star-forming sequence, such that α = 1 at log (M/M {sub ☉}) < 10.5 and α = 0.7-0.13z (Whitaker et al.) at log (M/M {sub ☉}) > 10.5, greatly improves agreement with the evolution of the stellar mass function. We then derive a star-forming sequence that reproduces the evolution of the mass function by design. This star-forming sequence is also well described by a broken power law, with a shallow slope at high masses and a steep slope at low masses. At z = 2, it is offset by ∼0.3 dex from the observed star-forming sequence, consistent with the mild disagreement between the cosmic star formation rate (SFR) and recent observations of the growth of the stellar mass density. It is unclear whether this problem stems from errors in stellar mass estimates, errors in SFRs, or other effects. We show that a mass-dependent slope is also seen in other self-consistent models of galaxy evolution, including semianalytical, hydrodynamical, and abundance-matching models. As part of the analysis, we demonstrate that neither mergers nor hidden low-mass quiescent galaxies are likely to reconcile the evolution of the mass function and the star-forming sequence. These results are supported by observations from Whitaker et al.

  19. Charge-exchange X-ray emission of nearby star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Liu, Jiren; Wang, Q. Daniel; Mao, Shude

    2012-03-01

    Properties of hot gas outflows from galaxies are generally measured from associated X-ray line emission assuming that it represents atomic transitions in thermally excited hot gas. X-ray line emission, however, can also arise from the charge exchange between highly ionized ions and neutral species. The Kα triplet of He-like ions can be used as a powerful diagnostic, because the charge-exchange X-ray emission (CXE) favours the intercombination and forbidden lines, while the thermal emission favours the resonance line. We analyse the O VII triplet of a sample of nine nearby star-forming galaxies observed by the XMM-Newton Reflection Grating Spectrometers. For most galaxies, the forbidden lines are comparable to or stronger than the resonance lines, which is in contrast to the thermal prediction. For NGC 253, M51, M83, M61, NGC 4631, and the Antennae (Arp 244), the observed line ratios are consistent with the ratio of CXE; for M94 and NGC 2903, the observed ratios indicate multiple origins; for M82, different regions show different line ratios, also indicating multiple origins. We discuss other possible mechanisms that can produce a relatively strong forbidden line, such as a collisional non-equilibrium-ionization recombining/ionizing plasma, which are not favoured. These results suggest that the CXE may be a common phenomenon and contribute a significant fraction of the soft X-ray line emission for galaxies with massive star formation.

  20. Mass accretion flows in the high-mass star forming complex NGC 6334

    NASA Astrophysics Data System (ADS)

    Sánchez-Monge, Á.; Schilke, P.; Zernickel, A.; Schmiedeke, A.; Möller, Th.; Qin, S.-L.

    2016-05-01

    The formation of high-mass stars is one of the major topics of astrophysical research, in particular the process of accretion from large-scale clouds down to small-scale cores. We have selected the nearby, filamentary, high-mass star forming complex NGC 6334 to study the gas velocity at different scales and probe the infall rates onto the protostellar cores embedded in the NGC 6334-I and I(N) clusters. This study makes use of single-dish and interferometric submillimeter observations, complemented with 3D numerical non-LTE radiative transfer modeling. We measure a mass accretion rate of 10-5 M⊙ yr-1 throughout the filament increasing up to 10-3 M⊙ yr-1 towards the densest regions where high-mass stars are forming. At smaller scales, our 3D model is consistent with accretion rates of 10-3 M⊙ yr-1 towards the clusters, and 10-4 M⊙ yr-1 onto the protostars.

  1. OUTFLOW, INFALL, AND PROTOSTARS IN THE STAR-FORMING CORE W3-SE

    SciTech Connect

    Zhu Lei; Zhao Junhui; Wright, M. C. H. E-mail: jzhao@cfa.harvard.edu

    2011-10-20

    We report new results on outflow and infall in the star-forming cores W3-SE SMA-1 and SMA-2 based on analysis of {approx}2.''5 resolution observations of the molecular lines HCN(3-2), HCO{sup +}(3-2), N{sub 2}H{sup +}(3-2), and CH{sub 3}OH(5{sub 2,3}-4{sub 1,3}) with the Submillimeter Array (SMA). A high-velocity bipolar outflow originating from the protostellar core SMA-1 was observed in the HCN(3-2) line, with a projected outflow axis at a position angle of 48{sup 0}. The detection of the outflow is confirmed from other molecular lines. An inverse P-Cygni profile in the HCN(3-2) line toward SMA-1 suggests that at least one of the double cores accretes matter from the molecular core. A filamentary structure in the molecular gas surrounds SMA-1 and SMA-2. Based on the SMA observations, our analysis suggests that the double pre-stellar cores SMA-1 and SMA-2 result from fragmentation in the collapsing massive molecular core W3-SE, and it is likely that they are forming intermediate- to high-mass stars which will be new members of a star cluster in the W3-SE region.

  2. Chandra/ACIS Observations of the 30 Doradus Star-Forming Complex

    NASA Astrophysics Data System (ADS)

    Townsley, Leisa; Broos, Patrick; Feigelson, Eric; Burrows, David; Chu, You-Hua; Garmire, Gordon; Griffiths, Richard; Maeda, Yoshitomo; Pavlov, George; Tsuboi, Yohko

    2002-04-01

    30 Doradus is the archetype giant extragalactic H II region, a massive star-forming complex in the Large Magellanic Cloud. We examine high-spatial-resolution X-ray images and spectra of the essential parts of 30 Doradus, obtained with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-ray Observatory. The central cluster of young high-mass stars, R136, is resolved at the arcsecond level, allowing spectral analysis of bright constituents; other OB/Wolf-Rayet binaries and multiple systems (e.g. R139, R140) are also detected. Spatially-resolved spectra are presented for N157B, the composite SNR containing a 16-msec pulsar. The spectrally soft superbubble structures seen by ROSAT are dramatically imaged by Chandra; we explore the spectral differences they exhibit. Taken together, the components of 30 Doradus give us an excellent microscopic view of high-energy phenomena seen on larger scales in more distant galaxies as starbursts and galactic winds.

  3. A Hard X-Ray Study of the Normal Star-forming Galaxy M83 with NuSTAR

    NASA Astrophysics Data System (ADS)

    Yukita, M.; Hornschemeier, A. E.; Lehmer, B. D.; Ptak, A.; Wik, D. R.; Zezas, A.; Antoniou, V.; Maccarone, T. J.; Replicon, V.; Tyler, J. B.; Venters, T.; Argo, M. K.; Bechtol, K.; Boggs, S.; Christensen, F. E.; Craig, W. W.; Hailey, C.; Harrison, F.; Krivonos, R.; Kuntz, K.; Stern, D.; Zhang, W. W.

    2016-06-01

    We present the results from sensitive, multi-epoch NuSTAR observations of the late-type star-forming galaxy M83 (d = 4.6 Mpc). This is the first investigation to spatially resolve the hard (E\\gt 10 keV) X-ray emission of this galaxy. The nuclear region and ˜20 off-nuclear point sources, including a previously discovered ultraluminous X-ray source, are detected in our NuSTAR observations. The X-ray hardnesses and luminosities of the majority of the point sources are consistent with hard X-ray sources resolved in the starburst galaxy NGC 253. We infer that the hard X-ray emission is most likely dominated by intermediate accretion state black hole binaries and neutron star low-mass X-ray binaries (Z-sources). We construct the X-ray binary luminosity function (XLF) in the NuSTAR band for an extragalactic environment for the first time. The M83 XLF has a steeper XLF than the X-ray binary XLF in NGC 253, which is consistent with previous measurements by Chandra at softer X-ray energies. The NuSTAR integrated galaxy spectrum of M83 drops quickly above 10 keV, which is also seen in the starburst galaxies NGC 253, NGC 3310, and NGC 3256. The NuSTAR observations constrain any active galactic nucleus (AGN) to be either highly obscured or to have an extremely low luminosity of ≲1038 erg s‑1 (10–30 keV), implying that it is emitting at a very low Eddington ratio. An X-ray point source that is consistent with the location of the nuclear star cluster with an X-ray luminosity of a few times 1038 erg s‑1 may be a low-luminosity AGN but is more consistent with being an X-ray binary.

  4. Sub-millimeter Telescope CO (2-1) Observations of Nearby Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Jiang, Xue-Jian; Wang, Zhong; Gu, Qiusheng; Wang, Junzhi; Zhang, Zhi-Yu

    2015-01-01

    We present CO J = 2-1 observations toward 32 nearby gas-rich star-forming galaxies selected from the ALFALFA and Wide-field Infrared Survey Explorer (WISE) catalogs, using the Sub-millimeter Telescope (SMT). Our sample is selected to be dominated by intermediate-M * galaxies. The scaling relations between molecular gas, atomic gas, and galactic properties (stellar mass, NUV - r, and WISE color W3 - W2) are examined and discussed. Our results show the following. (1) In the galaxies with stellar mass M * <=1010 M ⊙, the H I fraction (f H I ≡ M H I /M *) is significantly higher than that of more massive galaxies, while the H2 gas fraction (f_H_2 ≡ M_H_2/M *) remains nearly unchanged. (2) Compared to f_H_2, f H I correlates better with both M * and NUV - r. (3) A new parameter, WISE color W3 - W2 (12-4.6 μm), is introduced, which is similar to NUV - r in tracing star formation activity, and we find that W3 - W2 has a tighter anti-correlation with log f_H_2 than the anti-correlation of (NUV - r)-f H I , (NUV - r)-f_H_2, and (W3 - W2)-f H I . This indicates that W3 - W2 can trace the H2 fraction in galaxies. For the gas ratio M_H_2/M H I , only in the intermediate-M * galaxies it appears to depend on M * and NUV - r. We find a tight correlation between the molecular gas mass M_H_2 and 12 μm (W3) luminosities (L 12 μm), and the slope is close to unity (1.03 ± 0.06) for the SMT sample. This correlation may reflect that the cold gas and dust are well mixed on a global galactic scale. Using the all-sky 12 μm (W3) data available in WISE, this correlation can be used to estimate CO flux for molecular gas observations and can even predict H2 mass for star-forming galaxies.

  5. Active Region Release Two CMEs

    NASA Video Gallery

    Solar material can be seen blowing off the sun in this video captured by NASA’s Solar Dynamics Observatory (SDO) on the night of Feb. 5, 2013. This active region on the sun sent out two coronal ...

  6. Rapid growth of black holes in massive star-forming galaxies.

    PubMed

    Alexander, D M; Smail, I; Bauer, F E; Chapman, S C; Blain, A W; Brandt, W N; Ivison, R J

    2005-04-01

    The tight relationship between the masses of black holes and galaxy spheroids in nearby galaxies implies a causal connection between the growth of these two components. Optically luminous quasars host the most prodigious accreting black holes in the Universe, and can account for greater than or approximately equal to 30 per cent of the total cosmological black-hole growth. As typical quasars are not, however, undergoing intense star formation and already host massive black holes (> 10(8)M(o), where M(o) is the solar mass), there must have been an earlier pre-quasar phase when these black holes grew (mass range approximately (10(6)-10(8))M(o)). The likely signature of this earlier stage is simultaneous black-hole growth and star formation in distant (redshift z > 1; >8 billion light years away) luminous galaxies. Here we report ultra-deep X-ray observations of distant star-forming galaxies that are bright at submillimetre wavelengths. We find that the black holes in these galaxies are growing almost continuously throughout periods of intense star formation. This activity appears to be more tightly associated with these galaxies than any other coeval galaxy populations. We show that the black-hole growth from these galaxies is consistent with that expected for the pre-quasar phase.

  7. The Infrared Spectral Energy Distribution of Normal Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Dale, Daniel A.; Helou, George; Contursi, Alessandra; Silbermann, Nancy A.; Kolhatkar, Sonali

    2001-03-01

    We present a new phenomenological model for the spectral energy distribution of normal star-forming galaxies between 3 and 1100 μm. A sequence of realistic galaxy spectra are constructed from a family of dust emission curves assuming a power-law distribution of dust mass over a wide range of interstellar radiation fields. For each interstellar radiation field heating intensity, we combine emission curves for large and very small grains and aromatic feature carriers. The model is constrained by IRAS and ISOCAM broadband photometric and ISOPHOT spectrophotometric observations for our sample of 69 normal galaxies; the model reproduces well the empirical spectra and infrared color trends. These model spectra allow us to determine the infrared energy budget for normal galaxies and in particular to translate far-infrared fluxes into total (bolometric) infrared fluxes. The 20-42 μm range appears to show the most significant growth in relative terms as the activity level increases, suggesting that the 20-42 μm continuum may be the best dust emission tracer of current star formation in galaxies. The redshift dependence of infrared color-color diagrams and the far-infrared-to-radio correlation for galaxies are also explored.

  8. MODELING THE STAR-FORMING UNIVERSE AT z = 2: IMPACT OF COLD ACCRETION FLOWS

    SciTech Connect

    Khochfar, Sadegh; Silk, Joseph

    2009-07-20

    We present results of a semianalytic model (SAM) that includes cold accretion and a porosity-based prescription for star formation. We can recover the puzzling observational results of low V/{sigma} seen in various massive disk or disk-like galaxies, if we allow 18% of the accretion energy from cold flows to drive turbulence in gaseous disks at z = 2. The increase of gas mass through cold flows is by itself not sufficient to increase the star formation rate sufficiently to recover the number density of M-dot{sub *}>120 M{sub odot} yr{sup -1} galaxies in our model. In addition, it is necessary to increase the star formation efficiency. This can be achieved naturally in the porosity model, where star formation efficiency scales {proportional_to}{sigma}, which scales as cloud velocity dispersion. As cold accretion is the main driver for gas velocity dispersion in our model, star formation efficiency parallels cold accretion rates and allows fast conversion into stars. At z {approx} 2, we find a space density 10{sup -4} Mpc{sup -3} in star-forming galaxies with M-dot{sub *}>120 M{sub odot} yr{sup -1}, in better agreement than earlier estimates from SAMs. However, the fundamental relation between M-dot{sub *} and M {sub *} is still offset from the observed relation, indicating the need for possibly more efficient star formation at high-z perhaps associated with a role for active galactic nucleus (AGN) triggering.

  9. ACIS Study of the Perseus Star Forming Cloud

    NASA Astrophysics Data System (ADS)

    Feigelson, Eric

    1999-09-01

    The Perseus cloud (d = 320 pc) is the nearest giant molecular cloud and harbors two rich clusters of pre-main sequence stars: NGC 1333 and IC 348. The proposed ACIS exposures will provide the deepest study of young stellar X-ray emission ever achieved and should detect about 400 sources. This study will improve the census of young stars in the clusters; probe the relationship between X-rays, disks and outflows; and investigate X-ray properties as a function of stellar luminosity, mass and especially age. The findings should give insight into possible effects of magnetic activity on protostars and T Tauri stars, such as X-ray and particle irradiation of the disk.

  10. Properties of massive star-forming clumps with infall motions

    NASA Astrophysics Data System (ADS)

    He, Yu-Xin; Zhou, Jian-Jun; Esimbek, Jarken; Ji, Wei-Guang; Wu, Gang; Tang, Xin-Di; Komesh, Toktarkhan; Yuan, Ye; Li, Da-Lei; Baan, W. A.

    2016-09-01

    In this work, we aim to characterize high-mass clumps with infall motions. We selected 327 clumps from the Millimetre Astronomy Legacy Team 90-GHz survey, and identified 100 infall candidates. Combined with the results of He et al., we obtained a sample of 732 high-mass clumps, including 231 massive infall candidates and 501 clumps where infall is not detected. Objects in our sample were classified as pre-stellar, proto-stellar, H II or photodissociation region (PDR). The detection rates of the infall candidates in the pre-stellar, proto-stellar, H II and PDR stages are 41.2 per cent, 36.6 per cent, 30.6 per cent and 12.7 per cent, respectively. The infall candidates have a higher H2 column density and volume density compared with the clumps where infall is not detected at every stage. For the infall candidates, the median values of the infall rates at the pre-stellar, proto-stellar, H II and PDR stages are 2.6 × 10-3, 7.0 × 10-3, 6.5 × 10-3 and 5.5 × 10-3 M⊙ yr-1, respectively. These values indicate that infall candidates at later evolutionary stages are still accumulating material efficiently. It is interesting to find that both infall candidates and clumps where infall is not detected show a clear trend of increasing mass from the pre-stellar to proto-stellar, and to the H II stages. The power indices of the clump mass function are 2.04 ± 0.16 and 2.17 ± 0.31 for the infall candidates and clumps where infall is not detected, respectively, which agree well with the power index of the stellar initial mass function (2.35) and the cold Planck cores (2.0).

  11. Observational Searches for Star-Forming Galaxies at z > 6

    NASA Astrophysics Data System (ADS)

    Finkelstein, Steven L.

    2016-08-01

    Although the universe at redshifts greater than six represents only the first one billion years (< 10%) of cosmic time, the dense nature of the early universe led to vigorous galaxy formation and evolution activity which we are only now starting to piece together. Technological improvements have, over only the past decade, allowed large samples of galaxies at such high redshifts to be collected, providing a glimpse into the epoch of formation of the first stars and galaxies. A wide variety of observational techniques have led to the discovery of thousands of galaxy candidates at z > 6, with spectroscopically confirmed galaxies out to nearly z = 9. Using these large samples, we have begun to gain a physical insight into the processes inherent in galaxy evolution at early times. In this review, I will discuss (i) the selection techniques for finding distant galaxies, including a summary of previous and ongoing ground and space-based searches, and spectroscopic follow-up efforts, (ii) insights into galaxy evolution gleaned from measures such as the rest-frame ultraviolet luminosity function, the stellar mass function, and galaxy star-formation rates, and (iii) the effect of galaxies on their surrounding environment, including the chemical enrichment of the universe, and the reionisation of the intergalactic medium. Finally, I conclude with prospects for future observational study of the distant universe, using a bevy of new state-of-the-art facilities coming online over the next decade and beyond.

