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Sample records for active star-forming region

  1. Chemical Fingerprints of Star Forming Regions and Active Galaxies

    NASA Astrophysics Data System (ADS)

    Pérez-Beaupuits, Juan-Pablo

    2010-10-01

    This thesis is devoted to the study of the physical conditions of the interstellar medium (ISM) in active galactic nuclei (AGNs) and Galactic star-forming regions, using mostly single-dish millimeter observations. I first study the excitation conditions of dense gas in a group of Seyfert galaxies using radiative transfer models (Chapter 2). I then study the galaxy NGC 1068, and try to distinguish signatures of the contributions from the AGN and the starburst ring by incorporating observations of high-J transitions of dense gas tracers (Chapter 3). Later, I venture into the mid-infrared spectral region to study different aspects of the AGN and starburst components in the galaxy NGC 4945 (Chapter 4). In Chapter 5 I delve into theoretical aspects of the dynamical evolution of gas in an AGN torus. I use a 3D hydrodynamic simulation with chemical abundances driven by X-rays. The aim is to understand the effects of X-ray irradiation by the AGN on the temperature, formation and destruction of the molecular gas. I finally explore a Galactic star-forming region, the Omega Nebula, with high resolution single dish observations, to study the properties of the warm gas and to constrain chemical models (Chapters 6 and 7).

  2. Production and evolution of light elements in active star-forming regions.

    PubMed

    Cassé, M; Lehoucq, R; Vangioni-Flam, E

    1995-01-26

    Collisions between cosmic rays (energetic protons and alpha-particles) and carbon, nitrogen and oxygen in the interstellar medium have been considered to be the main source of lithium, beryllium and boron, through fragmentation of the larger nuclei. But this mechanism is unable to account for the observed Solar System abundances of the isotopes 7Li and 11B. The recent detection of an excess of gamma-rays in the direction of the star-forming region in the Orion cloud has been interpreted as arising from the excitation of carbon and oxygen nuclei ejected from supernovae when they collide with the surrounding gas, which is primarily molecular and atomic hydrogen. Here we investigate the consequences of the two-body interactions of the ejected carbon and oxygen nuclei (and the alpha-particles ejected with them) with the hydrogen and helium in the surrounding gas, using a model developed previously. We show that these interactions offer a way to make lithium, beryllium and boron that is independent of the abundance of heavy elements in the surrounding medium. Such supernova-driven interactions, combined with the effect of galactic cosmic rays, can explain the observed Solar System abundances of these light elements. PMID:7830765

  3. 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. PMID:10622767

  4. Molecular Outflows in Massive Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Cunningham, Nichol

    2015-11-01

    This thesis presents millimetre continuum and molecular line observations exploring the properties of molecular outflows towards massive star forming regions. Massive stars produce some of the most energetic phenomena in the Galaxy, yet we still do not have a comprehensive understanding of how they actually form. Outflows are known to play a key role in this formation process and their properties, particularly how they change depending on the mass, luminosity and evolution of the driving source can shed light on how massive stars actually form. This thesis presents observations at both high (SMA 3 arcsecond) and low (JCMT 15 arcsecond) spatial resolution of the known jet/outflow tracers, SiO and 12CO, towards a sample massive star forming region drawn from the RMS survey. Furthermore, the presence of infall signatures is explored through observations of HCO+ and H13CO+, and the hot core nature of the regions is probed using tracers such as CH3CN, HC3N and CH3OH. SiO is detected towards approximately 50% of the massive young stellar objects and HII regions in the JCMT sample. The detection of SiO appears to be linked to the age of the RMS source, with the likely younger sources showing a stronger dependence with SiO. The presence of SiO also appears to be linked to the CO velocity, with SiO more efficiently tracing sources with higher velocity dispersions. In the MOPRA observations towards a sample of 33 RMS sources, CH3CN is detected towards 66% of the sources, with the redder likely younger sources having the largest rotational temperatures. This thesis presents the first interferometric SiO (5-4) and 12CO (2-1) observations, taken with the SMA, towards the massive star forming region G203.3166/NGC 2264-C. In this intermediate/massive star forming cluster, SiO is again tracing the youngest sources. Both the SiO and 12CO emission trace two bipolar, high velocity outflows towards the mm brightest, IR-dark, likely youngest sources in this reg! ion. In contrast the IR

  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. PMID:16833724

  9. Chemical Evolution of Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    van Dishoeck, Ewine F.; Blake, Geoffrey A.

    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 H_2O emission. The role of future instrumentation in further developing these chemical and temporal diagnostics is discussed.

  10. 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.

  11. 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.

  12. 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.

  13. Herschel observation of C3 in star forming regions

    NASA Astrophysics Data System (ADS)

    Mookerjea, B.; Giesen, T.; Stutzki, J.; Cernicharo, J.; Goicoechea, J. R.; Black, J. H.

    2011-05-01

    We present spectrally resolved observations of triatomic carbon (C3) in several ro-vibrational transitions between the vibrational ground state and the low-energy ν2 bending mode at frequencies above 1.6 THz using HIFI onboard Herschel, towards several Galactic star forming regions including W31C, W49N, DR21(OH), W33A and W51. These observations have been performed as part of the Herschel key programme PRISMAS. C3 lines arising from the warm envelopes surrounding the hot cores associated with these star forming regions are detected in absorption. We shall present results of detailed radiative transfer models in which the C3 lines are excited by FIR pumping by the dust continuum.

  14. The Massive Star Forming Region Cygnus OB2

    NASA Astrophysics Data System (ADS)

    Wright, Nicholas James; Drake, J. J.; Drew, J. E.

    2009-12-01

    We present a multi-wavelength study of the massive star forming Cygnus OB2. Cygnus OB2 is the northern hemisphere's most massive star forming region and hosts a tremendously rich and diverse stellar population, with thousands of OB stars. The strong and highly variable extinction in the direction of the association have hindered previous studies of the region, but recent deep photometric surveys in the optical and near-infrared are opening the region up for study. The appreciation of the pivotal status of Cyg OB2 has led to a number of recent ambitious surveys of the cluster and its setting within the Cygnus-X region at X-ray, infrared and radio wavelengths. Chandra X-ray observations of two fields in the center of the association reveal 1720 X-ray sources, which we have combined with optical and near-IR photometry from the IPHAS and UKIDSS surveys. Near-IR photometry reveals a stellar population with a spread of ages greater than previously thought, overturning the picture of coeval star formation in the region. The distribution of young sources in the region shows evidence for clustering and significant mass segregation, which we judge to be primordial given the cluster's age.

  15. Massive star-forming regions across the galaxy

    NASA Astrophysics Data System (ADS)

    Rygl, Kazi Lucie Jessica

    2010-04-01

    Star-forming regions trace the spiral structure of the Galaxy. They are regions of increased column density and therefore traced well by the extinction in the mid-infrared based on the Spitzer/GLIMPSE 3.6-4.5 micron color excess maps. A sample of 25 high extinction clouds (HECs) was studied in the 1.2 mm dust continuum emission, and followed up by observations of ammonia plus several other molecules using the Effelsberg 100m, IRAM 30m and APEX telescopes. With these data we want to investigate the most early stages of massive star formation, which are currently still largely unknown. Three cloud classes were defined from their morphology in the 1.2 mm continuum maps: the early diffuse HECs, with a low contrast between the clump and cloud emission; the peaked HECs, with an increased contrast; the late multiply peaked HECs, with more than one clump and a high contrast between the clump and the cloud emission. The clouds are cold (T 16 K) and massive (M 800 M_sun) and contain dense clumps (n 10^5 cm^{-3}) of 0.3 pc in size. These clumps were investigated for evidence of gravitational collapse or expansion, for high velocity outflows, and for the presence of young stellar objects. Based on these results we interpret the three cloud classes as an evolutionary sequence of star-forming clouds. Accurate distances are a crucial parameter for establishing the mass, size, and luminosity of an object. Also, for understanding the spiral structure of the Galaxy trustworthy distances are necessary. The most accurate method to measure these is the trigonometric parallax. Using the European Very Large Baseline Interferometry Network of radio antennas we measured, for the first time, parallaxes of 6.7 GHz methanol masers. This transition belongs to the strongest maser species in the Galaxy, it is stable and observed toward numerous massive star-forming regions. We measured distances and proper motions toward L 1287, L 1206, NGC 281-W, ON 1 and S 255, and obtained their 3-dimensional

  16. Chandra Discoveries in High-mass Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Townsley, L. K.; Broos, P. S.; Feigelson, E. D.; Garmire, G. P.

    2004-08-01

    Chandra is providing remarkable new views of high-mass star-forming regions, revealing all stages in the life cycle of high-mass stars and their effects on their surroundings. We present a Chandra/ACIS tour of several high-mass star-forming regions, highlighting physical processes that characterize the life of a cluster of high-mass stars, from deeply-embedded cores too young to have established an HII region to superbubbles so large that they shape our views of galaxies. Along the way we see that X-ray observations reveal hundreds of stellar sources powering great HII region complexes, suffused by both hard and soft diffuse X-ray structures caused by fast O-star winds thermalized in wind-wind collisions or by termination shocks against the surrounding media. Finally, we examine the effects of the deaths of high-mass stars that remained close to their birthplaces, exploding as supernovae within the superbubbles that these clusters created.

  17. The Fragmentation of Massive Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Rodon, Javier Adrian

    2009-11-01

    Since its discovery by E. Salpeter in 1955, the high-mass end of the Initial Mass Function (IMF) has been continuously tested, and its slope has not changed from the value -2.35 originally calculated by Salpeter, the "Salpeter value". Furthermore, it is found that this value is universal. It not only describes the mass distribution of stellar masses in the Milky Way but also in other galaxies. Stars form individually or in systems within molecular clouds, from local condensations of sizes on the order of ~0.01 pc, the so-called "dense cores". In the case of low-mass star-forming regions, it is found that the Core Mass Function (CMF) resembles the Salpeter IMF. However, in the case of massive star-forming (MSF) regions, the answer is not that clear. The first CMF for a MSF region was derived in 2004 by H. Beuther and P. Schilke for the MSF IRAS 19410+2336. They found that this CMF also resembled the Salpeter IMF. Since then, a few more CMFs for MSF regions have been derived, always with exponents comparable to Salpeter. This suggested that the CMF and the IMF are related in a one-to-one or nearly one-to-one relationship, and that the fragmentation processes within a molecular cloud would set the shape of the IMF at an early evolutionary stage. Attempting to test that scenario, in this thesis I present and analyse high angular resolution interferometric observations of several MSF regions at millimeter wavelengths, describing their protostellar content and deriving their CMF whenever is possible. We confirm the result of Beuther & Schilke (2004) and obtain a CMF with a power-law slope similar to the Salpeter IMF, however for other MSF regions we obtain a CMF with a power-law slope flatter than Salpeter. This difference suggests that the IMF might not be set at the moment of the fragmentation of the cloud, but instead would be a result of the evolution of the cloud, starting with a flatter mass distribution that becomes steeper at later evolutionary stages. This

  18. Chandra Observations of the RCW 108 Star Forming Region.

    NASA Astrophysics Data System (ADS)

    Wolk, S. J.; Vigil, M.; Bourke, T. L.; Spitzbart, B. D.

    2004-12-01

    We present our recent (October 2004) Chandra observations of the embedded star forming region RCW 108. RCW 108 contains a deeply embedded young cluster lying in a dark cloud to the west of the young open cluster NGC 6193 (excited by two early O stars). Our motivation for this obsrvation was to followup on our discovery of diffuse X-ray emission in the older less embedded RCW 38. If the diffuse emission seen in RCW 38 is the result of plasma being trapped within the star forming region by overlaying molecular material, then RCW 108 should contain even more trapped plasma. At 8-20 μ m microns, the Midcourse Space Experiment Galactic Plane Survey data shows a ridge of warm dust passing through the eastern edge of the emission peak parallel to but west of an optical ridge. Our SEST mm continuum observations show a cold component to this dust ridge peaking strongly at the cluster. The far infrared luminosity suggests that there is more than one significant heating source, i.e., OB stars and/or intermediate mass protostars. The extended infrared nebulosity to the east of the main cluster is due to emission and not reflection, suggesting a break-out of radiation in this direction. The goals of the observations are to: 1) Study triggered star formation. 2) Investigate the origin and nature of diffuse X-ray emission within regions of massive star formation. 3) Identify deeply embedded PMS stars via their X-ray emission and derive an IMF and XLF. 4) Investigate the X-ray properties of the embedded sources. This work is supported by the Chandra X-ray Center NASA contact NAS8-39073 and by the Chandra guest observer program.

  19. 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

  20. 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.

  1. Stellar Feedback in Massive Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Baldwin, Jack; Pellegrini, Eric; Ferland, Gary; Murray, Norm; Hanson, Margaret

    2008-02-01

    Star formation rates and chemical evolution are controlled in part by the interaction of stellar radiation and winds with the remnant molecular gas from which the stars have formed. We are carrying out a detailed, panchromatic study in the two nearest giant star-forming regions to nail down the physics that produces the 10-20 parsec bubbles seen to surround young massive clusters in the Milky Way. This will determine if and how the clusters disrupt their natal giant molecular clouds (GMCs). Here we request 4 nights on the Blanco telescope to obtain dense grids of optical long-slit spectra criss-crossing each nebula. These will cover the [S II] doublet (to measure N_e) and also [O III], H(beta), [O I], H(alpha) and [N II] to measure the ionization mechanism and ionization parameter, at ~3000 different spots in each nebula. From this we can determine a number of dynamically important quantities, such as the gas density and temperature, hence pressure in and around these bubbles. These quantities can be compared to the dynamical (gravitationally induced) pressure, and the radiation pressure. All can be employed in dynamical models for the evolution of a GMC under the influence of an embedded massive star cluster. This research will elucidate the detailed workings of the star-forming regions which dominate the star formation rate in the Milky Way, and also will steadily improve our calibration and understanding of more distant, less well-resolved objects such as ULIRGS, Lyman break, and submillimeter galaxies.

  2. Young, Star Forming Regions in NGC 3994 and NGC 3995

    NASA Astrophysics Data System (ADS)

    Weistrop, D.; Eggers, D.; Stone, A.; Nelson, C. H.; Bachilla, R.

    2000-12-01

    NGC 3991, NGC 3994, and NGC 3995 comprise a small group of interacting galaxies. Groundbased images indicate significantly distorted morphology in NGC 3991 and NGC 3995, while NGC 3994 appears to be a normal, inclined spiral. Spectra of NGC 3991 and NGC 3995 have features typical of strong HII regions. NGC 3994 is a LINER. All three galaxies have strong ultraviolet emission and have been observed with IUE (Kinney, et al. 1993). As part of an investigation of star formation in interacting galaxies, we have obtained ultraviolet and visible images of the central regions of NGC 3994 and 3995 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 in both galaxies. In NGC 3994 star-forming knots are found tracing the spiral arms. Results from ground based spectroscopy indicate nuclear reddening of E(B-V) ~ 0.3- 0.4, suggesting that the lack of UV-bright knots in the center is real and not due to extinction. The knots in NGC 3995 have a distorted, 'hook shaped' distribution. The knots are typically 12 - 45 pc in diameter (FWHM), with observed FUV fluxes of approximately 10-17 to 10-16 ergs cm-2sec-1 Å-1. We compare our imaging and spectroscopy data to current starburst models to constrain knot ages and masses. Knot characteristics as a function of location in the galaxy will also be discussed. This work has been supported in part by NASA, under contract NAS5-31231, and through the Nevada Space Grant Consortium.

  3. 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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2000-05-01

    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 (Kinney, et al. 1993). Malkan et al.'s (1998) HST survey of Seyfert and starburst galaxies notes NGC 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 sizes 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. This work has been supported in part by NASA, under contract NAS5-31231.

  6. 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

  7. Water in star-forming regions with Herschel (WISH)

    NASA Astrophysics Data System (ADS)

    van Dishoeck, Ewine

    2015-08-01

    Water is a key molecule in the physics and chemistry of regions in which new stars and planets are born. This poster summarizes recent results on the chemistry of water in protostellar envelopes and protoplanetary disks obtained with the Herschel-HIFI and PACS instruments in the context of the 'Water in Star-forming Regions with Herschel' (WISH) Key Program. About 80 sources have been observed, covering a wide range of masses as well as evolutionary stages -from the earliest stages represented by pre-stellar cores to the late stages represented by the pre-main sequence stars surrounded only by disks. The data elucidate the physical and dynamical processes associated with forming stars and planets (outflow, infall, expansion), test basic gas-phase and gas-grain chemical processes, and reveal the chemical evolution of water and the oxygen-reservoir into planet-forming disks.This poster is presented on behalf of the WISH team. See http://www.strw.leidenuniv.nl/WISH for list of papers and results.

  8. Magnetic fields in star-forming regions - Observations

    NASA Technical Reports Server (NTRS)

    Heiles, Carl; Goodman, Alyssa A.; Mckee, Christopher F.; Zweibel, Ellen G.

    1993-01-01

    We review the observational aspects of magnetic fields in dense, star-forming regions. First we discuss ways to observe the field. These include direct methods, which consist of the measurement of both linear and circular polarization of spectral line and continuum radiation; and indirect methods, consisting of the angular distribution of H2O masers on the sky and the measurement of ambipolar diffusion. Next we discuss selected observational results, focusing on detailed discussions of a small number of points rather than a generalized discussion that covers the waterfront. We discuss the Orion/BN-KL region in detail, both on the small and large scales. Next we discuss the derivation of the complete magnetic vector, including both the systematic and fluctuating component, from a large sample of Zeeman and linear polarization measurements for the L204 dark cloud. We examine the virial theorem as it applies to dark clouds in general and one dark cloud, Barnard 1, in particular. We critically discuss the numerous claims for alignment of cloud structural features with the plane-of-the-sky component of the magnetic field, and find that many of these have not been definitively established.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. The Physics of Molecular Shocks in Star-Forming Regions

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Cuzzi, Jeffrey (Technical Monitor)

    1996-01-01

    Molecular shocks are produced by the impact of the supersonic infall of gas and dust onto protostars and by the interaction of the supersonic outflow from the protostar with the circumstellar material. Infalling gas creates an accretion shock around the circumstellar disk which emits a unique infrared spectrum and which processes the interstellar dust as it enters the disk. The winds and jets from protostars also impact the disk, the infalling material, and the ambient molecular cloud core creating shocks whose spectrum and morphology diagnose the mass loss processes of the protostar and the orientation and structure of the star forming system. We discuss the physics of these shocks, the model spectra derived from theoretical models, and comparisons with observations of H2O masers, H2 emission, as well as other shocks tracers. We show the strong effect of magnetic fields on molecular shock structure, and elucidate the chemical changes induced by the shock heating and compression.

  16. 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 \

  17. The distribution of warm gas in the G327.3-0.6 star forming region

    NASA Astrophysics Data System (ADS)

    Leurini, S.; Wyrowski, F.; van der Tak, F.; Herpin, F.; Herschel WISH Team

    2011-05-01

    Water is a key molecule for determining the physical chemical structure of star forming regions because of its large abundance variations between warm and cold regions. As a part of the HIFI-led Key Program WISH (P.I. E. van Dishoeck), we are mapping six massive star forming region in different H2O lines with HIFI and PACS to investigate the effects of clustered star formation on feedback by protostellar outflow in such regions. Our Herschel observation are complemented by APEX CO and 13CO observations in mid- high-J transitions to study the distribution of warm gas and its physical conditions for comparison with the Herschel data. I will present large scale maps of the massive star forming region G327.3-0.6 obtained with APEX (CO isotopologues) and PACS (H2O) and report on our analysis of the region.

  18. 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.

  19. Star forming regions in gas-rich SO galaxies

    NASA Technical Reports Server (NTRS)

    Pogge, Richard W.; Eskridge, Paul B.

    1987-01-01

    The first results of an H alpha imaging survey of HI rich SO galaxies, which were searched for HII regions and other sources of emission, are presented. The charge coupled device H alpha interference filter images were made of 16 galaxies. Eight of these galaxies show evidence for on-going star formation, one has nuclear emission but no HII regions, and the remaining seven have no emissions detected within well defined upper limits. With the exception of one notably peculiar galaxy in which the emission from HII regions appears pervasive, the HII regions are either organized into inner-disk rings or randomly distributed throughout the disk. A few of these galaxies are found to be clearly not SO's; or peculiar objects atypical of the SO class. Using simple models star formation rates (SFRs) and gas depletion times from the observed H alpha fluxes were estimated. In general, the derived SFRs are much lower than those found in isolated field spiral galaxies and the corresponding gas depletion time scales are also longer.

  20. 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.

  1. Preferential Pathway for Glycine Formation in Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Pilling, S.; Boechat-Roberty, H. M.; Baptista, L.; Santos A. C., F.

    Interstellar clouds, similar to that from which the solar system was formed, contain many organic molecules including aldehydes, acids, ketones, and sugars Ehrenfreund & Charnley (2000). Those organic compounds have important functions in terrestrial biochemistry and could also have been important in prebiotic synthesis. The simplest amino acid, glycine (NH2CH2COOH), was recently detected in the hot molecular cores Sgr B2(N-LMH), Orion KL, and W51 e1/e2 Kuan et al. (2003). The formic acid (HCOOH) and acetic acid(CH3COOH) have also been detected in those regions Liu et al. (2002), Remijan et al. (2004). The goal of this work is to study experimentally photoionization and photodissociation processes of glycine precursor molecules, acetic acid and formic acid to elucidate a possible preferentially in the glycine synthesis between ice and gas phase. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS), employing soft X-ray photons from a toroidal grating monochromator TGM) beamline (100 - 310 eV). The experimental set up consists of a high vacuum chamber with a Time-Of-Flight Mass Spectrometer (TOF-MS). Mass spectra were obtained using PhotoElectron PhotoIon Coincidence (PEPICO) technique. Kinetic energy distributions and abundances for each ionic fragment have been obtained from the analysis of the corresponding peak shapes in the mass spectra. Dissociative and non-dissociative photoionization cross sections for both molecules were also determined Boechat-Roberty, Pilling & Santos (2005). Due to the high photodissociation cross section of formic acid it is possible that in PDRs regions, just after molecules evaporation from the grains surface, it is almost destructed by soft X-rays, justifying the observed low abundance of HCOOH in gaseous phase Ehrenfreund et al. (2001). Acetic acid have shown to be more stable to the ionizing field, and its main outcomes from dissociation process were the reactive ionic fragments COOH+ and CH3CO+. To

  2. 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.

  3. 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.

  4. A quest for rotating disks in high-mass star forming regions

    NASA Astrophysics Data System (ADS)

    Sánchez-Monge, Á.; Beltrán, M. T.; Cesaroni, R.

    2016-05-01

    We present ALMA observations towards two high-mass star forming regions. These reveal extended filamentary structures fragmenting into a number of dense cores. The detection of a multitude of lines from complex molecular species permits to study the physical and kinematic properties of three dense cores. Signposts of Keplerian rotation are identified and suggest the presence of disks rotating about stars with masses 4-18 M⊙. These results likely confirm that B-type stars form via disk-mediated accretion, and set the stage for the quest for similar structures toward the most massive O-type stars.

  5. High resolution NH3 studies of nearby star-forming regions

    NASA Astrophysics Data System (ADS)

    Friesen, Rachel

    2014-07-01

    Stars form within dense molecular cores. These cores are often embedded within larger structures, such as clumps and filaments, particularly in clustered star-forming environments. Indeed, large-scale maps of the continuum emission from dust have revealed the ubiquity of filaments in star-forming regions. The condensation and fragmentation of cores within larger structures is therefore a critical step in the star formation process, but continuum data alone do not provide key information, such as the gas kinematics, needed to discern between evolutionary scenarios. I will present new results from large NH3 studies of nearby star-forming regions, including Taurus and Serpens South. While NH3 primarily traces high density gas, sensitive observations over Serpens South reveal extensive, low brightness emission between the prominent cores and filaments, and show directly the frequently (but not invariably) sharp transitions between turbulent and quiescent gas in the high density regions. I will discuss the hierarchical structure of the dense gas in Serpens South, with comparisons between two- and three-dimensional analysis, and analyze the importance of thermal fragmentation in the filaments and cores over a range of physical scales.

  6. 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).

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. The Extended Star-Forming Environments of Galactic H II Regions

    NASA Astrophysics Data System (ADS)

    Povich, Matthew S.

    2009-01-01

    H II regions are the bright beacons marking active sites of star formation throughout the Milky Way and other galaxies. The GLIMPSE and MIPSGAL Galactic plane surveys with the Spitzer Space Telescope have provided new views of the structure of H II regions and their relationship to extended star-forming environments in molecular cloud complexes. M17 is an excellent example of a well-studied H II region that is the most prominent part of a much larger star-formation event. We have found that the M17 H II region lies on the rim of a large shell structure, 0.5° in diameter ( 18 pc at 2.1 kpc), that is outlined both in diffuse IR emission from dust and in CO line emission near v=20 km/s. The molecular shell is best interpreted as an extended, expanding bubble outlining the photodissociation region of a faint, diffuse H II region several Myr old. We identify several candidate ionizing stars lying inside the bubble. We also find a concentration of candidate young stellar objects (YSOs) on the rim of the bubble. These location of these YSOs with respect to the diffuse IR and CO line emission indicates that star formation was triggered when the expanding bubble compressed one edge of an otherwise quiescent molecular cloud. The expansion of this precursor H II region may also have helped trigger the formation of the massive cluster ionizing the M17 H II region itself. The star formation history of the M17 extended molecular cloud environment has been punctuated by successive waves of massive star formation propagating through a giant molecular cloud complex.

  12. Gravity as main driver of non-thermal motions in massive star forming regions

    NASA Astrophysics Data System (ADS)

    Traficante, A.; Fuller, G. A.; Smith, R.; Billot, N.; Duarte-Cabral, A.; Peretto, N.; Molinari, S.; Pineda, J. E.

    2016-05-01

    The origin of the observed non-thermal motions in massive star forming regions is still unclear. These motions can originate from local turbulence or from self-gravity and the two scenarios lead to two different star formation mechanisms. The recent findings of Heyer et al. ([5]) have supported self-gravity as main driver of the non-thermal motions, although without a clear interpretation of the results. In this contribution we introduce a new formalism to describe the relation between gravity and kinetic motion in massive star formation. We show that the Heyer findings are a particular result of this description and have a direct physical interpretation. We applied this formalism to different surveys of massive star forming regions covering all spatial scales from giant molecular clouds down to massive cores, including new data from massive candidate starless clumps. The results presented in this contribution strongly support a chaotic, gravitationally driven global collapse scenario as massive star formation mechanism.

  13. 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.

  14. VizieR Online Data Catalog: Star-forming regions deuteration (Gerner+, 2015)

    NASA Astrophysics Data System (ADS)

    Gerner, T.; Shirley, Y. L.; Beuther, H.; Semenov, D.; Linz, H.; Albertsson, T.; Henning, T.

    2015-10-01

    The sources were taken from Gerner et al. (2014, Cat. J/A+A/563/A97) and were initially selected from different source lists. The total sample contains 59 high-mass star-forming regions, consisting of 19 IRDCs and 20 HMPOs as well as 11 HMCs and 9 UCHIIs. The sources were selected from well-known source catalogs of the literature without specific selection criteria such as spherical symmetry. (3 data files).

  15. 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.

    2016-08-01

    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 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 artifact of varying detection limits for galaxies at different distances.

  16. Not Your Grandmother's HII Regions: An X-ray Tour of Massive Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Townsley, Leisa K.

    2006-09-01

    Chandra and XMM-Newton are providing remarkable new views of massive star-forming regions, revealing all stages in the life cycle of high-mass stars and their effects on their surroundings. We will tour several such regions, highlighting physical processes that characterize the life of a cluster of massive stars, from deeply-embedded cores too young to have established an HII region to superbubbles so large that they shape our views of galaxies. Along the way we see that X-ray observations reveal hundreds of pre-main sequence stars accompanying the massive stars that power great HII region complexes. The most massive stars themselves are often anomalously hard X-ray emitters; this may be a new indicator of close binarity. These complexes are sometimes suffused by diffuse X-ray structures, signatures of multi-million-degree plasmas created by fast O-star winds. In older regions we see the X-ray remains of the deaths of massive stars that stayed close to their birthplaces, exploding as cavity supernovae within the superbubbles that these clusters created.

  17. 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.

  18. 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.

  19. Herschel spectral surveys of star-forming regions. Overview of the 555-636 GHz range

    NASA Astrophysics Data System (ADS)

    Ceccarelli, C.; Bacmann, A.; Boogert, A.; Caux, E.; Dominik, C.; Lefloch, B.; Lis, D.; Schilke, P.; van der Tak, F.; Caselli, P.; Cernicharo, J.; Codella, C.; Comito, C.; Fuente, A.; Baudry, A.; Bell, T.; Benedettini, M.; Bergin, E. A.; Blake, G. A.; Bottinelli, S.; Cabrit, S.; Castets, A.; Coutens, A.; Crimier, N.; Demyk, K.; Encrenaz, P.; Falgarone, E.; Gerin, M.; Goldsmith, P. F.; Helmich, F.; Hennebelle, P.; Henning, T.; Herbst, E.; Hily-Blant, P.; Jacq, T.; Kahane, C.; Kama, M.; Klotz, A.; Langer, W.; Lord, S.; Lorenzani, A.; Maret, S.; Melnick, G.; Neufeld, D.; Nisini, B.; Pacheco, S.; Pagani, L.; Parise, B.; Pearson, J.; Phillips, T.; Salez, M.; Saraceno, P.; Schuster, K.; Tielens, X.; van der Wiel, M. H. D.; Vastel, C.; Viti, S.; Wakelam, V.; Walters, A.; Wyrowski, F.; Yorke, H.; Liseau, R.; Olberg, M.; Szczerba, R.; Benz, A. O.; Melchior, M.