  12. Dust temperature distributions in star-forming condensations

    NASA Technical Reports Server (NTRS)

    Xie, Taoling; Goldsmith, Paul F.; Snell, Ronald L.; Zhou, Weimin

    1993-01-01

    The FIR spectra of the central IR condensations in the dense cores of molecular clouds AFGL 2591. B335, L1551, Mon R2, and Sgr B2 are reanalyzed here in terms of the distribution of dust mass as a function of temperature. FIR spectra of these objects can be characterized reasonably well by a given functional form. The general shapes of the dust temperature distributions of these objects are similar and closely resemble the theoretical computations of de Muizon and Rouan (1985) for a sample of 'hot centered' clouds with active star formation. Specifically, the model yields a 'cutoff' temperature below which essentially no dust is needed to interpret the dust emission spectra, and most of the dust mass is distributed in a broad temperature range of a few tens of degrees above the cutoff temperature. Mass, luminosity, average temperature, and column density are obtained, and it is found that the physical quantities differ considerably from source to source in a meaningful way.

  13. EXTINCTION IN STAR-FORMING DISK GALAXIES FROM INCLINATION-DEPENDENT COMPOSITE SPECTRA

    SciTech Connect

    Yip, Ching-Wa; Szalay, Alex S.; Wyse, Rosemary F. G.; Budavari, Tamas; Dobos, Laszlo; Csabai, Istvan E-mail: szalay@pha.jhu.ed

    2010-02-01

    Extinction in galaxies affects their observed properties. In scenarios describing the distribution of dust and stars in individual disk galaxies, the amplitude of the extinction can be modulated by the inclination of the galaxies. In this work, we investigate the inclination dependency in composite spectra of star-forming disk galaxies from the Sloan Digital Sky Survey Data Release 5. In a volume-limited sample within a redshift range 0.065-0.075 and a r-band Petrosian absolute magnitude range -19.5 to -22 mag which exhibits a flat distribution of inclination, the inclined relative to face-on extinction in the stellar continuum is found empirically to increase with inclination in the g, r, and i bands. Within the central 0.5 intrinsic half-light radius of the galaxies, the g-band relative extinction in the stellar continuum for the highly inclined objects (axis ratio b/a = 0.1) is 1.2 mag, agreeing with previous studies. The extinction curve of the disk galaxies is given in the rest-frame wavelengths 3700-8000 A, identified with major optical emission and absorption lines in diagnostics. The Balmer decrement, Halpha/Hbeta, remains constant with inclination, suggesting a different kind of dust configuration and/or reddening mechanism in the H II region from that in the stellar continuum. One factor is shown to be the presence of spatially non-uniform interstellar extinction, presumably caused by clumped dust in the vicinity of the H II region.

  14. Structure and dynamics of star-forming galaxies across the history of the Universe using GRBs

    NASA Astrophysics Data System (ADS)

    Thöne, Christina; Fynbo, Johan; de Ugarte Postigo, Antonio

    2015-08-01

    Gamma-ray bursts are exploding massive stars and some of the most luminous explosions in the Universe. They can serve as powerful light houses that probe the structure and abundances of the dense ISM in their hosts at almost any redshift and not accessible by other types of observations, e.g. using quasars. Since 2009 our collaboration has collected UV to nIR medium-resolution spectra of over 70 GRB afterglows using the ESO/VLT X-shooter spectrograph. Our sample covers a redshift range from 0.06 to 6.3 allowing us to study the dynamics of the ISM in star-forming galaxies from the nearby Universe out to the epoch of reionization and for the first time in a statistically sound way. Absorption lines usually show a rich structure of different components due to galaxy dynamics, turbulences or in-/outflows and different ionization levels seem to arise from different regions in the host. Fine-structure lines some of which are uniquely observed in GRB hosts are excited in the dense regions close to the GRB site itself. For some host with z < 3 we can also simultaenously observe emission lines from the hot ISM, comparing the origin of hot and cold gas within the same galaxy. The large wavelength coverage of the sample gives us the unique opportunity to study the evolution of gas dynamics across most of the time galaxies have existed, how the gas structure changed over time and what is the importance and consistency of in- and ouflows. Here we will present the X-shooter GRB afterglow sample, our results on the study of absorption and emission line features and compare the observed structures with theoretical models of galaxies to get a unique insight on the distrubution and dynamics of the ISM in starforming galaxies at any redshift.

  15. VizieR Online Data Catalog: Star-forming compact groups (Hernandez-Fernandez+, 2015)

    NASA Astrophysics Data System (ADS)

    Hernandez-Fernandez, J. D.; Mendes de Oliveira, C.

    2016-03-01

    This article provides a local sample (z<~0.15) of compact groups of star-forming galaxies. In this type of groups, galaxies strongly interact among themselves and with the rest of the group components (ICM, dark matter halo). This induces morphological changes and star formation events which are currently taking place. The peculiar evolutionary stage of these groups provides a wealth of galaxy observables that may clarify the theoretical framework about galaxy evolution in groups. We have performed an all-sky search for compact groups of star-forming galaxies in the GALEX UV catalogues. (3 data files).

  16. Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution

    NASA Astrophysics Data System (ADS)

    Esteban, C.; García-Rojas, J.; Carigi, L.; Peimbert, M.; Bresolin, F.; López-Sánchez, A. R.; Mesa-Delgado, A.

    2014-09-01

    We present deep echelle spectrophotometry of the brightest emission-line knots of the star-forming galaxies He 2-10, Mrk 1271, NGC 3125, NGC 5408, POX 4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the H II region Hubble V in the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10420 Å range. We determine electron densities and temperatures of the ionized gas from several emission-line intensity ratios for all the objects. We derive the ionic abundances of C2+ and/or O2+ from faint pure recombination lines in several of the objects, permitting to derive their C/H and C/O ratios. We have explored the chemical evolution at low metallicities analysing the C/O versus O/H, C/O versus N/O and C/N versus O/H relations for Galactic and extragalactic H II regions and comparing with results for Galactic halo stars and damped Lyα systems. We find that H II regions in star-forming dwarf galaxies occupy a different locus in the C/O versus O/H diagram than those belonging to the inner discs of spiral galaxies, indicating their different chemical evolution histories, and that the bulk of C in the most metal-poor extragalactic H II regions should have the same origin than in halo stars. The comparison between the C/O ratios in H II regions and in stars of the Galactic thick and thin discs seems to give arguments to support the merging scenario for the origin of the Galactic thick disc. Finally, we find an apparent coupling between C and N enrichment at the usual metallicities determined for H II regions and that this coupling breaks in very low metallicity objects.

  17. The Evolution of the Fractions of Quiescent and Star-forming Galaxies as a Function of Stellar Mass Since z = 3: Increasing Importance of Massive, Dusty Star-forming Galaxies in the Early Universe

    NASA Astrophysics Data System (ADS)

    Martis, Nicholas S.; Marchesini, Danilo; Brammer, Gabriel B.; Muzzin, Adam; Labbé, Ivo; Momcheva, Ivelina G.; Skelton, Rosalind E.; Stefanon, Mauro; van Dokkum, Pieter G.; Whitaker, Katherine E.

    2016-08-01

    Using the UltraVISTA DR1 and 3D-HST catalogs, we construct a stellar-mass-complete sample, unique for its combination of surveyed volume and depth, to study the evolution of the fractions of quiescent galaxies, moderately unobscured star-forming galaxies, and dusty star-forming galaxies as a function of stellar mass over the redshift interval 0.2 ≤ z ≤ 3.0. We show that the role of dusty star-forming galaxies within the overall galaxy population becomes more important with increasing stellar mass and grows rapidly with increasing redshift. Specifically, dusty star-forming galaxies dominate the galaxy population with {log}({M}{{star}}/{M}ȯ )≳ 10.3 at z ≳ 2. The ratio of dusty and non-dusty star-forming galaxies as a function of stellar mass changes little with redshift. Dusty star-forming galaxies dominate the star-forming population at {log}({M}{{star}}/{M}ȯ )≳ 10.0{--}10.5, being a factor of ˜3–5 more common, while unobscured star-forming galaxies dominate at {log}({M}{{star}}/{M}ȯ )≲ 10. At {log}({M}{{star}}/{M}ȯ )\\gt 10.5, red galaxies dominate the galaxy population at all redshift z < 3, either because they are quiescent (at late times) or dusty star-forming (in the early universe).

  18. The Evolution of the Fractions of Quiescent and Star-forming Galaxies as a Function of Stellar Mass Since z = 3: Increasing Importance of Massive, Dusty Star-forming Galaxies in the Early Universe

    NASA Astrophysics Data System (ADS)

    Martis, Nicholas S.; Marchesini, Danilo; Brammer, Gabriel B.; Muzzin, Adam; Labbé, Ivo; Momcheva, Ivelina G.; Skelton, Rosalind E.; Stefanon, Mauro; van Dokkum, Pieter G.; Whitaker, Katherine E.

    2016-08-01

    Using the UltraVISTA DR1 and 3D-HST catalogs, we construct a stellar-mass-complete sample, unique for its combination of surveyed volume and depth, to study the evolution of the fractions of quiescent galaxies, moderately unobscured star-forming galaxies, and dusty star-forming galaxies as a function of stellar mass over the redshift interval 0.2 ≤ z ≤ 3.0. We show that the role of dusty star-forming galaxies within the overall galaxy population becomes more important with increasing stellar mass and grows rapidly with increasing redshift. Specifically, dusty star-forming galaxies dominate the galaxy population with {log}({M}{{star}}/{M}⊙ )≳ 10.3 at z ≳ 2. The ratio of dusty and non-dusty star-forming galaxies as a function of stellar mass changes little with redshift. Dusty star-forming galaxies dominate the star-forming population at {log}({M}{{star}}/{M}⊙ )≳ 10.0{--}10.5, being a factor of ˜3-5 more common, while unobscured star-forming galaxies dominate at {log}({M}{{star}}/{M}⊙ )≲ 10. At {log}({M}{{star}}/{M}⊙ )\\gt 10.5, red galaxies dominate the galaxy population at all redshift z < 3, either because they are quiescent (at late times) or dusty star-forming (in the early universe).

  19. C+/H2 gas in star-forming clouds and galaxies

    NASA Astrophysics Data System (ADS)

    Nordon, Raanan; Sternberg, Amiel

    2016-11-01

    We present analytic theory for the total column density of singly ionized carbon (C+) in the optically thick photon dominated regions (PDRs) of far-UV irradiated (star-forming) molecular clouds. We derive a simple formula for the C+ column as a function of the cloud (hydrogen) density, the far-UV field intensity, and metallicity, encompassing the wide range of galaxy conditions. When assuming the typical relation between UV and density in the cold neutral medium, the C+ column becomes a function of the metallicity alone. We verify our analysis with detailed numerical PDR models. For optically thick gas, most of the C+ column is mixed with hydrogen that is primarily molecular (H2), and this `C+/H2' gas layer accounts for almost all of the `CO-dark' molecular gas in PDRs. The C+/H2 column density is limited by dust shielding and is inversely proportional to the metallicity down to ˜0.1 solar. At lower metallicities, H2 line blocking dominates and the C+/H2 column saturates. Applying our theory to CO surveys in low-redshift spirals, we estimate the fraction of C+/H2 gas out of the total molecular gas to be typically ˜0.4. At redshifts 1 < z < 3 in massive disc galaxies the C+/H2 gas represents a very small fraction of the total molecular gas (≲ 0.16). This small fraction at high redshifts is due to the high gas surface densities when compared to local galaxies.

  20. Modelling the nebular emission from primeval to present-day star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Gutkin, Julia; Charlot, Stéphane; Bruzual, Gustavo

    2016-10-01

    We present a new model of the nebular emission from star-forming galaxies in a wide range of chemical compositions, appropriate to interpret observations of galaxies at all cosmic epochs. The model relies on the combination of state-of-the-art stellar population synthesis and photoionization codes to describe the ensemble of H II regions and the diffuse gas ionized by young stars in a galaxy. A main feature of this model is the self-consistent yet versatile treatment of element abundances and depletion on to dust grains, which allows one to relate the observed nebular emission from a galaxy to both gas-phase and dust-phase metal enrichment. We show that this model can account for the rest-frame ultraviolet and optical emission-line properties of galaxies at different redshifts and find that ultraviolet emission lines are more sensitive than optical ones to parameters such as C/O abundance ratio, hydrogen gas density, dust-to-metal mass ratio and upper cut-off of the stellar initial mass function. We also find that, for gas-phase metallicities around solar to slightly subsolar, widely used formulae to constrain oxygen ionic fractions and the C/O ratio from ultraviolet and optical emission-line luminosities are reasonable faithful. However, the recipes break down at non-solar metallicities, making them inappropriate to study chemically young galaxies. In such cases, a fully self-consistent model of the kind presented in this paper is required to interpret the observed nebular emission.

  1. The clustering of merging star-forming haloes: dust emission as high frequency arcminute CMB foreground

    NASA Astrophysics Data System (ADS)

    Righi, M.; Hernández-Monteagudo, C.; Sunyaev, R. A.

    2008-02-01

    Context: Future observations of CMB anisotropies will be able to probe high multipole regions of the angular power spectrum, corresponding to a resolution of a few arcminutes. Dust emission from merging haloes is one of the foregrounds that will affect such very small scales. Aims: We estimate the contribution to CMB angular fluctuations from objects that are bright in the sub-millimeter band due to intense star formation bursts following merging episodes. Methods: We base our approach on the Lacey-Cole merger model and on the Kennicutt relation which connects the star formation rate in galaxies with their infrared luminosity. We set the free parameters of the model in order to not exceed the SCUBA source counts, the Madau plot of star formation rate in the universe and COBE/FIRAS data on the intensity of the sub-millimeter cosmic background radiation. Results: We show that the angular power spectrum arising from the distribution of such star-forming haloes will be one of the most significant foregrounds in the high frequency channels of future CMB experiments, such as PLANCK, ACT and SPT. The correlation term, due to the clustering of multiple haloes at redshift z ~ 2-6, is dominant in the broad range of angular scales 200 ⪉ l ⪉ 3000. Poisson fluctuations due to bright sub-millimeter sources are more important at higher l, but since they are generated from the bright sources, such contribution could be strongly reduced if bright sources are excised from the sky maps. The contribution of the correlation term to the angular power spectrum depends strongly on the redshift evolution of the escape fraction of UV photons and the resulting temperature of the dust. The measurement of this signal will therefore give important information about the sub-millimeter emission and the escape fraction of UV photons from galaxies, in the early stage of their evolution.

  2. Complex Gas Kinematics in Compact, Rapidly Assembling Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Amorín, R.; Vílchez, J. M.; Hägele, G. F.; Firpo, V.; Pérez-Montero, E.; Papaderos, P.

    2012-08-01

    Deep, high-resolution spectroscopic observations have been obtained for six compact, strongly star-forming galaxies at redshift z ~ 0.1-0.3, most of them also known as green peas. Remarkably, these galaxies show complex emission-line profiles in the spectral region including Hα, [N II] λλ6548, 6584, and [S II] λλ6717, 6731, consisting of the superposition of different kinematical components on a spatial extent of few kiloparsecs: a very broad line emission underlying more than one narrower component. For at least two of the observed galaxies some of these multiple components are resolved spatially in their two-dimensional spectra, whereas for another one a faint detached Hα blob lacking stellar continuum is detected at the same recessional velocity ~7 kpc away from the galaxy. The individual narrower Hα components show high intrinsic velocity dispersion (σ ~ 30-80 km s-1), suggesting together with unsharped masking Hubble Space Telescope images that star formation proceeds in an ensemble of several compact and turbulent clumps, with relative velocities of up to ~500 km s-1. The broad underlying Hα components indicate in all cases large expansion velocities (full width zero intensity >=1000 km s-1) and very high luminosities (up to ~1042 erg s-1), probably showing the imprint of energetic outflows from supernovae. These intriguing results underline the importance of green peas for studying the assembly of low-mass galaxies near and far. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  3. EVIDENCE FOR INFLOW IN HIGH-MASS STAR-FORMING CLUMPS

    SciTech Connect

    Reiter, Megan; Shirley, Yancy L.; Wu Jingwen; Brogan, Crystal; Wootten, Alwyn; Tatematsu, Ken'ichi E-mail: yshirley@as.arizona.edu E-mail: cbrogan@nrao.edu E-mail: k.tatematsu@nao.ac.jp

    2011-10-10

    We analyze the HCO{sup +} 3-2 and H{sup 13}CO{sup +} 3-2 line profiles of 27 high-mass star-forming regions to identify asymmetries that are suggestive of mass inflow. Three quantitative measures of line asymmetry are used to indicate whether a line profile is blue, red, or neither-the ratio of the temperature of the blue and red peaks, the line skew, and the dimensionless parameter {delta}v. We find nine HCO{sup +} 3-2 line profiles with a significant blue asymmetry and four with significant red asymmetric profiles. Comparing our HCO{sup +} 3-2 results to HCN 3-2 observations from Wu et al., we find that eight of the blue and three of the red have profiles with the same asymmetry in HCN. The eight sources with blue asymmetries in both tracers are considered strong candidates for inflow. Quantitative measures of the asymmetry (e.g., {delta}v) tend to be larger for HCN. This, combined with possible HCO{sup +} abundance enhancements in outflows, suggests that HCN may be a better tracer of inflow. Understanding the behavior of common molecular tracers like HCO{sup +} in clumps of different masses is important for properly analyzing the line profiles seen in a sample of sources representing a broad range of clump masses. Such studies will soon be possible with the large number of sources with possible self-absorption seen in spectroscopic follow-up observations of clumps identified in the Bolocam Galactic Plane Survey.

  4. Everything you ever wanted to know about the ultraviolet spectra of star-forming galaxies but were afraid to ask

    NASA Technical Reports Server (NTRS)

    Kinney, A. L.; Bohlin, R.; Calzetti, D.; Panagia, N.; Wyse, R.

    1993-01-01

    We present ultraviolet spectra of 143 star-forming galaxies of different morphological types and activity classes including S0, Sa, Sb, Sc, Sd, irregular, starburst, blue compact, blue compact dwarf, Liner, and Seyfert 2 galaxies. These IUE spectra cover the wavelength range from 1200 to 3200 A and are taken in a large aperture (10 x 20 inch). The ultraviolet spectral energy distributions are shown for a subset of the galaxies, ordered by spectral index, and separated by type for normal galaxies, Liners, starburst galaxies, blue compact (BCG) and blue compact dwarf (BCDG) galaxies, and Seyfert 2 galaxies. The ultraviolet spectra of Liners are, for the most part, indistinguishable from the spectra of normal galaxies. Starburst galaxies have a large range of ultraviolet slope, from blue to red. The star-forming galaxies which are the bluest in the optical (BCG and BCDG), also have the 'bluest' average ultraviolet slope of beta = -1.75 +/- 0.63. Seyfert 2 galaxies are the only galaxies in the sample that consistently have detectable UV emission lines.

  5. FROM BLUE STAR-FORMING TO RED PASSIVE: GALAXIES IN TRANSITION IN DIFFERENT ENVIRONMENTS

    SciTech Connect

    Vulcani, Benedetta; Poggianti, Bianca M.; Fasano, Giovanni; Moretti, Alessia; Fritz, Jacopo; Calvi, Rosa; Paccagnella, Angela

    2015-01-01

    Exploiting a mass-complete (M {sub *} > 10{sup 10.25} M {sub ☉}) sample at 0.03 activity and/or morphology: green galaxies, red passive late types, and blue star-forming early types. Color fractions depend on mass and only for M {sub *} < 10{sup 10.7} M {sub ☉} on environment. The incidence of red galaxies increases with increasing mass, and, for M {sub *} < 10{sup 10.7} M {sub ☉}, decreases toward the group outskirts and in binary and single galaxies. The relative abundance of green and blue galaxies is independent of environment and increases monotonically with galaxy mass. We also inspect galaxy structural parameters, star-formation properties, histories, and ages and propose an evolutionary scenario for the different subpopulations. Color transformations are due to a reduction and suppression of the star-formation rate in both bulges and disks that does not noticeably affect galaxy structure. Morphological transitions are linked to an enhanced bulge-to-disk ratio that is due to the removal of the disk, not to an increase of the bulge. Our modeling suggests that green colors might be due to star-formation histories declining with long timescales, as an alternative scenario to the classical ''quenching'' processes. Our results suggest that galaxy transformations in star-formation activity and morphology depend neither on the environment nor on being a satellite or the most massive galaxy of a halo. The only environmental dependence we find is the higher fast quenching efficiency in groups giving origin to poststarburst signatures.

  6. Early star-forming galaxies and the reionization of the Universe.

    PubMed

    Robertson, Brant E; Ellis, Richard S; Dunlop, James S; McLure, Ross J; Stark, Daniel P

    2010-11-01

    Star-forming galaxies trace cosmic history. Recent observational progress with the NASA Hubble Space Telescope has led to the discovery and study of the earliest known galaxies, which correspond to a period when the Universe was only ∼800 million years old. Intense ultraviolet radiation from these early galaxies probably induced a major event in cosmic history: the reionization of intergalactic hydrogen.

  7. SDO Sees Active Region Outbursts

    NASA Video Gallery

    This close up video by NASA’s Solar Dynamics Observatory shows an active region near the right-hand edge of the sun’s disk, which erupted with at least a dozen minor events over a 30-hour period fr...

  8. Scaled up low-mass star formation in massive star-forming cores in the G333 giant molecular cloud

    NASA Astrophysics Data System (ADS)

    Wiles, B.; Lo, N.; Redman, M. P.; Cunningham, M. R.; Jones, P. A.; Burton, M. G.; Bronfman, L.

    2016-06-01

    Three bright molecular line sources in G333 have recently been shown to exhibit signatures of infall. We describe a molecular line radiative transfer (RT) modelling process which is required to extract the infall signature from Mopra and Nanten2 data. The observed line profiles differ greatly between individual sources but are reproduced well by variations upon a common unified model where the outflow viewing angle is the most significant difference between the sources. The models and data together suggest that the observed properties of the high-mass star-forming regions such as infall, turbulence and mass are consistent with scaled-up versions of the low-mass case with turbulent velocities that are supersonic and an order of magnitude larger than those found in low-mass star-forming regions. Using detailed RT modelling, we show that the G333 cores are essentially undergoing a scaled-up version of low-mass star formation. This is an extension of earlier work in that the degree of infall and the chemical abundances are constrained by the RT modelling in a way that is not practical with a standard analysis of observational data. We also find high velocity infall and high infall mass rates, possibly suggesting accelerated collapse due to external pressure. Molecular depletion due to freeze-out on to dust grains in central regions of the cores is suggested by low molecular abundances of several species. Strong evidence for a local enhancement of 13C-bearing species towards the outflow cloud cores is discussed, consistent with the presence of shocks caused by the supersonic motions within them.

  9. Direct Measurement of Dust Attenuation in z approx. 1.5 Star-Forming Galaxies from 3D-HST: Implications for Dust Geometry and Star Formation Rates

    NASA Technical Reports Server (NTRS)

    Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B; Conroy, Charlie; Schreiber, Natascha M. Foerster; Franx, Marijn; Fumagalli, Mattia; Lundren, Britt; Momcheva, Ivelina; Nelson, Erica J.; Rix, Hans-Walter; Skelton, Rosalind E.; VanDokkum, Pieter G.; Tease, Katherine Whitaker; Wuyts, Stijn

    2013-01-01

    The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust towards star-forming regions (measured using Balmer decrements) and the integrated dust properties (derived by comparing spectral energy distributions [SEDs] with stellar population and dust models) for a statistically significant sample of distant galaxies. We select a sample of 163 galaxies between 1.36< or = z< or = 1.5 with H(alpha) SNR > or = 5 and measure Balmer decrements from stacked spectra. First, we stack spectra in bins of integrated stellar dust attenuation, and find that there is extra dust extinction towards star-forming regions (AV,HII is 1.81 times the integrated AV, star), though slightly lower than found for low-redshift starburst galaxies. Next, we stack spectra in bins of specific star formation rate (log sSFR), star formation rate (log SFR), and stellar mass (logM*). We find that on average AV,HII increases with SFR and mass, but decreases with increasing sSFR. The amount of extra extinction also decreases with increasing sSFR and decreasing stellar mass. Our results are consistent with the two-phase dust model - in which galaxies contain both a diffuse and a stellar birth cloud dust component - as the extra extinction will increase once older stars outside the star-forming regions become more dominant. Finally, using our Balmer decrements we derive dust-corrected H(alpha) SFRs, and find evidence that SED fitting produces incorrect SFRs if very rapidly declining SFHs are included in the explored parameter space. Subject headings: dust, extinction- galaxies: evolution- galaxies: high-redshift

  10. SUB-MILLIMETER TELESCOPE CO (2-1) OBSERVATIONS OF NEARBY STAR-FORMING GALAXIES

    SciTech Connect

    Jiang, Xue-Jian; Gu, Qiusheng; Wang, Zhong; Wang, Junzhi; Zhang, Zhi-Yu

    2015-01-20

    We present CO J = 2-1 observations toward 32 nearby gas-rich star-forming galaxies selected from the ALFALFA and Wide-field Infrared Survey Explorer (WISE) catalogs, using the Sub-millimeter Telescope (SMT). Our sample is selected to be dominated by intermediate-M {sub *} galaxies. The scaling relations between molecular gas, atomic gas, and galactic properties (stellar mass, NUV – r, and WISE color W3 – W2) are examined and discussed. Our results show the following. (1) In the galaxies with stellar mass M {sub *} ≤10{sup 10} M {sub ☉}, the H I fraction (f {sub H} {sub I} ≡ M {sub H} {sub I}/M {sub *}) is significantly higher than that of more massive galaxies, while the H{sub 2} gas fraction (f{sub H{sub 2}} ≡ M{sub H{sub 2}}/M {sub *}) remains nearly unchanged. (2) Compared to f{sub H{sub 2}}, f {sub H} {sub I} correlates better with both M {sub *} and NUV – r. (3) A new parameter, WISE color W3 – W2 (12-4.6 μm), is introduced, which is similar to NUV – r in tracing star formation activity, and we find that W3 – W2 has a tighter anti-correlation with log f{sub H{sub 2}} than the anti-correlation of (NUV – r)-f {sub H} {sub I}, (NUV – r)-f{sub H{sub 2}}, and (W3 – W2)-f {sub H} {sub I}. This indicates that W3 – W2 can trace the H{sub 2} fraction in galaxies. For the gas ratio M{sub H{sub 2}}/M {sub H} {sub I} , only in the intermediate-M {sub *} galaxies it appears to depend on M {sub *} and NUV – r. We find a tight correlation between the molecular gas mass M{sub H{sub 2}} and 12 μm (W3) luminosities (L {sub 12} {sub μm}), and the slope is close to unity (1.03 ± 0.06) for the SMT sample. This correlation may reflect that the cold gas and dust are well mixed on a global galactic scale. Using the all-sky 12 μm (W3) data available in WISE, this correlation can be used to estimate CO flux for molecular gas observations and can even predict H{sub 2} mass for star-forming galaxies.

  11. Ionized gas outflows and global kinematics of low-z luminous star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Arribas, S.; Colina, L.; Bellocchi, E.; Maiolino, R.; Villar-Martín, M.

    2014-08-01

    We study the kinematic properties of the ionised gas outflows and ambient interstellar medium (ISM) in a large and representative sample of local luminous and ultra-luminous infrared galaxies (U/LIRGs) (58 systems, 75 galaxies) at galactic and sub-galactic (i.e., star-forming clumps) scales, thanks to integral field spectroscopy (IFS)-based high signal-to-noise integrated spectra. The velocity dispersion of the ionized ISM in U/LIRGs (⟨ σ ⟩ ~ 70 km s-1) is larger than in lower luminosity local star-forming galaxies (⟨ σ ⟩ ~ 25 km s-1). While for isolated disc LIRGs star formation appears to sustain turbulence, gravitational energy release associated with interactions and mergers plays an important role in driving σ in the U/LIRG range. We find that σ has a dependency on the star formation rate density (ΣSFR), which is weaker than expected if it were driven by the energy released by the starburst. The relatively small role of star formation (SF) driving the σ in U/LIRGs is reinforced by the lack of an increase in σ associated with high luminosity SF clumps. We also find that the impact of an active galactic nucleus (AGN) in ULIRGs is strong, increasing on average σ by a factor 1.5. Low-z U/LIRGs cover a range of velocity dispersion (σ ~ 30 to 100 km s-1) and star formation rate density (ΣSFR ~ 0.1 to 20 M⊙ yr-1 kpc-2) similar to those of high-z SFGs. Moreover, the observed weak dependency of σ on ΣSFR for local U/LIRGs (σ ∝ ΣSFR+0.06) is in very good agreement with that measured in some high-z samples. The presence of ionized gas outflows in U/LIRGs seems universal based on the detection of a broad, usually blueshifted, Hα line. The observed dependency of the maximum velocity of the outflow (Vmax) on the star formation rate (SFR) is of the type Vmax(non - AGN) ∝ SFR(LIR)+ 0.24. We find that AGNs in U/LIRGs are able to generate faster (~×2) and more massive (~× 1.4) ionized gas outflows than pure starbursts. The derived ionized mass

  12. The star-forming environment of an ultraluminous X-ray source in NGC4559: an optical study

    NASA Astrophysics Data System (ADS)

    Soria, Roberto; Cropper, Mark; Pakull, Manfred; Mushotzky, Richard; Wu, Kinwah

    2005-01-01

    We have studied the candidate optical counterparts and the stellar population in the star-forming complex around the bright ultraluminous X-ray source (ULX) in the western part of the spiral galaxy NGC4559, using the HST Wide Field Planetary Camera 2 (WFPC2), XMM-Newton/Optical Monitor and ground-based data. We find that the ULX is located near a small group of OB stars, but is not associated with any massive young clusters nor with any extraordinary massive stars. The brightest point source in the Chandra error circle is consistent with a single blue supergiant (BSG) of mass ~20Msolar and age ~10 Myr. A few other stars are resolved inside the error circle: mostly BSGs and red supergiants (RSGs) with inferred masses ~10-15Msolar and ages ~20 Myr. This is consistent with the interpretation of this ULX as a black hole (BH) accreting from a high-mass donor star in its supergiant phase, with mass transfer occurring via Roche-lobe overflow. The observed optical colours and the blue-to-red supergiant ratio suggest a low metal abundance for the stellar population: 0.2 <~Z/Zsolar<~ 0.4 (using the Padua tracks), or 0.05 <~Z/Zsolar<~ 0.2 (using the Geneva tracks). The age of the star-forming complex is <~30 Myr. Hα images show that this star-forming region has a ring-like appearance. We propose that it is an expanding wave of star formation, triggered by an initial density perturbation, in a region where the gas was only marginally stable to gravitational collapse. We also suggest that the most likely trigger was a collision with a satellite dwarf galaxy going through the gas-rich outer disc of NGC4559 less than 30 Myr ago. The culprit could be the dwarf galaxy visible a few arcsec north-west of the complex. If this is the case, this system is a scaled-down version of the Cartwheel galaxy. The X-ray data favour a BH more massive (M > 50Msolar) than typical Milky Way BH candidates. The optical data favour a young BH originating in the recent episode of massive star formation

  13. Metallicities of Low Mass Inefficient Star Forming Dwarfs in S4G: Testing the Closed Box Paradigm

    NASA Astrophysics Data System (ADS)

    McKay, Myles; Stirewalt, Sabrina; Sheth, Kartik; de Swardt, Bonita; Walter, Donald

    2015-03-01

    Low mass dwarf galaxies are the most numerous extragalactic population in the Local Universe. Many gas-rich dwarfs appear to be forming stars less efficiently than normal, massive disk galaxies and are therefore important laboratories for the study of star formation. Here we present new observations using the Palomar Double Spectrograph for 19 dwarf galaxies from the S4G Survey with the lowest stellar to HI mass ratios. Preliminary analysis of the data indicate a wide range of metallicities which vary by as much as 0.5 dex in a single galaxy in different star forming regions. Such a dispersion in metallicities favors an open box model and the results suggest a varied star formation history, possibly induced via minor mergers and accretion. The National Radio Astronomy Observatory(NRAO), National Science Foundation(NSF), and the National Astronomy Consortium (NAC) Cville Cohort. Additional support was provided by NSF Awards AST-0750814 and AST-1358913 to South Carolina State University.

  14. The structural evolution of Milky-Way-like star-forming galaxies since z ∼ 1.3

    SciTech Connect

    Patel, Shannon G.; Fumagalli, Mattia; Franx, Marijn; Labbé, Ivo; Muzzin, Adam; Van Dokkum, Pieter G.; Leja, Joel; Skelton, Rosalind E.; Momcheva, Ivelina; Nelson, Erica June; Van der Wel, Arjen; Rix, Hans-Walter; Brammer, Gabriel; Whitaker, Katherine E.; Lundgren, Britt; Wake, David A.; Quadri, Ryan F.

    2013-12-01

    We follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to z ∼ 1.3 based on the stellar mass growth inferred from the evolution of the star-forming sequence. We select our sample from the 3D-HST survey, which utilizes spectroscopy from the HST/WFC3 G141 near-IR grism and enables precise redshift measurements for our sample of SFGs. Structural properties are obtained from Sérsic profile fits to CANDELS WFC3 imaging. The progenitors of z = 0 SFGs with stellar mass M = 10{sup 10.5} M {sub ☉} are typically half as massive at z ∼ 1. This late-time stellar mass growth is consistent with recent studies that employ abundance matching techniques. The descendant SFGs at z ∼ 0 have grown in half-light radius by a factor of ∼1.4 since z ∼ 1. The half-light radius grows with stellar mass as r{sub e} ∝M {sup 0.29}. While most of the stellar mass is clearly assembling at large radii, the mass surface density profiles reveal ongoing mass growth also in the central regions where bulges and pseudobulges are common features in present day late-type galaxies. Some portion of this growth in the central regions is due to star formation as recent observations of Hα maps for SFGs at z ∼ 1 are found to be extended but centrally peaked. Connecting our lookback study with galactic archeology, we find the stellar mass surface density at R = 8 kpc to have increased by a factor of ∼2 since z ∼ 1, in good agreement with measurements derived for the solar neighborhood of the Milky Way.

  15. The Structural Evolution of Milky-Way-Like Star-Forming Galaxies zeta is approximately 1.3

    NASA Technical Reports Server (NTRS)

    Patel, Shannon G.; Fumagalli, Mattia; Franx, Marun; VanDokkum, Pieter G.; VanDerWel, Arjen; Leja, Joel; Labbe, Ivo; Brammr, Gabriel; Whitaker, Katherine E.; Skelton, Rosalind E.; Momcheva, Ivelina; Lundgren, Britt; Muzzin, Adam; Quadri, Ryan F.; Nelson, Erica June; Wake, David A.; Rix, Hans-Walter

    2013-01-01

    We follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to zeta is approx. 1.3 based on the stellar mass growth inferred from the evolution of the star-forming sequence. We select our sample from the 3D-HT survey, which utilizes spectroscopy from the HST-WFC3 G141 near-IR grism and enables precise redshift measurements for our sample of SFGs. Structural properties are obtained from Sersic profile fits to CANDELS WFC3 imaging. The progenitors of zeta = 0 SFGs with stellar mass M = 10(exp 10.5) solar mass are typically half as massive at zeta is approx. 1. This late-time stellar mass grow is consistent with recent studies that employ abundance matching techniques. The descendant SFGs at zeta is approx. 0 have grown in half-light radius by a factor of approx. 1.4 zeta is approx. 1. The half-light radius grows with stellar mass as r(sub e) alpha stellar mass(exp 0.29). While most of the stellar mass is clearly assembling at large radii, the mass surface density profiles reveal ongoing mass growth also in the central regions where bulges and pseudobulges are common features in present day late-type galaxies. Some portion of this growth in the central regions is due to star formation as recent observations of H(a) maps for SFGs at zeta approx. are found to be extended but centrally peaked. Connecting our lookback study with galactic archeology, we find the stellar mass surface density at R - 8 kkpc to have increased by a factor of approx. 2 since zeta is approx. 1, in good agreement with measurements derived for the solar neighborhood of the Milky Way.