    2010-10-01

    High resolution line spectra of star-forming regions are mines of information: they provide unique clues to reconstruct the chemical, dynamical, and physical structure of the observed source. We present the first results from the Herschel key project “Chemical HErschel Surveys of Star forming regions”, CHESS. We report and discuss observations towards five CHESS targets, one outflow shock spot and four protostars with luminosities bewteen 20 and 2 × 105 L_⊙: L1157-B1, IRAS 16293-2422, OMC2-FIR4, AFGL 2591, and NGC 6334I. The observations were obtained with the heterodyne spectrometer HIFI on board Herschel, with a spectral resolution of 1 MHz. They cover the frequency range 555-636 GHz, a range largely unexplored before the launch of the Herschel satellite. A comparison of the five spectra highlights spectacular differences in the five sources, for example in the density of methanol lines, or the presence/absence of lines from S-bearing molecules or deuterated species. We discuss how these differences can be attributed to the different star-forming mass or evolutionary status. Herschel is an ESA space observatory with science instruments provided by European-led principal Investigator consortia and with important participation from NASA.Figures [see full textsee full text]-[see full textsee full text] and Tables 3, 4 (pages 6 to 8) are only available in electronic form at http://www.aanda.org

  20. 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

  1. 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.

  2. 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

  3. THE STAR FORMATION IN RADIO SURVEY: GBT 33 GHz OBSERVATIONS OF NEARBY GALAXY NUCLEI AND EXTRANUCLEAR STAR-FORMING REGIONS

    SciTech Connect

    Murphy, E. J.; Bremseth, J.; Mason, B. S.; Condon, J. J.; Schinnerer, E.; Aniano, G.; Armus, L.; Helou, G.; Turner, J. L.; Jarrett, T. H.

    2012-12-20

    We present 33 GHz photometry of 103 galaxy nuclei and extranuclear star-forming complexes taken with the Green Bank Telescope as part of the Star Formation in Radio Survey. Among the sources without evidence for an active galactic nucleus, and also having lower frequency radio data, we find a median thermal fraction at 33 GHz of Almost-Equal-To 76% with a dispersion of Almost-Equal-To 24%. For all sources resolved on scales {approx}<0.5 kpc, the thermal fraction is even larger, being {approx}>90%. This suggests that the rest-frame 33 GHz emission provides a sensitive measure of the ionizing photon rate from young star-forming regions, thus making it a robust star formation rate (SFR) indicator. Taking the 33 GHz SFRs as a reference, we investigate other empirical calibrations relying on different combinations of warm 24 {mu}m dust, total infrared (IR; 8-1000 {mu}m), H{alpha} line, and far-UV continuum emission. The recipes derived here generally agree with others found in the literature, albeit with a large dispersion that most likely stems from a combination of effects. Comparing the 33 GHz to total IR flux ratios as a function of the radio spectral index, measured between 1.7 and 33 GHz, we find that the ratio increases as the radio spectral index flattens which does not appear to be a distance effect. Consequently, the ratio of non-thermal to total IR emission appears relatively constant, suggesting only moderate variations in the cosmic-ray electron injection spectrum and ratio of synchrotron to total cooling processes among star-forming complexes. Assuming that this trend solely arises from an increase in the thermal fraction sets a maximum on the scatter of the non-thermal spectral indices among the star-forming regions of {sigma}{sub {alpha}{sup N}{sup T}}{approx}<0.13.

  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. PMID:23862691

  6. MYStIX: Subclusters of Young Stars in Massive Star Forming Regions

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    The MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray; Feigelson et al. 2013) project provides improved censuses of young stars in 20 nearby OB-dominated star-forming regions that were observed by the Chandra X-ray observatory, the Spitzer Space Telescope, and the UKIRT/UKIDSS and 2MASS surveys. The sample of >33,000 members reveals new details about the structure of clusters in these regions. Clusters of young stars are identified using finite mixture models -\\ the sums of isothermal ellipsoids used to model individual (sub)clusters. Maximum likelihood estimation is used to estimate the model parameters and the Akaike Information Criterion is used to detemine the number of subclusters. In the MYStIX star-forming regions, ˜150 subclusters are found (1 to >10 per region). The distribution of cluster core radii is log-normal, peaked at 0.18 pc (similar to the ONC) with a standard deviation of 0.4 dex. The locations of subclusters are often correlated with molecular-cloud clumps or cores. We also recover several well-known embedded subclusters such as the BN-KL region in Orion and the KW Object cluster in M 17. MYStIX star-forming regions typically have one dominant cluster surrounded by smaller subclusters and filamentary groups of young stars. Some clusters are well fit by the ellipsoid model (e.g. Flame Nebula), but others have lumpy structure and are poorly fit (e.g. M 17). A few clusters have a core-halo structure modeled with two overlapping ellipsoids (e.g. RCW 36). Clumpy and core-halo structures could originate in the merger of subclusters. There is a power-law relation between the fitted cluster central density and core radius (index slightly shallower than -3), which may be an effect of cluster expansion. There is also a statistically significant negative relation between median gas/dust absorption of a subcluster and the subcluster's size that can also be explained by cluster expansion if absorption acts as a proxy for age.

  7. Parsec-scale X-ray flows in high-mass star-forming regions

    NASA Astrophysics Data System (ADS)

    Townsley, L. K.; Broos, P. S.; Feigelson, E. D.; Garmire, G. P.

    The Chandra X-ray Observatory is providing remarkable new views of massive star-forming regions, revealing all stages in the life cycle of high-mass stars and their effects on their surroundings. We present a Chandra tour of several high-mass star-forming regions, highlighting physical processes that characterize the life of a cluster of high-mass stars, from deeply-embedded cores too young to have established an HII region to superbubbles so large that they shape our views of galaxies. Along the way we see that X-ray observations reveal hundreds of stellar sources powering great HII region complexes, suffused by both hard and soft diffuse X-ray structures caused by fast O-star winds thermalized in wind-wind collisions or by termination shocks against the surrounding media. Finally, we examine the effects of the deaths of high-mass stars that remained close to their birthplaces, exploding as supernovae within the superbubbles that these clusters created. We present new X-ray results on W51 IRS2E and 30 Doradus and we introduce new data on Trumpler 14 in Carina and the W3 HII region complexes W3 Main and W3(OH).

  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. 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.

  10. VLBI Water Maser Proper Motion Measurements in Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Torrelles, J. M.; Patel, N.; Gómez, J. F.; Anglada, G.; Uscanga, L.

    We review some of the recent water maser proper motion measurements in star-forming regions performed through VLBI multi-epoch observations. These observations are starting to reveal exciting perspectives, providing the full kinematics of the gas within the outflows/circumstellar disks around YSOs at scales of AUs, discovering new phenomena (e.g., isotropic mass ejections, watermaser "micro-structures" exhibiting remarkable coherent and well ordered spatio-kinematical behavior at AU scale), and opening new, puzzling questions related to the early stellar evolution.

  11. Vlbi Water Maser Proper Motion Measurements in Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Torrelles, J. M.; Patel, N.; Gómez, J. F.; Anglada, G.; Uscanga, L.

    2005-01-01

    We review some of the recent water maser proper motion measurements in star-forming regions performed through VLBI multi-epoch observations. These observations are starting to reveal exciting perspectives, providing the full kinematics of the gas within the outflows/circumstellar disks around YSOs at scales of AUs, discovering new phenomena (e.g., isotropic mass ejections, water maser "micro-structures" exhibiting remarkable coherent and well ordered spatio-kinematical behavior at AU scale), and opening new, puzzling questions related to the early stellar evolution.

  12. 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.

  13. High Circular Polarization in the Star Forming Region NGC 6334: Implications

    NASA Astrophysics Data System (ADS)

    Ménard, François; Chrysostomou, A.; Gledhill, T.; Hough, J. H.; Bailey, J.

    The amino-acids which form the building blocks of biological proteins are all left-handed molecules. By contrast, when these molecules are made in the laboratory equal numbers of the right and left-handed versions are made. This homochirality found in biological material may then well be a prerequisite for the origin of life and a number of processes have been proposed to produce the required enantiomeric excess in prebiotic organic molecules. We report here on the detection of high degrees of circular polarisation in the star forming complex NGC 6334, in the constellation Scorpius. This important finding suggests the widespread nature of a potentially efficient process to produce biomolecules with large chiral excess, namely selective (asymmetric) photolysis by circularly polarised light. The mechanism, well known in the laboratory, was first suggested to take place in a star forming region by Bailey et al. (1998) (Science, 281, 672; and this conference), following our discovery of high degrees of near-infrared circular polarisation in the Orion molecular cloud, OMC-1. NGC 6334 is a giant HII region and molecular cloud similar to Orion. These two detections of large circular polarisation, among the small number of sources surveyed so far, lead us to suggest that selective photolysis by circular polarisation may be quite widespread in massive star formation regions.

  14. TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. IX. THE OUTER ARM IN THE FIRST QUADRANT

    SciTech Connect

    Sanna, A.; Menten, K. M.; Brunthaler, A.; Reid, M. J.; Dame, T. M.; Moscadelli, L.; Zheng, X. W.; Xu, Y.

    2012-01-20

    We report a trigonometric parallax measurement with the Very Long Baseline Array for the water maser in the distant high-mass star-forming region G75.30+1.32. This source has a heliocentric distance of 9.25{sup +0.45}{sub -0.40} kpc, which places it in the Outer arm in the first Galactic quadrant. It lies 200 pc above the Galactic plane and is associated with a substantial H I enhancement at the border of a large molecular cloud. At a Galactocentric radius of 10.7 kpc, G75.30+1.32 is in a region of the Galaxy where the disk is significantly warped toward the North Galactic Pole. While the star-forming region has an instantaneous Galactic orbit that is nearly circular, it displays a significant motion of 18 km s{sup -1} toward the Galactic plane. The present results, when combined with two previous maser studies in the Outer arm, yield a pitch angle of about 12 Degree-Sign for a large section of the arm extending from the first quadrant to the third.

  15. 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.

  16. A spectral and photometric study of 102 star-forming regions in seven spiral galaxies

    NASA Astrophysics Data System (ADS)

    Gusev, A. S.; Sakhibov, F.; Piskunov, A. E.; Kharchenko, N. V.; Bruevich, V. V.; Ezhkova, O. V.; Guslyakova, S. A.; Lang, V.; Shimanovskaya, E. V.; Efremov, Y. N.

    2016-04-01

    We present a study of complexes of young massive star clusters (YMCs), embedded in extragalactic giant H II regions, based on the coupling of spectroscopic with photometric and spectrophotometric observations of about 100 star-forming regions in seven spiral galaxies (NGC 628, NGC 783, NGC 2336, NGC 6217, NGC 6946, NGC 7331, and NGC 7678). The complete observational data base has been observed and accumulated within the framework of our comprehensive study of extragalactic star-forming regions. This paper presents the last part of either unpublished or refreshed photometric and spectrophotometric observations of the galaxies NGC 6217, NGC 6946, NGC 7331, and NGC 7678. We derive extinctions, chemical abundances, continuum, and line emissions of ionized gas, ages, and masses for cluster complexes. We find the YMC complexes to have ages no greater than 10 Myr and masses between 104 M⊙ and 107 M⊙, and the extinctions AV vary between ˜0 and 3 mag, while the impact of the nebular emission on integrated broad-band photometry mainly is not greater than 40 per cent of the total flux and is comparable with accuracies of dereddened photometric quantities. We also find evidence of differential extinction of stellar and gas emissions in some clusters, which hinders the photometric determination of ages and masses in these cases. Finally, we show that young massive cluster complexes in the studied galaxies and open clusters in the Milky Way form a continuous sequence of luminosities/masses and colour/ages.

  17. 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.

  18. 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

  19. A Near-Infrared Study of the NGC 7538 Star-forming Region

    NASA Astrophysics Data System (ADS)

    Ojha, D. K.; Tamura, M.; Nakajima, Y.; Fukagawa, M.; Sugitani, K.; Nagashima, C.; Nagayama, T.; Nagata, T.; Sato, S.; Vig, S.; Ghosh, S. K.; Pickles, A. J.; Momose, M.; Ogura, K.

    2004-12-01

    We present subarcsecond (FWHM~0.7"), near-infrared (NIR) JHKs-band images and a high-sensitivity radio continuum image at 1280 MHz, using SIRIUS on the University of Hawaii 88 inch (2.2 m) telescope and the Giant Metrewave Radio Telescope (GMRT). The NIR survey covers an area of ~24 arcmin2 with 10 σ limiting magnitudes of ~19.5, 18.4, and 17.3 in the J, H, and Ks bands, respectively. Our NIR images are deeper than any JHK surveys to date for the larger area of the NGC 7538 star-forming region. We construct JHK color-color and J-H/J and H-K/K color-magnitude diagrams to identify young stellar objects (YSOs) and to estimate their masses. Based on these color-color and color-magnitude diagrams, we identified a rich population of YSOs (Class I and Class II) associated with the NGC 7538 region. A large number of red sources (H-K>2) have also been detected around NGC 7538. We argue that these red stars are most probably pre-main-sequence stars with intrinsic color excesses. Most of the YSOs in NGC 7538 are arranged from the northwest toward the southeast regions, forming a sequence in age: a diffuse H II region (northwest and oldest, where most of the Class II and Class I sources are detected), a compact IR core (center), and regions with an extensive IR reflection nebula and a cluster of red young stars (southeast and south). We find that the slope of the Ks-band luminosity function of NGC 7538 is lower than the typical values reported for young embedded clusters, although equally low values have also been reported in the W3 Main star-forming region. From the slope of the Ks-band luminosity function and the analysis by Megeath and coworkers, we infer that the embedded stellar population is composed of YSOs with an age of ~1 Myr. Based on the comparison of models of pre-main-sequence stars with the observed color-magnitude diagram, we find that the stellar population in NGC 7538 is primarily composed of low-mass pre-main-sequence stars similar to those observed in the

  20. 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.

  1. CS multitransitional study of density distribution in star-forming regions. 2: The S140 region

    NASA Technical Reports Server (NTRS)

    Zhou, Shudong; Butner, Harold M.; Evans, Neal J., II; Guesten, Rolf; Kutner, Marc L.; Mundy, Lee G.

    1994-01-01

    The S140 molecular cloud was observed in five transitions of CS with resolutions of 11 to 45 arcsec. The data were analyzed with both the LVG and microturbulent models of radiative transfer to derive the density structure. It was found that the CS emission comes from three components of gas: a spherical component centered on the infrared cluster, an arc component along the ionization front between the S140 H II region and the dense molecular cloud core, and a high-velocity component from the dense part of a molecular outflow. The spherical component contributes most to the CS emission and was analyzed in more detail than the other components. Using a temperature distribution derived from an analysis of the dust emission from S140, we fit a power-law density distribution of n(r) = n(sub i)(r/r(sub i))(exp -alpha) to the spherical component. The best fit was for n(sub i) = 1.4 x 10(exp 6) (density at r(sub i) = 0.026 pc) and alpha = 0.8. The density (n(sub i)) was found to be greater than or equal to the density required to account for the dust emission, depending on the dust opacity laws adopted. The presence of optical emission (Dinerstein, Lester, & Rank 1979) suggests a clumpy structure for the dense gas. Considerations of the virial mass and the lowest amount of column density required to produce dust emission put the volume filling factor (f(sub nu)) of the dense gas at approximately 0.14-0.5. We compared S140 with other regions of star formation where the density structure has been derived from excitation analysis. Source-source variations in density gradients and clumpiness clearly exist, ranging from alpha = 2 and f(sub nu) approximately 1 in B335 to alpha approximately 0, f(sub nu) approximately 0.1 in M17. There is a tendency for more massive star-forming regions to have a flatter density distribution, a more clumpy structure, and a large number of young stars. The implications of this tendency are discussed.

  2. 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.

  3. 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.

  4. Nitric oxide in star-forming regions - Further evidence for interstellar N-O bonds

    NASA Technical Reports Server (NTRS)

    Ziurys, L. M.; Mcgonagle, D.; Minh, Y.; Irvine, W. M.

    1991-01-01

    Nitric oxide has been newly detected toward 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 toward all sources. Column densities derived for nitric oxide in these clouds are 10 to the 15th-10 to the 16th/sq cm, corresponding to fractional abundances of 0.5-1.0 x 10 to the -8th, relative to H2. Toward 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.

  5. 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. PMID:11538086

  6. 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.

  7. 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.

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

    PubMed

    Roberts, Helen; Millar, T J

    2006-11-15

    Observations of molecular D/H ratios in the interstellar medium are used to probe the physical conditions, such as temperature, ionization fraction and the importance of gas-grain reactions. In cold, dense regions, such as cores which are collapsing to form stars, the level of deuterium fractionation depends on the conversion of H3+ into its deuterated isotopologues (H2D+, D2H+ and D3+). The relative abundances of these molecules uniquely probe the centres of these cores where other, heavier, species have frozen onto dust grains. We present models of the deuterium chemistry close to the centre of a pre-stellar core, in the last stage before the star forms, showing the dependence of the observable molecular D/H ratios on the physical parameters and rate coefficients that are assumed. We compare model predictions with the latest observations of these regions. PMID:17015383

  9. Analyzing Structure in Star Forming Region AFGL 490 Using Spitzer and Near-IR Photometry

    NASA Astrophysics Data System (ADS)

    Masiunas, Lauren; Gutermuth, R.; Pipher, J.; Meyers, P.; Megeath, T.; Allen, L.

    2011-01-01

    We present an analysis of expanded Spitzer IRAC and MIPS imaging of the AFGL 490 star forming region and deep SQIID near-IR imaging of its central cluster. Using the combined 1-24 micron photometric catalog derived from these data, we have identified 56 class I and 283 class II young stellar objects (YSOs) forming in this region. We isolated several locally over-dense cluster cores from the spatial distribution of YSOs via analysis of the Minimal Spanning Tree of their positions (Gutermuth et al. 2009). The most populated group contains 215 YSOs (63% of the cluster's members) and has an area of 12 square parsecs. The intermediate mass YSO, AFGL 490, contained within this group, resides 0.73-0.98 parsecs away from the center of the group. We compare these statistics to similarly analyzed clusters (Gutermuth et al. 2009), and briefly explore the mass segregation implications of AFGL 490's position within its cluster.

  10. Internal and Relative Motions of the Taurus and Ophiuchus Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Rivera, Juana L.; Loinard, Laurent; Dzib, Sergio A.; Ortiz-León, Gisela N.; Rodríguez, Luis F.; Torres, Rosa M.

    2015-07-01

    We investigate the internal and relative motions of the Taurus and Ophiuchus star-forming regions using a sample of young stars with accurately measured radial velocities and proper motions. We find no evidence for expansion or contraction of the Taurus complex, but a clear indication of global rotation, resulting in velocity gradients of the order of 0.1 km s-1 pc-1 across the region. In the case of Ophichus, more data are needed to reliably establish its internal kinematics. Both Taurus and Ophiuchus, have a bulk motion relative to the LSR (i.e., a non-zero mean peculiar velocity) of the order of 5 km s-1. Interestingly, these velocities are roughly equal in magnitude, but nearly exactly opposite in direction. Moving back in time, we find that Taurus and Ophiuchus must have been very near each other 20-25 Myr ago. This suggests a common origin, possibly related to that of Gould's Belt.

  11. 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.

  12. 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.

  13. Properties of dense cores in clustered massive star-forming regions at high angular resolution

    NASA Astrophysics Data System (ADS)

    Sánchez-Monge, Álvaro; Palau, Aina; Fontani, Francesco; Busquet, Gemma; Juárez, Carmen; Estalella, Robert; Tan, Jonathan C.; Sepúlveda, Inma; Ho, Paul T. P.; Zhang, Qizhou; Kurtz, Stan

    2013-07-01

    We aim at characterizing dense cores in the clustered environments associated with intermediate-/high-mass star-forming regions. For this, we present a uniform analysis of Very Large Array NH3 (1,1) and (2,2) observations towards a sample of 15 intermediate-/high-mass star-forming regions, where we identify a total of 73 cores, classify them as protostellar, quiescent starless, or perturbed starless, and derive some physical properties. The average sizes and ammonia column densities of the total sample are ˜0.06 pc and ˜1015 cm-2, respectively, with no significant differences between the starless and protostellar cores, while the linewidth and rotational temperature of quiescent starless cores are smaller, ˜1.0 km s-1 and 16 K, than linewidths and temperatures of protostellar (˜1.8 km s-1 and 21 K), and perturbed starless (˜1.4 km s-1 and 19 K) cores. Such linewidths and temperatures for these quiescent starless cores in the surroundings of intermediate-/high-mass stars are still significantly larger than the typical linewidths and rotational temperatures measured in starless cores of low-mass star-forming regions, implying an important non-thermal component. We confirm at high angular resolutions (spatial scales ˜0.05 pc) the correlations previously found with single-dish telescopes (spatial scales ≳ 0.1 pc) between the linewidth and the rotational temperature of the cores, as well as between the rotational temperature and the linewidth with respect to the bolometric luminosity. In addition, we find a correlation between the temperature of each core and the incident flux from the most massive star in the cluster, suggesting that the large temperatures measured in the starless cores of our sample could be due to heating from the nearby massive star. A simple virial equilibrium analysis seems to suggest a scenario of a self-similar, self-gravitating, turbulent, virialized hierarchy of structures from clumps (˜0.1-10 pc) to cores (˜0.05 pc). A closer

  14. 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

  15. 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.

  16. The distribution of warm dust in the star forming region Cepheus A: Infrared constraints

    NASA Technical Reports Server (NTRS)

    Colome, Cecilia; Harvey, Paul M.

    1995-01-01

    We have obtained new, high angular resolution far-infrared (FIR) maps (at 50 and 100 microns) of the star forming region Cepheus A and polarimetric images (1.65 and 2.2 microns) of the reflection nebulosity, IRS6, associated with this young stellar object. Our results are consistent with current star formation theories: a young stellar object surrounded by an infalling envelope with a characteristic density distribution of n(sub d)(r) proportional to r(exp -1.5), a circumstellar disk, and a cavity (R(sub i) approx. 0.07 pc) in which n(sub d) is constant, created by the dispersal of the initial dust cloud by a strong stellar wind.

  17. Mid- to far-infrared properties of star-forming galaxies and active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Magdis, G. E.; Rigopoulou, D.; Helou, G.; Farrah, D.; Hurley, P.; Alonso-Herrero, A.; Bock, J.; Burgarella, D.; Chapman, S.; Charmandaris, V.; Cooray, A.; Dai, Y. Sophia; Dale, D.; Elbaz, D.; Feltre, A.; Hatziminaoglou, E.; Huang, J.-S.; Morrison, G.; Oliver, S.; Page, M.; Scott, D.; Shi, Y.

    2013-10-01

    We study the mid- to far-IR properties of a 24 μm-selected flux-limited sample (S24> 5 mJy) of 154 intermediate redshift (⟨ z ⟩ ~ 0.15), infrared luminous galaxies, drawn from the 5 Milli-Jansky Unbiased Spitzer Extragalactic Survey. By combining existing mid-IR spectroscopy and new Herschel SPIRE submm photometry from the Herschel Multi-tiered Extragalactic Survey, we derived robust total infrared luminosity (LIR) and dust mass (Mdust) estimates and infered the relative contribution of the AGN to the infrared energy budget of the sources. We found that the total (8-1000 μm) infrared emission of galaxies with weak 6.2 μm PAH emission (EW6.2 ≤ 0.2 μm) is dominated by AGN activity, while for galaxies with EW6.2> 0.2 μm more than 50% of the LIR arises from star formation. We also found that for galaxies detected in the 250-500 μm Herschel bands an AGN has a statistically insignificant effect on the temperature of the cold dust and the far-IR colours of the host galaxy, which are primarily shaped by star formation activity. For star-forming galaxies we reveal an anti-correlation between the LIR-to-rest-frame 8 μm luminosity ratio, IR8 ≡ LIR/L8 and the strength of PAH features. We found that this anti-correlation is primarily driven by variations in the PAHsemission, and not by variations in the 5-15 μm mid-IR continuum emission. Using the [Ne iii]/[Ne ii] line ratio as a tracer of the hardness of the radiation field, we confirm that galaxies with harder radiation fields tend to exhibit weaker PAH features, and found that they have higher IR8 values and higher dust-mass-weighted luminosities (LIR/Mdust), the latter being a proxy for the dust temperature (Td). We argue that these trends originate either from variations in the environment of the star-forming regions or are caused by variations in the age of the starburst. Finally, we provide scaling relations that will allow estimating LIR, based on single-band observations with the mid-infrared instrument

  18. 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.

  19. 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.

  20. CHEMICAL EVOLUTION IN HIGH-MASS STAR-FORMING REGIONS: RESULTS FROM THE MALT90 SURVEY

    SciTech Connect

    Hoq, Sadia; Jackson, James M.; Foster, Jonathan B.; Sanhueza, Patricio; Claysmith, Christopher; Guzmán, Andrés; Whitaker, J. Scott; Rathborne, Jill M.; Vasyunina, Tatiana; Vasyunin, Anton E-mail: jackson@bu.edu E-mail: claysmit@bu.edu E-mail: aguzmanf@cfa.harvard.edu E-mail: rathborne@csiro.au E-mail: aiv3f@virginia.edu

    2013-11-10

    The chemical changes of high-mass star-forming regions provide a potential method for classifying their evolutionary stages and, ultimately, ages. In this study, we search for correlations between molecular abundances and the evolutionary stages of dense molecular clumps associated with high-mass star formation. We use the molecular line maps from Year 1 of the Millimetre Astronomy Legacy Team 90 GHz (MALT90) Survey. The survey mapped several hundred individual star-forming clumps chosen from the ATLASGAL survey to span the complete range of evolution, from prestellar to protostellar to H II regions. The evolutionary stage of each clump is classified using the Spitzer GLIMPSE/MIPSGAL mid-IR surveys. Where possible, we determine the dust temperatures and H{sub 2} column densities for each clump from Herschel/Hi-GAL continuum data. From MALT90 data, we measure the integrated intensities of the N{sub 2}H{sup +}, HCO{sup +}, HCN and HNC (1-0) lines, and derive the column densities and abundances of N{sub 2}H{sup +} and HCO{sup +}. The Herschel dust temperatures increase as a function of the IR-based Spitzer evolutionary classification scheme, with the youngest clumps being the coldest, which gives confidence that this classification method provides a reliable way to assign evolutionary stages to clumps. Both N{sub 2}H{sup +} and HCO{sup +} abundances increase as a function of evolutionary stage, whereas the N{sub 2}H{sup +} (1-0) to HCO{sup +} (1-0) integrated intensity ratios show no discernable trend. The HCN (1-0) to HNC(1-0) integrated intensity ratios show marginal evidence of an increase as the clumps evolve.

  1. 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

  2. DIFFERENT EVOLUTIONARY STAGES IN THE MASSIVE STAR-FORMING REGION W3 MAIN COMPLEX

    SciTech Connect

    Wang Yuan; Jiang Zhibo; Beuther, Henrik; Bik, Arjan; Zhang Qizhou; Rodon, Javier A.; 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 {sup 13}CO channel maps, which may indicate triggered star formation.

  3. 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

  4. 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.

    2016-04-01

    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

  5. Infrared polarization images of star-forming regions. I - The ubiquity of bipolar structure

    NASA Technical Reports Server (NTRS)

    Tamura, M.; Gatley, Ian; Joyce, R. R.; Ueno, M.; Suto, H.; Sekiguchi, M.

    1991-01-01

    The inefficiency of the stellar formation process leads rather generally to high residual dust densities, and so to the existence of infrared reflection nebulosity (IRN), in regions of star formation. Polarization images of several star-forming regions with mass outflows (GSS 30, S255, GL 5180, GL 2591, GGD 27, and NGC 7538) presented here: (1) establish the universality of bipolarity and of shell or cavity structure in the IRN consistent with that of CO outflow; (2) identify the source of the mass outflow in each case; (3) show that the opening angle near this central source is large; and (4) demonstrate several instances of multiple shells, probably arising from episodic mass loss. Astrometry of 2.2-micron sources with arcsecond accuracy identifies the illuminating source of each IRN uniquely with a compact H II region or a bright IR source. The polarization images provide strong evidence for large-scale dust toroids around each of these sources. The density and mass of these disks are estimated from the extinction through the disk.

  6. The Structure of the Nearby Giant Star-Forming Region 30 Doradus

    NASA Astrophysics Data System (ADS)

    Pellegrini, Eric; Baldwin, Jack; Hanson, Margaret; Ferland, Gary; Troland, Thomas

    2007-08-01

    The rates of star formation and chemical evolution are controlled in part by the interaction of stellar radiation and winds with the remnant molecular gas from which the stars have formed. We are carrying out a detailed, panchromatic study of these processes in the two nearest giant star-forming regions, 30 Doradus and NGC 3603, as an aide in understanding the nature of Giant Extragalactic H II Regions, starbursts, and Ultra-Luminous IR Galaxies. We recently completed our observations of NGC 3603. Here we request 2 nights on the Blanco telescope to obtain a dense grid of optical long-slit spectra criss- crossing 30 Dor. These will cover the [S II] doublet (to measure N_e) and also [O III], H(beta), [O I], H(alpha) and [N II] to measure the ionization mechanism and ionization parameter, at ~3800 different spots in the nebula. We also request 3 nights on SOAR to take K-band long slit spectra covering H^+ Br(gamma) and several H_2 lines across three representative edge-on ionization fronts in 30 Dor. The IR spectra will be taken in locations also covered by the optical spectra, and will tell us about the structure, pressure support and heating mechanisms in the photo-dissociation regions (PDRs) at these points. Either half of this project can stand on its own, but both parts together will permit the PI to complete his PhD thesis.