  16. Star-forming dwarf galaxies in the Virgo cluster: the link between molecular gas, atomic gas, and dust

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Corbelli, E.; Bizzocchi, L.; Giovanardi, C.; Bomans, D.; Coelho, B.; De Looze, I.; Gonçalves, T. S.; Hunt, L. K.; Leonardo, E.; Madden, S.; Menéndez-Delmestre, K.; Pappalardo, C.; Riguccini, L.

    2016-05-01

    We present 12CO(1-0) and 12CO(2-1) observations of a sample of 20 star-forming dwarfs selected from the Herschel Virgo Cluster Survey, with oxygen abundances ranging from 12 + log (O / H) ~ 8.1 to 8.8. CO emission is observed in ten galaxies and marginally detected in another one. CO fluxes correlate with the FIR 250 μm emission, and the dwarfs follow the same linear relation that holds for more massive spiral galaxies extended to a wider dynamical range. We compare different methods to estimate H2 molecular masses, namely a metallicity-dependent CO-to-H2 conversion factor and one dependent on H-band luminosity. The molecular-to-stellar mass ratio remains nearly constant at stellar masses ≲ 109 M⊙, contrary to the atomic hydrogen fraction, MHI/M∗, which increases inversely with M∗. The flattening of the MH2/M∗ ratio at low stellar masses does not seem to be related to the effects of the cluster environment because it occurs for both Hi-deficient and Hi-normal dwarfs. The molecular-to-atomic ratio is more tightly correlated with stellar surface density than metallicity, confirming that the interstellar gas pressure plays a key role in determining the balance between the two gaseous components of the interstellar medium. Virgo dwarfs follow the same linear trend between molecular gas mass and star formation rate as more massive spirals, but gas depletion timescales, τdep, are not constant and range between 100 Myr and 6 Gyr. The interaction with the Virgo cluster environment is removing the atomic gas and dust components of the dwarfs, but the molecular gas appears to be less affected at the current stage of evolution within the cluster. However, the correlation between Hi deficiency and the molecular gas depletion time suggests that the lack of gas replenishment from the outer regions of the disc is lowering the star formation activity. Based on observations carried out with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany

  17. Ab Initio Active Region Formation

    NASA Astrophysics Data System (ADS)

    Stein, Robert F.; Nordlund, A.

    2013-01-01

    The tachocline is not necessary to produce active regions with their global properties. Dynamo action within the convection zone can produce large scale reversing polarity magnetic fields as shown by ASH code and Charboneau et al simulations. Magneto-convection acting on this large scale field produces Omega-loops which emerge through the surface to produce active regions. The field first emerges as small bipoles with horizontal field over granules anchored in vertical fields in the intergranular lanes. The fields are quickly swept into the intergranular lanes and produce a mixed polarity "pepper and salt" pattern. The opposite polarities then migrate toward separate unipolar regions due to the underlying large scale loop structure. When sufficient flux concentrates, pores and sunspots form. We will show movies of magneto-convection simulations of the emerging flux, its migration, and concentration to form pores and spots, as well as the underlying magnetic field evolution. In addition, the same atmospheric data has been used as input to the LILIA Stokes Inversion code to calculate Stokes spectra for the Fe I 630 nm lines and then invert them to determine the magnetic field. Comparisons of the inverted field with the simulation field shows that small-scale, weak fields, less than 100 G, can not be accurately determined because of vertical gradients that are difficult to match in fitting the line profiles. Horizontal smoothing by telescope diffraction further degrades the inversion accuracy.

  18. Solar active region display system

    NASA Astrophysics Data System (ADS)

    Golightly, M.; Raben, V.; Weyland, M.

    2003-04-01

    The Solar Active Region Display System (SARDS) is a client-server application that automatically collects a wide range of solar data and displays it in a format easy for users to assimilate and interpret. Users can rapidly identify active regions of interest or concern from color-coded indicators that visually summarize each region's size, magnetic configuration, recent growth history, and recent flare and CME production. The active region information can be overlaid onto solar maps, multiple solar images, and solar difference images in orthographic, Mercator or cylindrical equidistant projections. Near real-time graphs display the GOES soft and hard x-ray flux, flare events, and daily F10.7 value as a function of time; color-coded indicators show current trends in soft x-ray flux, flare temperature, daily F10.7 flux, and x-ray flare occurrence. Through a separate window up to 4 real-time or static graphs can simultaneously display values of KP, AP, daily F10.7 flux, GOES soft and hard x-ray flux, GOES >10 and >100 MeV proton flux, and Thule neutron monitor count rate. Climatologic displays use color-valued cells to show F10.7 and AP values as a function of Carrington/Bartel's rotation sequences - this format allows users to detect recurrent patterns in solar and geomagnetic activity as well as variations in activity levels over multiple solar cycles. Users can customize many of the display and graph features; all displays can be printed or copied to the system's clipboard for "pasting" into other applications. The system obtains and stores space weather data and images from sources such as the NOAA Space Environment Center, NOAA National Geophysical Data Center, the joint ESA/NASA SOHO spacecraft, and the Kitt Peak National Solar Observatory, and can be extended to include other data series and image sources. Data and images retrieved from the system's database are converted to XML and transported from a central server using HTTP and SOAP protocols, allowing

  19. Revealing the nature of star forming blue early-type galaxies at low redshift

    NASA Astrophysics Data System (ADS)

    George, Koshy; Zingade, Kshama

    2015-11-01

    Context. Star forming early-type galaxies with blue optical colours at low redshift can be used to test our current understanding of galaxy formation and evolution. Aims: We want to reveal the fuel and triggering mechanism for star formation in these otherwise passively evolving red and dead stellar systems. Methods: We undertook an optical and ultraviolet study of 55 star forming blue early-type galaxies, searching for signatures of recent interactions that could be driving the molecular gas into the galaxy and potentially triggering the star formation. Results: We report here our results on star forming blue early-type galaxies with tidal trails and in close proximity to neighbouring galaxies that are evidence of ongoing or recent interactions between galaxies. There are 12 galaxies with close companions with similar redshifts, among which two galaxies are having ongoing interactions that potentially trigger the star formation. Two galaxies show a jet feature that could be due to the complete tidal disruption of the companion galaxy. The interacting galaxies have high star formation rates and very blue optical colours. Galaxies with no companion could have undergone a minor merger in the recent past. Conclusions: The recent or ongoing interaction with a gas-rich neighbouring galaxy could be responsible for bringing cold gas to an otherwise passively evolving early-type galaxy. The sudden gas supply could trigger the star formation, eventually creating a blue early-type galaxy. The galaxies with ongoing tidal interaction are blue and star forming, thereby implying that blue early-type galaxies can exist even when the companion is on flyby so does not end up in a merger. Based on data compiled from Galaxy Zoo project, and the volunteers contribution are acknowledged at http://www.galaxyzoo.org/Volunteers.aspx

  20. Evolution and Feedback Effects of High-z Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Ouchi, Masami

    2015-08-01

    I review the recent observational progresses of star-forming galaxies at a redshift up to z~10. In conjunction with gravitational lensing magnifications, deep HST observations obtain first density estimates of UV-continuum radiation given by young massive stars, and reveal that the star-formation rate density (SFRD) continuously decreases from z~2-3 to z~10. This SFRD decrease towards high-z should be explained by the combination of the cosmic structure formation and radiative cooling+feedback effects in a halo. To decouple the contribution of the cosmic structure formation from the SFRD decrease, the stellar-to-halo mass ratios (SHMR) of high-z galaxies are derived by intensive clustering analyses with HST and Subaru survey data. The SHMR-halo mass relation shows a clear evolution from z~0 to 6, suggesting that the cooling and feedback effects are different between the present and early epochs of the cosmic history. By deep imaging and spectroscopic observations, feedback signatures are found in 10-100 kpc-scale outflow of ionized oxgen gas identified around star-forming galaxies with and without an AGN heating. There are similarly-large hydrogen Lya halos and blobs associated with high-z star-forming galaxies, but the physical origin of these Ly halos and blobs is an open question. At z>~6, UV radiation of ionizing photons produced by star-forming galaxies contribute to the cosmic reionization, while it is thought that the UV radiation prevent formation of next generation stars in dwarf galaxies at the early cosmic epoch, which works as a cosmological feedback effect. I discuss this reionization’s cosmological feedback effect with the up-to-date results from the HST and Planck data.

  1. Early star-forming galaxies and the reionization of the Universe.

    PubMed

    Robertson, Brant E; Ellis, Richard S; Dunlop, James S; McLure, Ross J; Stark, Daniel P

    2010-11-01

    Star-forming galaxies trace cosmic history. Recent observational progress with the NASA Hubble Space Telescope has led to the discovery and study of the earliest known galaxies, which correspond to a period when the Universe was only ∼800 million years old. Intense ultraviolet radiation from these early galaxies probably induced a major event in cosmic history: the reionization of intergalactic hydrogen. PMID:21048759

  2. A Survey of Star-forming Galaxies in the 1.4<~Z<~ 2.5 Redshift Desert: Overview

    NASA Astrophysics Data System (ADS)

    Steidel, Charles C.; Shapley, Alice E.; Pettini, Max; Adelberger, Kurt L.; Erb, Dawn K.; Reddy, Naveen A.; Hunt, Matthew P.

    2004-04-01

    The redshift interval 1.4<~z<~2.5 has been described by some as the ``redshift desert'' because of historical difficulties in spectroscopically identifying galaxies in that range. In fact, galaxies can be found in large numbers with standard broadband color selection techniques coupled with follow-up spectroscopy with UV and blue-sensitive spectrographs. In this paper we present the first results of a large-scale survey of such objects, carried out with the blue channel of the LRIS spectrograph (LRIS-B) on the Keck I Telescope. We introduce two samples of star-forming galaxies, ``BX'' galaxies at =2.20+/-0.32 and ``BM'' galaxies at =1.70+/-0.34. In seven survey fields we have spectroscopically confirmed 749 of the former and 114 of the latter. Interlopers (defined as objects at z<1) account for less than 10% of the photometric candidates, and the fraction of faint active galactic nuclei is ~3% in the combined BX/BM sample. Deep near-IR photometry of a subset of the BX sample indicates that, compared with a sample of similarly UV-selected galaxies at z~3, the z~2 galaxies are on average significantly redder in (R-Ks), indicating longer star formation histories, increased reddening by dust, or both. Using near-IR Hα spectra of a subset of BX/BM galaxies to define the galaxies' systemic redshifts, we show that the galactic-scale winds that are a feature of star-forming galaxies at z~3 are also common at later epochs and have similar bulk outflow speeds of 200-300 km s-1. We illustrate with examples the information that can be deduced on the stellar populations, metallicities, and kinematics of redshift desert galaxies from easily accessible rest-frame far-UV and rest-frame optical spectra. Far from being hostile to observations, the universe at z~2 is uniquely suited to providing information on the astrophysics of star-forming galaxies and the intergalactic medium, and the relationship between the two. Based, in part, on data obtained at the W. M. Keck

  3. OUTSIDE-IN SHRINKING OF THE STAR-FORMING DISK OF DWARF IRREGULAR GALAXIES

    SciTech Connect

    Zhang Hongxin; Hunter, Deidre A.; Elmegreen, Bruce G.; Gao Yu; Schruba, Andreas E-mail: dah@lowell.edu E-mail: bge@us.ibm.com

    2012-02-15

    We have studied multi-band surface brightness profiles of a representative sample of 34 nearby dwarf irregular galaxies. Our data include Galaxy Evolution Explorer (GALEX) FUV/NUV, UBV, and H{alpha} and Spitzer 3.6 {mu}m images. These galaxies constitute the majority of the LITTLE THINGS survey (Local Irregulars That Trace Luminosity Extremes-The H I Nearby Galaxy Survey). By modeling the azimuthal averages of the spectral energy distributions with a complete library of star formation histories, we derived the stellar mass surface density distributions and the star formation rate averaged over three different timescales: the recent 0.1 Gyr, 1 Gyr, and a Hubble time. We find that, for {approx}80% (27 galaxies) of our sample galaxies, radial profiles (at least in the outer part) at shorter wavelengths, corresponding to younger stellar populations, have shorter disk scale lengths than those at longer wavelengths, corresponding to older stellar populations. This indicates that the star-forming disk has been shrinking. In addition, the radial distributions of the stellar mass surface density are well described as piece-wise exponential profiles, and {approx}80% of the galaxies have steeper mass profiles in the outer disk than in the inner region. The steep radial decline of the star formation rate in the outer parts compared to that in the inner disks gives a natural explanation for the down-bending stellar mass surface density profiles. Within the inner disks, our sample galaxies on average have constant ratios of recent star formation rate to stellar mass with radius. Nevertheless, {approx}35% (12 galaxies, among which 7 have baryonic mass {approx}<10{sup 8} M{sub Sun} ) of the sample exhibit negative slopes across the observed disk, which is in contrast with the so-called inside-out disk growth scenario suggested for luminous spiral galaxies. The tendency of star formation to become concentrated toward the inner disks in low-mass dwarf irregular galaxies is

  4. Outside-in Shrinking of the Star-forming Disk of Dwarf Irregular Galaxies

    NASA Astrophysics Data System (ADS)

    Zhang, Hong-Xin; Hunter, Deidre A.; Elmegreen, Bruce G.; Gao, Yu; Schruba, Andreas

    2012-02-01

    We have studied multi-band surface brightness profiles of a representative sample of 34 nearby dwarf irregular galaxies. Our data include Galaxy Evolution Explorer (GALEX) FUV/NUV, UBV, and Hα and Spitzer 3.6 μm images. These galaxies constitute the majority of the LITTLE THINGS survey (Local Irregulars That Trace Luminosity Extremes—The H I Nearby Galaxy Survey). By modeling the azimuthal averages of the spectral energy distributions with a complete library of star formation histories, we derived the stellar mass surface density distributions and the star formation rate averaged over three different timescales: the recent 0.1 Gyr, 1 Gyr, and a Hubble time. We find that, for ~80% (27 galaxies) of our sample galaxies, radial profiles (at least in the outer part) at shorter wavelengths, corresponding to younger stellar populations, have shorter disk scale lengths than those at longer wavelengths, corresponding to older stellar populations. This indicates that the star-forming disk has been shrinking. In addition, the radial distributions of the stellar mass surface density are well described as piece-wise exponential profiles, and ~80% of the galaxies have steeper mass profiles in the outer disk than in the inner region. The steep radial decline of the star formation rate in the outer parts compared to that in the inner disks gives a natural explanation for the down-bending stellar mass surface density profiles. Within the inner disks, our sample galaxies on average have constant ratios of recent star formation rate to stellar mass with radius. Nevertheless, ~35% (12 galaxies, among which 7 have baryonic mass lsim108 M ⊙) of the sample exhibit negative slopes across the observed disk, which is in contrast with the so-called inside-out disk growth scenario suggested for luminous spiral galaxies. The tendency of star formation to become concentrated toward the inner disks in low-mass dwarf irregular galaxies is interpreted as a result of their susceptibility to

  5. High molecular gas fractions in normal massive star-forming galaxies in the young Universe.

    PubMed

    Tacconi, L J; Genzel, R; Neri, R; Cox, P; Cooper, M C; Shapiro, K; Bolatto, A; Bouché, N; Bournaud, F; Burkert, A; Combes, F; Comerford, J; Davis, M; Schreiber, N M Förster; Garcia-Burillo, S; Gracia-Carpio, J; Lutz, D; Naab, T; Omont, A; Shapley, A; Sternberg, A; Weiner, B

    2010-02-11

    Stars form from cold molecular interstellar gas. As this is relatively rare in the local Universe, galaxies like the Milky Way form only a few new stars per year. Typical massive galaxies in the distant Universe formed stars an order of magnitude more rapidly. Unless star formation was significantly more efficient, this difference suggests that young galaxies were much more molecular-gas rich. Molecular gas observations in the distant Universe have so far largely been restricted to very luminous, rare objects, including mergers and quasars, and accordingly we do not yet have a clear idea about the gas content of more normal (albeit massive) galaxies. Here we report the results of a survey of molecular gas in samples of typical massive-star-forming galaxies at mean redshifts of about 1.2 and 2.3, when the Universe was respectively 40% and 24% of its current age. Our measurements reveal that distant star forming galaxies were indeed gas rich, and that the star formation efficiency is not strongly dependent on cosmic epoch. The average fraction of cold gas relative to total galaxy baryonic mass at z = 2.3 and z = 1.2 is respectively about 44% and 34%, three to ten times higher than in today's massive spiral galaxies. The slow decrease between z approximately 2 and z approximately 1 probably requires a mechanism of semi-continuous replenishment of fresh gas to the young galaxies.

  6. C III] EMISSION IN STAR-FORMING GALAXIES NEAR AND FAR

    SciTech Connect

    Rigby, J. R.; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Johnson, T.; Wuyts, E.; Dahle, H.; Peña-Guerrero, M.

    2015-11-20

    We measure [C iii] 1907, C iii] 1909 Å emission lines in 11 gravitationally lensed star-forming galaxies at z ∼ 1.6–3, finding much lower equivalent widths than previously reported for fainter lensed galaxies. While it is not yet clear what causes some galaxies to be strong C iii] emitters, C iii] emission is not a universal property of distant star-forming galaxies. We also examine C iii] emission in 46 star-forming galaxies in the local universe, using archival spectra from GHRS, FOS, and STIS on HST and IUE. Twenty percent of these local galaxies show strong C iii] emission, with equivalent widths < −5 Å. Three nearby galaxies show C iii] emission equivalent widths as large as the most extreme emitters yet observed in the distant universe; all three are Wolf–Rayet galaxies. At all redshifts, strong C iii] emission may pick out low-metallicity galaxies experiencing intense bursts of star formation. Such local C iii] emitters may shed light on the conditions of star formation in certain extreme high-redshift galaxies.

  7. THE PRESSURE OF THE STAR-FORMING INTERSTELLAR MEDIUM IN COSMOLOGICAL SIMULATIONS

    SciTech Connect

    Munshi, Ferah; Quinn, Thomas R.; Governato, Fabio; Christensen, Charlotte; Wadsley, James; Loebman, Sarah; Shen, Sijing

    2014-01-20

    We examine the pressure of the star-forming interstellar medium (ISM) of Milky-Way-sized disk galaxies using fully cosmological SPH+N-body, high-resolution simulations. These simulations include explicit treatment of metal-line cooling in addition to dust and self-shielding, H{sub 2}-based star formation. The four simulated halos have masses ranging from a few times 10{sup 10} to nearly 10{sup 12} solar masses. Using a kinematic decomposition of these galaxies into present-day bulge and disk components, we find that the typical pressure of the star-forming ISM in the present-day bulge is higher than that in the present-day disk by an order of magnitude. We also find that the pressure of the star-forming ISM at high redshift is, on average, higher than ISM pressures at low redshift. This explains why the bulge forms at higher pressures: the disk assembles at lower redshift when the ISM exhibits lower pressure and the bulge forms at high redshift when the ISM has higher pressure. If ISM pressure and IMF variation are tied together, these results could indicate a time-dependent IMF in Milky-Way-like systems as well as a different IMF in the bulge and the disk.

  8. GEOMETRY OF STAR-FORMING GALAXIES FROM SDSS, 3D-HST, AND CANDELS

    SciTech Connect

    Van der Wel, A.; Chang, Yu-Yen; Rix, H.-W.; Martig, M.; Bell, E. F.; Holden, B. P.; Koo, D. C.; Mozena, M.; Faber, S. M.; Giavalisco, M.; Skelton, R.; Whitaker, K.; Momcheva, I.; Van Dokkum, P. G.; Dekel, A.; Ceverino, D.; Franx, M.; and others

    2014-09-01

    We determine the intrinsic, three-dimensional shape distribution of star-forming galaxies at 0 < z < 2.5, as inferred from their observed projected axis ratios. In the present-day universe, star-forming galaxies of all masses 10{sup 9}-10{sup 11} M {sub ☉} are predominantly thin, nearly oblate disks, in line with previous studies. We now extend this to higher redshifts, and find that among massive galaxies (M {sub *} > 10{sup 10} M {sub ☉}) disks are the most common geometric shape at all z ≲ 2. Lower-mass galaxies at z > 1 possess a broad range of geometric shapes: the fraction of elongated (prolate) galaxies increases toward higher redshifts and lower masses. Galaxies with stellar mass 10{sup 9} M {sub ☉} (10{sup 10} M {sub ☉}) are a mix of roughly equal numbers of elongated and disk galaxies at z ∼ 1 (z ∼ 2). This suggests that galaxies in this mass range do not yet have disks that are sustained over many orbital periods, implying that galaxies with present-day stellar mass comparable to that of the Milky Way typically first formed such sustained stellar disks at redshift z ∼ 1.5-2. Combined with constraints on the evolution of the star formation rate density and the distribution of star formation over galaxies with different masses, our findings imply that, averaged over cosmic time, the majority of stars formed in disks.

  9. C III] Emission in Star-Forming Galaxies Near and Far

    NASA Technical Reports Server (NTRS)

    Rigby, J, R.; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.; Johnson, T.; Pena-Guerrero, M.

    2015-01-01

    We measure C III Lambda Lambda 1907, 1909 Angstrom emission lines in eleven gravitationally-lensed star-forming galaxies at zeta at approximately 1.6-3, finding much lower equivalent widths than previously reported for fainter lensed galaxies (Stark et al. 2014). While it is not yet clear what causes some galaxies to be strong C III] emitters, C III] emission is not a universal property of distant star-forming galaxies. We also examine C III] emission in 46 star-forming galaxies in the local universe, using archival spectra from GHRS, FOS, and STIS on HST, and IUE. Twenty percent of these local galaxies show strong C III] emission, with equivalent widths less than -5 Angstrom. Three nearby galaxies show C III] emission equivalent widths as large as the most extreme emitters yet observed in the distant universe; all three are Wolf-Rayet galaxies. At all redshifts, strong C III] emission may pick out low-metallicity galaxies experiencing intense bursts of star formation. Such local C III] emitters may shed light on the conditions of star formation in certain extreme high-redshift galaxies.

  10. ALMA Imaging and Gravitational Lens Models of South Pole Telescope—Selected Dusty, Star-Forming Galaxies at High Redshifts

    NASA Astrophysics Data System (ADS)

    Spilker, J. S.; Marrone, D. P.; Aravena, M.; Béthermin, M.; Bothwell, M. S.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; de Breuck, C.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y.; Litke, K.; Ma, J.; Malkan, M.; Rotermund, K. M.; Strandet, M.; Vieira, J. D.; Weiss, A.; Welikala, N.

    2016-08-01

    The South Pole Telescope has discovered 100 gravitationally lensed, high-redshift, dusty, star-forming galaxies (DSFGs). We present 0.″5 resolution 870 μ {{m}} Atacama Large Millimeter/submillimeter Array imaging of a sample of 47 DSFGs spanning z=1.9{--}5.7, and construct gravitational lens models of these sources. Our visibility-based lens modeling incorporates several sources of residual interferometric calibration uncertainty, allowing us to properly account for noise in the observations. At least 70% of the sources are strongly lensed by foreground galaxies ({μ }870μ {{m}}\\gt 2), with a median magnification of {μ }870μ {{m}}=6.3, extending to {μ }870μ {{m}}\\gt 30. We compare the intrinsic size distribution of the strongly lensed sources to a similar number of unlensed DSFGs and find no significant differences in spite of a bias between the magnification and intrinsic source size. This may indicate that the true size distribution of DSFGs is relatively narrow. We use the source sizes to constrain the wavelength at which the dust optical depth is unity and find this wavelength to be correlated with the dust temperature. This correlation leads to discrepancies in dust mass estimates of a factor of two compared to estimates using a single value for this wavelength. We investigate the relationship between the [C ii] line and the far-infrared luminosity and find that the same correlation between the [C ii]/{L}{{FIR}} ratio and {{{Σ }}}{{FIR}} found for low-redshift star-forming galaxies applies to high-redshift galaxies and extends at least two orders of magnitude higher in {{{Σ }}}{{FIR}}. This lends further credence to the claim that the compactness of the IR-emitting region is the controlling parameter in establishing the “[C ii] deficit.”

  11. The formation efficiency of high-mass X-ray binaries in our two nearest star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Antoniou, Vallia; Zezas, Andreas

    2016-04-01

    We present the results of our investigation of the link between high-mass X-ray binaries (HMXBs) and star formation in the Magellanic Clouds, our nearest star-forming galaxies. Using the most complete census of HMXBs in the Large Magellanic Cloud (LMC) and the published spatially resolved star-formation history map of this galaxy, we find that the HMXBs (and as expected the X-ray pulsars) are present in regions with star-formation bursts ˜6-25 Myr ago. In contrast, this population peaks at later ages (˜25-60 Myr ago) in the Small Magellanic Cloud (SMC). Thus, this study (in combination with previous works) reinforces the idea that the HMXBs are associated with young stellar populations of ages ˜10-40 Myr. In addition, we estimate an HMXB production rate of 1 system per ˜(23.0-4.1+4.4)×10-3 M⊙/yr or 1 system per ˜143M⊙ of stars formed during the associated star-formation episode. Therefore, the formation efficiency of HMXBs in the LMC is ˜17 times lower than that in the SMC. We attribute this difference primarily in the different ages and metallicity of the HMXB populations in the two galaxies. We also set limits on the kicks imparted on the neutron star during the supernova explosion. We find that the time elapsed since the supernova kick is ˜3 times shorter in the LMC than the SMC. This in combination with the average offsets of the HMXBs from their nearest star clusters results in ˜4 times faster transverse velocities for HMXBs in the LMC than in the SMC.

  12. What makes active regions grow.

    NASA Technical Reports Server (NTRS)

    Weart, S.

    1972-01-01

    A study of magnetic flux growth or growth failure in over 100 active regions is shown to indicate that most growth is connected with the emergence of a large batch of flux in the shape of a new arch filament system (AFS). During the recent sunspot maximum, new AFSs appeared at a rate of nearly one per day over the entire sun. Evidence is presented for two proposed hypotheses, namely: (1) a twist in the flux tubes of new AFSs is a key factor in determining which new AFSs will grow; and (2) this twist is related to the well-known asymmetry of sunspot groups.

  13. Cometary nucleus and active regions

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1984-01-01

    On the basis of the icy conglomerate model of cometary nuclei, various observations demonstrate the spotted nature of many or most nuclei, i.e., regions of unusual activity, either high or low. Rotation periods, spin axes and even precession of the axes are determined. The observational evidence for variations in activity over the surfaces of cometary nuclei are listed and discussed. On June 11 the comet IRAS-ARAKI-ALCOCK approached the Earth to a distance of 0.031 AU, the nearest since C/Lexell, 1770 I, providing a unique opportunity for near-nucleus observations. Preliminary analysis of these images establishes the spin axis of the nucleus, with an oblioquity to the orbit plane of approximately 50 deg, and a lag angle of sublimation approximately 35 deg from the solar meridian on the nucleus. Asymmetries of the inner coma suggests a crazy-quilt distribution of ices with differing volatility over the surface of the nucleus. The observations of Comet P/Homes 1892 III, exhibiting two 8-10 magnitude bursts, are carefully analyzed. The grazing encounter produced, besides the first great burst, an active area on the nucleus, which was rotating retrograde with a period of 16.3hr and inclination nearly 180 deg. After the first burst the total magnitude fell less than two magnitudes from November 7 to November 30 (barely naked eye) while the nuclear region remained diffuse or complex, rarely if ever showing a stellar appearance. The fading was much more rapid after the second burst. The grazing encounter distributed a volume of large chunks in the neighborhood of the nucleus, maintaining activity for weeks.

  14. Comparing ligo merger rate observations with theory: distribution of star-forming conditions

    SciTech Connect

    Belczynski, Kryzysztof; Kopparapu, R; O' Shaughnessy, R

    2008-01-01

    Within the next decade, ground based gravitational wave detectors are in principle capable of determining the compact object merger rate per unit volume of the local universe to better than 20% with more than 30 detections. Though these measurements can constrain our models of stellar, binary, and cluster evolution in the nearby present-day and ancient universe, we argue that the universe is sufficiently heterogeneous (in age and metallicity distribution at least) and that merger rates predicted by these models can be sufficiently sensitive to those heterogeneities so that a fair comparison of models per unit similar star forming mass necessarily introduces at least an additional 30%--50% systematic error into any constraints on compact binary evolution models. Without adding new electromagnetic constraints on massive binary evolution or relying on more information from each merger (e.g. , binary masses and spins), as few as the {approx_equal}5 merger detections could exhaust the information available in a naive comparison to merger rate predictions. As a concrete example immediately relevant to analysis of initial and enhanced LIGO results, we use a nearby-universe catalog to demonstrate that no one tracer of stellar content can be consistently used to constrain merger rates without introducing a systematic error of order 0(30%) at 90% confidence (depending on the type of binary involved). For example, though binary black holes typically take many Gyr to merge, binary neutron stars often merge rapidly; different tracers of stellar content are required for these two types. More generally, we argue that theoretical binary evolution can depend sufficiently sensitively on star-forming conditions -- even assuming no uncertainty in binary evolution model -- that the distribution of star forming conditions must be incorporated to reduce the systematic error in merger rate predictions below roughly 40%. We emphasize that the degree of sensitivity to star-forming

  15. Color-magnitude Diagrams of the Star-forming Galaxies Ho IX, Cam B, NGC 2976, and UGC 1281

    NASA Astrophysics Data System (ADS)

    Georgiev, T. B.; Bomans, D. J.

    We report results on a study of nearby late type galaxies performed with the 2m RC telescope of the Rozhen NAO with with 1×1 K CCD camera. The scale and the frame size are 0.32''/pix and 5.4'×5.4', respectively. At typical seeing of 1'' the data reach routinely a limiting magnitude of ˜4 mag. With these parameters many nearby galaxies, including the members of the IC 342 and M81 groups can be resolved into star-like and diffuse objects. This allows the determination of several fundamental properties of the galaxies, based on surface photometry and study of the brightest resolved objects. The most crucial parameter is the distance to the galaxy. It can be estimated to a standard error of 20 % using the brightest red and blue stars. Selection of these stars is greatly improved by analysis of the image shapes, which allows to detect diffuse objects, like cluster candidates and background galaxies. Further improvement gives the analysis of color-magnitude (CMD) and color-color diagrams. The CMDs also allow to estimate the age of the most recent star formation event and may hint at the metallicity. The CMDs of the low surface brightness irregular galaxies Ho IX and Cam B are very similar. Especially Cam B seems to be an extreme case of a low-mass star-forming dwarf galaxy. The CMD of NGC 2976 is very similar to this of the star burst galaxy M82 (Georgiev T., 2000, Compt. Rend. Acad. Bulg. Sci. 53/2, 5-8). The edge-on galaxy UGC 1281 is of intermediate star-forming activity, but the CMD is quite sparse.

  16. Star-forming galaxies as the origin of diffuse high-energy backgrounds: gamma-ray and neutrino connections, and implications for starburst history

    SciTech Connect

    Tamborra, Irene; Ando, Shin'ichiro; Murase, Kohta E-mail: s.ando@uva.nl

    2014-09-01

    Star-forming galaxies have been predicted to contribute considerably to the diffuse gamma-ray background as they are guaranteed reservoirs of cosmic rays. Assuming that the hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos and that O(100) PeV cosmic rays can be produced and confined in starburst galaxies, we here discuss the possibility that star-forming galaxies are also the main sources of the high-energy neutrinos observed by the IceCube experiment. First, we compute the diffuse gamma-ray background from star-forming galaxies, adopting the latest Herschel PEP/HerMES luminosity function and relying on the correlation between the gamma-ray and infrared luminosities reported by Fermi observations. Then we derive the expected intensity of the diffuse high-energy neutrinos from star-forming galaxies including normal and starburst galaxies. Our results indicate that starbursts, including those with active galactic nuclei and galaxy mergers, could be the main sources of the high-energy neutrinos observed by the IceCube experiment. We find that assuming a cosmic-ray spectral index of 2.1–2.2 for all starburst-like galaxies, our predictions can be consistent with both the Fermi and IceCube data, but larger indices readily fail to explain the observed diffuse neutrino flux. Taking the starburst high-energy spectral index as free parameter, and extrapolating from GeV to PeV energies, we find that the spectra harder than E{sup -2.15} are likely to be excluded by the IceCube data, which can be more constraining than the Fermi data for this population.

  17. GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4

    SciTech Connect

    Pannella, M.; Elbaz, D.; Daddi, E.; Hwang, H. S.; Schreiber, C.; Strazzullo, V.; Aussel, H.; Bethermin, M.; Cibinel, A.; Juneau, S.; Floc’h, E. Le; Leiton, R.; Buat, V.; Charmandaris, V.; Magdis, G.; Ivison, R. J.; Borgne, D. Le; Lin, L.; Morrison, G. E.; and others

    2015-07-10

    We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate–M{sub *} correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR–radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5–4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z ≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts.

  18. Evolution of active region outflows throughout an active region lifetime

    NASA Astrophysics Data System (ADS)

    Zangrilli, L.; Poletto, G.

    2016-10-01

    Context. We have shown previously that SOHO/UVCS data allow us to detect active region (AR) outflows at coronal altitudes higher than those reached by other instrumentation. These outflows are thought to be a component of the slow solar wind. Aims: Our purpose is to study the evolution of the outflows in the intermediate corona from AR 8100, from the time the AR first forms until it dissolves, after several transits at the solar limb. Methods: Data acquired by SOHO/UVCS at the time of the AR limb transits, at medium latitudes and at altitudes ranging from 1.5 to 2.3 R⊙, were used to infer the physical properties of the outflows through the AR evolution. To this end, we applied the Doppler dimming technique to UVCS spectra. These spectra include the H i Lyα line and the O vi doublet lines at 1031.9 and 1037.6 Å. Results: Plasma speeds and electron densities of the outflows were inferred over several rotations of the Sun. AR outflows are present in the newly born AR and persist throughout the entire AR life. Moreover, we found two types of outflows at different latitudes, both possibly originating in the same negative polarity area of the AR. We also analyzed the behavior of the Si xii 520 Å line along the UVCS slit in an attempt to reveal changes in the Si abundance when different regions are traversed. Although we found some evidence for a Si enrichment in the AR outflows, alternative interpretations are also plausible. Conclusions: Our results demonstrate that outflows from ARs are detectable in the intermediate corona throughout the whole AR lifetime. This confirms that outflows contribute to the slow wind.

  19. THE DISTANCE TO A STAR-FORMING REGION IN THE OUTER ARM OF THE GALAXY

    SciTech Connect

    Hachisuka, K.; Brunthaler, A.; Menten, K. M.; Reid, M. J.; Hagiwara, Y.; Mochizuki, N.