  7. 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.

  8. 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

  9. 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

  10. Offerings from the COMPLETE Survey of Star-Forming Regions, c. 2005

    NASA Astrophysics Data System (ADS)

    Goodman, A. A.; Alves, J. F.; Arce, H. G.; Bethell, T.; Borkin, M. A.; Caselli, P.; Di Francesco, J.; Foster, J. B.; Halle, M.; Heyer, M.; Johnstone, D.; Kirk, H.; Kosslyn, D. A.; Li, D.; Li, J.; Lombardi, M.; Pineda, J.; Ridge, N. A.; Schnee, S. L.; Tafalla, M.; Whitehorn, N.

    2005-12-01

    The COMPLETE (COordinated Molecular Probe Line Extinction Thermal Emission) Survey of Star-Forming Regions has now mapped the full extent (as defined by the Spitzer c2d Legacy Survey) of the Perseus, Ophiuchus, and Serpens star-forming regions in: 1) 12CO and 13CO maps (featuring >200,000 spectra) from FCRAO with 40 arcsec resolution; 2) extinction, using the ``NICER" method on 2MASS data; and 3) thermal emission using a combination of IRAS (60 and 100 micron) and SCUBA (850 micron) data. The molecular line maps give kinematic information, while the combination of the extinction and thermal emission maps give the most accurate view of the clouds' dust column density and temperature distributions to date. The COMPLETEd ``wide-field" maps represent ``Phase 1" of the Survey, and ``Phase 2," which offers close-up views of nearly all of the embedded ``cores" within the COMPLETE fields is well underway. Our key results to date include: 1) a new methodology for calibrating dust emission maps with extinction maps (Schnee et al. 2005); 2) a new appreciation of the fundamental uncertainty in the line-of-sight variations in dust temperature introduced into column-density measurements using dust emission (Schnee et al. 2006) 3) evidence for important interactions of spherical winds from B-type stars with molecular clouds (see Ridge et al. 2006a); 4) an extinction ``threshold" for star formation in Ophiuchus (Johnstone et al. 2004); 5) demonstration that extinction mapping routinely yields log-normal density distributions, which disagree with molecular-line map based density distributions, because the line data is biased by excitation and optical depth effects (Goodman et al. 2006); 6) the discovery of ubiquitous ``cloudshine" coming from dark clouds (Foster & Goodman 2005); 7) measurement and identification of uncertainties in the clump mass function for Perseus (Pineda et al. 2006); and 8) testing and new use of 3D medical-imaging software for identification and analysis of

  11. Cluster and nebular properties of the central star-forming region of NGC 1140

    NASA Astrophysics Data System (ADS)

    Moll, S. L.; Mengel, S.; de Grijs, R.; Smith, L. J.; Crowther, P. A.

    2007-12-01

    We present new high spatial resolution Hubble Space Telescope/Advanced Camera for Surveys (ACS) imaging of NGC 1140 and high spectral resolution Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph spectroscopy of its central star-forming region. The central region contains several clusters, the two brightest of which are clusters 1 and 6 from Hunter, O'Connell & Gallagher, located within star-forming knots A and B, respectively. A nebular analysis indicates that the knots have a Large Magellanic Cloud-like metallicity of 12 + logO/H = 8.29 +/-0.09. According to continuum-subtracted Hα ACS imaging, cluster 1 dominates the nebular emission of the brighter knot A. Conversely, negligible nebular emission in knot B originates from cluster 6. Evolutionary synthesis modelling implies an age of 5 +/-1 Myr for cluster 1, from which a photometric mass of (1.1 +/-0.3) × 106Msolar is obtained. For this age and photometric mass, the modelling predicts the presence of ~5900 late O stars within cluster 1. Wolf-Rayet (WR) features are observed in knot A, suggesting 550 late-type nitrogen-rich (WNL) and 200 early-type carbon-rich (WCE) stars. Therefore, N(WR)/N(O) ~ 0.1, assuming that all the WR stars are located within cluster 1. The velocity dispersions of the clusters were measured from constituent red supergiants as σ ~ 23 +/-1kms-1 for cluster 1 and σ ~ 26 +/-1kms-1 for cluster 6. Combining σ with half-light radii of 8 +/- 2 and 6.0 +/-0.2 pc measured from the F625W ACS image implies virial masses of (10 +/-3) × 106 and (9.1 +/-0.8) × 106Msolar for clusters 1 and 6, respectively. The most likely reason for the difference between the dynamical and photometric masses of cluster 1 is that the velocity dispersion of knot A is not due solely to cluster 1, as assumed, but has an additional component associated with cluster 2. E-mail: s.moll@sheffield.ac.uk Based on observations collected at the European Southern Observatory, Chile, under programme ESO 71.B-0058(A

  12. High-Sensitivity Broadband Spectral Line Surveys of Star Forming Regions with the CSO

    NASA Astrophysics Data System (ADS)

    Weaver, Susanna L. Widicus; Sumner, Matthew C.; Rice, Frank; Zmuidzinas, Jonas; Blake, Geoffrey A.

    2009-06-01

    Spectral line surveys are powerful tools for astrochemistry because they circumvent the one-line-at-a-time approach that has historically hampered new molecule identification. Until recently, line surveys were typically motivated by the need to characterize the major components of interstellar clouds, i.e. the so-called ``interstellar weeds." Previously reported surveys therefore often do not provide the sensitivity levels required for identification of new molecules with weak spectral signatures. The goal of our recent observations with the Caltech Submillimeter Observatory (CSO) is to shift the focus of spectral line surveys away from the interstellar weeds and toward detection of new interstellar molecules. We have obtained broadband, high-sensitivity spectra toward several star forming regions with the new λ=1 mm receiver at the CSO. When used with the facility AOS's, this receiver affords 4 GHz of DSB spectral coverage for each LO setting. We have employed a stepped frequency-offset approach to allow for full spectral deconvolution. The noise temperature of this receiver is ˜100 K (SSB), resulting in spectral RMS levels that far surpass those reported in similar previous studies. Our initial observations targeted the Orion and Sagittarius B2(N-LMH) hot cores and a collection of Class 0 sources. We have now completed our coverage of these initial targets, and upcoming observing time has been allocated for similar surveys of the hot cores W51 e1/e2 and G34.3+0.2. We have fully deconvolved 28 GHz of spectra on Orion with RMS levels of T_A^*˜20 mK. Our coverage on Sgr was more limited, yielding ˜8 GHz of fully-deconvolved spectra to the same RMS level. In this talk, we will report on the data analysis for the Orion and Sgr observations, discuss our progress on line surveys of other star-forming regions, and discuss the implications of these results in the context of recent hot core astrochemical models.

  13. 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.

  14. The Massive Star-Forming Regions Omnibus X-Ray Catalog

    NASA Astrophysics Data System (ADS)

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

    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.

  15. VLBA Surveys of OH Masers in Star-forming Regions. I. Satellite Lines

    NASA Astrophysics Data System (ADS)

    Ruiz-Velasco, A. E.; Felli, D.; Migenes, V.; Wiggins, B. K.

    2016-05-01

    Using the Very Long Baseline Array we performed a high-resolution OH maser survey in Galactic star-forming regions (SFRs). We observed all the ground state spectral lines: the main lines at 1665 and 1667 MHz and the satellite lines at 1612 and 1720 MHz. Due to the exceptionality of finding satellite lines in SFRs, we will focus our discussion on those lines. In our sample of 41 OH maser sources, five (12%) showed the 1612 MHz line and ten (24%) showed the 1720 MHz line, with only one source showing both lines. We find that 1720 MHz emission is correlated with the presence of H ii regions, suggesting that this emission could be used to diagnose or trace high-mass star formation. We include an analysis of the possible mechanisms that could be causing this correlation as well as assessing the possible relationships between lines in our sample. In particular, the presence of magnetic fields seems to play an important role as we found Zeeman splitting in four of our sources (W75 N, W3(OH), W51 and NGC 7538). Our results have implications for current understanding of the formation of high-mass stars as well as on the masing processes present in SFRs.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Deep Near-Infrared Observations of the W3 Main Star-forming Region

    NASA Astrophysics Data System (ADS)

    Ojha, D. K.; Tamura, M.; Nakajima, Y.; Fukagawa, M.; Sugitani, K.; Nagashima, C.; Nagayama, T.; Nagata, T.; Sato, S.; Pickles, A. J.; Ogura, K.

    2004-06-01

    We present a deep JHKs-band imaging survey of the W3 Main star-forming region, using the near-infrared camera SIRIUS mounted on the University of Hawaii 2.2 m telescope. The near-infrared survey covers an area of ~24 arcmin2 with 10 σ limiting magnitudes of ~19.0, 18.1, and 17.3 in the J, H, and Ks bands, respectively. We construct JHK color-color and J versus J-H and K versus H-K color-magnitude diagrams to identify young stellar objects and estimate their masses. Based on these color-color and color-magnitude diagrams, a rich population of young stellar objects is identified that is associated with the W3 Main region. A large number of previously unreported red sources (H-K>2) have also been detected around W3 Main. We argue that these red stars are most probably pre-main-sequence stars with intrinsic color excesses. We find that the slope of the Ks-band luminosity function (KLF) of W3 Main is lower than the typical values reported for young embedded clusters. The derived slope of the KLF is the same as that found in 1996 by Megeath and coworkers, from which analysis indicated that the W3 Main region has an age in the range of 0.3-1 Myr. Based on the comparison between models of pre-main-sequence stars and the observed color-magnitude diagram, we find that the stellar population in W3 Main is primarily composed of low-mass pre-main-sequence stars. We also report the detection of isolated young stars with large infrared excesses that are most probably in their earliest evolutionary phases.

  5. 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.

  6. 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.

  7. 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.

  8. 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).

  9. CHEMICAL SEGREGATION TOWARD MASSIVE HOT CORES: THE AFGL2591 STAR-FORMING REGION

    SciTech Connect

    Jimenez-Serra, I.; Zhang, Q.; Viti, S.; Martin-Pintado, J.; De Wit, W.-J. E-mail: qzhang@cfa.harvard.edu E-mail: jmartin@cab.inta-csic.es

    2012-07-01

    We present high angular resolution observations (0.''5 Multiplication-Sign 0.''3) carried out with the Submillimeter Array (SMA) toward the AFGL2591 high-mass star-forming region. Our SMA images reveal a clear chemical segregation within the AFGL2591 VLA 3 hot core, where different molecular species (Types I, II, and III) appear distributed in three concentric shells. This is the first time that such a chemical segregation is ever reported at linear scales {<=}3000 AU within a hot core. While Type I species (H{sub 2}S and {sup 13}CS) peak at the AFGL2591 VLA 3 protostar, Type II molecules (HC{sub 3}N, OCS, SO, and SO{sub 2}) show a double-peaked structure circumventing the continuum peak. Type III species, represented by CH{sub 3}OH, form a ring-like structure surrounding the continuum emission. The excitation temperatures of SO{sub 2}, HC{sub 3}N, and CH{sub 3}OH (185 {+-} 11 K, 150 {+-} 20 K, and 124 {+-} 12 K, respectively) show a temperature gradient within the AFGL2591 VLA 3 envelope, consistent with previous observations and modeling of the source. By combining the H{sub 2}S, SO{sub 2}, and CH{sub 3}OH images, representative of the three concentric shells, we find that the global kinematics of the molecular gas follow Keplerian-like rotation around a 40 M{sub Sun} star. The chemical segregation observed toward AFGL2591 VLA 3 is explained by the combination of molecular UV photodissociation and a high-temperature ({approx}1000 K) gas-phase chemistry within the low extinction innermost region in the AFGL2591 VLA 3 hot core.

  10. Abundances and Excitation of H2, H3+ & CO in Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Kulesa, Craig A.

    Although most of the 123 reported interstellar molecules to date have been detected through millimeter-wave emission-line spectroscopy, this technique is inapplicable to non-polar molecules like H2 and H3+, which are central to our understanding of interstellar chemistry. Thus high resolution infrared absorption-line spectroscopy bears an important role in interstellar studies: chemically important non-polar molecules can be observed, and their abundances and excitation conditions can be referred to the same ``pencil beam'' absorbing column. In particular, through a weak quadrupole absorption line spectrum at near-infrared wavelengths, the abundance of cold H2 in dark molecular clouds and star forming regions can now be accurately measured and compared along the same ``pencil beam'' line of sight with the abundance of its most commonly cited surrogate, CO, and its rare isotopomers. Also detected via infrared line absorption is the pivotal molecular ion H3+, whose abundance provides the most direct measurement of the cosmic ray ionization rate in dark molecular clouds, a process that initiates the formation of many other observed molecules there. Our growing sample of H2 and CO detections now includes detailed multi-beam studies of the ρ Ophiuchi molecular cloud and NGC 2024 in Orion. We explore the excitation and degree of ortho- and para-H2 thermalization in dark clouds, variation of the CO abundance over a cloud, and the relation of H2 column density to infrared extinction mapping, far-infrared/submillimeter dust continuum emission, and large scale submillimeter CO, [C I] and HCO+ line emission -- all commonly invoked to indirectly trace H2 during the past 30+ years. For each of the distinct velocity components seen toward some embedded young stellar objects, we are also able to determine the temperature, density, and a CO/H2 abundance ratio, thus unraveling some of the internal structure of a star-forming cloud. H2 and H3+ continue to surprise and delight us

  11. A WIYN Lithium Survey for Young Stars in the λ Orionis Star-Forming Region

    NASA Astrophysics Data System (ADS)

    Dolan, Christopher J.; Mathieu, Robert D.

    1999-11-01

    We have found 72 pre-main-sequence (PMS) stars near the center of the λ Orionis star-forming region by spectroscopically testing a magnitude-limited sample for the presence of lithium λ6708 absorption, a diagnostic of youth. All of these stars show large lithium equivalent widths and radial velocities consistent with Orion membership, but only two were discovered previously via Hα or X-ray surveys. Comparison with PMS evolutionary tracks show that the low-mass star formation did not begin prior to the initiation of high-mass star formation 5-7 Myr ago. However, the subsequent detailed star formation history is model dependent. Baraffe et al. isochrones imply that high- and low-mass stars began to form together 5-7 Myr ago, with the low-mass stellar formation ceasing abruptly 1 Myr ago. On the other hand, D'Antona & Mazzitelli isochrones indicate a narrow spread of PMS ages, which suggests a burst of low-mass star formation 1-2 Myr ago. Furthermore, kinematic arguments require that the parent molecular cloud gravitationally bound the stars together until recently, but at present the requisite gas mass is not visible. This leads us to conjecture that both the high- and low-mass stars were in a tightly bound cluster until a supernova blast about 1 Myr ago disrupted the parent cloud. This supernova also impacted on the PMS formation process by either (1) ceasing formation through removal of the gas supply or (2) triggering star births via cloud compression, depending on choice of stellar evolution models. Finally, we find that despite their youth, only four of the 72 PMS stars have T Tauri-like Hα emission, suggesting the absence of accretion disks. We conjecture that this may be the result of photoevaporation of the disks while the low-mass stars were in much closer proximity to the OB stars prior to becoming gravitationally unbound.

  12. 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.

  13. Evolution of Protoplanetary Disks in the Orion A Star-Forming Region

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung Hee

    2014-01-01

    We present our investigation of the characteristics of Class II protoplanetary disks in Orion A star-forming region. Our major goal is to analyze a large sample of protoplanetary disks with near- and mid-IR spectra, by statistical approaches, to understand protoplanetary disk evolution in Orion A. For this work, 303 protoplanetary disks in Orion A region observed by IRS/Spitzer and the follow-up observation of 120 objects from SpeX/IRTF are used to reveal the characteristics of Class II disks in Orion A. For clues on environmental effects on disk evolution and planet formation, we compare the disk properties and dust properties of Orion A disks to that of Taurus disks and examine trends with respect to position within Orion A. We extract spectral indices, equivalent widths, and integrated fluxes from IRS spectra of Class II objects in Orion A which pertain to disk structure and dust composition. We measure mass accretion rates using hydrogen recombination lines in SpeX spectra of our targets. Utilizing the properties, we analyze the general distribution of properties of disks in ONC, L1641, and Taurus from their histograms. Our main findings are as follows. (1) From the high frequency (>20%) of transitional disks and the similar vertical structure of the Orion A disks to those of Taurus, we infer that giant planet formation and dust sedimentation is well under way, if not complete, even in the youngest Class II objects. (2) Less grain processing - crystallization and growth of grains to diameter of 1-10 μm - has occurred among the dust grains in the Orion A disks than in Taurus. The time scales for dust processing must therefore lie in the range of ages of the nearby clouds like Orion, NGC 1333, Taurus, Ophiuchus and Chamaeleon. (3) We detected PAH emission at 6-14 μm from disks around low-mass and low-luminosity young stars, excited externally by UV from the Trapezium stars. (4) As others have found for the Trapezium region of Orion, the disks of the surrounding

  14. 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.

  15. A Search for Companions to Brown Dwarfs in the Taurus and Chamaeleon Star-Forming Regions

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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 ⊙). 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^{+0.05}_{-0.03} for M4-M6 (M ~ 0.1-0.3 M ⊙) and 4/108 = 0.04^{+0.03}_{-0.01} for >M6 (M <~ 0.1 M ⊙) 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. Based on observations performed with the NASA/ESA Hubble Space Telescope, Gemini Observatory, and the W. M. Keck Observatory. The Hubble observations are associated with proposal IDs 11203, 11204, and 11983 and were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  16. 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

  17. 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

  18. The Stellar Population of the Chamaeleon I Star-forming Region

    NASA Astrophysics Data System (ADS)

    Luhman, K. L.

    2007-11-01

    I present a new census of the stellar population in the Chamaeleon I star-forming region. Using optical and near-IR photometry and follow-up spectroscopy, I have discovered 50 new members of Chamaeleon I, expanding the census of known members to 226 objects. Fourteen of these new members have spectral types later than M6, which doubles the number of known members that are likely to be substellar. I have estimated extinctions, luminosities, and effective temperatures for the known members, used these data to construct an H-R diagram for the cluster, and inferred individual masses and ages with the theoretical evolutionary models of Baraffe and Chabrier. The distribution of isochronal ages indicates that star formation began 3-4 and 5-6 Myr ago in the southern and northern subclusters, respectively, and has continued to the present time at a declining rate. The IMF in Chamaeleon I reaches a maximum at a mass of 0.1-0.15 Msolar and thus closely resembles the IMFs in IC 348 and the Orion Nebula Cluster. In logarithmic units where the Salpeter slope is 1.35, the IMF is roughly flat in the substellar regime and shows no indication of reaching a minimum down to a completeness limit of 0.01 Msolar. The low-mass stars are more widely distributed than members at other masses in the northern subcluster, but this is not the case in the southern subcluster. Meanwhile, the brown dwarfs have the same spatial distribution as the stars out to a radius of 3° (8.5 pc) from the center of Chamaeleon I. Based on observations performed with the Magellan Telescopes at Las Campanas Observatory, Cerro Tololo Inter-American Observatory (CTIO), Gemini Observatory, and the NASA/ESA Hubble Space Telescope (HST). CTIO is operated by the Association of Universities for Research in Astronomy (AURA) under a contract with the National Science Foundation (NSF). Gemini Observatory is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NSF (US), the

  19. Inferring the Evolutionary Stages of High-mass Star-forming Regions from Chemistry

    NASA Astrophysics Data System (ADS)

    Feng, Siyi; Beuther, H.; Henning, T.; Semenov, D.; Linz, H.; InstituteAstronomy, Max-Planck

    2014-01-01

    The earliest phases of the high-mass star-forming regions (HMSFRs) have so many extremely complicated astrophysical processes, such as infall, outflows, and fragmentations that kinematic studies are not enough to understand all the mysteries, therefore, chemistry has developed into a powerful tool in probing the nature of them. Using PdBI at 1.3 mm, we observed two typical HMSFRs, NGC 7538 S and NGC 7538 IRS. Continuums are presented, the spectra from different substructures in each source are extracted and the intensity-integrated distribution maps for different species are imaged. We then calculate their column densities, and abundances in each identified substructure, assuming local thermal equilibrium, optically thin and uniform widths lines for all species. With spatial resolution of 0.4'' (800 AU), NGC 7538 S fragmentations into at least three cores, having similar continuum flux densities but different kinematic temperatures nor line properties, and exhibiting evolutionary sequence from northeast to southwest: MM1 is more evolved, and is a typical hot molecular core, associated with an accretion disk and several outflows, which enhance certain molecular abundances in the projected direction; MM2 is a high mass protostar object, where majority of molecules have abundances lower than in MM1, except for the lower temperature tracers, e.g., ketene, formaldehyde; whereas MM3 is still a cold starless core, and the spectral emissions in this substructure are only from molecules with low vibration temperatures. Since they are embedded in the same cluster but behave different properties, they should have the similar ages but different warm-up timescales. In comparison, IRS1 remains unresolved, though, large amount of complex organic molecules indicates it as the most evolved hot core in all the substructures here we studied. Absorption feature only appears on the spectrum extracted from the continuum peak, and that may come from its precession accretion disk

  20. 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.

  1. 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.

  2. 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

  3. Sulfur-bearing Molecules in Massive Star-forming Regions: Observations of OCS, CS, H2S, and SO

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    We studied the sulfur chemistry of massive star-forming regions through single-dish submillimeter spectroscopy. OCS, O13CS, 13CS, H2S, 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 CH3CN 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 13CS. H2S 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.

  4. 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.

  5. ALMA Resolves the Properties of Star-forming Regions in a Dense Gas Disk at z ˜ 3

    NASA Astrophysics Data System (ADS)

    Swinbank, A. M.; Dye, S.; Nightingale, J. W.; Furlanetto, C.; Smail, Ian; Cooray, A.; Dannerbauer, H.; Dunne, L.; Eales, S.; Gavazzi, R.; Hunter, T.; Ivison, R. J.; Negrello, M.; Oteo-Gomez, I.; Smit, R.; van der Werf, P.; Vlahakis, C.

    2015-06-01

    We exploit long baseline ALMA submillimeter observations of the lensed star-forming galaxy SDP 81 at z = 3.042 to investigate the properties of the interstellar medium (ISM) on scales of 50-100 pc. The kinematics of the 12CO gas within this system are well described by a rotationally supported disk with an inclination-corrected rotation speed, {{v}rot} = 320 ± 20 km s-1, and a dynamical mass of {{M}dyn} = (3.5 ± 1.0)× 1010 {{M}⊙ } within a radius of 1.5 kpc. The disk is gas-rich and unstable, with a Toomre parameter, Q = 0.30 ± 0.10, and so into star-forming regions with Jeans length {{L}J} ˜ 130 pc. We identify five star-forming regions within the ISM on these scales and show that their scaling relations between luminosity, line widths, and sizes are significantly offset from those typical of molecular clouds in local galaxies (Larson’s relations). These offsets are likely to be caused by the high external hydrostatic pressure for the ISM, {{P}tot}/{{k}B}˜ 40-20+30 × 107 K cm-3, which is ˜104× higher than the typical ISM pressure in the Milky Way. The physical conditions of the star-forming ISM and giant molecular clouds appear to be similar to those found in the densest environments in the local universe, such as those in the Galactic center.

  6. 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

  7. 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.

  8. 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.

  9. Three-dimensional molecular line transfer: a simulated star-forming region

    NASA Astrophysics Data System (ADS)

    Rundle, David; Harries, Tim J.; Acreman, David M.; Bate, Matthew R.

    2010-09-01

    We present the first non-local thermodynamic equilibrium (non-LTE), comoving frame molecular line calculations of a star-forming cluster simulated using smoothed particle hydrodynamics (SPH), from which we derive high-resolution synthetic observations. We have resampled a particle representation on to an adaptive mesh and self-consistently solved the equations of statistical equilibrium in the comoving frame, using TORUS, a three-dimensional adaptive mesh refined radiative transfer code. We verified the applicability of the code to the conditions of the SPH simulation by testing its output against other codes. We find that the level populations obtained for optically thick and thin scenarios closely match the ensemble average of the other codes. We have used the code to obtain non-LTE level populations of multiple molecular species throughout the cluster and have created three-dimensional velocity-resolved spatial maps of the emergent intensity. Line profiles of cores traced by N2H+ (1-0) are compared to probes of low-density gas, 13CO (1-0) and C18O (1-0), surrounding the cores along the line of sight. The relative differences of the line centre velocities are shown to be small compared to the velocity dispersion, matching recent observations. We conclude that one cannot reject competitive accretion as a viable theory of star formation based on observed velocity profiles.

  10. CO observations of the galactic star-forming region W58

    NASA Technical Reports Server (NTRS)

    Israel, F. P.

    1980-01-01

    Observations of (C-12)O and (C-13)O have been made in the direction of the strong galactic radio source W58, which contains the compact H II regions K3-50 and ON-3. An extended molecular cloud with dimensions of 55 x 40 pc is associated with the northern part of the H II region complex. The density of the molecular cloud increases from west to east; the molecular cloud is bounded on the east by a larger H I cloud. Present star-formation activity is taking place at the position of maximum molecular density, at what appears to be the interface of the H I cloud and the H II region complex. The velocity structure of the CO cloud and the compact H II regions are in agreement with the blister model. Radio continuum and H I line observations show indications of a shell structure in the southwest of W58. Present star formation in W58 may be caused by this expanding shell.

  11. 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.

  12. 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.

  13. Luminosity functions of YSO clusters in Sh-2 255, W3 Main and NGC 7538 star forming regions

    NASA Astrophysics Data System (ADS)

    Ojha, Devendra; Tamura, Motohide

    We have conducted deep near-infrared surveys of the Sh-2 255, W3 Main and NGC 7538 massive star forming regions using simultaneous observations of the JHKs-band with the near-infrared camera SIRIUS on the UH 88-inch telescope and with SUBARU. The near-infrared surveys cover a total area of ~72 square arcmin of three regions with 10-sigma limiting magnitudes of ~19.5, 18.4 and 17.3 in J, H and Ks-band, respectively. Based on the color-color and color-magnitude diagrams and their clustering properties, the candidate young stellar objects are identified and their luminosity functions are constructed in Sh-2 255, W3 Main and NGC 7538. A large number of previously unreported red sources (H-K > 2) have also been detected around these regions. We argue that these red stars are most probably pre-main sequence stars with intrinsic color excesses. The detected young stellar objects show a clear clustering pattern in each region: the Class I-like sources are mostly clustered in molecular cloud region, while the Class II-like sources in or around more evolved optical HII regions. We find that the slopes of the Ks-band luminosity functions of Sh-2 255, W3 Main and NGC 7538 are lower than the typical values reported for the young embedded clusters and their stellar populations are primarily composed of low mass pre-main sequence stars. From the slopes of the Ks-band luminosity functions, we infer that Sh-2 255, W3 Main and NGC 7538 star forming regions are rather young (age <=1 Myr).

  14. Luminosity functions of YSO clusters in Sh-2 255, W3 main and NGC 7538 star forming regions

    NASA Astrophysics Data System (ADS)

    Ojha, Devendra; Tamura, Motohide; Sirius Team

    2006-03-01

    We have conducted deep near-infrared surveys of the Sh-2 255, W3 Main and NGC 7538 massive star forming regions using simultaneous observations of the JHKs -band with the near-infrared camera SIRIUS on the UH 88-inch telescope. The near-infrared surveys cover a total area of ~72 square arcmin of three regions with 10-sigma limiting magnitudes of ~19.5, 18.4 and 17.3 in J, H and Ks-band, respectively. Based on the colour-colour and colour- magnitude diagrams and their clustering properties, the candidate young stellar objects are identified and their luminosity functions are constructed in Sh-2 255, W3 Main and NGC 7538. A large number of previously unreported red sources (H - K > 2) have also been detected around these regions. We argue that these red stars are most probably pre-main sequence stars with intrinsic colour excesses. The detected young stellar objects show a clear clustering pattern in each region: the Class I-like sources are mostly clustered in molecular cloud region, while the Class II-like sources in or around more evolved optical H II regions. We find that the slopes of the Ks -band luminosity functions of Sh-2 255, W3 Main and NGC 7538 are lower than the typical values reported for the young embedded clusters and their stellar populations are primarily composed of low mass pre-main sequence stars. From the slopes of the Ks -band luminosity functions, we infer that Sh-2 255, W3 Main and NGC 7538 star forming regions are rather young (age 1 Myr).

  15. 15N fractionation in star-forming regions and Solar System objects

    NASA Astrophysics Data System (ADS)

    Wirström, Eva; Milam, Stefanie; Adande, Gilles; Charnley, Steven B.; Cordiner, Martin A.

    2015-08-01

    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 pristine molecular content of comets, interplanetary dust particles and carbonaceous chondrites show significant bulk nitrogen isotopic fractionation relative to the solar value, 14N/15N ~ 440. In addition, high spatial resolution measurements in primitive materials locally show even more extreme enhancements of 14N/15N < 100.The coherent 15N enrichment in comets from different formation zones suggests that these isotopic enhancements are remnants of the interstellar chemistry in the natal molecular cloud core and the outer protosolar nebula. Indeed, early chemical models of gas-phase ion-molecule nitrogen fractionation showed that HCN and HNC (nitriles) can hold significant 15N enrichments in cold dark clouds where CO is depleted onto dust grains. In addition, 15N fractionation in nitriles and amines (NH2, NH3) follow different chemical pathways. More recently we have shown that once the spin-state dependence in rates of reactions with H2 is included in the models, amines can either be enhanced or depleted in 15N, depending on the core’s evolutionary stage. Observed 15N fractionation in amines and nitriles therefore cannot be expected to be the same, instead their ratio is a potential chemical clock.Observations of molecular isotope ratios in dark cores are challenging. Limited published results in general show higher 15N/14N ratios in HCN and HNC than ammonia, but more measurements are necessary to confirm these trends. We will present recent results from our ongoing observing campaign of 14N/15N isotopic ratios in HCN, HNC and NH3 in dense cores and protostars which seem consistent with significant fractionation in nitriles as compared to other molecules in each object. The few 14N/15N ratios observed in N2H+ are similar to

  16. 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

  17. 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.

  18. 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.

  19. Sub-Eddington star-forming regions are super-Eddington: momentum-driven outflows from supersonic turbulence

    NASA Astrophysics Data System (ADS)

    Thompson, Todd A.; Krumholz, Mark R.

    2016-01-01

    We show that the turbulent gas in the star-forming regions of galaxies is unstable to wind formation via momentum deposition by radiation pressure or other momentum sources like supernova explosions, even if the system is below the average Eddington limit. This conclusion follows from the fact that the critical momentum injection rate per unit mass for unbinding gas from a self-gravitating system is proportional to the gas surface density and that a turbulent medium presents a broad distribution of column densities to the sources. For an average Eddington ratio of <Γ> ≃ 0.1 and for turbulent Mach numbers ≳ 30, we find that ˜1 per cent of the gas is ejected per dynamical time-scale at velocities larger than the local escape velocity. Because of the lognormal shape of the surface density distribution, the mass-loss rate is highly sensitive to the average Eddington ratio, reaching ˜20-40 per cent of the gas mass per dynamical time for <Γ> ≃ 1. Using this model we find a large scatter in the mass-loading factor for star-forming galaxies, ranging from ˜10-3-10, but with significant uncertainties. Implications for the efficiency of star formation in giant molecular clouds are highlighted. For radiation pressure feedback alone, we find an increasing star formation efficiency as a function of initial gas surface density. Uncertainties are discussed.

  20. IR Studies of dust and ices in star-forming regions

    NASA Astrophysics Data System (ADS)

    Whittet, Douglas C. B.

    2009-05-01

    I will review the current status of research on the properties of interstellar dust and ices studied by infrared spectroscopy. Ongoing investigations of the thermal evolution of ices in molecular clouds and regions of active star formation will be described. Data from the infrared spectrometer on board the Spitzer Space Telescope will be compared with data for laboratory analogs to demonstrate the value of the analogs as an indispensable aid to interpretation of the observations. Data for reddened background field stars establish the properties of the ices in cold, quiescent clouds, and provide a benchmark for studying their physical and chemical evolution in the environments of young dust-embedded stars. I will conclude with a brief review of prospects for future research with new infrared facilities that will become available in the next few years. This research is supported by funding from the NASA Astrobiology Institute and from the NASA Exobiology and Evolutionary Biology program.

  1. 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).

  2. 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.

  3. The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1. II. Shock dynamics

    NASA Astrophysics Data System (ADS)

    Lefloch, B.; Cabrit, S.; Codella, C.; Melnick, G.; Cernicharo, J.; Caux, E.; Benedettini, M.; Boogert, A.; Caselli, P.; Ceccarelli, C.; Gueth, F.; Hily-Blant, P.; Lorenzani, A.; Neufeld, D.; Nisini, B.; Pacheco, S.; Pagani, L.; Pardo, J. R.; Parise, B.; Salez, M.; Schuster, K.; Viti, S.; Bacmann, A.; Baudry, A.; Bell, T.; Bergin, E. A.; Blake, G.; Bottinelli, S.; Castets, A.; Comito, C.; Coutens, A.; Crimier, N.; Dominik, C.; Demyk, K.; Encrenaz, P.; Falgarone, E.; Fuente, A.; Gerin, M.; Goldsmith, P.; Helmich, F.; Hennebelle, P.; Henning, T.; Herbst, E.; Jacq, T.; Kahane, C.; Kama, M.; Klotz, A.; Langer, W.; Lis, D.; Lord, S.; Maret, S.; Pearson, J.; Phillips, T.; Saraceno, P.; Schilke, P.; Tielens, X.; van der Tak, F.; van der Wiel, M.; Vastel, C.; Wakelam, V.; Walters, A.; Wyrowski, F.; Yorke, H.; Bachiller, R.; Borys, C.; de Lange, G.; Delorme, Y.; Kramer, C.; Larsson, B.; Lai, R.; Maiwald, F. W.; Martin-Pintado, J.; Mehdi, I.; Ossenkopf, V.; Siegel, P.; Stutzki, J.; Wunsch, J. H.

    2010-07-01

    Context. The outflow driven by the low-mass class 0 protostar L1157 is the prototype of the so-called chemically active outflows. The bright bowshock B1 in the southern outflow lobe is a privileged testbed of magneto-hydrodynamical (MHD) shock models, for which dynamical and chemical processes are strongly interdependent. Aims: We present the first results of the unbiased spectral survey of the L1157-B1 bowshock, obtained in the framework of the key program “Chemical HErschel Surveys of star forming regions” (CHESS). The main aim is to trace the warm and chemically enriched gas and to infer the excitation conditions in the shock region. Methods: The CO 5-4 and o-H2O 110-101 lines have been detected at high-spectral resolution in the unbiased spectral survey of the HIFI-band 1b spectral window (555-636 GHz), presented by Codella et al. in this volume. Complementary ground-based observations in the submm window help establish the origin of the emission detected in the main-beam of HIFI and the physical conditions in the shock. Results: Both lines exhibit broad wings, which extend to velocities much higher than reported up to now. We find that the molecular emission arises from two regions with distinct physical conditions : an extended, warm (100 K), dense (3 × 105 cm-3) component at low-velocity, which dominates the water line flux in Band 1; a secondary component in a small region of B1 (a few arcsec) associated with high-velocity, hot (>400 K) gas of moderate density ((1.0-3.0) × 104 cm-3), which appears to dominate the flux of the water line at 179μm observed with PACS. The water abundance is enhanced by two orders of magnitude between the low- and the high-velocity component, from 8 × 10-7 up to 8 × 10-5. The properties of the high-velocity component agree well with the predictions of steady-state C-shock models. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important

  4. 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

  5. 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.

  6. Infall motions in massive star-forming regions: results from years 1 and 2 of the MALT90 survey

    NASA Astrophysics Data System (ADS)

    He, Yu-Xin; Zhou, Jian-Jun; Esimbek, Jarken; Ji, Wei-Guang; Wu, Gang; Tang, Xin-Di; Yuan, Ye; Li, Da-Lei; Baan, W. A.

    2015-06-01

    Massive star-forming regions with observed infall motions are good sites for studying the birth of massive stars. In this paper, 405 compact sources have been extracted from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) compact sources that also have been observed in the Millimetre Astronomy Legacy Team 90-GHz (MALT90) survey during years 1 and 2. These observations are complemented with Spitzer GLIMPSE/MIPSGAL mid-IR survey data to help classify the elected star-forming clumps into three evolutionary stages: pre-stellar, proto-stellar and UCHII regions. The results suggest that 0.05 g cm-2 is a reliable empirical lower bound for the clump surface densities required for massive-star formation to occur. The optically thick HCO+(1-0) and HNC(1-0) lines, as well as the optically thin N2H+(1-0) line were used to search for infall motions towards these sources. By analysing the asymmetries of the optically thick HCO+(1-0) and HNC(1-0) lines and the mapping observations of HCO+(1-0), a total of 131 reliable infall candidates have been identified. The HCO+(1-0) line shows the highest occurrence of obvious asymmetric features, suggesting that it may be a better infall motion tracer than other lines such as HNC(1-0). The detection rates of infall candidates towards pre-stellar, proto-stellar and UCHII clumps are 0.3452, 0.3861 and 0.2152, respectively. The relatively high detection rate of infall candidates towards UCHII clumps indicates that many UCHII regions are still accreting matter. The peak column densities and masses of the infall candidates, in general, display an increasing trend with progressing evolutionary stages. However, the rough estimates of the mass infall rate show no obvious variation with evolutionary stage.

  7. Evidence for lithium and boron from star-forming regions implanted in presolar SiC grains

    NASA Astrophysics Data System (ADS)

    Lyon, I. C.; Tizard, J. M.; Henkel, T.

    2007-03-01

    We report the first measurements of lithium and boron isotope ratios and abundances measured in "gently separated" presolar SiC grains. Almost all analyses of presolar SiC grains since their first isolation in 1987 have been obtained from grains that were separated from their host meteorite by harsh acid dissolution. We recently reported a new method of "gently" separating the grains from meteorites by using freeze-thaw disaggregation, size, and density separation to retain any nonrefractory coatings or alteration to the surfaces of the grains that have been acquired in interstellar space. Nonrefractory coats or amorphized surfaces will almost certainly be removed or altered by the traditional acid separation procedure. High Li/Si and B/Si ratios of up to ˜10-2 were found implanted in the outer 0.5 μm of the grains dropping to ˜10-5 in the core of the grains.7Li/6Li and 11B/10B ratios indistinguishable from solar system average values were found. Analyses obtained from SiC grains from the acid dissolution technique showed isotope ratios that were the same as those of gently separated grains, but depth profiles that were different. These results are interpreted as evidence of implantation of high velocity (1200-1800 km s-1) Li and B ions into the grains by shock waves as the grains traveled through star-forming regions some time after their condensation in the outflow of an AGB star that was their progenitor. The results are in line with spectroscopic measurements of Li and B isotope ratios in star-forming regions and may be used to infer abundances and isotopic sources in these regions.

  8. MYSTIX: AGE GRADIENTS IN STELLAR POPULATIONS OF MASSIVE STAR FORMING REGIONS BASED ON A NEW STELLAR CHRONOMETER

    NASA Astrophysics Data System (ADS)

    Getman, Konstantin V.; Feigelson, E.; Kuhn, M. A.; Broos, P. S.; Townsley, L. K.; Naylor, T.; Povich, M. S.; Luhman, K.; Garmire, G.

    2014-01-01

    The MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray, Feigelson et al. 2013) project characterizes 20 OB-dominated massive star forming regions (MSFRs) at distances <4 kpc using photometric X-ray, NIR, and MIR catalogues. As part of MYStIX, we developed a new stellar chronometer that employs NIR and X-ray data, AgeJX. The method is sensitive to wide stages of evolution, from embedded in a cloud disk-bearing stars to widely dispersed older pre-main sequence stars. AgeJX has been applied to >5500 out of >31000 MYStIX Probable Complex Members. To overcome the dispersion of highly uncertain individual ages, we report median ages of stellar samples within (sub)clusters that are spatially discriminated by Kuhn et al. (2013). The important science result is the discovery of age gradients across MYStIX regions as well as within some individual rich clusters. We find narrowly constrained ages in these spatially distinct structures. Spatial gradients in median age values are often seen consistent with astronomically reasonable patterns of star formation histories, with older lightly absorbed structures on one side, younger heavily absorbed structures on the other side, and intermediate-age structures in the middle. Widely distributed populations are nearly always have older ages than the principle clusters. The progression of star formation within a MSFR can be traced over spatial scales of several parsecs and time scales of several million years. We provide a homogeneous set of averaged AgeJX for >130 MYStIX (sub)clusters and regions of interest, so patterns of star formation histories can be compared between MSFRs. In addition we report age gradients within the NGC 2024 and Orion Nebula clusters with implications for cluster formation astrophysics.

  9. The structure of NGC 7538 IRS9: A massive star forming region with spatially constrained warm gas

    NASA Astrophysics Data System (ADS)

    Doty, Steven; Bowers, Brant

    2015-08-01

    An important question in the study of massive protostars is the physical structure of the star forming region. An extension of the Shu infall model to high masses would suggest the existence of a spherical envelope surrounding a central, massive disk. On the other hand, turbulence, outflows, instabilities, or other forces might disrupt such a disk or prevent one from forming in the first place. Observations of acetylene in ro-vibrational absorption on GEMINI provide spatially constrained observations of high-lying transitions. We model the absorption and compare the model predictions with the observations, in order to constrain the models. The implications for the physical structure are discussed, and future observations to test the results are suggested.

  10. 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.

  11. 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.

  12. Sub-stellar Companions and Stellar Multiplicity in the Taurus Star-Forming Region - A High-Contrast Survey

    NASA Astrophysics Data System (ADS)

    Daemgen, Sebastian; Bonavita, Mariangela; Jayawardhana, Ray

    2013-07-01

    In recent years the rapid improvement of high-contrast imaging instrumentation and techniques lead to the discovery of a number of wide sub-stellar companions to nearby young stars, down to planetary mass. Some of these objects have mass ratios with respect to their parent stars of only ~1%, and due also to their extreme separation are hard to explain in any formation paradigm suggested so far, whether based on core accretion or disk instabilities. Hence, these objects may represent an extreme outcome of their underlying formation mechanisms, regardless of which it is. Previous surveys in nearby star forming regions such as Upper-Sco and Sco-Cen are consistent with the existence of a continuous population of companions, which suggests that binary formation may extend all the way down to planetary masses for wide separations, or at least that mass alone is not a clear-cut observational diagnostic for distinguishing between formation mechanisms. Moreover, the same studies suggest a higher frequency of wide companions in young star forming regions, with respect to young moving groups or in the field, implying that ejection mechanisms could be relevant already within the first few Myrs after formation. In this poster we present initial results of a large, coherent survey for sub-stellar companions and stellar multiplicity of Taurus stars of all masses. It uses high-spatial resolution NIRI/Gemini North adaptive optics imaging in K-band, allowing us to detect companions as close as 0.07" out to 12" (corresponding to ~10AU-1500AU at the distance of Taurus) with masses down to ~1 MJup. The findings will be compared with those of deep high-spatial resolution studies of other young associations. Such a comparison gives insight to, e.g., the interplay between the low-mass multiplicity fraction and mass ratios or primary mass and age, respectively.

  13. 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.

  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. 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.

  16. TADPOL: A 1.3 mm Survey of Dust Polarization in Star-forming Cores and Regions

    NASA Astrophysics Data System (ADS)

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

    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.

  17. 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.

  18. 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).

  19. A Study of Interstellar Ultraviolet Extinction in OB Associations and Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Aiello, S.; Barsella, B.; Chlewicki, G.; Greenberg, J. M.; Patriarchi, P.; Perinotto, M.

    The authors studied the interstellar UV extinction towards 115 stars, selected from the IUE data bank. The complete catalogue, including extinction data for the whole sample as well as the reduction procedure and error analysis, is in preparation (Aiello et al., 1986). Here the authors present the results referring to two regions (Carina and Ophiuchus Complexes) where the interstellar medium is disturbed by the effects of recent and ongoing star formation. For comparison purposes, the extinction towards Cas OB6 is also reported.

  20. 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.

  1. 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.

  2. 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.

  3. CH3CN Observations toward Southern Massive Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Araya, Esteban; Hofner, Peter; Kurtz, Stan; Bronfman, Leonardo; DeDeo, Simon

    2005-04-01

    In an effort to identify very young sites of massive star formation, we have conducted a survey for hot and dense molecular cores toward a sample of 17 southern sources. The sample consists of sources with IRAS color characteristics of ultracompact H II regions for which high-density molecular material had previously been detected. We observed the J=5-4, 6-5, 8-7, and 12-11 rotational transitions of CH3CN and derived rotation temperatures and column densities using the population-diagram technique. We identify four sources with a high-temperature molecular component (Trot>90 K) as new candidates for hot molecular cores. We also observed the transitions H35α, CS J=3-2, and the continuum in the 3, 2 mm bands toward 17 sources, and the 1.3 mm continuum, H41α and 13CO J=2-1 transitions toward 10 sources. Eight sources show blue and red wings in the CS J=3-2 line, whereas three sources show wings in the 13CO J=2-1 spectra, suggestive of molecular outflows. Our continuum and recombination line data show that the 91 GHz continuum emission is dominated by free-free emission from ionized regions, whereas at 147 GHz emission from dust grains contributes significantly.

  4. SPECTRAL CLASSIFICATION OF THE BRIGHTEST OBJECTS IN THE GALACTIC STAR-FORMING REGION W40

    SciTech Connect

    Shuping, R. Y.; Vacca, William D.; Kassis, Marc; Yu, Ka Chun

    2012-10-01

    We present high signal-to-noise, moderate resolution (R Almost-Equal-To 2000) near-infrared spectra, as well as 10 {mu}m imaging, for the brightest members of the central stellar cluster in the W40 H II region, obtained using the SpeX and MIRSI instruments at NASA's Infrared Telescope Facility. Using these observations combined with archival Spitzer Space Telescope data, we have determined the spectral classifications, extinction, distances, and spectral energy distributions (SEDs) for the brightest members of the cluster. Of the eight objects observed, we identify four main-sequence (MS) OB stars (one late-O, three early-B), two Herbig Ae/Be stars, and two low-mass young stellar objects (Class II). Strong He I absorption at 1.083 {mu}m in the MS star spectra strongly suggests that at least some of these sources are in fact close binaries. Two out of the four MS stars also show significant infrared excesses typical of circumstellar disks. Extinctions and distances were determined for each MS star by fitting model stellar atmospheres to the SEDs. We estimate a distance to the cluster of between 455 and 535 pc, which agrees well with earlier (but far less precise) distance estimates. We conclude that the late-O star we identify is the dominant source of Lyman continuum luminosity needed to power the W40 H II region and is the likely source of the stellar wind that has blown a large ( Almost-Equal-To 4 pc) pinched-waist bubble observed in wide-field mid-IR images. We also suggest that 3.6 cm radio emission observed from some of the sources in the cluster is likely not due to emission from ultracompact H II regions, as suggested in other work, due to size constraints based on our derived distance to the cluster. Finally, we also present a discussion of the curious source IRS 3A, which has a very strong mid-IR excess (despite its B3 MS classification) and appears to be embedded in a dusty envelope roughly 2700 AU in size.

  5. Hard X-Ray Emission in the Star-Forming Region ON 2: Discovery with XMM-Newton

    NASA Astrophysics Data System (ADS)

    Oskinova, L. M.; Gruendl, R. A.; Ignace, R.; Chu, Y.-H.; Hamann, W.-R.; Feldmeier, A.

    2010-04-01

    We obtained X-ray XMM-Newton observations of the open cluster Berkeley 87 and the massive star-forming region (SFR) ON 2. In addition, archival infrared Spitzer Space Telescope observations were used to study the morphology of ON 2, to uncover young stellar objects, and to investigate their relationship with the X-ray sources. It is likely that the SFR ON 2 and Berkeley 87 are at the same distance, 1.23 kpc, and hence are associated. The XMM-Newton observations detected X-rays from massive stars in Berkeley 87 as well as diffuse emission from the SFR ON 2. The two patches of diffuse X-ray emission are encompassed in the shell-like H II region GAL 75.84+0.40 in the northern part of ON 2 and in the ON 2S region in the southern part of ON 2. The diffuse emission from GAL 75.84+0.40 suffers an absorption column equivalent to A V ≈ 28 mag. Its spectrum can be fitted either with a thermal plasma model at T >~ 30 MK or by an absorbed power-law model with γ ≈ -2.6. The X-ray luminosity of GAL 75.84+0.40 is L X ≈ 6 × 1031 erg s-1. The diffuse emission from ON 2S is adjacent to the ultra-compact H II (UCH II) region Cygnus 2N, but does not coincide with it or with any other known UCH II region. It has a luminosity of L X ≈ 4 × 1031 erg s-1. The spectrum can be fitted with an absorbed power-law model with γ ≈ -1.4. We adopt the view of Turner & Forbes that the SFR ON 2 is physically associated with the massive star cluster Berkeley 87 hosting the WO-type star WR 142. We discuss different explanations for the apparently diffuse X-ray emission in these SFRs. These include synchrotron radiation, invoked by the co-existence of strongly shocked stellar winds and turbulent magnetic fields in the star-forming complex, cluster wind emission, or an unresolved population of discrete sources.

  6. An Unbiased Search for Molecular Hydrogen Outflows in the Orion B Star Forming Region

    NASA Astrophysics Data System (ADS)

    Froebrich, D.; Ziener, R.; Eislöffel, J.

    The formation of stars is often accompanied by molecular outflows. One possible tracer of these outflows is the shocked emission of molecular hydrogen in the near-infrared. We conducted an unbiased survey for molecular outflows in the Orion B region with MAGIC at the 1.23 m telescope on Calar Alto in the 1-0 S(1) line of molecular hydrogen at 2.212μm and in the K' bandpass (continuum). The observed field was about 2.7 square degrees, including the known outflows of NGC2071, HH19, HH24, HH25, HH26, HH27, HH37, HH67, HH91, HH92, HH93, HH94, HH212, HH247, HH248, HH249 and HH260. In addition to these known H2 flows, we find ten new groups of H2 emission features, and discuss their morphology and possible outflow sources.

  7. Hubble Space Telescope imaging of the central star forming region in NGC 1140 (exp 1)

    NASA Technical Reports Server (NTRS)

    Hunter, Deidre A.; O'Connell, Robert W.; Gallagher, John S. Iii

    1994-01-01

    We present broadband images taken with the Hubble Space Telescope's Planetary Camera of the central supergiant H II region in the amorphous galaxy NGC 1140. These images allow observations to a resolution of about 13 pc at the galaxy, and they reveal that its central 1/2 kpc contains 6-7 blue, luminous, compact super star clusters, many of which would be comparable in luminosity to globular clusters at the same age. A blue arc-shaped structure near the center may be a grouping of less luminous, R136/NGC 2070-sized clusters or a sheet of OB stars. Additional somewhat less luminous and redder clusters are also found farther out from the center. If these clusters are older, they too could have had luminosities comparable to those of the central six clusters at a comparable age. Thus, we find that NGC 1140 is remarkable in the number of extreme clusters that it has formed recently in a relatively small area of the galaxy. Since NGC 1140 exhibits global characteristics that are consistent with a recent merger, these clusters are likely to be a product of that event. This galaxy adds to the number of cases where rapid star formation has evidently produced super star clusters.

  8. A Rich Star-forming Region in the Direction of RCW 95

    NASA Astrophysics Data System (ADS)

    Roman-Lopes, A.; Abraham, Z.

    2004-11-01

    Near-IR imaging in the direction of the IRAS 15408-5356 point source, which is associated with the RCW 95 H II region, revealed a young and massive stellar cluster. We detected 136 member candidates up to our completeness limit, embedded in an infrared nebula and concentrated in an area of about 3 pc2. About 60% of the candidates detected in all three of the J, H, and K bands present infrared excess at 2.2 μm. The UV photons provided by the most massive stars are enough to explain the observed free-free emission at radio wavelengths and the integrated infrared luminosity produced by the heated dust. The near-IR counterpart of the IRAS point source was identified using a more accurate position from the Midcourse Space Experiment (MSX) catalog; it coincides with the peak of emission in the MSX mid-IR bands. The measured integrated flux density of the infrared nebula at the K band is compatible with the expected free-free emission derived from the radio data, but an excess at the J and H bands was detected and may be due to either nonhomogeneous absorption across the nebula or to the presence of scattered stellar light, more prominent at smaller wavelengths. Based on observations made at Laboratório Nacional de Astrofisica/MCT, Brazil.

  9. Observational studies of the structure, content and environment of intermediate and high-mass star-forming regions

    NASA Astrophysics Data System (ADS)

    Arvidsson, Kim

    This thesis describes observational studies of star-forming regions and their influence on the interstellar medium. First, in an effort to understand the factors that govern the transition from low- to high-mass star formation, a sample of intermediate-mass star-forming regions (IM SFRs) is identified for the first time. IM SFRs constitute embedded clusters where stars up to---but not exceeding--- ˜ 8 M⊙ are being produced. They are at an early evolutionary stage akin to compact H II regions, but they lack the massive ionizing central star(s). IRAS colors, Spitzer Space Telescope mid-IR images, millimeter continuum and 13CO maps were used to compile a sample of 50 IM SFRs in the inner Galaxy. The photodissociation regions that demarcate IM SFRs have typical diameters of ˜ 1 pc and luminosities of ˜ 104 L⊙ , making them an order of magnitude less luminous than (ultra)compact H II regions. IM SFRs coincide with molecular clumps of mass ˜ 103 M⊙ which, in turn, lie within larger molecular clouds spanning the lower end of the giant molecular cloud mass range, 104--10 5 M⊙ . 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 ˜ 0.1--0.5 g cm-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 ˜ 1 g cm -2. Second, an investigation into the enormous H II region CTB 102 was carried out for the first time. Through a combination of new radio recombination line observations and available archival data, analysis shows that the filamentary structure surrounding the central region is physically associated with the central region. The first ever distance estimate for this H II region is provided, 4.3 kpc. The overall morphology and size of CTB 102 indicates that it is likely a large H II region combined with a wind

  10. 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'.

  11. 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.

  12. Water deuteration in star-forming regions : Contribution of Herschel/HIFI spectroscopic data

    NASA Astrophysics Data System (ADS)

    Coutens, Audrey

    2012-11-01

    HDO/H2O ratios as well as the D2O/HDO ratios determined in IRAS 16293-2422 enable to constrain the conditions of water formation in this kind of objects and in particular suggest that water would be formed before the gravitational collapse of the cloud. This study was then extended to other solar-type protostars NGC1333 IRAS4A and NGC1333 IRAS4B, for which I estimated the abundances of deuterated water and noticed that an extended absorbing layer also surrounds these sources. The high HDO/H2O ratios determined in IRAS 16293-2422 suggest that mechanisms are required between the Class 0 stage and the comets formation to decrease these isotopic ratios. It is however necessary to study a larger sample of protostars to know if this trend is observed in most of the sources. The HDO abundances obtained in NGC1333 IRAS4A and NGC1333 IRAS4B will consequently be useful to estimate their HDO/H2O ratios. Finally, I also studied deuterated water in protostellar objects more massive and more luminous than solar-type protostars and show here the case of the ultra-compact HII region G34.26+0.15.

  13. VLBI study of maser kinematics in high-mass star-forming regions. I. G16.59-0.05

    NASA Astrophysics Data System (ADS)

    Sanna, A.; Moscadelli, L.; Cesaroni, R.; Tarchi, A.; Furuya, R. S.; Goddi, C.

    2010-07-01

    Aims: To study the high-mass star-forming process, we started a large project to unveil the gas kinematics close to young stellar objects (YSOs) through the Very Long Baseline Interferometry (VLBI) of maser associations. By comparing the high spatial resolution maser data that traces the inner kinematics of the (proto)stellar cocoon with interferometric thermal data that traces the large-scale environment of the hot molecular core (HMC) harboring the (proto)stars, we can investigate the nature and identify the sources of large-scale motions. The present paper focuses on the high-mass star-forming region G16.59-0.05. Methods: Using the VLBA and the EVN arrays, we conducted phase-referenced observations of the three most powerful maser species in G16.59-0.05: H2O at 22.2 GHz (4 epochs), CH3OH at 6.7 GHz (3 epochs), and OH at 1.665 GHz (1 epoch). In addition, we performed high-resolution (≥0.1 arcsec), high-sensitivity (< 0.1 mJy) VLA observations of the radio continuum emission from the star-forming region at 1.3 and 3.6 cm. Results: This is the first work to report accurate measurements of the relative proper motions of the 6.7 GHz CH3OH masers. The different spatial and 3-D velocity distributions clearly indicate that the 22 GHz water and 6.7 GHz methanol masers trace different kinematic environments. The bipolar distribution of 6.7 GHz maser line-of-sight velocities and the regular pattern of observed proper motions suggest that these masers are tracing rotation around a central mass of about 35 M⊙. The flattened spatial distribution of the 6.7 GHz masers, oriented NW-SE, suggests that they can originate in a disk/toroid rotating around the massive YSO that drives the 12CO (2-1) outflow, oriented NE-SW, observed on an arcsec scale. The extended, radio continuum source observed close to the 6.7 GHz masers could be excited by a wide-angle wind emitted from the YSO associated with the methanol masers, and such a wind has proven to be energetic enough to drive the

  14. Nearby supernova host galaxies from the CALIFA Survey. I. Sample, data analysis, and correlation to star-forming regions

    NASA Astrophysics Data System (ADS)

    Galbany, L.; Stanishev, V.; Mourão, A. M.; Rodrigues, M.; Flores, H.; García-Benito, R.; Mast, D.; Mendoza, M. A.; Sánchez, S. F.; Badenes, C.; Barrera-Ballesteros, J.; Bland-Hawthorn, J.; Falcón-Barroso, J.; García-Lorenzo, B.; Gomes, J. M.; González Delgado, R. M.; Kehrig, C.; Lyubenova, M.; López-Sánchez, A. R.; de Lorenzo-Cáceres, A.; Marino, R. A.; Meidt, S.; Mollá, M.; Papaderos, P.; Pérez-Torres, M. A.; Rosales-Ortega, F. F.; van de Ven, G.