    2009-05-10

    We performed astrometric observations with the Very Long Baseline Army of WB89-437, an H{sub 2}O maser source in the Outer spiral arm of the Galaxy. We measure an annual parallax of 0.167 {+-} 0.006 mas, corresponding to a heliocentric distance of 6.0 {+-} 0.2 kpc or a Galactocentric distance of 13.4 {+-} 0.2 kpc. This value for the heliocentric distance is considerably smaller than the kinematic distance of 8.6 kpc. This confirms the presence of a faint Outer arm toward l = 135 deg. We also measured the full space motion of the object and find a large peculiar motion of {approx}20 km s{sup -1} toward the Galactic center. This peculiar motion explains the large error in the kinematic distance estimate. We also find that WB89-437 has the same rotation speed as the LSR, providing more evidence for a flat rotation curve and thus the presence of dark matter in the outer Galaxy.

  20. The Intermediate-mass Star-forming Region Lynds 1340. An Optical View

    NASA Astrophysics Data System (ADS)

    Kun, Mária; Moór, Attila; Szegedi-Elek, Elza; Reipurth, Bo

    2016-05-01

    We have performed an optical spectroscopic and photometric search for young stellar objects associated with the molecular cloud Lynds 1340, and examined the structure of the cloud by constructing an extinction map, based on SDSS data. The new extinction map suggests a shallow, strongly fragmented cloud, having a mass of some 3700 M ⊙. Longslit spectroscopic observations of the brightest stars over the area of L1340 revealed that the most massive star associated with L1340 is a B4-type, ˜5 M ⊙ star. The new spectroscopic and photometric data of the intermediate-mass members led to a revised distance of {825}-80+110 pc, and revealed seven members of the young stellar population with M ≳ 2 M ⊙. Our search for Hα emission line stars, conducted with the Wide Field Grism Spectrograph 2 on the 2.2 m telescope of the University of Hawaii and covering a 30‧ × 40‧ area, resulted in the detection of 75 candidate low-mass pre-main sequence stars, 58 of which are new. We constructed spectral energy distributions (SEDs) of our target stars, based on SDSS, 2MASS, Spitzer, and WISE photometric data, derived their spectral types, extinctions, and luminosities from BVRIJ fluxes, estimated masses by means of pre-main sequence evolutionary models, and examined the disk properties utilizing the 2-24 μm interval of the SED. We measured the equivalent width of the Hα lines and derived accretion rates. The optically selected sample of pre-main sequence stars has a median effective temperature of 3970 K, a stellar mass of 0.7 M ⊙, and an accretion rate of 7.6 × 10-9 M ⊙ yr-1.

  1. Comparing the spatial distributions of HMXBs and star-forming regions in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Bodaghee, Arash; Antoniou, Vallia; Zezas, Andreas; Tomsick, John; Agnew, Ryan; Frechette, Eric; Jackson, Brenton; Jordan, Zachary

    2016-04-01

    Initial results are presented comparing the spatial distribution of high-mass X-ray binaries (HMXBs) and massive stellar nurseries (OB associations) in the Small Magellanic Cloud (SMC). The analysis involves constructing the two-point cross-correlation function between pairs of 72 HMXBs and 234 OB associations with the latter being randomly reshuffled following a homogenous distribution, a Gaussian distribution, and a distribution that mimics the star-formation history of the SMC. We find a significant (>5-sigma) correlation between the observed HMXB and OB catalogs compared with a random catalog in which the OB associations are distributed homogeneously across the SMC field. On average, within a kpc of a given HMXB, there are 4 OB associations from the observed catalog for every one from the randomized catalog. There is no significant difference when comparing the HMXBs with the observed catalog versus the random catalog in which the OB distribution traces the star-formation history. This suggests that HMXBs in the SMC have had less time to migrate away from their birthplaces (or, alternatively, that they have a lower average velocity) than HMXBs in the Milky Way. One explanation is that the HMXBs in our sample all host B-emission-line stars that have not yet left the main sequence.

  2. VizieR Online Data Catalog: Circumnuclear star-forming regions (Alvarez-Alvarez+, 2015)

    NASA Astrophysics Data System (ADS)

    Alvarez-Alvarez, M.; Diaz, A. I.; Terlevich, E.; Terlevich, R.

    2016-01-01

    In order to achieve our scientific goals, we have studied a diverse population of galaxies with reported circumnuclear rings of SFRs in the bibliography. The data were acquired during five observing runs. For the first two runs (from 1988 to 1990), we used a blue sensitive GEC CCD at the f/15 Cassegrain focus of the 1.0m. Jacobus Kaptein Telescope of the Isaac Newton Group at the Observatorio del Roque de los Muchachos, La Palma, Spain. The CCD had 578x385 pixels 22um wide. The last three observing runs were carried on from 1999 to 2000 at the Centro Astronomico Hispano Aleman de Calar Alto, Almeria, Spain. (3 data files).

  3. Investigating Molecular Inheritance of Carbon in Star-forming Regions along a Galactic Gradient

    NASA Astrophysics Data System (ADS)

    Smith, Rachel L.; Blake, Geoffrey; Boogert, Adwin; Pontoppidan, Klaus Martin; Lockwood, Alexandra C.

    2015-08-01

    Observations of CO isotopologues taken at high spectral resolution toward young stellar objects (YSOs) are valuable tools for investigating protoplanetary chemical reservoirs, and enable robust comparisons between YSOs and solar system material (meteorites and the Sun). Investigating a range of YSO environments also helps parameterize variations in the distribution and evolution of carbon-based molecules, furthering an understanding of prebiotic chemistry. We have begun a wide survey of massive YSOs using Keck-NIRSPEC at high spectral resolution (R=25,000). Fundamental and first-overtone near-IR CO rovibrational absorption spectra have thus far been obtained toward 14 massive, luminous YSOs at Galactocentric radii (RGC) ranging from ~4.5 to 9.7 kpc. From these data we can obtain precise [12CO]/[13CO] gas-phase abundance ratios along a Galactic gradient, and [12CO]/[13CO]Gas can be further evaluated against published [12CO2]/[13CO2]Ice and [12CO]/[13CO]Ice because all observations are in absorption, a robust study of molecular inheritance is possible by virtue of comparing 12C/13C along the same lines-of-sight. Initial results for cold CO gas at RGC ~ 6.1 kpc and 9.4 kpc reveal [12C16O]/[13C16O] of 59+/-8 and 74+/-3, respectively, roughly following an expected 12C/13C Galactic gradient. Thus far, we find [12CO]/[13CO] in the cold CO gas to be lower than [12CO2]/[13CO2]Ice, suggesting that CO2 may not originate from CO reservoirs as often assumed. While very high-resolution observations of CO gas toward low-mass YSOs observed with VLT-CRIRES show significant heterogeneity in [12CO]/[13CO] at RGC ~ 8 kpc, this dispersion is not found for the massive YSOs. Both the low-mass and massive YSOs have higher [12CO]/[13CO] in warm vs. cold gas, and both show signatures suggesting possible interplay between CO ice and gas reservoirs. Overall, our results indicate that carbon isotopic evolution in massive YSO environments may follow different paths compared to low-mass YSOs, and assumptions used in determining carbon-based molecular pathways should be considered in concert with robust observations of a range of YSO environments.

  4. Connecting AGN Feedback, the Star-Forming Interstellar Medium, and Galaxy Formation

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip

    The biggest shortcoming in our models of star, supermassive black hole, and galaxy formation is our poor and incomplete understanding of 'feedback' processes. In nearly all models, strong feedback from stars and black holes plays a critical role in regulating the nature of the interstellar medium (ISM) and subsequent generations of star formation and black hole growth. But our theoretical understanding of these processes has largely been restricted to either idealized cases, or simple phenomenological 'sub-grid' prescriptions. These have limited predictive power, and invoke highly uncertain assumptions for the unresolved ISM physics. As such, developing more realistic, explicit treatment of these processes is critical, and one of the primary challenges facing models of both galaxy and star formation. In this proposal, we focus on improving our understanding of AGN feedback by combining novel, high-resolution studies of both black hole growth and galaxy evolution. Critically, these will simultaneously resolve the ISM and both fueling and feedback from black holes, and include fundamentally new physics on galactic scales. Our goal is to anchor these calculations as much as possible in first principles, eliminating large uncertainties in the current models, and enable new predictions on galactic scales. Recently, we developed new numerical models to resolve star formation and feedback on scales from molecular cloud star-forming regions through galaxies. These simulations explicitly follow the energy, momentum, mass, and metal fluxes from stellar radiation pressure, photo-heating, supernovae, and stellar winds; in all cases feedback is tied directly to stellar evolution models. Unlike those previous, the models naturally produce an ISM in which molecular clouds form and disperse rapidly, with realistic phase structure and turbulence. These mechanisms simultaneously drive large galactic outflows; the galactic environment is radically different from the smooth medium of

  5. Physical Conditions of the Interstellar Medium in Star-forming Galaxies at z1.5

    NASA Technical Reports Server (NTRS)

    Hayashi, Masao; Ly, Chun; Shimasaku, Kazuhiro; Motohara, Kentaro; Malkan, Matthew A.; Nagao, Tohru; Kashikawa, Nobunari; Goto, Ryosuke; Naito, Yoshiaki

    2015-01-01

    We present results from Subaru/FMOS near-infrared (NIR) spectroscopy of 118 star-forming galaxies at z approximately equal to 1.5 in the Subaru Deep Field. These galaxies are selected as [O II] lambda 3727 emitters at z approximately equal to 1.47 and 1.62 from narrow-band imaging. We detect H alpha emission line in 115 galaxies, [O III] lambda 5007 emission line in 45 galaxies, and H Beta, [N II] lambda 6584, and [S II]lambda lambda 6716, 6731 in 13, 16, and 6 galaxies, respectively. Including the [O II] emission line, we use the six strong nebular emission lines in the individual and composite rest-frame optical spectra to investigate physical conditions of the interstellar medium in star-forming galaxies at z approximately equal to 1.5. We find a tight correlation between H alpha and [O II], which suggests that [O II] can be a good star formation rate (SFR) indicator for galaxies at z approximately equal to 1.5. The line ratios of H alpha / [O II] are consistent with those of local galaxies. We also find that [O II] emitters have strong [O III] emission lines. The [O III]/[O II] ratios are larger than normal star-forming galaxies in the local Universe, suggesting a higher ionization parameter. Less massive galaxies have larger [O III]/[O II] ratios. With evidence that the electron density is consistent with local galaxies, the high ionization of galaxies at high redshifts may be attributed to a harder radiation field by a young stellar population and/or an increase in the number of ionizing photons from each massive star.

  6. Ultraviolet ISM Diagnostics for Star-forming Galaxies. I. Tracers of Metallicity and Extinction

    NASA Astrophysics Data System (ADS)

    Zetterlund, Erika; Levesque, Emily M.; Leitherer, Claus; Danforth, Charles W.

    2015-06-01

    We have observed a sample of 14 nearby (z˜ 0.03) star-forming blue compact galaxies (BCGs) in the rest-frame far-UV (˜1150-2200 Å) using the Cosmic Origins Spectrograph on the Hubble Space Telescope. We have also generated a grid of stellar population synthesis models using the Starburst99 evolutionary synthesis code, allowing us to compare observations and theoretical predictions for the Si iv_1400 and C iv_1550 UV indices; both are comprised of a blend of stellar wind and interstellar lines and have been proposed as metallicity diagnostics in the UV. Our models and observations both demonstrate that there is a positive linear correlation with metallicity for both indices, and we find generally good agreement between our observations and the predictions of the Starburst99 models (with the models slightly under-estimating the value of the indices due to contributions from interstellar lines not simulated by a stellar population synthesis code). By combining the rest-frame UV observations with pre-existing rest-frame optical spectrophotometry of our BCG sample, we also directly compare the predictions of metallicity and extinction diagnostics across both wavelength regimes. This comparison reveals a correlation between the UV absorption and optical strong-line diagnostics, offering the first means of directly comparing interstellar medium (ISM) properties determined across different rest-frame regimes. Finally, using our Starburst99 model grid, we determine theoretical values for the short-wavelength UV continuum slope, {{β }18}, which can be used for determining extinction in rest-frame UV spectra of star-forming galaxies. We consider the implications of these results and discuss future work aimed at parameterizing these and other environmental diagnostics in the UV (a suite of diagnostics that could offer particular utility in the study of star-forming galaxies at high redshift) as well as the development of robust comparisons between ISM diagnostics across a

  7. The rest-frame submillimeter spectrum of high-redshift, dusty, star-forming galaxies

    SciTech Connect

    Spilker, J. S.; Marrone, D. P.; Aguirre, J. E.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bothwell, M. S.; Brodwin, M.; Carlstrom, J. E.; Crawford, T. M.; Chapman, S. C.; De Breuck, C.; Gullberg, B.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y.; Holzapfel, W. L.; and others

    2014-04-20

    We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250 to 770 GHz. This spectrum was constructed by stacking Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z = 2.0-5.7. In addition to multiple bright spectral features of {sup 12}CO, [C I], and H{sub 2}O, we also detect several faint transitions of {sup 13}CO, HCN, HNC, HCO{sup +}, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the {sup 13}CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which {sup 13}CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO{sup +}, and CN is consistent with a warm, dense medium with T {sub kin} ∼ 55 K and n{sub H{sub 2}}≳10{sup 5.5} cm{sup –3}. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4 to 1.2 mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.

  8. The Rest-frame Submillimeter Spectrum of High-redshift, Dusty, Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Spilker, J. S.; Marrone, D. P.; Aguirre, J. E.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bradford, C. M.; Bothwell, M. S.; Brodwin, M.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; de Breuck, C.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Gullberg, B.; Hezaveh, Y.; Holzapfel, W. L.; Husband, K.; Ma, J.; Malkan, M.; Murphy, E. J.; Reichardt, C. L.; Rotermund, K. M.; Stalder, B.; Stark, A. A.; Strandet, M.; Vieira, J. D.; Weiß, A.; Welikala, N.

    2014-04-01

    We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250 to 770 GHz. This spectrum was constructed by stacking Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z = 2.0-5.7. In addition to multiple bright spectral features of 12CO, [C I], and H2O, we also detect several faint transitions of 13CO, HCN, HNC, HCO+, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the 13CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which 13CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense medium with T kin ~ 55 K and n_{H_2} \\gtrsim 10^{5.5} cm-3. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4 to 1.2 mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.

  9. Chemo-Kinematic Survey of z ~ 1 Star Forming Galaxies using Keck OSIRIS LGS-AO

    NASA Astrophysics Data System (ADS)

    Mieda, Etsuko; Wright, Shelley A.; Larkin, James E.; Armus, Lee; Juneau, Stephanie

    2015-02-01

    We present first results from the Intermediate Redshift OSIRIS Chemo-Kinematic Survey (IROCKS) of z ~ 1 star forming galaxies (Mieda et al. in prep). We have targeted Hα and [NII] emission lines in J-band and have spatially resolved the galaxies at sub-kilo parsec scale. We have combined our sample with deep HST continuum images, and are able to reveal the dynamics, morphologies, metallicity distribution, emission-line diagnostics, and star formation rates of galaxies spanning this crucial z ~ 1 epoch.

  10. Constraining the Star Forming History in Monoceros: A Study of Embedded Cluster Ages and Spatial Structure

    NASA Astrophysics Data System (ADS)

    Lada, Elizabeth A.; Marinas, Naibi; Levine, Joanna L.; Ferreira, Bruno

    2009-08-01

    We propose to use FLAMINGOS multi-object spectrometer on the KPNO 4 meter telescope to complete a spectroscopic survey of 7 clusters in the Monoceros GMC. The data will be combined with existing FLAMINGOS photometry to determine the ages and masses of the stars in the clusters using the HR Diagram and PMS evolutionary models. This information, combined with the spatial distribution of clusters in the cloud, determined from previous observations, will allow us to investigate the ages and age spreads of the embedded clusters and the star forming histories of the clusters and the molecular cloud.

  11. Constraining the Star Forming History in Monoceros: A Study of Embedded Cluster Ages and Spatial Structure

    NASA Astrophysics Data System (ADS)

    Marinas, Naibi; Lada, Elizabeth; Ybarra, Jason; Fleming, Scott

    2010-08-01

    We propose to use FLAMINGOS multi-object spectrometer on the KPNO 4 meter telescope to complete a spectroscopic survey of 5 clusters in the Monoceros GMC. The data will be combined with existing FLAMINGOS photometry to determine the ages and masses of the stars in the clusters using the HR Diagram and PMS evolutionary models. This information, combined with the spatial distribution of clusters in the cloud, determined from previous observations, will allow us to investigate the ages and age spreads of the embedded clusters and the star forming histories of the clusters and the molecular cloud.

  12. Faint Lyα Emitters, Star-forming Galaxies, and Damped Lyα Systems

    NASA Astrophysics Data System (ADS)

    Rauch, M.; Haehnelt, M.; Bunker, A.; Becker, G.; Marleau, F.; Graham, J.; Cristiani, S.; Jarvis, M.; Lacey, C.; Morris, S.; Peroux, C.; Roettgering, H.; Theuns, T.

    2008-10-01

    We have discovered a population of faint single line emitters, likely to be identified with faint z˜ 3 Lyα emitters and with the host galaxies of damped Lyman alpha systems. The objects appear to constitute the bulk of the star-forming galaxies detected so far from the ground, and are likely to provide the gaseous reservoir from which present-day Milky way type galaxies have formed. Unlike color-selected (yman break galaxies, these objects appear to have low star-formation rates, relatively strong Lyalpha emission, and low masses, metallicities, and dust content (s.a. arXiv:0711.1354).

  13. Investigating nearby star-forming galaxies in the ultraviolet with HST/COS spectroscopy. I. Spectral analysis and interstellar abundance determinations

    SciTech Connect

    James, B. L.; Aloisi, A.; Sohn, S. T.; Wolfe, M. A.; Heckman, T.