    2014-12-01

    We use optical integral field spectroscopy (IFS) of nearby supernova (SN) host galaxies (0.005 star-forming regions by using several indicators of the ongoing and recent SF related to both the ionized gas and the stellar populations. While the total ongoing SF is on average the same for the three SN types, SNe Ibc/IIb tend to occur closer to star-forming regions and in higher SF density locations than SNe II and SNe Ia; the latter shows the weakest correlation. SNe Ia host galaxies have masses that are on average ~0.3-0.8 dex higher than those of the core collapse (CC) SNe hosts because the SNe Ia hosts contain alarger fraction of old stellar populations. Using the recent SN Ia delay-time distribution and the SFHs of the galaxies, we show that the SN Ia hosts in our sample are expected to produce twice as many SNe Ia as the CC SN hosts. Since both types occur in hosts with a similar SF rate and hence similar CC SN rate, this can explain the mass difference between the SN Ia and CC SN hosts, and reinforces the finding that at least part of the SNe Ia originate from very old progenitors. By comparing the mean SFH of the eight least massive galaxies with that of the massive SF SN Ia hosts, we find that the low-mass galaxies formed their stars during a longer time (0.65%, 24.46%, and 74.89% in the intervals 0-0.42 Gyr, 0.42-2.4 Gyr, and >2.4 Gyr, respectively) than the massive SN Ia hosts (0.04%, 2.01%, and 97.95% in these intervals). We estimate that the low-mass galaxies produce ten times fewer SNe Ia and three times fewer CC SNe than the high-mass group. Therefore the ratio between the number of CC SNe and SNe Ia is

  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. 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.

  17. 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.

  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. Observations of two ``millimetre-only'' cores as candidates for early high-mass star-forming regions

    NASA Astrophysics Data System (ADS)

    Balnozan, Egon; Lo, Nadia; Jones, Paul; Cunningham, Maria; Hill, Tracey; Bronfman, Leonardo

    2013-04-01

    We wish to image at high spectral resolution two “millimetre-only” sources from a subset of 10 identified by Hill et al. (2005) in a 1.2-mm continuum survey. These very bright mm-only sources (also featuring strong NH3 emission) are believed to be excellent candidates for early-stage protostars (C2102-2009JULS) through their characteristic similarity to known massive star-forming sources, despite lacking typical features of massive star formation such as methanol masers and radio continuum. We present evidence of methanol emission in these sources from a recent spectral analysis, along with other molecular species indicative of very early-stage star-formation in cores featuring outflows but devoid of HII regions. High-resolution observations are critical in discriminating between maser and thermal methanol line emission mechanisms that can distinguish between early-stage massive star formation and lower-mass objects. These observations will allow us to quantify the frequency, spatial position and scale of molecular emission to further understanding of the chemistry that distinguishes between low and high-mass star formation, investigate the possible relation between mm-only radio sources and massive protostars, while also gathering data relevant to creating chemical timelines of their early evolution.

  20. Source Contamination in X-ray Studies of Star-forming Regions: Application to the Chandra Carina Complex Project

    NASA Astrophysics Data System (ADS)

    Getman, Konstantin V.; Broos, Patrick S.; Feigelson, Eric D.; Townsley, Leisa K.; Povich, Matthew S.; Garmire, Gordon P.; Montmerle, Thierry; Yonekura, Yoshinori; Fukui, Yasuo

    2011-05-01

    We describe detailed simulations of X-ray-emitting populations to evaluate the levels of contamination by both Galactic and extragalactic X-ray sources unrelated to a star-forming region under study. For Galactic contaminations, we consider contribution from main-sequence stars and giants (not including cataclysmic variables and other classes of accretion-driven X-ray binary systems), as they make the dominant contribution at the position of the Carina Nebula. The simulations take into consideration a variety of technical factors involving a Galactic population synthesis model, stellar X-ray luminosity functions, Chandra telescope response, source detection methodology, and possible spatial variations in the X-ray background and absorption through molecular clouds. When applied to the 1.42 deg2 field of the Chandra Carina Complex Project (CCCP), the simulations predict ~5000 contaminating sources (1 source arcmin-2 of the survey), evenly distributed across the field. The results of the simulations are further employed in a companion CCCP study to assign membership probabilities to individual sources.

  1. A GALEX-based Search for the Sparse Young Stellar Population in the Taurus-Aurigae Star Forming Region

    NASA Astrophysics Data System (ADS)

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

    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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. The Dust Content and Opacity of Actively Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

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

    2000-04-01

    We present far-infrared (FIR) photometry at 150 and 205 μm of eight low-redshift starburst galaxies obtained with the Infrared Space Observatory (ISO) ISOPHOT. Five of the eight galaxies are detected in both wave bands, and these data are used, in conjunction with IRAS archival photometry, to model the dust emission at λ>~40 μm. The FIR spectral energy distributions (SEDs) are best fitted by a combination of two modified Planck functions, with T~40-55 K (warm dust) and T~20-23 K (cool dust) and with a dust emissivity index ɛ=2. The cool dust can be a major contributor to the FIR emission of starburst galaxies, representing up to 60% of the total flux. This component is heated not only by the general interstellar radiation field, but also by the starburst itself. The cool dust mass is up to ~150 times larger than the warm dust mass, bringing the gas-to-dust ratios of the starbursts in our sample close to Milky Way values, once rescaled for the appropriate metallicity. The ratio between the total dust FIR emission in the range 1-1000 μm and the IRAS FIR emission in the range 40-120 μm is ~1.75, with small variations from galaxy to galaxy. This ratio is about 40% larger than previously inferred from data at millimeter wavelengths. Although the galaxies in our sample are generally classified as ``UV bright,'' for four of them the UV energy emerging shortward of 0.2 μm is less than 15% of the FIR energy. On average, about 30% of the bolometric flux is coming out in the UV-to-near-IR wavelength range; the rest is emitted in the FIR. Energy balance calculations show that the FIR emission predicted by the dust reddening of the UV-to-near-IR stellar emission is within a factor of ~2 of the observed value in individual galaxies and within 20% when averaged over a large sample. If our sample of local starbursts is representative of high-redshift (z>~1), UV-bright, star-forming galaxies, these galaxies' FIR emission will be generally undetected in submillimeter surveys

  7. 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).

  8. The distribution of warm gas in the G327.3-0.6 massive star-forming region

    NASA Astrophysics Data System (ADS)

    Leurini, S.; Wyrowski, F.; Herpin, F.; van der Tak, F.; Güsten, R.; van Dishoeck, E. F.

    2013-02-01

    Aims: Most studies of high-mass star formation focus on massive and/or luminous clumps, but the physical properties of their larger scale environment are poorly known. In this work, we aim at characterising the effects of clustered star formation and feedback of massive stars on the surrounding medium by studying the distribution of warm gas through mid-J12CO and 13CO observations. Methods: We present APEX 12CO(6-5), (7-6), 13CO(6-5), (8-7) and HIFI 13CO(10-9) maps of the star forming region G327.36-0.6 with a linear size of ~3 pc × 4 pc. We infer the physical properties of the emitting gas on large scales through a local thermodynamic equilibrium analysis, while we apply a more sophisticated large velocity gradient approach on selected positions. Results: Maps of all lines are dominated in intensity by the photon dominated region around the Hii region G327.3-0.5. Mid-J12CO emission is detected over the whole extent of the maps with excitation temperatures ranging from 20 K up to 80 K in the gas around the Hii region, and H2 column densities from few 1021 cm-2 in the inter-clump gas to 3 × 1022 cm-2 towards the hot core G327.3-0.6. The warm gas (traced by 12 and 13CO(6-5) emission) is only a small percentage (~10%) of the total gas in the infrared dark cloud, while it reaches values up to ~35% of the total gas in the ring surrounding the Hii region. The 12CO ladders are qualitatively compatible with photon dominated region models for high density gas, but the much weaker than predicted 13CO emission suggests that it comes from a large number of clumps along the line of sight. All lines are detected in the inter-clump gas when averaged over a large region with an equivalent radius of 50''(~0.8 pc), implying that the mid-J12CO and 13CO inter-clump emission is due to high density components with low filling factor. Finally, the detection of the 13CO(10-9) line allows to disentangle the effects of gas temperature and gas density on the CO emission, which are

  9. 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

  10. A study of the Galactic star forming region IRAS 02593+6016/S 201 in infrared and radio wavelengths

    NASA Astrophysics Data System (ADS)

    Ojha, D. K.; Ghosh, S. K.; Kulkarni, V. K.; Testi, L.; Verma, R. P.; Vig, S.

    2004-03-01

    We present infrared and radio continuum observations of the S 201 star forming region. A massive star cluster is seen, which contains different classes of young stellar objects. The near-infrared colour-colour and colour-magnitude diagrams are studied to determine the nature of these sources. We have discovered knots of molecular hydrogen emission at 2.122 μm in the central region of S 201. These knots are clearly seen along the diffuse emission to the north-west and are probably obscured Herbig-Haro objects. High sensitivity and high resolution radio continuum images from GMRT observations at 610 and 1280 MHz show an arc-shaped structure due to the interaction between the HII region and the adjacent molecular cloud. The ionization front at the interface between the HII region and the molecular cloud is clearly seen comparing the radio, molecular hydrogen and Brγ images. The emission from the carriers of Unidentified Infrared Bands in the mid-infrared 6-9 μm (possibly due to PAHs) as extracted from the Midcourse Space Experiment survey (at 8, 12, 14 and 21 μm) is compared with the radio emission. The HIRES processed IRAS maps at 12, 25, 60 and 100 μm have also been used for comparison. The spatial distribution of the temperature and the optical depth of the warm dust component around the S 201 region has been generated from the mid-infrared images. This paper is based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Centro Galileo Galilei of the CNAA (Consorzio Nazionale per l'Astronomia e l'Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. 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

  11. PTF10iya: a short-lived, luminous flare from the nuclear region of a star-forming galaxy

    NASA Astrophysics Data System (ADS)

    Cenko, S. Bradley; Bloom, Joshua S.; Kulkarni, S. R.; Strubbe, Linda E.; Miller, Adam A.; Butler, Nathaniel R.; Quimby, Robert M.; Gal-Yam, Avishay; Ofek, Eran O.; Quataert, Eliot; Bildsten, Lars; Poznanski, Dovi; Perley, Daniel A.; Morgan, Adam N.; Filippenko, Alexei V.; Frail, Dale A.; Arcavi, Iair; Ben-Ami, Sagi; Cucchiara, Antonio; Fassnacht, Christopher D.; Green, Yoav; Hook, Isobel M.; Howell, D. Andrew; Lagattuta, David J.; Law, Nicholas M.; Kasliwal, Mansi M.; Nugent, Peter E.; Silverman, Jeffrey M.; Sullivan, Mark; Tendulkar, Shriharsh P.; Yaron, Ofer

    2012-03-01

    We present the discovery and characterization of PTF10iya, a short-lived (Δt≈ 10 d, with an optical decay rate of ˜0.3 mag d-1), luminous (? mag) transient source found by the Palomar Transient Factory. The ultraviolet/optical spectral energy distribution is reasonably well fitted by a blackbody with T≈ (1-2) × 104 K and peak bolometric luminosity LBB≈ (1-5) × 1044 erg s-1 (depending on the details of the extinction correction). A comparable amount of energy is radiated in the X-ray band that appears to result from a distinct physical process. The location of PTF10iya is consistent with the nucleus of a star-forming galaxy (z= 0.224 05 ± 0.000 06) to within 350 mas (99.7 per cent confidence radius), or a projected distance of less than 1.2 kpc. At first glance, these properties appear reminiscent of the characteristic 'big blue bump' seen in the near-ultraviolet spectra of many active galactic nuclei (AGNs). However, emission-line diagnostics of the host galaxy, along with a historical light curve extending back to 2007, show no evidence for AGN-like activity. We therefore consider whether the tidal disruption of a star by an otherwise quiescent supermassive black hole may account for our observations. Though with limited temporal information, PTF10iya appears broadly consistent with the predictions for the early 'super-Eddington' phase of a solar-type star being disrupted by a ˜107 M⊙ black hole. Regardless of the precise physical origin of the accreting material, the large luminosity and short duration suggest that otherwise quiescent galaxies can transition extremely rapidly to radiate near the Eddington limit; many such outbursts may have been missed by previous surveys lacking sufficient cadence.

  12. Image restoration and superresolution as probes of small scale far-IR structure in star forming regions

    NASA Technical Reports Server (NTRS)

    Lester, D. F.; Harvey, P. M.; Joy, M.; Ellis, H. B., Jr.

    1986-01-01

    Far-infrared continuum studies from the Kuiper Airborne Observatory are described that are designed to fully exploit the small-scale spatial information that this facility can provide. This work gives the clearest picture to data on the structure of galactic and extragalactic star forming regions in the far infrared. Work is presently being done with slit scans taken simultaneously at 50 and 100 microns, yielding one-dimensional data. Scans of sources in different directions have been used to get certain information on two dimensional structure. Planned work with linear arrays will allow us to generalize our techniques to two dimensional image restoration. For faint sources, spatial information at the diffraction limit of the telescope is obtained, while for brighter sources, nonlinear deconvolution techniques have allowed us to improve over the diffraction limit by as much as a factor of four. Information on the details of the color temperature distribution is derived as well. This is made possible by the accuracy with which the instrumental point-source profile (PSP) is determined at both wavelengths. While these two PSPs are different, data at different wavelengths can be compared by proper spatial filtering. Considerable effort has been devoted to implementing deconvolution algorithms. Nonlinear deconvolution methods offer the potential of superresolution -- that is, inference of power at spatial frequencies that exceed D lambda. This potential is made possible by the implicit assumption by the algorithm of positivity of the deconvolved data, a universally justifiable constraint for photon processes. We have tested two nonlinear deconvolution algorithms on our data; the Richardson-Lucy (R-L) method and the Maximum Entropy Method (MEM). The limits of image deconvolution techniques for achieving spatial resolution are addressed.

  13. 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.

  14. 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

  15. Revealing the Nature of Faint X-Ray Sources in the Giant Star-Forming Region NGC 3603

    NASA Astrophysics Data System (ADS)

    Poteet, C.; Marchenko, S.; Corcoran, M.; Andersen, M.

    2004-12-01

    NGC 3603, an open cluster embedded in the largest Galactic H II region, contains some of the most luminous, massive stars known in the Galaxy. It may serve as a good analog of star-forming regions in external starburst galaxies. The recent deep (50 Ksec) {Chandra} imaging of NGC 3603 revealed that its X-Ray emission is dominated by the bright Wolf-Rayet and O stars in the cluster core. However, there are hundreds of extremely weak point-like X-ray sources surrounding the central region. They tend to concentrate towards the cluster's center, suggestive of real cluster membership. Studying this population, we find that absolute majority of the weak sources does not belong to the lists of known OB and WR cluster members. Practically all the 263 weak X-ray sources have faint near-IR counterparts in the deep J,H,K images obtained by the ISAAC instrument on the VLT. Around 50% of the X-ray sources can be considered as visual binaries, an additional ˜ 20% as multiple systems (up to six stars in a r=1.5" ˜ 3σ circle). The composite spectrum of these sources is quite hard (kT ˜ 6 keV) and fairly absorbed (NH ˜ 1022). There is no obvious line emission, in particular, no strong Fe XXV line, so presently we cannot distinguish between thermal and non-thermal emission. The JHK colour-colour and colour-magnitude diagrams of the X-ray selected sources indicate that the X-ray data are very efficient in discriminating between field stars and cluster members. The X-ray sources have similar near-infrared properties as the whole near-infrared sample of the known cluster members. Hence, the discovered population of weak X-ray sources provide an effective means to obtain a "clean" sample of pre-main sequence stars down to 1 M⊙ assuming the cluster is 1 Myr old.

  16. 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

  17. Formation, Excitation and Destruction of CH+ under the Influence of Water and Irradiation in Star Forming Regions

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    Simple ionized hydrides were observed for the first time with Herschel/HIFI towards young star-forming objects of low to high mass. Of particular interest is CH+, a fundamental precursor molecule for carbon hydrides. Gaseous H2O reduces the abundance of C and C+, the starting products of CH+. The abundances of H2O and CH+ cannot be enhanced at the same place. Strong irradiation by FUV or X-rays reduces H2O, and CH+ gets more abundant. Thus CH+ signals high irradiation, but low H2O abundance.CH+ was observed to be enhanced in most objects to an abundance of typically 10-10 relative to hydrogen. This suggests an internal source of irradiation. The observed ratio of CH+/OH+ is consistent with irradiation by far UV as expected from chemical modelling. For low-mass objects the required FUV flux is between 1 - 200 times the ISRF at the location of the molecules. If the FUV flux originates at the central protostar, an FUV luminosity up to 1.5 Lsun is required. The UV flux in two high-mass objects is 30 and 90 times the ISRF using absorption lines, and of the order of 500 ISRF using emission lines. It is smaller than the unattenuated flux expected from the central object(s). The observed CH+/OH+ ratio, and other ratios such as OH+/H2O+ and CH+/C+, can only be modelled for low molecular hydrogen densities.The targeted lines of CH+, OH+, H2O+, and C+ are detected mostly in blue-shifted absorption. They are proposed to origin 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/s. It is driven by the outward motion of the wind to blue shifts of 0 to -10 km/s. The blue-shifted H2O emission line (Kristensen et al. 2013) may be related but not coincident with the CH+ emitting region.

  18. 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

  19. Search for OB stars running away from young star clusters. II. The NGC 6357 star-forming region

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Kniazev, A. Y.; Kroupa, P.; Oh, S.

    2011-11-01

    Dynamical few-body encounters in the dense cores of young massive star clusters are responsible for the loss of a significant fraction of their massive stellar content. Some of the escaping (runaway) stars move through the ambient medium supersonically and can be revealed via detection of their bow shocks (visible in the infrared, optical or radio). In this paper, which is the second of a series of papers devoted to the search for OB stars running away from young ( ≲ several Myr) Galactic clusters and OB associations, we present the results of the search for bow shocks around the star-forming region NGC 6357. Using the archival data of the Midcourse Space Experiment (MSX) satellite and the Spitzer Space Telescope, and the preliminary data release of the Wide-Field Infrared Survey Explorer (WISE), we discovered seven bow shocks, whose geometry is consistent with the possibility that they are generated by stars expelled from the young (~1-2 Myr) star clusters, Pismis 24 and AH03 J1725-34.4, associated with NGC 6357. Two of the seven bow shocks are driven by the already known OB stars, HD 319881 and [N78] 34. Follow-up spectroscopy of three other bow-shock-producing stars showed that they are massive (O-type) stars as well, while the 2MASS photometry of the remaining two stars suggests that they could be B0 V stars, provided that both are located at the same distance as NGC 6357. Detection of numerous massive stars ejected from the very young clusters is consistent with the theoretical expectation that star clusters can effectively lose massive stars at the very beginning of their dynamical evolution (long before the second mechanism for production of runaway stars, based on a supernova explosion in a massive tight binary system, begins to operate) and lends strong support to the idea that probably all field OB stars have been dynamically ejected from their birth clusters. A by-product of our search for bow shocks around NGC 6357 is the detection of three circular

  20. 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.

  1. Linking pre- and proto-stellar objects in the intermediate-/high-mass star forming region IRAS 05345+3157

    NASA Astrophysics Data System (ADS)

    Fontani, F.; Zhang, Q.; Caselli, P.; Bourke, T. L.

    2009-05-01

    Context: To better understand the initial conditions of the high-mass star formation process, it is crucial to study at high angular resolution the morphology, the kinematics, and the interactions of the coldest condensations associated with intermediate-/high-mass star forming regions. Aims: This paper studies the cold condensations in the intermediate-/high-mass proto-cluster IRAS 05345+3157, focusing on the interaction with the other objects in the cluster. Methods: We performed millimeter high-angular resolution observations, both in the continuum and several molecular lines, with the PdBI and the SMA. In a recent paper, we published part of these data. The main finding of that work was the detection of two cold and dense gaseous condensations, called N and S (masses ˜ 2 and ˜ 9 M_⊙), characterised by high values of deuterium fractionation (˜ 0.1 in both cores) obtained from the column density ratio N(N{2}D+)/N(N{2}H+). In this paper, we present a full report of the observations, and a complete analysis of the data obtained. Results: The millimeter maps reveal the presence of 3 cores inside the interferometer primary beam, called C1-a, C1-b and C2. None of them are associated with cores N and S. C1-b is very likely associated with a newly formed early-B ZAMS star embedded inside a hot core, while C1-a is more likely associated with a class 0 intermediate-mass protostar. The nature of C2 is unclear. Both C1-a and C1-b are good candidates as driving sources of a powerful 12CO outflow, which strongly interacts with N, as demonstrated by the velocity gradient of the gas along this condensation. The N{2}H+ linewidths are between ˜ 1 and 2 km s-1 in the region where the continuum cores are located, and smaller (˜ 0.5-1.5 km s-1) towards N and S, indicating that the gas in the deuterated condensations is more quiescent than that associated with the continuum sources. This is consistent with the fact that they are still in the pre-stellar phase and hence the

  2. SUBMILLIMETER ARRAY OBSERVATIONS OF THE MOLECULAR OUTFLOW IN HIGH-MASS STAR-FORMING REGION G240.31+0.07

    SciTech Connect

    Qiu Keping; Zhang Qizhou; Wu Jingwen; Chen, H.-R.

    2009-05-01

    We present Submillimeter Array observations toward the 10{sup 4.7} L {sub sun} star-forming region G240.31+0.07, in the J = 2-1 transition of {sup 12}CO and {sup 13}CO and at 1.3 mm continuum, as well as the {sup 12}CO and {sup 13}CO observations from the Caltech Submillimeter Observatory to recover the extended emission filtered out by the interferometer. Maps of the {sup 12}CO and {sup 13}CO emission show a bipolar, wide-angle, quasi-parabolic molecular outflow, roughly coincident with an infrared nebula revealed by the Spitzer 3.6 and 4.5 {mu}m emission. The outflow has {approx}98 M {sub sun} molecular gas, making it one of the most massive molecular outflows known, and resulting in a very high mass-loss rate of 4.1 x 10{sup -3} M {sub sun} yr{sup -1} over a dynamical timescale of 2.4 x 10{sup 4} yr. The 1.3 mm continuum observations with a 4'' x 3'' beam reveal a flattened dusty envelope of {approx}150 M {sub sun}, which is further resolved with a 1.''2 x 1'' beam into three dense cores with a total mass of {approx}40 M {sub sun}. The central mm core, showing evidence of active star formation, approximately coincides with the geometric center of the bipolar outflow thus most likely harbors the powering source of the outflow. Overall, our observations provide the best case to date of a well defined wide-angle molecular outflow in a higher than 10{sup 4} L {sub sun} star-forming region. The outflow is morphologically and kinematically similar to low-mass protostellar outflows but has two to three orders of magnitude greater mass, momentum, and energy, and is apparently driven by an underlying wide-angle wind, hence further supports that high-mass stars up to late-O types, even in a crowded clustering environment, can form as a scaled-up version of low-mass star formation.

  3. Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

    NASA Astrophysics Data System (ADS)

    Vogt, N.; Schmidt, T. O. B.; Neuhäuser, R.; Bedalov, A.; Roell, T.; Seifahrt, A.; Mugrauer, M.

    2012-10-01

    Context. The star-forming regions in Chamaeleon (Cha) are one of the nearest (distance ~ 165 pc) and youngest (age ~ 2 Myr) conglomerates of recently formed stars and the ideal target for population studies of star formation. Aims: We investigate a total of 16 Cha targets that have been suggested, but not confirmed, to be binaries or multiple systems in previous literature. Methods: We used the adaptive optics instrument Naos-Conica (NACO) at the Very Large Telescope Unit Telescope (UT) 4 / YEPUN of the Paranal Observatory, at 2-5 different epochs, in order to obtain relative and absolute astrometric measurements, as well as differential photometry in the J, H, and K band. On the basis of known proper motions and these observations, we analyse the astrometric results in our proper motion diagram (PMD: angular separation / position angle versus time), to eliminate possible (non-moving) background stars, establish co-moving binaries and multiples, and search for curvature as indications for orbital motion. Results: All previously suggested close components are co-moving and no background stars are found. The angular separations range between 0.07 and 9 arcsec, corresponding to projected distances between the components of 6-845 AU. Thirteen stars are at least binaries and the remaining three (RX J0919.4-7738, RX J0952.7-7933, VW Cha) are confirmed high-order multiple systems with up to four components. In 13 cases, we found significant slopes in the PMDs, which are compatible with orbital motion whose periods (estimated from the observed gradients in the position angles) range from 60 to 550 years. However, in only four cases there are indications of a curved orbit, the ultimate proof of a gravitational bond. Conclusions: A statistical study based on the 2MASS catalogue confirms the high probability of all 16 stellar systems being gravitationally bound. Most of the secondary components are well above the mass limit of hydrogen burning stars (0.08 M⊙), and have

  4. PARALLAXES FOR W49N AND G048.60+0.02: DISTANT STAR FORMING REGIONS IN THE PERSEUS SPIRAL ARM

    SciTech Connect

    Zhang, B.; Menten, K. M.; Brunthaler, A.; Reid, M. J.; Dame, T. M.; Zheng, X. W.; Xu, Y.

    2013-09-20

    We report trigonometric parallax measurements of 22 GHz H{sub 2}O masers in two massive star-forming regions from Very Long Baseline Array observations as part of the Bar and Spiral Structure Legacy Survey. The distances of 11.11{sup +0.79}{sub -0.69} kpc to W49N (G043.16+0.01) and 10.75{sup +0.61}{sub -0.55} kpc to G048.60+0.02 locate them in a distant section of the Perseus arm near the solar circle in the first Galactic quadrant. This allows us to locate accurately the inner portion of the Perseus arm for the first time. Combining the present results with sources measured in the outer portion of the arm in the second and third quadrants yields a global pitch angle of 9.°5 ± 1.°3 for the Perseus arm. We have found almost no H{sub 2}O maser sources in the Perseus arm for 50° activity.

  5. A Multilevel Study of Ammonia in Star Forming Regions - Part Five - the SAGITTARIUS-B2 Region

    NASA Astrophysics Data System (ADS)

    Huttemeister, S.; Wilson, T. L.; Henkel, C.; Mauersberger, R.

    1993-09-01

    Maps of the Sgr B2 region covering up to 4' have been made in 5 metastable (J = K) and 4 non-metastable (J > K) NH3 inversion transitions with a 40" resolution. Toward Sgr B2 (M) and (N), spectra of 20 additional inversion transitions have been taken arising from energy levels up to E/k=1340 K above ground. From the NH3 data, we obtained rotational and kinetic temperatures (Tkin), cloud sizes, virial masses, NH3 column densities, spatial densities (n(H2)), and NH3 abundances relative to H2 (X(NH3)). In addition to a cool (Tkin˜20K) component detected at -40km s-1 (presumably a foreground cloud associated with the 3 kpc arm), seven regions containing gas with Tkin≥100 K are identified. All are part of the Sgr B2 molecular complex. (1) A low density (n(H2) ˜1O4 cm-3) molecular cloud at υLSR=5O to 80 km s-1 is shown to be extended over several arcmin in metastable transitions up to at least the (6,6) line. A second cooler component (Trot ˜ 20K) appears to coexist with the warm gas. Together, their area filling factor is almost one. Of all mapped lines from other molecular species, only HC3N emission from the vibrational ground state may arise from the same two gas components. (2) Another warm low density feature, at υLSR ˜ 85 km s-1, is detected in the metastable lines toward Sgr B2 (N) and becomes increasingly prominent as J rises. (3) Toward the peak positions Sgr B2 (M) and (N) the metastable lines with J ≤ 5 show an absorption feature at υLSR ˜ 0 km s-1. (4) A region with υLSR ˜ 65 km s-1 has n(H2) 105 cm-3 and is observed in non-metastable NH3 emission lines. It is centered along a ridge 10" west of the main continuum sources. (5) Three Ori-KL like hot cores are identified, one at υLSR ˜65 km s-1 toward SgrB2 (N) and two, at 55 and 65km s-1 toward Sgr B2(M). Provided that the NH3 inversion lines are thermalized and that the clouds are approximately in virial equilibrium, these are the three most massive hot cores known to exist in the galaxy. With

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. Star-forming regions of the Aquila rift cloud complex. II. Turbulence in molecular cores probed by NH3 emission

    NASA Astrophysics Data System (ADS)

    Levshakov, S. A.; Henkel, C.; Reimers, D.; Wang, M.

    2014-07-01

    Aims: We intend to derive statistical properties of stochastic gas motion inside the dense, low-mass star-forming molecular cores that are traced by NH3(1, 1) and (2, 2) emission lines. Methods: We use the spatial two-point autocorrelation (ACF) and structure functions calculated from maps of the radial velocity fields. Results: The observed ammonia cores are characterized by complex intrinsic motions of stochastic nature. The measured kinetic temperature ranges between 8.8 K and 15.1 K. From NH3 excitation temperatures of 3.5-7.3 K, we determine H2 densities with typical values of nH2~ (1-6) × 104 cm-3. The ammonia abundance, X = [NH3]/[H2], varies from 2 × 10-8 to 1.5 × 10-7. We find oscillating ACFs, which eventually decay to zero with increasing lags on scales of 0.04 ≲ ℓ ≲ 0.5 pc. The current paradigm supposes that the star-formation process is controlled by the interplay between gravitation and turbulence with the latter preventing molecular cores from a rapid collapse due to their own gravity. Thus, oscillating ACFs may indicate a damping of the developed turbulent flows surrounding the dense but less turbulent core, a transition to dominating gravitational forces and, hence, to gravitational collapse. Appendix A is available in electronic form at http://www.aanda.org

  12. A UKIDSS-based search for low-mass stars and small stellar clumps in off-cloud parts of young star-forming regions *

    NASA Astrophysics Data System (ADS)

    Perger, M.; Lodieu, N.; Martín, E. L.; Barrado Y Navascués, D.

    2011-07-01

    The form and universality of the mass function of young and nearby star-forming regions is still under debate. Its relation to the stellar density, its mass peak and the dependency on most recent models shows significant differencies for the various regions and remains unclear up to date. We aim to get a more complete census of two of such regions. We investigate yet unexplored areas of Orion and Taurus-Auriga, observed by the UKIDSS survey. In the latter, we search for low-mass stars via photometric and proper motion criteria and signs for variability. In Orion, we search for small stellar clumps via nearest-neighbor methods. Highlights in Taurus would be the finding of the missing low-mass stars and the detection of a young cluster T dwarf. In Orion, we discovered small stellar associations of its OB1b and OB1c populations. Combined with what is known in literature, we will provide by this investigations a general picture of the results of the star-forming processes in large areas of Taurus and Orion and probe the most recent models. Based on data of the UKIRT (operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the U.K.) Infrared Deep Sky Survey (UKIDSS).Supported by the Marie Curie Research Training Network `CONSTELLATION' under grant no. MRTN-CT-2006-035890.

  13. 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

  14. X-Ray and IR Point Source Identification and Characteristics in the Embedded, Massive Star-Forming Region RCW 108

    NASA Astrophysics Data System (ADS)

    Wolk, Scott J.; Spitzbart, Bradley D.; Bourke, Tyler L.; Gutermuth, Robert A.; Vigil, Miquela; Comerón, Fernando

    2008-02-01

    We report on the results of an approximately 90 ks Chandra observation of a complex region that hosts multiple sites of recent and active star formation in ARA OB1a. The field is centered on the embedded cluster RCW 108-IR and includes a large portion of the open cluster NGC 6193. We detect over 420 X-ray sources in the field and combined these data with deep near-IR, Spitzer/IRAC and Midcourse Space Experiment (MSX) mid-IR data. We find about 360 of the X-ray sources have near-IR counterparts. We divide the region into five parts based on the X-ray point source characteristics and extended 8 μm emission. The most clearly defined regions are the central region, identified by embedded sources with high luminosities in the both the near-IR and X-ray as well as high X-ray temperatures (~3 keV), and the eastern region, identified by low extinction and ~1 keV X-ray temperatures. Other regions, identified by their directional relationship to RCW 108-IR, are less uniform—representing combinations of the first two regions, independent star formation epochs, or both. The cluster members range in X-ray luminosity from 1029 to 1033 erg s-1. Over 18% of the cluster members with over 100 counts exhibit flares. All sources with over 350 counts are variable. Overall about 10% (16% in RCW 108-IR) appear to have optically thick disks as derived from their position in the (J - H), (H - K) diagram. The disk fraction becomes much higher when IRAC data are employed. The largest fraction of X-ray sources is best described as possessing some disk material via a more detailed extinction fitting. We fit the bulk of the X-ray spectra as absorbed Raymond-Smith-type plasmas, and find that the column to the RCW 108-IR members varies from 1021 to 1023 cm-2. We find that the field contains 41 candidate O or B stars, and estimate that the total number of pre-main-sequence stars in the field is about 1600 ± 200. Approximately 800 are confined to the 3' (~1.1 pc) central region.

  15. 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.

  16. 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

  17. 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

  18. Iras-Selected Galactic Star-Forming Regions - Part One - New 6/16-5/23 Water Maser Detections in Molecular Cores North of DEC +15DEG

    NASA Astrophysics Data System (ADS)

    Palumbo, G. G. C.; Scappini, F.; Pareschi, G.; Codella, C.; Caselli, P.; Attolini, M. R.

    1994-01-01

    The results are presented of a survey, performed with the Medicina 32-m parabolic reflector, of a sample of IRAS-selected sources associated with molecular clouds for water masers at 22 GHz (616 → 523). The final aim is to study the occurrence of maser emission from star-forming regions in the very early stages of evolution. The whole sample consists of 1409 IRAS sources selected by applying Emerson's colour criteria. In the present paper, results are given for sources with declinations greater than +15°, belonging to two subsamples that satisfy more restrictive colour criteria which should identify ultracompact H II regions (subsample A, 288 sources) and H II regions (subsample B, 133 sources). The main result of the present study is that 59 IRAS sources in the samples are water maser emitters, 11 of which are new detections from the present survey.

  19. 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

  20. HIGH-ANGULAR RESOLUTION DUST POLARIZATION MEASUREMENTS: SHAPED B-FIELD LINES IN THE MASSIVE STAR-FORMING REGION ORION BN/KL

    SciTech Connect

    Tang, Ya-Wen; Ho, Paul T. P.; Koch, Patrick M.; Rao, Ramprasad

    2010-07-10

    We present observational results of the thermal dust continuum emission and its linear polarization in one of the nearest massive star-forming sites Orion BN/KL in Orion Molecular Cloud-1. The observations were carried out with the Submillimeter Array. With an angular resolution of 1'' ({approx}2 mpc; 480 AU), we have detected and resolved the densest cores near the BN/KL region. At a wavelength of {approx}870 {mu}m, the polarized dust emission can be used to trace the structure of the magnetic field in this star-forming core. The dust continuum appears to arise from a V-shaped region, with a cavity nearly coincident with the center of the explosive outflows observed on larger scales. The position angles (P.A.s) of the observed polarization vary significantly by a total of about 90{sup 0} but smoothly, i.e., curl-like, across the dust ridges. Such a polarization pattern can be explained with dust grains being magnetically aligned instead of mechanically with outflows, since the latter mechanism would cause the P.A.s to be parallel to the direction of the outflow, i.e., radial-like. The magnetic field projected in the plane of sky is therefore derived by rotating the P.A.s of the polarization by 90{sup 0}. We find an azimuthally symmetric structure in the overall magnetic field morphology, with the field directions pointing toward 2.''5 west to the center of the explosive outflows. We also find a preferred symmetry plane at a P.A. of 36{sup 0}, which is perpendicular to the mean magnetic field direction (120{sup 0}) of the 0.5 pc dust ridge. Two possible interpretations of the origin of the observed magnetic field structure are discussed.

  1. THE ABUNDANCE, ORTHO/PARA RATIO, AND DEUTERATION OF WATER IN THE HIGH-MASS STAR-FORMING REGION NGC 6334 I

    SciTech Connect

    Emprechtinger, M.; Lis, D. C.; Monje, R. R.; Rolffs, R.; Schilke, P.; Comito, C.; Ceccarelli, C.; Van der Tak, F. F. S.

    2013-03-01

    We present Herschel/HIFI observations of 30 transitions of water isotopologues toward the high-mass star-forming region NGC 6334 I. The line profiles of H{sup 16} {sub 2}O, H{sup 17} {sub 2}O, H{sup 18} {sub 2}O, and HDO show a complex pattern of emission and absorption components associated with the embedded hot cores, a lower-density envelope, two outflow components, and several foreground clouds, some associated with the NGC 6334 complex, others seen in projection against the strong continuum background of the source. Our analysis reveals an H{sub 2}O ortho/para ratio of 3 {+-} 0.5 in the foreground clouds, as well as the outflow. The water abundance varies from {approx}10{sup -8} in the foreground clouds and the outer envelope to {approx}10{sup -6} in the hot core. The hot core abundance is two orders of magnitude below the chemical model predictions for dense, warm gas, but within the range of values found in other Herschel/HIFI studies of hot cores and hot corinos. This may be related to the relatively low gas and dust temperature ({approx}100 K), or time-dependent effects, resulting in a significant fraction of water molecules still locked up in dust grain mantles. The HDO/H{sub 2}O ratio in NGC 6334 I, {approx}2 Multiplication-Sign 10{sup -4}, is also relatively low, but within the range found in other high-mass star-forming regions.

  2. 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.

  3. 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.

  4. The PEP survey: evidence for intense star-forming activity in the majority of radio-selected AGN at z ≳ 1

    NASA Astrophysics Data System (ADS)

    Magliocchetti, M.; Lutz, D.; Santini, P.; Salvato, M.; Popesso, P.; Berta, S.; Pozzi, F.

    2016-02-01

    In order to investigate the far-infrared (FIR) properties of radio-active active galactic nuclei (AGN), we have considered three different fields where both radio and FIR observations are the deepest to date: GOODS-South, GOODS-North and the Lockman Hole. Out of a total of 92 radio-selected AGN, ˜64 per cent are found to have a counterpart in Herschel maps. The percentage is maximum in the GOODS-North (72 per cent) and minimum (˜50 per cent) in the Lockman Hole, where FIR observations are shallower. Our study shows that in all cases FIR emission is associated with star-forming activity within the host galaxy. Such an activity can even be extremely intense, with star-forming rates as high as ˜103-104 M⊙ yr-1. AGN activity does not inhibit star formation in the host galaxy, just as on-site star formation does not seem to affect AGN properties, at least those detected at radio wavelengths and for z ≳ 1. Given the very high rate of FIR detections, we stress that this refers to the majority of the sample: most radio-active AGN are associated with intense episodes of star formation. However, the two processes proceed independently within the same galaxy, at all redshifts but in the local universe, where powerful enough radio activity reaches the necessary strength to switch off the on-site star formation. Our data also show that for z ≳ 1 the hosts of radio-selected star-forming galaxies and AGN are indistinguishable from each other in terms of both mass and IR luminosity distributions. The two populations only differentiate in the very local universe, whereby the few AGN which are still FIR-active are found in galaxies with much higher masses and luminosities.

  5. 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.

  6. 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.

  7. Rotational Velocities for B0-B3 Stars in Seven Young Clusters: Further Study of the Relationship between Rotation Speed and Density in Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Wolff, S. C.; Strom, S. E.; Dror, D.; Venn, K.

    2007-03-01

    We present the results of a study aimed at assessing the differences in the distribution of rotation speeds N(vsini) among young (1-15 Myr) B stars spanning a range of masses 6 Msolar>1 Msolar pc-3) ensembles that will survive as rich, bound stellar clusters for ages well in excess of 108 yr. Our results demonstrate (1) that independent of environment, the rotation rates for stars in this mass range do not change by more than 0.1 dex over ages t~1 to ~15 Myr; and (2) that stars formed in high-density regions lack the cohort of slow rotators that dominate the low-density regions and young field stars. We suggest that the differences in N(vsini) between low- and high-density regions may reflect a combination of initial conditions and environmental effects: (1) the higher turbulent speeds that characterize molecular gas in high-density, cluster-forming regions; and (2) the stronger UV radiation fields and high stellar densities that characterize such regions. Higher turbulent speeds may lead to higher time-averaged accretion rates during the stellar assembly phase. In the context of stellar angular momentum regulation via ``disk-locking,'' higher accretion rates lead to both higher initial angular momenta and evolution-driven increases in surface rotation rates as stars contract from the birth line to the zero-age main sequence (ZAMS). Stronger UV radiation fields and higher densities may lead to shorter disk lifetimes in cluster-forming regions. If so, B stars formed in dense clusters are more likely to be ``released'' from their disks early during their pre-main-sequence lifetimes and evolve into rapid rotators as they conserve angular momentum and spin up in response to contraction. By contrast, the majority of their brethren in low-density, association-forming regions can retain

  8. 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.

  9. Modeling radiative transfer in molecular clouds. 1: HCO(+) in the star-forming region W49A North

    NASA Technical Reports Server (NTRS)

    Dickel, Helene R.; Auer, Lawrence H.

    1994-01-01

    A new general multilevel, non-Local Thermodynamic Equilibrium (LTE) radiative transfer code, valid for any velocity field, is applied to HCO(+) observations of W49A North. Three classes of collapse models are considered: free-fall collapse (v proportional to 1/sq. root of r), rho proportional to r(exp -3/2) throughout the molecular cloud, successfully reproduces the features of the observations and gives the best fit to the J = 1-0 and J = 3-2 profiles both toward the prominent H II component G of W49A North and off the center. In addition to a slow radial fall-off of density, the theoretical modeling implies the following for the molecular cloud: the large line widths result from motions occurring within the inner 1 pc, and there are probably one or more fragments with peculiar velocities within this same region.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. {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.

  16. 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

  17. 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

  18. Physical and chemical variations within the W3 star-forming region. 1: SO2, CH3OH, and H2CO

    NASA Astrophysics Data System (ADS)

    Helmich, F. P.; Jansen, D. J.; de Graauw, Th.; Groesbeck, T. D.; van Dishoeck, E. F.

    1994-03-01

    Submillimeter observations of SO2, CH3OH and H2CO towards three positions in the W3 star-forming molecular cloud (IRS4, IRS5 and W3(H2O)) are presented. Significant differences in the physical and chemical conditions between the three sources are found. The gas temperature appears highest with T approximately equals 220 K towards W3(H2O), followed by T approximately equals 100 K towards IRS5 and T approximately equals 55 K towards IRS4. Densities are 106/cu cm or larger. The chemical composition of W3(H2O) with strong CH3OH lines resembles that of a 'hot core' type region. In contrast, W3IRS5 appears at an earlier evolutionary stage where complex molecules are still depleted onto grains, but where energetic events have produced strong SO2 emission. W3IRS4 is the most evolved region with a chemistry similar to that found in quiescent molecular clouds. Here the time scale since star formation has probably been long enough for the gas-phase ion-molecule chemistry to become dominant again.

  19. 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.

  20. Fermi-LAT Detection of Gamma-Ray Emission in the Vicinity of the Star Forming Regions W43 and Westerlund 2

    NASA Technical Reports Server (NTRS)

    Lemoine-Goumard, M.; Ferrara, E.; Grondin, M.-H.; Martin, P.; Renaud, M.

    2011-01-01

    Particle acceleration in massive star forming regions can proceed via a large variety of possible emission scenarios, including high-energy gamma-ray production in the colliding wind zone of the massive Wolf-Rayet binary (here WR 20a and WR I2Ia), collective wind scenarios, diffusive shock acceleration at the boundaries of wind-blown bubbles in the stellar cluster, and outbreak phenomena from hot stellar winds into the interstellar medium. In view of the recent Fermi-LAT detection of HESS JI023-575 (in the vicinity of Westerlund 2), we examine another very high energy (VHE) gamma-ray source, HESS JI848-0145 (in the vicinity ofW43), possibly associated with a massive star cluster. Considering multi-wavelength data, in particular TeV gamma-rays, we examine the available evidence that the gamma-ray emission coincident with Westerlund 2 and W43 could originate in particles accelerated by the above-mentioned mechanisms in massive star clusters.

  1. 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.

  2. 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.

  3. 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.

  4. Outer rotation curve of the Galaxy with VERA. II. Annual parallax and proper motion of the star-forming region IRAS 21379+5106

    NASA Astrophysics Data System (ADS)

    Nakanishi, Hiroyuki; Sakai, Nobuyuki; Kurayama, Tomoharu; Matsuo, Mitsuhiro; Imai, Hiroshi; Burns, Ross A.; Ozawa, Takeaki; Honma, Mareki; Shibata, Katsunori M.; Kawaguchi, Noriyuki

    2015-08-01

    We conducted astrometric very long baseline interferometry (VLBI) observations of water-vapor maser emission in the massive star-forming region IRAS 21379+5106 in order to measure the annual parallax and proper motion, using VLBI Exploration of Radio Astrometry (VERA). The annual parallax measured 0.262 ± 0.031 mas, corresponding to a distance of 3.82^{+0.51}_{-0.41}kpc. The proper motion was (μαcos δ, μδ) = (-2.74 ± 0.08, -2.87 ± 0.18) mas yr-1. By using this result, the Galactic rotational velocity was estimated to be Vθ = 218 ± 19 km s-1 at the galactocentric distance R = 9.22 ± 0.43 kpc, when we adopted the Galactic constants R0 = 8.05 ± 0.45 kpc and V0 = 238 ± 14 km s-1. With the newly determined distance, the bolometric luminosity of the central young stellar object was reestimated to be (2.15 ± 0.54) × 103 L⊙, which corresponds to the spectral type of B2-B3. The maser features were found to be distributed along a straight line extending from the southwest to the northeast. In addition, a vector map of the internal motions, constructed from the residual proper motions, implies that the maser features trace a bipolar flow, and that it cannot be explained by simple ballistic motions.

  5. VLBA DETERMINATION OF THE DISTANCE TO NEARBY STAR-FORMING REGIONS. VI. THE DISTANCE TO THE YOUNG STELLAR OBJECT HW 9 IN CEPHEUS A

    SciTech Connect

    Dzib, Sergio; Loinard, Laurent; RodrIguez, Luis F.; Mioduszewski, Amy J.; Torres, Rosa M.

    2011-05-20

    Using the Very Long Baseline Array (VLBA), we have observed the radio continuum emission from the young stellar object HW 9 in the Cepheus A star-forming region at 10 epochs between 2007 February and 2009 November. Due to its strong radio variability, the source was detected at only four of the ten epochs. From these observations, the trigonometric parallax of HW 9 was determined to be {pi} = 1.43 {+-} 0.07 mas, in excellent agreement with a recent independent determination by Moscadelli et al. of the trigonometric parallax of a methanol maser associated with the nearby young stellar source HW 2 ({pi} = 1.43 {+-} 0.08 mas). This concordance in results, obtained in one case from continuum and in the other from line observations, confirms the reliability of VLBA trigonometric parallax measurements. By combining the two results, we constrain the distance to Cepheus A to be 700{sup +31}-{sub 28} pc, an uncertainty of 3.5%.

  6. 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.

  7. The Sins/zC-Sinf Survey of z ~ 2 Galaxy Kinematics: Evidence for Powerful Active Galactic Nucleus-Driven Nuclear Outflows in Massive Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Förster Schreiber, N. M.; Genzel, R.; Newman, S. F.; Kurk, J. D.; Lutz, D.; Tacconi, L. J.; Wuyts, S.; Bandara, K.; Burkert, A.; Buschkamp, P.; Carollo, C. M.; Cresci, G.; Daddi, E.; Davies, R.; Eisenhauer, F.; Hicks, E. K. S.; Lang, P.; Lilly, S. J.; Mainieri, V.; Mancini, C.; Naab, T.; Peng, Y.; Renzini, A.; Rosario, D.; Shapiro Griffin, K.; Shapley, A. E.; Sternberg, A.; Tacchella, S.; Vergani, D.; Wisnioski, E.; Wuyts, E.; Zamorani, G.

    2014-05-01

    We report the detection of ubiquitous powerful nuclear outflows in massive (>=1011 M ⊙) 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-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 ⊙ yr-1 and mass loading of ~3. At larger radii, a weaker broad component is detected but with lower FWHM ~485 km s-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. Based on observations obtained at the Very Large Telescope of the European Southern Observatory, Paranal, Chile (ESO program IDs 074.A-0911, 075.A-0466, 076.A-0527, 078.A-0600, 082.A-0396, 183.A-0781, 088.A-0202, 091.A-0126). Also based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the

  8. 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

  9. A TREASURY STUDY OF STAR-FORMING REGIONS IN THE LOCAL GROUP. I. HST PHOTOMETRY OF YOUNG POPULATIONS IN SIX DWARF GALAXIES

    SciTech Connect

    Bianchi, Luciana; Efremova, Boryana; Hodge, Paul; Massey, Philip; Olsen, K. A. G.

    2012-03-15

    We present a comprehensive study of young stellar populations in six dwarf galaxies in or near the Local Group: Phoenix, Pegasus, Sextans A, Sextans B, WLM, and NGC 6822. Their star-forming regions, selected from GALEX wide-field far-UV imaging, were imaged (at sub-pc resolution) with the WFPC2 camera on board the Hubble Space Telescope (HST) in six bandpasses from far-UV to I to detect and characterize their hot massive star content. This study is part of HST treasury survey program HST-GO-11079; the general data characteristics and reduction procedures are detailed in this paper and results are presented for the first six galaxies. From a total of 180 HST images, we provide catalogs of the multi-band stellar photometry and derive the physical parameters of massive stars by analyzing it with model-atmosphere colors. We use the results to infer ages, number of massive stars, extinction, and spatial characteristics of the young stellar populations. The hot massive star content varies largely across our galaxy sample, from an inconspicuous presence in Phoenix and Pegasus to the highest relative abundance of young massive stars in Sextans A and WLM. Albeit to a largely varying extent, most galaxies show a very young population (a few Myrs, except for Phoenix), and older ones (a few 10{sup 7} years in Sextans A, Sextans B, NGC 6822, and WLM, {approx}10{sup 8}yr in Phoenix and Pegasus), suggesting discrete bursts of recent star formation in the mapped regions. The hot massive star content (indicative of the young populations) broadly correlates with the total galaxy stellar mass represented by the integrated optical magnitude, although it varies by a factor of {approx}3 between Sextans A, WLM, and Sextans B, which have similar M{sub V}. Extinction properties are also derived.

  10. 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.

  11. Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data

    NASA Astrophysics Data System (ADS)

    Coutens, A.; Vastel, C.; Hincelin, U.; Herbst, E.; Lis, D. C.; Chavarría, L.; Gérin, M.; van der Tak, F. F. S.; Persson, C. M.; Goldsmith, P. F.; Caux, E.

    2014-12-01

    Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H_2^{18}O transitions were carried out towards the high-mass star-forming region G34.26+0.15 with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument onboard the Herschel Space Observatory, as well as with ground-based single-dish telescopes. 10 HDO lines and three H_2^{18}O lines covering a broad range of upper energy levels (22-204 K) were detected. We used a non-local thermal equilibrium 1D analysis to determine the HDO/H2O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H2O ratio is found to be lower in the hot core (˜3.5 × 10-4-7.5 × 10-4) than in the colder envelope (˜1.0 × 10-3-2.2 × 10-3). This is the first time that a radial variation of the HDO/H2O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modelled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of ˜105 yr after the infrared dark cloud stage.

  12. Infrared Study of the Southern Galactic Star-Forming Regions Associated with IRAS 10049-5657 and IRAS 10031-5632

    NASA Astrophysics Data System (ADS)

    Vig, S.; Ghosh, S. K.; Ojha, D. K.; Verma, R. P.

    2008-10-01

    We investigate the physical conditions of the interstellar medium and stellar components in the regions of the southern Galactic star-forming complexes associated with IRAS 10049-5657 and IRAS 10031-5632. These regions have been mapped simultaneously in two far-infrared bands (λeff ~ 150 and 210 μm), with ~1' angular resolution using the Tata Institute of Fundamental Research 1 m balloon-borne telescope. Spatial distribution of the temperature of cool dust and optical depth at 200 μm have been obtained taking advantage of the similar beams in the two bands. The HIRES processed Infrared Astronomical Satellite (IRAS) maps at 12, 25, 60, and 100 μm have been used for comparison. Using the Two Micron All Sky Survey near-infrared sources, we find the stellar populations of the embedded young clusters. A rich cluster of OB stars is seen in the IRAS 10049-5657 region. The fits to the stellar density radial profile of the cluster associated with IRAS 10049-5657 have been explored with the inverse radius profile as well as the King's profile; the cluster radius is ~2 pc. The source in the cluster closest to the IRAS peak is IRA-7, which lies above the zero-age main-sequence curve of spectral type O5 in the color-magnitude diagram. Unlike IRAS 10049-5657, a small cluster comprising a few deeply embedded sources is seen at the location of IRAS 10031-5632. Self-consistent radiative transfer modeling aimed at extracting important physical and geometrical details of the two IRAS sources shows that the best-fit models are in good agreement with the observed spectral energy distributions. The geometric details of the associated cloud and optical depths (τ100) have been estimated. A uniform density distribution of dust and gas is implied for both the sources. In addition, the infrared ionic fine-structure line emission from gas has been modeled for both the regions and compared with data from the IRAS low-resolution spectrometer. For IRAS 10049-5657, the observed and modeled

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. Unveiling the gas kinematics at 10 AU scales in high-mass star-forming regions. Milliarcsecond structure of 6.7 GHz methanol masers

    NASA Astrophysics Data System (ADS)

    Moscadelli, L.; Sanna, A.; Goddi, C.

    2011-12-01

    Context. High-mass stars play a prominent role in Galactic evolution, but their formation mechanism is still poorly understood. This lack of knowledge reflects the observational limitations of present instruments, whose angular resolution (at the typical distances of massive protostars) precludes probing circumstellar gas on scales of 1-100 AU, relevant for a detailed investigation of accretion structures and launch/collimation mechanims of outflows in high-mass star formation. Aims: This work presents a study of the milliarcsecond structure of the 6.7 GHz methanol masers at high-velocity resolution (0.09 km s-1) in four high-mass star-forming regions: G16.59-0.05, G23.01-0.41, IRAS 20126 + 4104, and AFGL 5142. Methods: We studied these sources by means of multi-epoch VLBI observations in the 22 GHz water and 6.7 GHz methanol masers, to determine the 3-D gas kinematics within a few thousand AU from the (proto)star. Our results demonstrate the ability of maser emission to trace kinematic structures close to the (proto)star, revealing the presence of fast wide-angle and/or collimated outflows (traced by the H2O masers), and of rotation and infall (indicated by the CH3OH masers). The present work exploits the 6.7 GHz maser data collected so far to investigate the milliarcsecond structure of this maser emission at high-velocity resolution. Results: Most of the detected 6.7 GHz maser features present an ordered (linear, or arc-like) distribution of maser spots on the plane of the sky, together with a regular variation in the spot LSR velocity (VLSR) with position. Typical values for the amplitude of the VLSR gradients (defined in terms of the derivative of the spot VLSR with position) are found to be 0.1-0.2 km s-1 mas-1. In each of the four target sources, the orientation and the amplitude of most of the feature VLSR gradients remain remarkably stable in time, on timescales of (at least) several years. We also find that the data are consistent with having the VLSR

  20. 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.

  1. 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.

  2. The extinction curves of star-forming regions from z = 0.1 to 6.7 using GRB afterglow spectroscopy

    NASA Astrophysics Data System (ADS)

    Zafar, T.; Watson, D.; Fynbo, J. P. U.; Malesani, D.; Jakobsson, P.; de Ugarte Postigo, A.

    2011-08-01

    Studies of extinction curves provide insights into the properties of interstellar dust. Until recently, however, very few extinction curves existed outside the local group. GRB afterglows are well suited to extinction studies due to their brightness, simple power-law spectra and their occurrence in distant star forming galaxies. In this paper we present results from the SED analysis of a sample of 41 GRB afterglows, from X-ray to NIR wavelengths. The sample is based on spectra from VLT-FORS, with additional data primarily from Swift. This is the largest sample of extinction curves outside the Local Group and, to date, the only extragalactic sample of absolute extinction curves based on spectroscopy. Estimates of the distribution of restframe visual extinctions, the extinction curves, and the intrinsic spectral shapes of GRB afterglows are obtained. Their correlation with H i column density as well as total and gas-phase metal column density are examined. The line-of-sight gas-to-dust and metals-to-dust ratios are determined and examined as a function of total column density, ISM metallicity and redshift. The intrinsic SEDs of the afterglows show that approximately half the sample require a cooling break between the optical and X-ray ranges. The broken power-law SEDs show an average change in the spectral index of Δβ = 0.51 with a very small standard deviation of 0.02 (excluding the outlier GRB 080210). This is consistent with the expectations from a simple synchrotron model. Such a close convergence of values suggests that the X-ray afterglows of GRBs may be used with considerably more confidence to set the absolute flux level and intrinsic spectral indices in the optical and UV. Of the sample, 63% are well described by a featureless (SMC-type) extinction curve. Almost a quarter of our sample is consistent with no significant extinction (typically AV ≲ 0.1). The 2175 Å extinction bump is detected unequivocally in 7% of our sample (3 GRBs), which all have AV

  3. HIRES Dust Imaging of the NGC 6334 Star Forming Complex

    NASA Technical Reports Server (NTRS)

    Jackson, James M.

    1997-01-01

    We present here our final report for the NASA grant "HIRES Dust Imaging of the NGC 6334 Star Forming Complex." This project was designed to study the photodissociation regions surrounding several OB stars in this cloud complex. NGC 6334 is unique in having at least seven distinct massive star forming regions in the same molecular cloud complex. The obvious advantage of studying young stars in the same molecular complex is that the stars all formed in the same global environment. Consequently, global factors like density waves, abundances, global magnetic field strength, and age of the parental molecular cloud cannot contribute to the differences among the star forming regions. Instead, the differences must arise only from local effects such as the mass, age, and UV fields of the individual stars. A study of NGC 6334 will greatly simplify the general problem of comparing different star formation regions by eliminating global effects.

  4. 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

  5. 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.

  6. Chemistry of Star-Forming Cores

    NASA Technical Reports Server (NTRS)

    Charnley, S. B.

    1994-01-01

    Chemical effects arising from the exchange of molecules between dust and gas in dense clumps are described. Selective desorption of CO and N2 from grains in cool cores can account for the presence of ammonia in several cores in the NGC 2024 cloud. Evaporation of ices containing methanol and ethanol can lead to detectable abundances of (C2H5)(sub 2)O and CH3OC2H5. Results are presented for the hot core chemistries of sulphur and phosphorus which are initiated by evaporated hydrogen sulphide and phosphine. The implications of these studies for understanding the nature of molecular mantles, the evolution of molecular complexity in the gas phase, and the presence of small-scale abundance gradients in star-forming regions, are briefly discussed.