    2014-11-10

    This is the first in a series of three papers describing a project with the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure abundances of the neutral interstellar medium (ISM) in a sample of nine nearby star-forming galaxies. The goal is to assess the (in)homogeneities of the multiphase ISM in galaxies where the bulk of metals can be hidden in the neutral phase, yet the metallicity is inferred from the ionized gas in the H II regions. The sample, spanning a wide range in physical properties, is to date the best suited to investigate the metallicity behavior of the neutral gas at redshift z = 0. ISM absorption lines were detected against the far-ultraviolet spectra of the brightest star-forming region(s) within each galaxy. Here we report on the observations, data reduction, and analysis of these spectra. Column densities were measured by a multicomponent line-profile fitting technique, and neutral-gas abundances were obtained for a wide range of elements. Several caveats were considered, including line saturation, ionization corrections, and dust depletion. Ionization effects were quantified with ad hoc CLOUDY models reproducing the complex photoionization structure of the ionized and neutral gas surrounding the UV-bright sources. An 'average spectrum of a redshift z = 0 star-forming galaxy' was obtained from the average column densities of unsaturated profiles of neutral-gas species. This template can be used as a powerful tool for studies of the neutral ISM at both low and high redshift.

  14. New Light in Star-Forming Dwarf Galaxies: The PMAS Integral Field View of the Blue Compact Dwarf Galaxy Mrk 409

    NASA Astrophysics Data System (ADS)

    Cairós, Luz M.; Caon, Nicola; Papaderos, Polychronis; Kehrig, Carolina; Weilbacher, Peter; Roth, Martin M.; Zurita, Cristina

    2009-12-01

    We present an integral field spectroscopic study of the central 2 × 2 kpc2 of the blue compact dwarf galaxy Mrk 409, observed with the Potsdam MultiAperture Spectrophotometer (PMAS). This study focuses on the morphology, two-dimensional chemical abundance pattern, excitation properties, and kinematics of the ionized interstellar medium in the starburst component. We also investigate the nature of the extended ring of ionized gas emission surrounding the bright nuclear starburst region of Mrk 409. PMAS spectra of selected regions along the ring, interpreted with evolutionary and population synthesis models, indicate that their ionized emission is mainly due to a young stellar population with a total mass of ~1.5 × 106 M sun, which started forming almost coevally ~10 Myr ago. This stellar component is likely confined to the collisional interface of a spherically expanding, starburst-driven super-bubble with denser, swept-up ambient gas, ~600 pc away from the central starburst nucleus. The spectroscopic properties of the latter imply a large extinction (CHβ>0.9), and the presence of an additional non-thermal ionization source, most likely a low-luminosity active galactic nucleus. Mrk 409 shows a relatively large oxygen abundance (12 + log(O/H) ~ 8.4) and no chemical abundance gradients out to R ~ 600 pc. The ionized gas kinematics displays an overall regular rotation on a northwest-southeast axis, with a maximum velocity of 60 km s-1 the total mass inside the star-forming ring is about 1.4 × 109 M sun. Based on observations obtained at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy.

  15. Impacts of a Flaring Star-forming Disc and Stellar Radial Mixing on the Vertical Metallicity Gradient

    NASA Astrophysics Data System (ADS)

    Kawata, Daisuke; Grand, Robert J. J.; Gibson, Brad K.; Casagrande, Luca; Hunt, Jason A. S.; Brook, Chris B.

    2016-09-01

    Using idealised N-body simulations of a Milky Way-sized disc galaxy, we qualitatively study how the metallicity distributions of the thin disc star particles are modified by the formation of the bar and spiral arm structures. The thin disc in our numerical experiments initially has a tight negative radial metallicity gradient and a constant vertical scale-height. We show that the radial mixing of stars drives a positive vertical metallicity gradient in the thin disc. On the other hand, if the initial thin disc is f flared, with vertical scale-height increasing with galactocentric radius, the metal poor stars originally in the outer disc become dominant in regions above the disc plane at every radii. This process can drive a negative vertical metallicity gradient, which is consistent with the current observed trend. This model mimics a scenario where the star-forming thin disc was flared in the outer region at earlier epochs. Our numerical experiment with an initial flared disc predicts that the negative vertical metallicity gradient of the mono-age relatively young thin disc population should be steeper in the inner disc, and the radial metallicity gradient of the mono-age population should be shallower at greater heights above the disc plane. We also predict that the metallicity distribution function of mono-age young thin disc populations above the disc plane would be more positively skewed in the inner disc compared to the outer disc.

  16. The structured environments of embedded star-forming cores . PACS and SPIRE mapping of the enigmatic outflow source UYSO 1

    NASA Astrophysics Data System (ADS)

    Linz, H.; Krause, O.; Beuther, H.; Henning, Th.; Klein, R.; Nielbock, M.; Stecklum, B.; Steinacker, J.; Stutz, A.

    2010-07-01

    The intermediate-mass star-forming core UYSO 1 has previously been found to exhibit intriguing features. While deeply embedded and previously only identified by means of its (sub-)millimeter emission, it drives two powerful, dynamically young, molecular outflows. Although the process of star formation has obviously started, the chemical composition is still pristine. We present Herschel PACS and SPIRE continuum data of this presumably very young region. The now complete coverage of the spectral energy peak allows us to precisely constrain the elevated temperature of 26-28 K for the main bulge of gas associated with UYSO1, which is located at the interface between the hot H ii region Sh 2-297 and the cold dark nebula LDN 1657A. Furthermore, the data identify cooler compact far-infrared sources of just a few solar masses, hidden in this neighbouring dark cloud. Herschel is an ESA space observatory, with its science instruments PACS, SPIRE, and HIFI provided by European-led Principal Investigator consortia, and with important participation from NASA.

  17. On the nature of star-forming filaments - II. Subfilaments and velocities

    NASA Astrophysics Data System (ADS)

    Smith, Rowan J.; Glover, Simon C. O.; Klessen, Ralf S.; Fuller, Gary A.

    2016-02-01

    We show that hydrodynamic turbulent cloud simulations naturally produce large filaments made up of a network of smaller and coherent subfilaments. Such simulations resemble observations of filaments and fibres in nearby molecular clouds. The subfilaments are dynamical features formed at the stagnation points of the turbulent velocity field where shocks dissipate the turbulent energy. They are a ubiquitous feature of the simulated clouds, which appear from the beginning of the simulation and are not formed by gradual fragmentation of larger filaments. Most of the subfilaments are gravitationally subcritical and do not fragment into cores, however, there is also a significant fraction of supercritical subfilaments which break up into star-forming cores. The subfilaments are coherent along their length, and the residual velocities along their spine show that they are subsonically contracting without any ordered rotation on scales of ˜0.1 pc. Accretion flows along the subfilaments can feed material into star-forming cores embedded within the network. The overall mass in subfilaments and the number of subfilaments increases as the cloud evolves. We propose that the formation of filaments and subfilaments is a natural consequence of the turbulent cascade in the complex multiphase interstellar medium. Subfilaments are formed by the high wavenumber, small-scale modes in the turbulent velocity field. These are then stretched by local shear motions and gathered together by a combination of low wavenumber modes and gravitational contraction on larger scales, and by doing so build up the extended filaments observed in column density maps.

  18. Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy.

    PubMed

    Izotov, Y I; Orlitová, I; Schaerer, D; Thuan, T X; Verhamme, A; Guseva, N G; Worseck, G

    2016-01-14

    One of the key questions in observational cosmology is the identification of the sources responsible for ionization of the Universe after the cosmic 'Dark Ages', when the baryonic matter was neutral. The currently identified distant galaxies are insufficient to fully reionize the Universe by redshift z ≈ 6 (refs 1-3), but low-mass, star-forming galaxies are thought to be responsible for the bulk of the ionizing radiation. As direct observations at high redshift are difficult for a variety of reasons, one solution is to identify local proxies of this galaxy population. Starburst galaxies at low redshifts, however, generally are opaque to Lyman continuum photons. Small escape fractions of about 1 to 3 per cent, insufficient to ionize much surrounding gas, have been detected only in three low-redshift galaxies. Here we report far-ultraviolet observations of the nearby low-mass star-forming galaxy J0925+1403. The galaxy is leaking ionizing radiation with an escape fraction of about 8 per cent. The total number of photons emitted during the starburst phase is sufficient to ionize intergalactic medium material that is about 40 times as massive as the stellar mass of the galaxy.

  19. Physical properties of local star-forming analogues to z ˜ 5 Lyman-break galaxies

    NASA Astrophysics Data System (ADS)

    Greis, Stephanie M. L.; Stanway, Elizabeth R.; Davies, Luke J. M.; Levan, Andrew J.

    2016-07-01

    Intense, compact, star-forming galaxies are rare in the local Universe but ubiquitous at high redshift. We interpret the 0.1-22 μm spectral energy distributions of a sample of 180 galaxies at 0.05 < z < 0.25 selected for extremely high surface densities of inferred star formation in the ultraviolet. By comparison with well-established stellar population synthesis models, we find that our sample comprises young (˜60-400 Myr), moderate mass (˜6 × 109 M⊙) star-forming galaxies with little dust extinction (mean stellar continuum extinction Econt(B - V) ˜ 0.1) and find star formation rates of a few tens of solar masses per year. We use our inferred masses to determine a mean specific star formation rate for this sample of ˜10-9 yr-1, and compare this to the specific star formation rates in distant Lyman-break galaxies (LBGs), and in other low-redshift populations. We conclude that our sample's characteristics overlap significantly with those of the z ˜ 5 LBG population, making ours the first local analogue population well tuned to match those high-redshift galaxies. We consider implications for the origin and evolution of early galaxies.

  20. The effect of disc inclination on the main sequence of star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Morselli, L.; Renzini, A.; Popesso, P.; Erfanianfar, G.

    2016-11-01

    We use the Sloan Digital Sky Survey (York et al.) data base to explore the effect of the disc inclination angle on the derived star formation rate (SFR), hence on the slope and width of the main-sequence (MS) relation for star-forming galaxies. We find that SFRs for nearly edge-on discs are underestimated by factors ranging from ˜0.2 dex for low-mass galaxies up to ˜0.4 dex for high-mass galaxies. This results in a substantially flatter MS relation for high-inclination discs compared to that for less inclined ones, though the global effect over the whole sample of star-forming galaxies is relatively minor, given the small fraction of high-inclination discs. However, we also find that galaxies with high-inclination discs represent a non-negligible fraction of galaxies populating the so-called green valley, with derived SFRs intermediate between the MS and those of quenched, passively evolving galaxies.

  1. Modeling tracers of young stellar population age in star-forming galaxies

    SciTech Connect

    Levesque, Emily M.; Leitherer, Claus

    2013-12-20

    The young stellar population of a star-forming galaxy is the primary engine driving its radiative properties. As a result, the age of a galaxy's youngest generation of stars is critical for a detailed understanding of its star formation history, stellar content, and evolutionary state. Here we present predicted equivalent widths for the Hβ, Hα, and Brγ recombination lines as a function of stellar population age. The equivalent widths are produced by the latest generations of stellar evolutionary tracks and the Starburst99 stellar population synthesis code, and are the first to fully account for the combined effects of both nebular emission and continuum absorption produced by the synthetic stellar population. Our grid of model stellar populations spans six metallicities (0.001 < Z < 0.04), two treatments of star formation history (a 10{sup 6} M {sub ☉} instantaneous burst and a continuous star formation rate of 1 M {sub ☉} yr{sup –1}), and two different treatments of initial rotation rate (v {sub rot} = 0.0v {sub crit} and 0.4v {sub crit}). We also investigate the effects of varying the initial mass function. Given constraints on galaxy metallicity, our predicted equivalent widths can be applied to observations of star-forming galaxies to approximate the age of their young stellar populations.

  2. Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy.

    PubMed

    Izotov, Y I; Orlitová, I; Schaerer, D; Thuan, T X; Verhamme, A; Guseva, N G; Worseck, G

    2016-01-14

    One of the key questions in observational cosmology is the identification of the sources responsible for ionization of the Universe after the cosmic 'Dark Ages', when the baryonic matter was neutral. The currently identified distant galaxies are insufficient to fully reionize the Universe by redshift z ≈ 6 (refs 1-3), but low-mass, star-forming galaxies are thought to be responsible for the bulk of the ionizing radiation. As direct observations at high redshift are difficult for a variety of reasons, one solution is to identify local proxies of this galaxy population. Starburst galaxies at low redshifts, however, generally are opaque to Lyman continuum photons. Small escape fractions of about 1 to 3 per cent, insufficient to ionize much surrounding gas, have been detected only in three low-redshift galaxies. Here we report far-ultraviolet observations of the nearby low-mass star-forming galaxy J0925+1403. The galaxy is leaking ionizing radiation with an escape fraction of about 8 per cent. The total number of photons emitted during the starburst phase is sufficient to ionize intergalactic medium material that is about 40 times as massive as the stellar mass of the galaxy. PMID:26762455

  3. Star Formation in Low-Mass Star-Forming Galaxies at intermediate redshifts

    NASA Astrophysics Data System (ADS)

    Gallego, Jesus; Rodriguez-Muñoz, Lucía; Pacifici, Camilla; Tresse, Laurence; Charlot, Stéphane; Gil de Paz, Armando; Gomez-Guijarro, Carlos

    2015-08-01

    Dwarf galaxies play a key role in galaxy formation and evolution: (1) hierarchical models predict that low-mass systems merged to form massive galaxies (building block paradigm; Dekel & Silk 1986); (2) dwarf systems might have been responsible for the reionization of the Universe (Wyithe & Loeb 2006); (3) theoretical models are particularly sensitive to the density of low-mass systems at diferent redshifts (Mamon et al. 2011), being one of the key science cases for the future E-ELT (Evans et al. 2013). While the history of low-mass dark matter halos is relatively well understood, the formation history of dwarf galaxies is still poorly reproduced by the models due to the distinct evolution of baryonic and dark matter.We present Star Formation properties of a sample of low-mass Star-Forming Galaxies (LMSFGs; 7.3 < log M∗/Mo < 8.0, at 0.3 < zspec < 0.9) selected by photometric stellar mass and apparent magnitude. The SFRs and overall properties were obtained through the analysis of their spectral energy distributions based on (1) HST and ground-based multi-broadband photometry and (2) deep spectroscopy from VLT and GTC telescopes.The SFRs and stellar masses derived for both samples place our targets on the standard main sequence of star-forming galaxies, but extending the sequence at least one dex to low mass systems.

  4. Young, Ultraviolet-bright Stars Dominate Dust Heating in Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Law, Ka-Hei; Gordon, Karl D.; Misselt, K. A.

    2011-09-01

    In star-forming galaxies, dust plays a significant role in shaping the ultraviolet (UV) through infrared (IR) spectrum. Dust attenuates the radiation from stars, and re-radiates the energy through equilibrium and non-equilibrium emission. Polycyclic aromatic hydrocarbons (PAHs), graphite, and silicates contribute to different features in the spectral energy distribution; however, they are all highly opaque in the same spectral region—the UV. Compared to old stellar populations, young populations release a higher fraction of their total luminosity in the UV, making them a good source of the energetic UV photons that can power dust emission. However, given their relative abundance, the question of whether young or old stellar populations provide most of these photons that power the IR emission is an interesting question. Using three samples of galaxies observed with the Spitzer Space Telescope and our dusty radiative transfer model, we find that young stellar populations (on the order of 100 million years old) dominate the dust heating in star-forming galaxies, and old stellar populations (13 billion years old) generally contribute less than 20% of the far-IR luminosity.

  5. [C II] emission in z ˜ 6 strongly lensed, star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Knudsen, Kirsten K.; Richard, Johan; Kneib, Jean-Paul; Jauzac, Mathilde; Clément, Benjamin; Drouart, Guillaume; Egami, Eiichi; Lindroos, Lukas

    2016-10-01

    The far-infrared fine-structure line [C II] at 1900.5 GHz is known to be one of the brightest cooling lines in local galaxies, and therefore it has been suggested to be an efficient tracer for star formation in very high redshift galaxies. However, recent results for galaxies at z > 6 have yielded numerous non-detections in star-forming galaxies, except for quasars and submillimetre galaxies. We report the results of ALMA observations of two lensed, star-forming galaxies at z = 6.029 and z = 6.703. The galaxy A383-5.1 (star formation rate [SFR] of 3.2 M⊙ yr-1 and magnification of μ = 11.4 ± 1.9) shows a line detection with L_[C II] = 8.9× 106 L⊙, making it the lowest L_[C II] detection at z > 6. For MS0451-H (SFR = 0.4 M⊙ yr-1 and μ = 100 ± 20) we provide an upper limit of L_[C II] < 3× 105 L⊙, which is 1 dex below the local SFR-L_[C II] relations. The results are consistent with predictions for low-metallicity galaxies at z > 6; however, other effects could also play a role in terms of decreasing L[CII]. The detection of A383-5.1 is encouraging and suggests that detections are possible, but much fainter than initially predicted.

  6. The structure of the interstellar medium of star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Quataert, Eliot; Murray, Norman

    2012-04-01

    We develop and implement numerical methods for including stellar feedback in galaxy-scale numerical simulations. Our models include simplified treatments of heating by Type I and Type II supernovae, gas recycling from young stars and asymptotic giant branch winds, heating from the shocked stellar winds, H II photoionization heating and radiation pressure from stellar photons. The energetics and time dependence associated with the feedback are taken directly from stellar evolution models. We implement these stellar feedback models in smoothed particle hydrodynamic simulations with pc-scale resolution, modelling galaxies from Small Magellanic Cloud (SMC) like dwarfs and Milky Way (MW) analogues to massive z˜ 2 star-forming discs. In the absence of stellar feedback, gas cools rapidly and collapses without limit into dense sub-units, inconsistent with observations. By contrast, in all cases with feedback, the interstellar medium (ISM) quickly approaches a statistical steady state in which giant molecular clouds (GMCs) continuously form, disperse and re-form, leading to a multiphase ISM. In this paper, we quantify the properties of the ISM and GMCs in this self-regulated state. In a companion paper we study the galactic winds driven by stellar feedback. Our primary results on the structure of the ISM in star-forming galaxies include the following. 1. Star-forming galaxies generically self-regulate so that the cool, dense gas maintains Toomre's Q˜ 1. Most of the volume is occupied by relatively diffuse hot gas, while most of the mass is in dense GMC complexes created by self-gravity. The phase structure of the gas and the gas mass fraction at high densities are much more sensitive probes of the physics of stellar feedback than integrated quantities such as the Toomre Q or gas velocity dispersion. 2. Different stellar feedback mechanisms act on different spatial (and density) scales. Radiation pressure and H II gas pressure are critical for preventing runaway collapse

  7. The history of star-forming galaxies in the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Asari, N. V.; Cid Fernandes, R.; Stasińska, G.; Torres-Papaqui, J. P.; Mateus, A.; Sodré, L.; Schoenell, W.; Gomes, J. M.