  7. Blue star-forming isolated elliptical galaxies

    NASA Astrophysics Data System (ADS)

    Lacerna, I.; Hernández-Toledo, H. M.; Avila-Reese, V.; Abonza-Sane, J.; del Olmo, A.

    2016-06-01

    The isolated environment seems to favor the formation of blue, star-forming galaxies that are not observed in a high-density environment such as the Coma supercluster. These galaxies, with masses between 7 × 10^9 and 2 × 10^10 h‑2 Msun, are also the youngest galaxies from a sample of isolated elliptical galaxies with light-weighted stellar ages ˜1 < Gyr and exhibit bluer colors toward the galaxy center. Around 30-60% of their present-day luminosity, but only <5% of their present-day mass, is due to star formation in the last 1 Gyr. The color and star-formation activity in these galaxies could be explained by rejuvenation of ellipticals by recent (<1 Gyr) cold gas accretion.

  8. Cosmic rays in star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Persic, Massimo; Rephaeli, Yoel

    2012-03-01

    The energy density of cosmic ray protons (CRp) in star-forming environments can be (i) measured from γ-ray πo-decay emission, (ii) inferred from the measured radio non-thermal synchrotron emission (once a theoretical p/e ratio and particle-field equipartition have been assumed), and (iii) estimated from the observed supernova rate and the deduced CRp residency time. For most of the currently available galaxies where these methods can be simultaneously applied, the results of the various methods agree and suggest that CRp energy densities range from Script O(10-1) eV cm-3 in very quiet environments up to Script O(102) eV cm-3 in very active ones. The only case for which the methods do not agree is the Small Magellanic Cloud, where the discrepancy between measured and estimated CRp energy density may be due to a smaller characteristic CR confinement volume.

  9. 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

  10. VLBA DETERMINATION OF THE DISTANCE TO NEARBY STAR-FORMING REGIONS. V. DYNAMICAL MASS, DISTANCE, AND RADIO STRUCTURE OF V773 Tau A

    SciTech Connect

    Torres, Rosa M.; Franco-Hernandez, Ramiro; Vlemmings, Wouter H. T.; Loinard, Laurent; Mioduszewski, Amy J.; Boden, Andrew F.; Rodriguez, Luis F.

    2012-03-01

    We present multi-epoch Very Long Baseline Array (VLBA) observations of V773 Tau A, the 51 day binary subsystem in the multiple young stellar system V773 Tau. Combined with previous interferometric and radial velocity measurements, these new data enable us to improve the characterization of the physical orbit of the A subsystem. In particular, we infer updated dynamical masses for the primary and the secondary components of 1.55 {+-} 0.11 M{sub Sun} and 1.293 {+-} 0.068 M{sub Sun }, respectively, and an updated orbital parallax distance to the system of 135.7 {+-} 3.2 pc, all consistent with previous estimates. Using the improved orbit, we can calculate the absolute coordinates of the barycenter of V773 Tau A at each epoch of our VLBA observations, and fit for its trigonometric parallax and proper motion. This provides a direct measurement of the distance to the system almost entirely independent of the orbit modeling. The best fit yields a distance of 129.9 {+-} 3.2 pc, in good agreement (i.e., within 1{sigma}) with the distance estimate based on the orbital fit. Taking the mean value of the orbital and trigonometric parallaxes, we conclude that V773 Tau is located at d = 132.8 {+-} 2.3 pc. The accuracy of this determination is nearly one order of magnitude better than that of previous estimates. In projection, V773 Tau and two other young stars (Hubble 4 and HDE 283572) recently observed with the VLBA are located toward the dark cloud Lynds 1495, in the central region of Taurus. These three stars appear to have similar trigonometric parallaxes, radial velocities, and proper motions, and we argue that the weighted mean and dispersion of their distances (d = 131.4 pc and {sigma}{sub d} = 2.4 pc) provide a good estimate of the distance to and depth of Lynds 1495 and its associated stellar population. The radio emission from the two sources in V773 Tau A is largely of gyrosynchrotron origin. Interestingly, both sources are observed to become typically five times

  11. 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.

  12. Sequential Star Formation in RCW 34: A Spectroscopic Census of the Stellar Content of High-Mass Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Bik, A.; Puga, E.; Waters, L. B. F. M.; Horrobin, M.; Henning, Th.; Vasyunina, T.; Beuther, H.; Linz, H.; Kaper, L.; van den Ancker, M.; Lenorzer, A.; Churchwell, E.; Kurtz, S.; Kouwenhoven, M. B. N.; Stolte, A.; de Koter, A.; Thi, W. F.; Comerón, F.; Waelkens, Ch.

    2010-04-01

    In this paper, we present VLT/SINFONI integral field spectroscopy of RCW 34 along with Spitzer/IRAC photometry of the surroundings. RCW 34 consists of three different regions. A large bubble has been detected in the IRAC images in which a cluster of intermediate- and low-mass class II objects is found. At the northern edge of this bubble, an H II region is located, ionized by 3 OB stars, of which the most massive star has spectral type O8.5V. Intermediate-mass stars (2-3 M sun) are detected of G- and K-spectral type. These stars are still in the pre-main-sequence (PMS) phase. North of the H II region, a photon-dominated region is present, marking the edge of a dense molecular cloud traced by H2 emission. Several class 0/I objects are associated with this cloud, indicating that star formation is still taking place. The distance to RCW 34 is revised to 2.5 ± 0.2 kpc and an age estimate of 2 ± 1 Myr is derived from the properties of the PMS stars inside the H II region. Between the class II sources in the bubble and the PMS stars in the H II region, no age difference could be detected with the present data. The presence of the class 0/I sources in the molecular cloud, however, suggests that the objects inside the molecular cloud are significantly younger. The most likely scenario for the formation of the three regions is that star formation propagated from south to north. First the bubble is formed, produced by intermediate- and low-mass stars only, after that, the H II region is formed from a dense core at the edge of the molecular cloud, resulting in the expansion similar to a champagne flow. More recently, star formation occurred in the rest of the molecular cloud. Two different formation scenarios are possible. (1) The bubble with the cluster of low- and intermediate-mass stars triggered the formation of the O star at the edge of the molecular cloud, which in its turn induces the current star formation in the molecular cloud. (2) An external triggering is

  13. 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.

  14. 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.

  15. Ultraviolet to optical spectral distributions of northern star-forming galaxies

    NASA Technical Reports Server (NTRS)

    Mcquade, Kerry; Calzetti, Daniela; Kinney, Anne L.

    1995-01-01

    We report spectral energy distribution from the UV to the optical for a sample of 31 northern star-forming galaxies. We also present measurements for emission-line fluxes, continuum levels, and equivalent widths of absorption features for each individual spectrum as well as averages for the eight galactic activity classes, including normal, starburst, Seyfert 2, blue compact dwarf, blue compact, Low-Inonization Nuclear Emission Regions (LINER), H II, and combination LINER-H II galaxies.

  16. 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)

  17. 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.

  18. Water in low-mass star-forming regions with Herschel. The link between water gas and ice in protostellar envelopes

    NASA Astrophysics Data System (ADS)

    Schmalzl, M.; Visser, R.; Walsh, C.; Albertsson, T.; van Dishoeck, E. F.; Kristensen, L. E.; Mottram, J. C.

    2014-12-01

    Aims: Our aim is to determine the critical parameters in water chemistry and the contribution of water to the oxygen budget by observing and modelling water gas and ice for a sample of eleven low-mass protostars, for which both forms of water have been observed. Methods: A simplified chemistry network, which is benchmarked against more sophisticated chemical networks, is developed that includes the necessary ingredients to determine the water vapour and ice abundance profiles in the cold, outer envelope in which the temperature increases towards the protostar. Comparing the results from this chemical network to observations of water emission lines and previously published water ice column densities, allows us to probe the influence of various agents (e.g., far-ultraviolet (FUV) field, initial abundances, timescales, and kinematics). Results: The observed water ice abundances with respect to hydrogen nuclei in our sample are 30-80 ppm, and therefore contain only 10-30% of the volatile oxygen budget of 320 ppm. The keys to reproduce this result are a low initial water ice abundance after the pre-collapse phase together with the fact that atomic oxygen cannot freeze-out and form water ice in regions with Tdust ≳ 15 K. This requires short prestellar core lifetimes ≲0.1 Myr. The water vapour profile is shaped through the interplay of FUV photodesorption, photodissociation, and freeze-out. The water vapour line profiles are an invaluable tracer for the FUV photon flux and envelope kinematics. Conclusions: The finding that only a fraction of the oxygen budget is locked in water ice can be explained either by a short pre-collapse time of ≲0.1 Myr at densities of nH ~ 104 cm-3, or by some other process that resets the initial water ice abundance for the post-collapse phase. A key for the understanding of the water ice abundance is the binding energy of atomic oxygen on ice. Herschel is an ESA space observatory with science instruments provided by European

  19. Chemical Models of Star-Forming Cores

    NASA Astrophysics Data System (ADS)

    Aikawa, Y.

    2013-10-01

    We review chemical models of low-mass star forming cores including our own work. Chemistry in molecular clouds are not in equilibrium. Molecular abundances in star forming cores change not only with physical conditions in cores but also with time. In prestellar cores, temperature stays almost constant ˜ 10 K, while the gas density increases as the core collapses. Three chemical phenomena are observed in this cold phase: molecular depletion, chemical fractionation, and deuterium enrichment. They are reproduced by chemical models combined with isothermal gravitational collapse. The collapse timescale of prestellar cores depends on the initial ratios of thermal, turbulent and magnetic pressure to gravitational energy. Since the chemical timescales, such as adsorption timescale of gas particle onto grains, are comparable to the collapse timescale, molecular abundances in cores should vary depending on the collapse timescale. Observations found that molecular abundances in some cores deviate from those in other cores, in spite of their similar central densities; it could originate in the pressure to gravity ratio in the cores. As the core contraction proceeds, compressional heating eventually overwhelms radiative cooling, and the core starts to warm up. Temperature of the infalling gas rises, as it approaches the central region. Grain-surface reactions of adsorbed molecules occur in this warm-up phase, as well as in prestellar phase. Hydrogenation is efficient at T ≤ 20 K, whereas radicals can migrate on grain surface and react with each other to form complex organic molecules (COMs) at T ≥ 30 K. Grain-surface species are sublimated to the gas phase and re-start gas-phase reactions; e.g. unsaturated carbon chains are formed from sublimated methane. Our model calculation predicts that COMs increases as the warm region extends outwards and the abundances of unsaturated carbon chains depend on the gas density in the CH4 sublimation zone. Recent detection of COMs in

  20. 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

  1. Polarized light from star forming regions

    NASA Technical Reports Server (NTRS)

    Weintraub, D.; Goodman, A.; Akeson, A.

    2000-01-01

    Studies of polarized radiation from molecular clouds and the environments of protostars are providing information about the orientations and strengths of magnetic fields and the sizes andcompositions of dust grains in these environments.

  2. Polarized Light From Star Forming Regions

    NASA Technical Reports Server (NTRS)

    Akeson, R.; Goodman, A.; Weintraub, D.

    1998-01-01

    Studies of polarized radiation from molecular clouds and the environments of protostars are providing information about the orientations and strengths of magnetic fields and the sizes and compositions of dust grains in these environments.

  3. 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

  4. STAR-FORMING GAS IN YOUNG CLUSTERS

    SciTech Connect

    Myers, Philip C.

    2010-05-10

    Initial conditions for star formation in clusters are estimated for protostars whose masses follow the initial mass function from 0.05 to 10 solar masses. Star-forming infall is assumed equally likely to stop at any moment, due to gas dispersal dominated by stellar feedback. For spherical infall, the typical initial condensation must have a steep density gradient, as in low-mass cores, surrounded by a shallower gradient, as in the clumps around cores. These properties match observed column densities in cluster-forming regions when the mean infall stopping time is 0.05 Myr and the accretion efficiency is 0.5. The infall duration increases with final protostar mass, from 0.01 to 0.3 Myr, and the mass accretion rate increases from 3 to 300 x 10{sup -6} solar masses yr{sup -1}. The typical spherical accretion luminosity is {approx}5 solar luminosities, reducing the 'luminosity problem' to a factor of {approx}3. The initial condensation density gradient changes from steep to shallow at radius 0.04 pc, enclosing 0.9 solar masses, with mean column density 2 x 10{sup 22} cm{sup -2} and with effective central temperature 16 K. These initial conditions are denser and warmer than those for isolated star formation.

  5. LARGE-SCALE KINEMATICS, ASTROCHEMISTRY, AND MAGNETIC FIELD STUDIES OF MASSIVE STAR-FORMING REGIONS THROUGH HC{sub 3}N, HNC, AND C{sub 2}H MAPPINGS

    SciTech Connect

    Li Juan; Wang Junzhi; Gu Qiusheng; Zheng Xingwu; Zhang Zhiyu

    2012-01-20

    We have mapped 27 massive star-forming regions associated with water masers using three dense gas tracers: HC{sub 3}N 10-9, HNC 1-0, and C{sub 2}H 1-0. The FWHM sizes of HNC clumps and C{sub 2}H clumps are about 1.5 and 1.6 times higher than those of HC{sub 3}N, respectively, which can be explained by the fact that HC{sub 3}N traces more dense gas than HNC and C{sub 2}H. We found evidence for an increase in the optical depth of C{sub 2}H with a 'radius' from the center to the outer regions in some targets, supporting the chemical model of C{sub 2}H. The C{sub 2}H optical depth is found to decline as molecular clouds evolve to a later stage, suggesting that C{sub 2}H might be used as a 'chemical clock' for molecular clouds. The large-scale kinematic structure of clouds was investigated with three molecular lines. All of these sources show significant velocity gradients. The magnitudes of gradient are found to increase toward the inner region, indicating the differential rotation of clouds. Both the ratio of rotational to gravitational energy and the specific angular momentum seem to decrease toward the inner region, implying the obvious angular momentum transfer, which might be caused by magnetic braking. The average magnetic field strength and number density of molecular clouds is derived using the uniform magnetic sphere model. The derived magnetic field strengths range from 3 to 88 {mu}G, with a median value of 13 {mu}G. The mass-to-flux ratio of the molecular cloud is calculated to be much higher than the critical value with derived parameters, which agrees well with numerical simulations.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

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

    NASA Technical Reports Server (NTRS)

    Myers, Philip C.

    2002-01-01

    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. The following summary is excerpted from our recent application for a new three-year grant, submitted in June, 2002.

  12. FORMALDEHYDE DENSITOMETRY OF GALACTIC STAR-FORMING REGIONS USING THE H{sub 2}CO 3{sub 12}-3{sub 13} AND 4{sub 13}-4{sub 14} TRANSITIONS

    SciTech Connect

    McCauley, Patrick I.; Mangum, Jeffrey G.; Wootten, Alwyn

    2011-11-20

    We present Green Bank Telescope observations of the 3{sub 12}-3{sub 13} (29 GHz) and 4{sub 13}-4{sub 14} (48 GHz) transitions of the H{sub 2}CO molecule toward a sample of 23 well-studied star-forming regions. Analysis of the relative intensities of these transitions can be used to reliably measure the densities of molecular cores. Adopting kinetic temperatures from the literature, we have employed a large velocity gradient (LVG) model to derive the average hydrogen number density (n(H{sub 2})) within a 16'' beam toward each source. Densities in the range of 10{sup 5.5}-10{sup 6.5} cm{sup -3} and ortho-formaldehyde column densities per unit line width between 10{sup 13.5} and 10{sup 14.5} cm{sup -2} (km s{sup -1}){sup -1} are found for most objects, in general agreement with existing measurements. A detailed analysis of the advantages and limitations to this densitometry technique is also presented. We find that H{sub 2}CO 3{sub 12}-3{sub 13}/4{sub 13}-4{sub 14} densitometry proves to be best suited to objects with T{sub K} {approx}> 100 K, above which the H{sub 2}CO LVG models become relatively independent of kinetic temperature. This study represents the first detection of these H{sub 2}CO K-doublet transitions in all but one object in our sample. The ease with which these transitions were detected, coupled with their unique sensitivity to spatial density, makes them excellent monitors of density in molecular clouds for future experiments. We also report the detection of the 9{sub 2}-8{sub 1} A {sup -} (29 GHz) transition of CH{sub 3}OH toward six sources.

  13. 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.

  14. Rotational Velocities for Early-Type Stars in the Young Large Magellanic Cloud Cluster R136: Further Study of the Relationship Between Rotation Speed and Density in Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Wolff, S. C.; Strom, S. E.; Cunha, K.; Daflon, S.; Olsen, K.; Dror, D.

    2008-09-01

    loss through stellar winds), but rather may reflect differences in the rotation speeds imprinted at the time the stars formed. This result appears most certain for stars with masses in the range 6-12 M sun; for stars of higher masses, larger samples from regions of differing densities are needed to more firmly establish that the observed differences are imprinted during the stellar assembly phase as opposed to being the result of subsequent evolution. We further argue that the differences in N(v sin i) between R136 and the LMC and MWG field stars likely result from a difference in the initial conditions in protostellar cores that are found in the types of molecular cloud regions that form rich, dense clusters (e.g., higher turbulent speeds) rather than from differences in the environment surrounding the core (e.g., stellar density, UV radiation field).

  15. 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

  16. Star-forming Substructure within Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Di Francesco, James

    2013-03-01

    Wide-field far-infrared/submillimeter continuum maps of molecular clouds by the Herschel Space Observatory GBS and HOBYS surveys are revealing the star-forming substructures that lead to star formation in dense gas. In particular, these maps have revealed the central role in clouds of filaments, likely formed through turbulent motions. These filaments appear to be non-isothermal and fragment into cores only when their column densities exceed a stability threshold. Organizations of filament networks suggest the relative role of turbulence and gravity can be traced in different parts of a cloud, and filament intersections may lead to larger amounts of mass flow that form the precursors of high-mass stars or clusters.

  17. 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.

  18. Ammonia Thermometry of Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Mangum, Jeffrey G.; Darling, Jeremy; Henkel, Christian; Menten, Karl M.; MacGregor, Meredith; Svoboda, Brian E.; Schinnerer, Eva

    2013-12-01

    With a goal toward deriving the physical conditions in external galaxies, we present a study of the ammonia (NH3) 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 NH3, 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 2Π3/2 J = 9/2 absorption toward Arp 220. We also report the first detections of non-metastable NH3 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.

  19. The Role of Star-forming Galaxies in Cosmic Reionization

    NASA Astrophysics Data System (ADS)

    Rehagen, Robin Eileen Mostardi

    One of the foremost goals in the study of cosmological reionization is understanding the nature of the sources of the ionizing photons. The search for leaking ionizing radiation from high-redshift star-forming galaxies has resulted in dozens of promising candidates, yet few confirmed detections. In this thesis, I present results from a survey for z ˜ 2.85 ionizing Lyman-Continuum (LyC) emission in the HS1549 + 1933 field and place constraints on the amount of ionizing radiation escaping from star-forming galaxies. Using a custom narrowband filter (NB3420) tuned to wavelengths just below the Lyman limit at z > = 2.82, I probe the LyC spectral region of 49 Lyman break galaxies (LBGs) and 91 Lyman-alpha emitters (LAEs) spectroscopically confirmed at z > =2.82. I also present high-resolution, UVJH follow-up HST observations of 16 z ˜ 3 candidate LyC emitters identified with the NB3420 filter. With these follow-up data, I obtain high spatial-resolution photometric redshifts of all subarcsecond components of the high-redshift galaxies in order to eliminate foreground contamination and identify robust candidates for leaking LyC emission. I find only one object with a robust LyC detection that is not due to foreground contamination. A comparison with representative samples of LBGs indicates that the most exceptional aspect of the stellar population fit to this object is its young age (< 50 Myr). I obtain a contamination-free estimate for the comoving specific ionizing emissivity at z = 2.85, indicating (with large uncertainties) that star-forming galaxies provide roughly the same contribution as QSOs to the ionizing background at this redshift. The results of my thesis work show that foreground contamination prevents ground-based LyC studies from obtaining a full understanding of LyC emission from z ˜ 3 star-forming galaxies. Future progress in direct LyC searches is contingent upon the elimination foreground contaminants through high spatial-resolution observations

  20. Understanding the star-forming environment in stellar clusters

    NASA Astrophysics Data System (ADS)

    Wang, Shiya

    The main goal of this thesis is to investigate the physical conditions of the star-forming environment in stellar clusters, especially for the formation of low-mass cluster members. Embedded, young, and intermediate-mass stellar clusters around Herbig Ae/Be stars are sampled. Mid- and near-infrared observations identifying young stars and millimeter interferometric observations probing dense molecular gas and dust continuum are presented. These observations are used to reveal the large-scale young stellar population around the vicinity where the sampled clusters form, probe the physical conditions of dense molecular clumps which are capable of forming individual low-mass cluster members, and examine the influence of the most massive star in the cluster on its siblings and natal cluster-forming cloud. This study shows that stars within the cluster tend to seem younger than those outside the cluster, suggesting a higher and continuous star-forming rate within the cluster than outside, or massive stars are initiated later than low-mass stars within the same cloud. A thorough investigation of young stars and dense gas toward the MWC 1080 cluster further suggests a domination of the most massive star in the cluster on both the natal cloud dispersal and its low-mass cluster members. As active outflows and winds from the Herbig Ae/Be stars increase the non-thermal motion in the cloud, low-mass cluster members are formed within denser and more turbulent cores, than isolated low-mass star-forming cores. In addition, the strong gas dispersal from the Herbig Ae/Be stars also helps the removal of the circumstellar material around nearby low-mass stars. This makes these low-mass cluster members appear older. In summary, this thesis provides the observational evidence showing how the most massive star in the cluster affects the formation and evolution of low-mass cluster members and the physical conditions of star formation in the cluster.

  1. Diffuse X-Ray Emission from Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Sarkar, Kartick C.; Nath, Biman B.; Sharma, Prateek; Shchekinov, Yuri

    2016-02-01

    We study the diffuse X-ray luminosity (LX) of star-forming galaxies using two-dimensional axisymmetric hydrodynamical simulations and analytical considerations of supernovae-(SNe-)driven galactic outflows. We find that the mass loading of the outflows, a crucial parameter for determining the X-ray luminosity, is constrained by the availability of gas in the central star-forming region, and a competition between cooling and expansion. We show that the allowed range of the mass loading factor can explain the observed scaling of LX with star formation rate (SFR) as {L}{{X}}\\quad \\propto SFR2 for SFR ≳ \\quad 1 {M}⊙ yr-1, and a flatter relation at low SFRs. We also show that the emission from the hot circumgalactic medium (CGM) in the halo of massive galaxies can explain the large scatter in the {L}{{X}}{--}{SFR} relation for low SFRs (≲few {M}⊙ yr-1). Our results suggest that galaxies with small SFRs and large diffuse X-ray luminosities are excellent candidates for the detection of the elusive CGM.

  2. 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).

  3. Distributions of Long-lived Radioactive Nuclei Provided by Star-forming Environments

    NASA Astrophysics Data System (ADS)

    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 40K, 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 40K 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.

  4. Infrared Properties of Star Forming Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Vaduvescu, Ovidiu

    2005-11-01

    Dwarf galaxies are the most common galaxies in the Universe. They are systems believed to consist of matter in a near-primordial state, from which giant galaxies probably form. As such, they are important probes for studying matter in its near-primordial state. In an effort to study the main physical and chemical properties of dwarfs, the present thesis focuses upon the main physical properties of dwarfs. Two classes of star forming dwarf galaxies are considered: dwarf irregulars (dIs), and blue compact dwarfs (BCDs). A third class, dwarf ellipticals (dEs), is studied based on its structural properties and compared with dIs. Possible evolutionary connections are addressed between dIs and BCDs. To measure the luminosity, deep imaging in the near-infrared (NIR) is considered. Compared with the visible, the NIR domain gives a better gauge of the galaxy mass contained in the old stellar populations, minimising the starburst contribution and also the effects of extinction. Two observing samples of star-forming dwarf galaxies are considered. The first includes 34 dIs in the Local Volume closer than 5 Mpc. The second sample includes 16 BCDs in the Virgo Cluster. In six observing runs between 2001 and 2004, we acquired deep NIR images (J and K_s) using the 3.6m Canada-France-Hawaii-Telescope (CFHT) in Hawaii and the 2.1m telescope at the National Astronomical Observatory ''San Pedro Martir'' (OAN-SPM) in Mexico. Deep spectrocopy was acquired in 2003 on the 8.1m Gemini-North telescope in Hawaii. We completed the observed samples with spectroscopic data from the literature, and photometry from the 2MASS survey and GOLDMine database. From a statistical study at CFHT, we derived some strategies necessary to image optimally faint extended sources in the NIR. Due to the airglow variation in the atmosphere and the thermal contribution of the dome, telescope and the instrumentation, repeated observations of the sky must be alternated every 3-4 minutes with the science images, in

  5. The Orion star-forming complex

    NASA Astrophysics Data System (ADS)

    Hasegawa, Tetsuo

    High-resolution images of the Orion Nebula in the millimeter wave emission lines of CS (49 GHz and 98 GHz), and CO (115 GHz) obtained with the Nobeyama telescope are presented and compared with optical, IR, and interferometric radio images. The images reveal activities associated with star formation. The images of the 49-GHz and 98-GHz lines of CS show a long and narrow N-S ridge of dense molecular gas. Two major clumps are recognized on the ridge: one is associated with the KL object, and the other is 100 arcsec south of it. The images of the 115 GHz CO line indicate interaction between the molecular cloud and the H II region, with shocks observed at the interaction between the two regions. The CO images reveal filamentary structures ('streamers') stretching radially from the KL region. They run far beyond the boundary of the molecular high-velocity flow and are accompanied by HH objects. They may manifest mostly unseen high-velocity flows driven by the activity of young stellar objects.

  6. 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.

  7. On the massive star-forming capacity of molecular clouds

    NASA Technical Reports Server (NTRS)

    Franco, Jose; Shore, Steven N.; Tenorio-Tagle, Guillermo

    1994-01-01

    Assuming that photoionization is the self-limiting process for continued star formation, we estimate the maximum number of massive (OB) stars that can form within a molecular cloud. The most efficient cloud destruction mechanism in the early stages of H II region evolution is the evaporation of the cloud by stars located near the cloud boundary. The maximum number of OB stars is of order 1 per 10(exp 4) solar mass of average molecular gas, or 10 per 10(exp 4) solar mass of dense molecular gas. The resulting star-forming efficiencies within cloud complexes range from 2% to 16% depending on both the location of the stars in the cloud and the details of the initial mass function, with an overall value of about 5% for average molecular gas.

  8. 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.

  9. 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).

  10. 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.

  11. 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

  12. 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.

  13. ATLASGAL - towards a complete sample of massive star forming clumps

    NASA Astrophysics Data System (ADS)

    Urquhart, J. S.; Moore, T. J. T.; Csengeri, T.; Wyrowski, F.; Schuller, F.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Menten, K. M.; Walmsley, C. M.; Bronfman, L.; Pfalzner, S.; König, C.; Wienen, M.

    2014-09-01

    By matching infrared-selected, massive young stellar objects (MYSOs) and compact H II regions in the Red MSX Source survey to massive clumps found in the submillimetre ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey, we have identified ˜1000 embedded young massive stars between 280° < ℓ < 350° and 10° < ℓ < 60° with | b | < 1.5°. Combined with an existing sample of radio-selected methanol masers and compact H II regions, the result is a catalogue of ˜1700 massive stars embedded within ˜1300 clumps located across the inner Galaxy, containing three observationally distinct subsamples, methanol-maser, MYSO and H II-region associations, covering the most important tracers of massive star formation, thought to represent key stages of evolution. We find that massive star formation is strongly correlated with the regions of highest column density in spherical, centrally condensed clumps. We find no significant differences between the three samples in clump structure or the relative location of the embedded stars, which suggests that the structure of a clump is set before the onset of star formation, and changes little as the embedded object evolves towards the main sequence. There is a strong linear correlation between clump mass and bolometric luminosity, with the most massive stars forming in the most massive clumps. We find that the MYSO and H II-region subsamples are likely to cover a similar range of evolutionary stages and that the majority are near the end of their main accretion phase. We find few infrared-bright MYSOs associated with the most massive clumps, probably due to very short pre-main-sequence lifetimes in the most luminous sources.

  14. 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.