    2007-10-01

    This paper, the sixth in the Semi-Empirical Analysis of Galaxies series, studies the evolution of 82302 star-forming (SF) galaxies from the Sloan Digital Sky Survey. Star formation histories (SFHs) are derived from detailed spectral fits obtained with our publicly available spectral synthesis code STARLIGHT. Our main goals are to explore new ways to derive SFHs from the synthesis results and apply them to investigate how SFHs vary as a function of nebular metallicity (Zneb). A number of refinements over our previous work are introduced, including (1) an improved selection criterion; (2) a careful examination of systematic residuals around Hβ (3) self-consistent determination of nebular extinctions and metallicities; (4) tests with several Zneb estimators; (5) a study of the effects of the reddening law adopted and of the relation between nebular and stellar extinctions and the interstellar component of the NaI D doublet. Our main achievements may be summarized as follows. (1) A conventional correlation analysis is performed to study how global properties relate to Zneb, leading to the confirmation of previously known relations, such as those between Zneb and galaxy luminosity, mass, dust content, mean stellar metallicity and mean stellar age. (2) A simple formalism which compresses the results of the synthesis while at the same time yielding time-dependent star formation rates (SFR) and mass assembly histories is presented. (3) A comparison of the current SFR derived from the population synthesis with that obtained from Hα shows that these independent estimators agree very well, with a scatter of a factor of 2. An important corollary of this finding is that we now have a way to estimate SFR in galaxies hosting active galactic nuclei, where the Hα method cannot be applied. (4) Fully time-dependent SFHs were derived for all galaxies, and then averaged over six Zneb bins spanning the entire SF wing in the diagram. (5) We find that SFHs vary systematically along the

  8. Direct measurements of dust attenuation in z ∼ 1.5 star-forming galaxies from 3D-HST: Implications for dust geometry and star formation rates

    SciTech Connect

    Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B.; Conroy, Charlie; Schreiber, Natascha M. Förster; Wuyts, Stijn; Franx, Marijn; Fumagalli, Mattia; Lundgren, Britt; Momcheva, Ivelina; Nelson, Erica J.; Van Dokkum, Pieter G.; Skelton, Rosalind E.; Whitaker, Katherine E.

    2014-06-10

    The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust around star-forming regions (A {sub V,} {sub H} {sub II}) and the integrated dust content (A {sub V,} {sub star}). We select a sample of 163 galaxies between 1.36 ≤ z ≤ 1.5 with Hα signal-to-noise ratio ≥5 and measure Balmer decrements from stacked spectra to calculate A {sub V,} {sub H} {sub II}. First, we stack spectra in bins of A {sub V,} {sub star}, and find that A {sub V,} {sub H} {sub II} = 1.86 A {sub V,} {sub star}, with a significance of σ = 1.7. Our result is consistent with the two-component dust model, in which galaxies contain both diffuse and stellar birth cloud dust. Next, we stack spectra in bins of specific star formation rate (log SSFR), star formation rate (log SFR), and stellar mass (log M {sub *}). We find that on average A {sub V,} {sub H} {sub II} increases with SFR and mass, but decreases with increasing SSFR. Interestingly, the data hint that the amount of extra attenuation decreases with increasing SSFR. This trend is expected from the two-component model, as the extra attenuation will increase once older stars outside the star-forming regions become more dominant in the galaxy spectrum. Finally, using Balmer decrements we derive dust-corrected Hα SFRs, and find that stellar population modeling produces incorrect SFRs if rapidly declining star formation histories are included in the explored parameter space.

  9. Emission measure distribution for diffuse regions in solar active regions

    SciTech Connect

    Subramanian, Srividya; Tripathi, Durgesh; Klimchuk, James A.; Mason, Helen E.

    2014-11-01

    Our knowledge of the diffuse emission that encompasses active regions is very limited. In this paper we investigate two off-limb active regions, namely, AR 10939 and AR 10961, to probe the underlying heating mechanisms. For this purpose, we have used spectral observations from Hinode/EIS and employed the emission measure (EM) technique to obtain the thermal structure of these diffuse regions. Our results show that the characteristic EM distributions of the diffuse emission regions peak at log T = 6.25 and the coolward slopes are in the range 1.4-3.3. This suggests that both low- as well as high-frequency nanoflare heating events are at work. Our results provide additional constraints on the properties of these diffuse emission regions and their contribution to the background/foreground when active region cores are observed on-disk.

  10. An X-ray and radio study of the massive star-forming cluster IRAS 20126+4104

    NASA Astrophysics Data System (ADS)

    Montes, Virginie; Hofner, Peter; Anderson, Crystal; Rosero, Viviana

    2015-08-01

    Two main competitive theories intent to explain massive star formation: the turbulent core model, which is an extension of the low-mass star formation model (McKee & Tan 2003), and models involving competitive accretion or stellar collisions (Bonnell & Bate 2006). The characterization of the cluster in which massive stars remain can help discriminate between the two main scenarios of their formation.Until recently it was believed that massive stars were only formed in dense molecular clouds leading to a substantial cluster. However, a previous study of the massive star forming region IRAS 20126+4104 using Spitzer observations by Qiu et al. (2008), suggested that the massive protostar was isolated, and the region was showing no obvious cluster.Here we adopt a multiwavelength technique to characterize the stellar environment of the IRAS 20126+4104 region combining Chandra X-ray ACIS-I and VLA 6cm continuum observations, and near-infrared (2MASS) data of the region. We detected 150 X-ray sources in the ACIS-I field and 13 radio sources within the 9’.2 VLA primary beam. Associating X-ray sources with their near-infrared counterparts from the 2MASS catalog and a color study of those counterparts, allow us to determine the galactic foreground/background contamination, and we conclude that 90 X-ray sources are associated with the region.This study shows an increasing surface density of X-ray sources toward the massive protostar and a number of at least 42 YSOs within 1.2 pc distance from the massive protostar. This number is consistent with typical B-type stars clusters (Lada & Lada 2003).

  11. DECIPHERING THE IONIZED GAS CONTENT IN THE MASSIVE STAR-FORMING COMPLEX G75.78+0.34

    SciTech Connect

    Sanchez-Monge, Alvaro; Kurtz, Stan; Lizano, Susana; Palau, Aina; Estalella, Robert; Shepherd, Debra; Franco, Jose; Garay, Guido

    2013-04-01

    We present subarcsecond observations toward the massive star-forming region G75.78+0.34. We used the Very Large Array to study the centimeter continuum and H{sub 2}O and CH{sub 3}OH maser emission, and the Owens Valley Radio Observatory and Submillimeter Array to study the millimeter continuum and recombination lines (H40{alpha} and H30{alpha}). We found radio continuum emission at all wavelengths, coming from three components: (1) a cometary ultracompact (UC) H II region with an electron density {approx}3.7 Multiplication-Sign 10{sup 4} cm{sup -3}, excited by a B0 type star, and with no associated dust emission; (2) an almost unresolved UCH II region (EAST), located {approx}6'' to the east of the cometary UCH II region, with an electron density {approx}1.3 Multiplication-Sign 10{sup 5} cm{sup -3}, and associated with a compact dust clump detected at millimeter and mid-infrared wavelengths; and (3) a compact source (CORE), located {approx}2'' to the southwest of the cometary arc, with a flux density increasing with frequency, and embedded in a dust condensation of 30 M{sub Sun }. The CORE source is resolved into two compact and unresolved sources which can be well fit by two homogeneous hypercompact H II regions each one photoionized by a B0.5 zero-age main sequence star, or by free-free radiation from shock-ionized gas resulting from the interaction of a jet/outflow system with the surrounding environment. The spatial distribution and kinematics of water masers close to the CORE-N and S sources, together with excess emission at 4.5 {mu}m and the detected dust emission, suggest that the CORE source is a massive protostar driving a jet/outflow.

  12. Size evolution of star-forming galaxies with 2

    NASA Astrophysics Data System (ADS)

    Ribeiro, B.; Le Fèvre, O.; Tasca, L. A. M.; Lemaux, B. C.; Cassata, P.; Garilli, B.; Maccagni, D.; Zamorani, G.; Zucca, E.; Amorín, R.; Bardelli, S.; Fontana, A.; Giavalisco, M.; Hathi, N. P.; Koekemoer, A.; Pforr, J.; Tresse, L.; Dunlop, J.

    2016-08-01

    Context. The size of a galaxy encapsulates the signature of the different physical processes driving its evolution. The distribution of galaxy sizes in the Universe as a function of cosmic time is therefore a key to understand galaxy evolution. Aims: We aim to measure the average sizes and size distributions of galaxies as they are assembling before the peak in the comoving star formation rate density of the Universe to better understand the evolution of galaxies across cosmic time. Methods: We used a sample of ~1200 galaxies in the COSMOS and ECDFS fields with confirmed spectroscopic redshifts 2 ≤ zspec ≤ 4.5 in the VIMOS Ultra Deep Survey (VUDS), representative of star-forming galaxies with iAB ≤ 25. We first derived galaxy sizes by applying a classical parametric profile-fitting method using GALFIT. We then measured the total pixel area covered by a galaxy above a given surface brightness threshold, which overcomes the difficulty of measuring sizes of galaxies with irregular shapes. We then compared the results obtained for the equivalent circularized radius enclosing 100% of the measured galaxy light r100T ~2.2 to those obtained with the effective radius re,circ measured with GALFIT. Results: We find that the sizes of galaxies computed with our non-parametric approach span a wide range but remain roughly constant on average with a median value r100T ~2.2 kpc for galaxies with 2 star-forming galaxies that are the largest at any redshift are, on average, more massive and form more stars. We discover that galaxies present more concentrated light profiles with

  13. CME Productivity of Active Regions.

    NASA Astrophysics Data System (ADS)

    Liu, L.; Wang, Y.; Wang, J.; Shen, C.; Ye, P.; Zhang, Q.; Liu, R.; Wang, S.

    2015-12-01

    Solar active regions (ARs) are the major sources of two kinds of the most violent solar eruptions, namely flares and coronal mass ejections (CMEs). Although they are believed to be two phenomena in the same eruptive process, the productivity of them could be quiet different for various ARs. Why is an AR productive? And why is a flare-rich AR CME-poor? To answer these questions, we compared the recent super flare-rich but CME-poor AR 12192, with other four ARs; two were productive in both flares and CMEs and the other two were inert to produce any M-class or intenser flares or CMEs. By investigating the photospheric parameters based on the SDO/HMI vector magnetogram, we find the three productive ARs have larger magnetic flux, current and free magnetic energy than the inert ARs. Furthermore, the two ARs productive in both flares and CMEs contain higher current helicity, concentrating along both sides of the flaring neutral lines, indicating the presence of a seed magnetic structure( that is highly sheared or twisted) of a CME; they also have higher decay index in the low corona, showing weak constraint. The results suggest that productive ARs are always large and have strong current system and sufficient free energy to power flares, and more importantly whether or not a flare is accompanied by a CME is seemingly related to (1) if there is significant sheared or twisted core field serving as the seed of the CME and (2) if the constraint of the overlying arcades is weak enough. Moreover, some productive ARs may frequently produce more than one CME. How does this happen? We do a statistical investigation of waiting times of quasi-homologous CMEs ( CME ssuccessive originating from the same ARs within short intervals) from super ARs in solar cycle 23 to answer this question. The waiting times of quasi-homologous CMEs have a two-component distribution with a separation at about 18 hours, the first component peaks at 7 hours. The correlation analysis among CME waiting times

  14. Lyman Continuum Escape Fraction of Star-forming Dwarf Galaxies at z ˜ 1

    NASA Astrophysics Data System (ADS)

    Rutkowski, Michael J.; Scarlata, Claudia; Haardt, Francesco; Siana, Brian; Henry, Alaina; Rafelski, Marc; Hayes, Matthew; Salvato, Mara; Pahl, Anthony J.; Mehta, Vihang; Beck, Melanie; Malkan, Matthew; Teplitz, Harry I.

    2016-03-01

    To date, no direct detection of Lyman continuum emission has been measured for intermediate-redshift (z˜ 1) star-forming galaxies. We combine Hubble Space Telescope grism spectroscopy with GALEX UV and ground-based optical imaging to extend the search for escaping Lyman continuum to a large (˜600) sample of z˜ 1 low-mass ({log}(\\bar{M}) ≃ 9.3{M}⊙ ), moderately star-forming (\\bar{{{\\Psi }}} ≲ 10{M}⊙ yr-1) galaxies selected initially on Hα emission. The characteristic escape fraction of LyC from star-forming galaxies (SFGs) that populate this parameter space remains weakly constrained by previous surveys, but these faint (sub-L⋆) SFGs are assumed to play a significant role in the reionization of neutral hydrogen in the intergalactic medium (IGM) at high redshift z\\gt 6. We do not make an unambiguous detection of escaping LyC radiation from this z˜ 1 sample, individual non-detections to constrain the absolute Lyman continuum escape fraction, {f}{esc} \\lt 2.1% (3σ). We measure an upper limit of {f}{esc} \\lt 9.6% from a sample of SFGs selected on high Hα equivalent width (EW \\gt 200 {{\\mathringA }}), which are thought to be close analogs of high redshift sources of reionization. For reference, we also present an emissivity-weighted escape fraction that is useful for measuring the general contribution SFGs to the ionizing UV background. In the discussion, we consider the implications of these intermediate redshift constraints for the reionization of hydrogen in the IGM at high (z\\gt 6) redshift. If we assume our z˜ 1 SFGs, for which we measure this emissivity-weighted {f}{esc}, are analogs to the high redshift sources of reionization, we find it is difficult to reconcile reionization by faint ({M}{UV}≲ -13) SFGs with a low escape fraction ({f}{esc} \\lt 3%), with constraints from independent high redshift observations. If {f}{esc} evolves with redshift, reionization by SFGs may be consistent with observations from Planck.

  15. Herschel protocluster survey: a search for dusty star-forming galaxies in protoclusters at z = 2-3

    NASA Astrophysics Data System (ADS)

    Kato, Y.; Matsuda, Y.; Smail, Ian; Swinbank, A. M.; Hatsukade, B.; Umehata, H.; Tanaka, I.; Saito, T.; Iono, D.; Tamura, Y.; Kohno, K.; Erb, D. K.; Lehmer, B. D.; Geach, J. E.; Steidel, C. C.; Alexander, D. M.; Yamada, T.; Hayashino, T.

    2016-08-01

    We present a Herschel/Spectral and Photometric Imaging Receiver (SPIRE) survey of three protoclusters at z = 2-3 (2QZCluster, HS1700, SSA22). Based on the SPIRE colours (S350/S250 and S500/S350) of 250 μm sources, we selected high-redshift dusty star-forming galaxies potentially associated with the protoclusters. In the 2QZCluster field, we found a 4σ overdensity of six SPIRE sources around 4.5 arcmin (˜2.2 Mpc) from a density peak of H α emitters at z = 2.2. In the HS1700 field, we found a 5σ overdensity of eight SPIRE sources around 2.1 arcmin (˜1.0 Mpc) from a density peak of Lyman-break galaxies at z = 2.3. We did not find any significant overdensities in SSA22 field, but we found three 500 μm sources are concentrated 3 arcmin (˜1.4 Mpc) east to the Ly α emitters overdensity. If all the SPIRE sources in these three overdensities are associated with protoclusters, the inferred star formation rate densities are 103-104 times higher than the average value at the same redshifts. This suggests that dusty star formation activity could be very strongly enhanced in z ˜ 2-3 protoclusters. Further observations are needed to confirm the redshifts of the SPIRE sources and to investigate what processes enhance the dusty star formation activity in z ˜ 2-3 protoclusters.

  16. Caught in the Act: Gas and Stellar Velocity Dispersions in a Fast Quenching Compact Star-Forming Galaxy at z~1.7

    NASA Astrophysics Data System (ADS)

    Barro, Guillermo; Faber, Sandra M.; Dekel, Avishai; Pacifici, Camilla; Pérez-González, Pablo G.; Toloba, Elisa; Koo, David C.; Trump, Jonathan R.; Inoue, Shigeki; Guo, Yicheng; Liu, Fengshan; Primack, Joel R.; Koekemoer, Anton M.; Brammer, Gabriel; Cava, Antonio; Cardiel, Nicolas; Ceverino, Daniel; Eliche, Carmen; Fang, Jerome J.; Finkelstein, Steven L.; Kocevski, Dale D.; Livermore, Rachael C.; McGrath, Elizabeth

    2016-04-01

    We present Keck I MOSFIRE spectroscopy in the Y and H bands of GDN-8231, a massive, compact, star-forming galaxy at a redshift of z ˜ 1.7. Its spectrum reveals both Hα and [N ii] emission lines and strong Balmer absorption lines. The Hα and Spitzer MIPS 24 μm fluxes are both weak, thus indicating a low star-formation rate of SFR ≲ 5{--}10 {M}⊙ yr-1. This, added to a relatively young age of ˜700 Myr measured from the absorption lines, provides the first direct evidence for a distant galaxy being caught in the act of rapidly shutting down its star formation. Such quenching allows GDN-8231 to become a compact, quiescent galaxy, similar to three other galaxies in our sample, by z ˜ 1.5. Moreover, the color profile of GDN-8231 shows a bluer center, consistent with the predictions of recent simulations for an early phase of inside-out quenching. Its line-of-sight velocity dispe