  15. Abundances in "Green Pea" Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Hawley, Steven A.

    2012-01-01

    He II λ4686 is identified in the spectra of nine of the original "Green Peas," a type of compact star-forming galaxy characterized by low mass; low metallicity; strong [O III] λλ4959, 5007; and redshifts in the range of ~0.1-0.4. Measured λ4686/Hβ ratios are roughly 1-2%, consistent with photoionization by Wolf-Rayet stars. Emission-line intensities are measured from Sloan Digital Sky Survey spectra for 71 Green Peas and are used to determine Te-based abundances of O, N, Ne, S, and He. Neon abundances confirm the mass-metallicity relation inferred from O/H. The N/O ratio is roughly constant with O/H, and the average N/O is evidence of a modest nitrogen enhancement compared with other low-metallicity galaxies. Nitrogen enrichment could be due to Wolf-Rayet stars or to intermediate-mass stars during a previous quiescent period. The Te-based abundances allow a reevaluation of some of the strong-line methods favored for estimating O/H or N/O in large spectroscopic surveys of star-forming galaxies. Photoionization by Wolf-Rayet stars raises questions about the validity of strong-line methods based on [N II]/Hα, [N II]/[O III], or [N II]/[S II], as those line ratios are known to be ionization-sensitive. Analysis of these measurements shows that ionization, low metallicity, and the small variation in important line ratios in the Green Pea spectra all affect the behavior of one or more of the N2, O3N2, N2O2 and N2S2 strong-line methods. The previous findings for trends in O/H and N/O in the Green Peas can be reproduced and the discrepancies can be explained. In particular, the reported increase of N/O with O/H appears to be a bias introduced by combining N2 with N2S2. N2O2 does not give valid results in the Green Peas, while N2 and N2S2 do, although the calibrations of the N2 and N2S2 methods based on Green Pea abundances are different from the existing calibrations based primarily on abundances in extragalactic H II regions and H II galaxies.

  16. A comprehensive photometric study of circumnuclear star-forming rings - I. The sample

    NASA Astrophysics Data System (ADS)

    Álvarez-Álvarez, Mar; Díaz, Angeles I.; Terlevich, Elena; Terlevich, Roberto

    2015-08-01

    We present photometry in U, B, V, R and I continuum bands and in Hα and Hβ emission lines for a sample of 336 circumnuclear star-forming regions located in early-type spiral galaxies with different levels of activity in their nuclei. They are nearby galaxies, with distances less than 100 Mpc, 60 per cent of which are considered as interacting objects. This survey of 20 nuclear rings aims to provide insight into their star formation properties as age, stellar population and star formation rate. Extinction-corrected Hα luminosities range from 1.3 × 1038 to 4 × 1041 erg s-1, with most of the regions showing values between 39.5 ≤ logL(Hα) ≤ 40, which implies masses for the ionizing clusters higher than 2 × 105 M⊙. Hα and Hβ images have allowed us to obtain an accurate measure of extinction. We have found an average value of AV = 1.85 mag. (U - B) colour follows a two maximum distribution around (U - B) ≃ -0.7, and -0.3; (R - I) also presents a bimodal behaviour, with maximum values of 0.6 and 0.9. Reddest (U - B) and (R - I) regions appear in non-interacting galaxies. Reddest (R - I) regions lie in strongly barred galaxies. For a significant number of H II regions, the observed colours and equivalent widths are not well reproduced by single burst evolutionary theoretical models.

  17. 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.

  18. NUCLEAR STAR-FORMING RING OF THE MILKY WAY: SIMULATIONS

    SciTech Connect

    Kim, Sungsoo S.; Jeon, Myoungwon; Saitoh, Takayuki R.; Figer, Donald F.; Merritt, David; Wada, Keiichi

    2011-07-01

    We present hydrodynamic simulations of gas clouds in the central kpc region of the Milky Way that is modeled with a three-dimensional bar potential. Our simulations consider realistic gas cooling and heating, star formation, and supernova feedback. A ring of dense gas clouds forms as a result of X{sub 1}-X{sub 2} orbit transfer, and our potential model results in a ring radius of {approx}200 pc, which coincides with the extraordinary reservoir of dense molecular clouds in the inner bulge, the Central Molecular Zone (CMZ). The gas clouds accumulated in the CMZ can reach high enough densities to form stars, and with an appropriate choice of simulation parameters, we successfully reproduce the observed gas mass and the star formation rate (SFR) in the CMZ, {approx}2 x 10{sup 7} M{sub sun} and {approx}0.1 M{sub sun} yr{sup -1}. Star formation in our simulations takes place mostly in the outermost X{sub 2} orbits, and the SFR per unit surface area outside the CMZ is much lower. These facts suggest that the inner Galactic bulge may harbor a mild version of the nuclear star-forming rings seen in some external disk galaxies. Furthermore, from the relatively small size of the Milky Way's nuclear bulge, which is thought to be a result of sustained star formation in the CMZ, we infer that the Galactic inner bulge probably had a shallower density profile or stronger bar elongation in the past.

  19. 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

  20. 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.

  1. 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

  2. THE STRUCTURE OF THE STAR-FORMING CLUSTER RCW 38

    SciTech Connect

    Winston, E.; Wolk, S. J.; Bourke, T. L.; Spitzbart, B.; Megeath, S. T.; Gutermuth, R.

    2011-12-20

    We present a study of the structure of the high-mass star-forming region RCW 38 and the spatial distribution of its young stellar population. Spitzer Infrared Array Camera (IRAC) photometry (3-8 {mu}m) is combined with Two Micron All Sky Survey near-IR data to identify young stellar objects (YSOs) by IR-excess emission from their circumstellar material. Chandra X-ray data are used to identify class III pre-main-sequence stars lacking circumstellar material. We identify 624 YSOs: 23 class 0/I and 90 flat spectrum protostars, 437 class II stars, and 74 class III stars. We also identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars exhibit IR-variability, including 7 class 0/I and 12 flat spectrum YSOs. A further 177 tentative candidates are identified by their location in the IRAC [3.6] versus [3.6]-[5.8] color-magnitude diagram. We find strong evidence of subclustering in the region. Three subclusters were identified surrounding the central cluster, with massive and variable stars in each subcluster. The central region shows evidence of distinct spatial distributions of the protostars and pre-main-sequence stars. A previously detected IR cluster, DB2001{sub O}bj36, has been established as a subcluster of RCW 38. This suggests that star formation in RCW 38 occurs over a more extended area than previously thought. The gas-to-dust ratio is examined using the X-ray derived hydrogen column density, N{sub H} and the K-band extinction, and found to be consistent with the diffuse interstellar medium, in contrast with Serpens and NGC 1333. We posit that the high photoionizing flux of massive stars in RCW 38 affects the agglomeration of the dust grains.

  3. 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.

  4. 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.

  5. Deep Imaging Surveys of Star-forming Clouds. III. Herbig-Haro Objects in the Perseus Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Walawender, Josh; Bally, John; Reipurth, Bo

    2005-05-01

    We present a catalog of 72 new Herbig-Haro (HH) objects discovered in the Perseus molecular cloud. There are 69 previously cataloged HH objects in this region, and the new discoveries bring the total number of known HH objects in Perseus to 141. Individual outflows often contain several distinct HH objects. These observations demonstrate that the Perseus molecular cloud is one of the most active star-forming regions in the solar vicinity. We explore different methods for probing the momentum injection rate of outflows and examine whether outflows can drive turbulence within the molecular cloud. On the scale of the entire Perseus cloud, the shocks produced by outflows from young stars may not inject momentum at a sufficient rate to counter the rate at which momentum decays. However, intense outflow activity within individual cloud cores with high star formation rates, such as NGC 1333, may be sufficient to locally support or even disrupt the core.

  6. 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…

  7. Chemical Abundance Gradients in the Star-forming Ring Galaxies

    NASA Astrophysics Data System (ADS)

    Korchagin, Vladimir; Vorobyov, Eduard; Mayya, Y. D.

    1999-09-01

    Ring waves of star formation, propagating outward in the galactic disks, leave chemical abundance gradients in their wakes. We show that the relative [Fe/O] abundance gradients in ring galaxies can be used as a tool for determining the role of the SN Ia explosions in their chemical enrichment. We consider two mechanisms--a self-induced wave and a density wave--that can create outwardly propagating star-forming rings in a purely gaseous disk and demonstrate that the radial distribution of the relative [Fe/O] abundance gradients depends neither on the particular mechanism of the wave formation anor on the parameters of the star-forming process. We show that the [Fe/O] profile is determined by the velocity of the wave, the initial mass function, and the initial chemical composition of the star-forming gas. If the role of SN Ia explosions is negligible in the chemical enrichment, the ratio [Fe/O] remains constant throughout the galactic disk with a steep gradient at the wave front. If SN Ia stars are important in the production of cosmic iron, the [Fe/O] ratio has a gradient in the wake of the star-forming wave with the value depending on the frequency of SN Ia explosions.

  8. New Herbig-Haro objects in star-forming regions

    NASA Technical Reports Server (NTRS)

    Reipurth, BO; Graham, J. A.

    1988-01-01

    A list of 25 new Herbig-Haro objects, HH 58 to HH 82, in the Orion molecular clouds and in southern molecular cloud complexes has been compiled. CCD images in the S II 6717, 6731 forbidden lines are presented for the objects, together with a few spectra and some IR observations. The individual objects and, when identified, their energy sources are discussed. HH 65 is located in the red lobe of the bipolar outflow associated with the highly variable reflection nebula Re 50. HH 67 is a 22-arcsec long sinusoidal jet. HH 68/69 consists of a long, linear chain of four HH knots. HH 72 emerges from a 120-solar luminosity IRAS source embedded in a Bok globule. HH 79 is the first HH object discovered in the Ophiuchus clouds. HH 80/81 in Sagittarius are among the brightest HH objects known, have complex velocities, high excitation conditions and emerge from a 6000-solar luminosity young B-star. HH 82 is associated with the bright variable star S Coronae Australis.

  9. 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.

  10. The HNC/HCN ratio in star-forming regions

    SciTech Connect

    Graninger, Dawn M.; Öberg, Karin I.; Herbst, Eric; Vasyunin, Anton I.

    2014-05-20

    HNC and HCN, typically used as dense gas tracers in molecular clouds, are a pair of isomers that have great potential as a temperature probe because of temperature dependent, isomer-specific formation and destruction pathways. Previous observations of the HNC/HCN abundance ratio show that the ratio decreases with increasing temperature, something that standard astrochemical models cannot reproduce. We have undertaken a detailed parameter study on which environmental characteristics and chemical reactions affect the HNC/HCN ratio and can thus contribute to the observed dependence. Using existing gas and gas-grain models updated with new reactions and reaction barriers, we find that in static models the H + HNC gas-phase reaction regulates the HNC/HCN ratio under all conditions, except for very early times. We quantitatively constrain the combinations of H abundance and H + HNC reaction barrier that can explain the observed HNC/HCN temperature dependence and discuss the implications in light of new quantum chemical calculations. In warm-up models, gas-grain chemistry contributes significantly to the predicted HNC/HCN ratio and understanding the dynamics of star formation is therefore key to model the HNC/HCN system.

  11. Water as a probe of star-forming regions

    NASA Technical Reports Server (NTRS)

    Rodriguez-Kuiper, E. N.; Kuiper, T. B. H.

    1982-01-01

    Preliminary calculations employing statistical equilibrium techniques were carried out to determine brightness temperatures of water transitions occurring in the submillimeter band. The interesting candidates appear to be the 325 GHz, 380 GHz, and 448 GHz transitions, they are compared with the 183 GHz and 380 GHz transitions observed in the Orion Kleinmann-Low nebula and the combined results seem to be consistent with H2 densities of 100,000 -1 million cm-3 and a water column density of approximately 10 to 18th power. This implies a relative abundance of approximately 0.00001 which means that water may be about one twentieth of CO. In addition, it was found that for the conditions of the Orion plateau source, the 448 GHz line is expected to be a mild maser.

  12. 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.

  13. The interstellar distance toolbox: deriving distances to star forming regions

    NASA Astrophysics Data System (ADS)

    Marshall, D. J.; Montier, L. A.; Ristorcelli, I.; Juvela, M.; Grenier, I. A.; McGehee, P.; Montillaud, J.; Paladini, R.; Pelkonen, V.-M.; Remy, Q.; Planck Collaboration

    Fully characterising interstellar clouds requires reliable distance estimates. The study of a large number of clouds is therefore quite challenging, as the different methods do not always agree and furthermore are only able to provide an inhomogeneous sampling of the cloud population. Distances to cold dark clouds are particularly interesting as these constitute the population of pre-stellar cores. The Planck Catalogue of Galactic Cold Clumps (PGCC) is an all-sky catalogue of Galactic cold clump candidates detected by Planck . The PGCC catalogue is an observational catalogue consisting exclusively of Galactic cold sources, thus potentially sites of future star formation. The three highest Planck bands (857, 545, 353 GHz) have been combined with IRAS data at 3 THz to perform a multi-frequency detection of sources colder than their local environment. It contains 13188 Galactic sources spread across the entire sky. Using seven independent methods, reliable distance estimates have been obtained for 5574 sources, which allows us to derive their physical properties such as their mass, physical size, mean density and luminosity. The PGCC sources are located mainly in the solar neighbourhood, up to a distance of 10.5 kpc towards the Galactic centre, and range from low-mass cores to large molecular clouds. Modifications to existing methods along with entirely new ones open up the possibility to re-analyse the catalogue with more robust distance information.

  14. Grain surface chemistry in star-forming regions

    NASA Astrophysics Data System (ADS)

    Taquet, Vianney

    2012-12-01

    The first stages of star formation are accompanied by an evolution of the chemistry, starting from simple molecules in cold dark clouds to the detection of complex organic molecules around Class 0 protostars. Although mostly composed of gas, these clouds also contain small amounts of microscopic dust. The contribution of this dust is nevertheless important because it acts as a catalyst for the formation of key molecules seen in cold interstellar ices, such as water or methanol. These ices are believed to be the first step towards the rich chemistry seen in the warm envelope of protostars. During my thesis, I focused on this first step and I did so by taking a twofold approach. i) Modelling. I have developed an astrochemical model coupling the chemistry in the gas phase and on the grain surfaces. This model follows the multilayer formation of interstellar ices and allows us to investigate the influence of key physical, chemical, and surface parameters, such as the grain porosity, on the chemical composition of ices via a multiparameter approach. The model has been applied to predict the chemical differentiation and the deuteration of interstellar ices. To this end, I have built up a chemical network taking into account the most recent experimental and theoretical works. I applied then the model to various cases. For example, I showed that ices are heterogeneous and their composition are sensitive to the physical conditions as well as several grain surface parameters. The high deuteration of formaldehyde, and methanol observed around low-mass protostars has been predicted by a dense (nH ∼ 5 × 10^6 cm-3) and fast (∼ 5000 years) phase while the lower deuteration of water is predicted for typical molecular cloud conditions. The deuterium fractionation is very sensitive and can be used as a tracer of the physical conditions. ii) Observations. I have been involved in observational projects whose goals are related to the grain surface chemical problems. I obtained the following three results. We showed an evolution of the selective deuteration with the protostar type, the [CH2DOH]/[CH3OD] abundance ratio decreasing with the protostar mass. Interferometric mapping of deuterated water towards low- mass protostars has allowed us to constrain a relatively high deuteration level of water in new sources. Finally, we detected several complex organic molecules in a cold prestellar core for the first time, challenging the current scenario of complex organic molecules in warm conditions.

  15. Star Formation in Isolated LIRGs: Clues to Star-forming Processes at Higher z

    NASA Astrophysics Data System (ADS)

    Fuentes-Carrera, Isaura; Olguín, Lorenzo; Ambrocio-Cruz, Patricia; Verley, Simon; Rosado, Margarita; Verdes-Montenegro, Lourdes; Repetto, Paolo; Vázquez, Celia; Aguilera, Verónica

    2011-12-01

    Luminous infrared galaxies (LIRGs) are galaxies with LIR > 1011 L⊙. For a star-forming galaxy to emit at a LIRG level, it must have a very high star formation rate (SFR). In the local Universe, the star formation (SF) is primarily triggered by interactions. However, at intermediate redshift, a large fraction of LIRGs are disk galaxies with little sign of recent merger activity. The question arises whether the intermediate redshift LIRGs are ``triggered'' or experiencing ``normal'', if elevated, SF. Understanding these SF processes is important since this type of systems may have contributed to 20% or more of the cosmic SFR in the early Universe. In order to address this issue we study similar systems in the Local Universe, that is isolated late-type galaxies displaying LIRG activity. We use different observational techniques in order to trace the star-forming history of these systems. Here we present preliminary results.

  16. 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

  17. Metal Abundances of KISS Galaxies. V. Nebular Abundances of 15 Intermediate Luminosity Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Hirschauer, Alec S.; Salzer, John J.; Bresolin, Fabio; Saviane, Ivo; Yegorova, Irina

    2015-09-01

    We present high signal-to-noise ratio spectroscopy of 15 emission-line galaxies cataloged in the KPNO International Spectroscopic Survey, selected for their possession of high equivalent width [O iii] lines. The primary goal of this study was to attempt to derive direct-method (Te) abundances for use in constraining the upper-metallicity branch of the {R}23 relation. The spectra cover the full optical region from [O ii]λλ3726,3729 to [S iii]λλ9069,9531 and include the measurement of [O iii]λ4363 in 13 objects. From these spectra, we determine abundance ratios of helium, nitrogen, oxygen, neon, sulfur, and argon. We find these galaxies to predominantly possess oxygen abundances in the range of 8.0 ≲ 12+log(O/H) ≲ 8.3. We present a comparison of direct-method abundances with empirical strong-emission-line techniques, revealing several discrepancies. We also present a comparison of direct-method oxygen abundance calculations using electron temperatures determined from emission lines of O++ and S++, finding a small systematic shift to lower Te (∼1184 K) and higher metallicity (∼0.14 dex) for sulfur-derived Te compared to oxygen-derived Te. Finally, we explore in some detail the different spectral activity types of targets in our sample, including regular star-forming galaxies, those with suspected AGN contamination, and a local pair of low-metallicity, high-luminosity compact objects.

  18. 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).

  19. The correlation of dust and gas emission in star-forming environments

    NASA Astrophysics Data System (ADS)

    Morgan, L. K.; Moore, T. J. T.; Eden, D. J.; Hatchell, J.; Urquhart, J. S.

    2014-05-01

    We present ammonia maps of portions of the W3 and Perseus molecular clouds in order to compare gas emission with submillimetre continuum thermal emission which are commonly used to trace the same mass component in star-forming regions, often under the assumption of local thermodynamic equilibrium (LTE). The Perseus and W3 star-forming regions are found to have significantly different physical characteristics consistent with the difference in size scales traced by our observations. Accounting for the distance of the W3 region does not fully reconcile these differences, suggesting that there may be an underlying difference in the structure of the two regions. Peak positions of submillimetre and ammonia emission do not correlate strongly. Also, the extent of diffuse emission is only moderately matched between ammonia and thermal emission. Source sizes measured from our observations are consistent between regions, although there is a noticeable difference between the submillimetre source sizes with sources in Perseus being significantly smaller than those in W3. Fractional abundances of ammonia are determined for our sources which indicate a dip in the measured ammonia abundance at the positions of peak submillimetre column density. Virial ratios are determined which show that our sources are generally bound in both regions, although there is considerable scatter in both samples. We conclude that sources in Perseus are bound on smaller scales than in W3 in a way that may reflect their previous identification as low- and high-mass, respectively. Our results indicate that assumptions of local thermal equilibrium and/or the coupling of the dust and gas phases in star-forming regions may not be as robust as commonly assumed.

  20. 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

  1. Diversity of chemistry and excitation conditions in the high-mass star forming complex W33

    NASA Astrophysics Data System (ADS)

    Immer, K.; Galván-Madrid, R.; König, C.; Liu, H. B.; Menten, K. M.

    2014-12-01

    The object W33 is a giant molecular cloud that contains star forming regions at various evolutionary stages from quiescent clumps to developed H ii regions. Since its star forming regions are located at the same distance and the primary material of the birth clouds is probably similar, we conducted a comparative chemical study to trace the chemical footprint of the different phases of evolution. We observed six clumps in W33 with the Atacama Pathfinder Experiment (APEX) telescope at 280 GHz and the Submillimeter Array (SMA) at 230 GHz. We detected 27 transitions of 10 different molecules in the APEX data and 52 transitions of 16 different molecules in the SMA data. The chemistry on scales larger than ~0.2 pc, which are traced by the APEX data, becomes more complex and diverse the more evolved the star forming region is. On smaller scales traced by the SMA data, the chemical complexity and diversity increase up to the hot core stage. In the H ii region phase, the SMA spectra resemble the spectra of the protostellar phase. Either these more complex molecules are destroyed or their emission is not compact enough to be detected with the SMA. Synthetic spectra modelling of the H2CO transitions, as detected with the APEX telescope, shows that both a warm and a cold component are needed to obtain a good fit to the emission for all sources except for W33 Main1. The temperatures and column densities of the two components increase during the evolution of the star forming regions. The integrated intensity ratios N2H+(3-2)/CS(6-5) and N2H+(3-2)/H2CO(42,2-32,1) show clear trends as a function of evolutionary stage, luminosity, luminosity-to-mass ratio, and H2 peak column density of the clumps and might be usable as chemical clocks. The integrated intensity line and continuum maps of the APEX telescope and the SMA are only available as FITS files at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc

  2. 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.

  3. 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.

  4. Submillimeter Array High-angular Resolution Observations of the Monoceros R2 Star-forming Cluster

    NASA Astrophysics Data System (ADS)

    Dierickx, M.; Jiménez-Serra, I.; Rivilla, V. M.; Zhang, Q.

    2015-04-01

    We present the first high-angular resolution study of the MonR2 star-forming complex carried out with the Submillimeter Array at (sub-)millimeter wavelengths. We image the continuum and molecular line emission toward the young stellar objects in MonR2 at 0.85 and 1.3 mm, with resolutions ranging from 0.″ 5 to ˜3″. While free-free emission dominates the IRS1 and IRS2 continuum, dust thermal emission prevails for IRS3 and IRS5, giving envelope masses of ˜0.1-0.3 {{M}⊙ }. IRS5 splits into at least two sub-arcsecond scale sources, IRS5B and the more massive IRS5A. Our 12CO(2-1) images reveal 11 previously unknown molecular outflows in the MonR2 clump. Comparing these outflows with known IR sources in the IRS5 and IRS3 subclusters allows for tentative identification of driving stars. Line images of molecular species such as CH3CN or CH3OH show that, besides IRS3 (a well-known hot molecular core), IRS5 is also a chemically active source in the region. The gas excitation temperature derived from CH3CN lines toward IRS5 is 144 ± 15 K, indicating a deeply embedded protostar at the hot-core evolutionary stage. Spectral energy distribution fitting of IRS5 gives a mass of ˜7 M ⊙ and a luminosity of 300 {{L}⊙ } for the central source. The derived physical properties of the CO outflows suggest that they contribute to the turbulent support of the MonR2 complex and to the gas velocity dispersion in the clump’s center. The detection of a large number of CO outflows widespread across the region supports the competitive accretion scenario as origin of the MonR2 star cluster.

  5. EXTENDED Ly{alpha} EMISSION AROUND STAR-FORMING GALAXIES

    SciTech Connect

    Zheng Zheng; Cen Renyue; Weinberg, David; Trac, Hy; Miralda-Escude, Jordi

    2011-10-01

    Ly{alpha} photons that escape the interstellar medium of star-forming galaxies may be resonantly scattered by neutral hydrogen atoms in the circumgalactic and intergalactic media, thereby increasing the angular extent of the galaxy's Ly{alpha} emission. We present predictions of this extended, low surface brightness Ly{alpha} emission based on radiative transfer modeling in a cosmological reionization simulation. The extended emission can be detected from stacked narrowband images of Ly{alpha} emitters (LAEs) or of Lyman break galaxies (LBGs). Its average surface brightness profile has a central cusp, then flattens to an approximate plateau beginning at an inner characteristic scale below {approx}0.2 Mpc (comoving), then steepens again beyond an outer characteristic scale of {approx}1 Mpc. The inner scale marks the transition from scattered light of the central source to emission from clustered sources, while the outer scale marks the spatial extent of scattered emission from these clustered sources. Both scales tend to increase with halo mass, UV luminosity, and observed Ly{alpha} luminosity. The extended emission predicted by our simulation is already within reach of deep narrowband photometry using large ground-based telescopes. Such observations would test radiative transfer models of emission from LAEs and LBGs, and they would open a new window on the circumgalactic environment of high-redshift star-forming galaxies.

  6. 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.

  7. ROSAT observations of the Chamaeleon star forming cloud

    NASA Technical Reports Server (NTRS)

    Feigelson, E. D.; Casanova, S.; Montmerle, T.; Guibert, J.

    1993-01-01

    Two-soft X-ray images of the Chamaeleon I star forming cloud obtained with the ROSAT Position Sensitive Proportional Counter (PSPC) are presented. Seventy reliable, and perhaps 19 additional, X-ray sources are found. Up to Ninety percent of these sources are certainly or probably identified with T Tauri stars formed in the cloud. Twenty to 35 are probably previously unrecognized 'weak' T Tauri (WTT) stars. T Tauri X-ray luminosities range from log bar-L(sub x) less than 28.8 to 31.1 erg/s, or 10(exp 2) - 10(exp 4) times solar levels, with mean value of log bar-L(sub x) = 10(exp 29.2) erg/s in the 0.2-2.5 keV band. The X-ray luminosities of well-studied Chamaeleon cloud members are correlated with a complex of four stellar properties: effective temperature, mass, radius and bolometric luminosity. The spatial distribution, Hertzsprung-Russell (H-R) diagram locations of the stars indicate WTT and CTT are coeval. The total premain sequence population of the cloud is likely to be greater than 100 stars, with WTT stars outnumbering 'classical' T Tauri (CTT) stars by approximately 2:1.

  8. 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.

  9. 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.

  10. Non-linearity and environmental dependence of the star-forming galaxies main sequence

    NASA Astrophysics Data System (ADS)

    Erfanianfar, G.; Popesso, P.; Finoguenov, A.; Wilman, D.; Wuyts, S.; Biviano, A.; Salvato, M.; Mirkazemi, M.; Morselli, L.; Ziparo, F.; Nandra, K.; Lutz, D.; Elbaz, D.; Dickinson, M.; Tanaka, M.; Altieri, M. B.; Aussel, H.; Bauer, F.; Berta, S.; Bielby, R. M.; Brandt, N.; Cappelluti, N.; Cimatti, A.; Cooper, M. C.; Fadda, D.; Ilbert, O.; Le Floch, E.; Magnelli, B.; Mulchaey, J. S.; Nordon, R.; Newman, J. A.; Poglitsch, A.; Pozzi, F.

    2016-01-01

    Using data from four deep fields (COSMOS, AEGIS, ECDFS, and CDFN), we study the correlation between the position of galaxies in the star formation rate (SFR) versus stellar mass plane and local environment at z < 1.1. To accurately estimate the galaxy SFR, we use the deepest available Spitzer/MIPS 24 and Herschel/PACS data sets. We distinguish group environments (Mhalo ˜ 1012.5-14.2 M⊙) based on the available deep X-ray data and lower halo mass environments based on the local galaxy density. We confirm that the main sequence (MS) of star-forming galaxies is not a linear relation and there is a flattening towards higher stellar masses (M* > 1010.4-10.6 M⊙), across all environments. At high redshift (0.5 < z < 1.1), the MS varies little with environment. At low redshift (0.15 < z < 0.5), group galaxies tend to deviate from the mean MS towards the region of quiescence with respect to isolated galaxies and less-dense environments. We find that the flattening of the MS towards low SFR is due to an increased fraction of bulge-dominated galaxies at high masses. Instead, the deviation of group galaxies from the MS at low redshift is caused by a large fraction of red disc-dominated galaxies which are not present in the lower density environments. Our results suggest that above a mass threshold (˜1010.4-1010.6 M⊙) stellar mass, morphology and environment act together in driving the evolution of the star formation activity towards lower level. The presence of a dominating bulge and the associated quenching processes are already in place beyond z ˜1. The environmental effects appear, instead, at lower redshifts and have a long time-scale.

  11. 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.

    2016-05-01

    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 metalicity 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% 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% of the observed broad-band X-ray luminosity of Arp 299.

  12. 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.

  13. The mean star-forming properties of QSO host galaxies

    NASA Astrophysics Data System (ADS)

    Rosario, D. J.; Trakhtenbrot, B.; Lutz, D.; Netzer, H.; Trump, J. R.; Silverman, J. D.; Schramm, M.; Lusso, E.; Berta, S.; Bongiorno, A.; Brusa, M.; Förster-Schreiber, N. M.; Genzel, R.; Lilly, S.; Magnelli, B.; Mainieri, V.; Maiolino, R.; Merloni, A.; Mignoli, M.; Nordon, R.; Popesso, P.; Salvato, M.; Santini, P.; Tacconi, L. J.; Zamorani, G.

    2013-12-01

    Quasi-stellar objects (QSOs) occur in galaxies in which supermassive black holes (SMBHs) are growing substantially through rapid accretion of gas. Many popular models of the co-evolutionary growth of galaxies and black holes predict that QSOs are also sites of substantial recent star formation (SF), mediated by important processes, such as major mergers, which rapidly transform the nature of galaxies. A detailed study of the star-forming properties of QSOs is a critical test of these models. We present a far-infrared Herschel/PACS study of the mean star formation rate (SFR) of a sample of spectroscopically observed QSOs to z ~ 2 from the COSMOS extragalactic survey. This is the largest sample to date of moderately luminous QSOs (with nuclear luminosities that lie around the knee of the luminosity function) studied using uniform, deep far-infrared photometry. We study trends of the mean SFR with redshift, black hole mass, nuclear bolometric luminosity, and specific accretion rate (Eddington ratio). To minimize systematics, we have undertaken a uniform determination of SMBH properties, as well as an analysis of important selection effects of spectroscopic QSO samples that influence the interpretation of SFR trends. We find that the mean SFRs of these QSOs are consistent with those of normal massive star-forming galaxies with a fixed scaling between SMBH and galaxy mass at all redshifts. No strong enhancement in SFR is found even among the most rapidly accreting systems, at odds with several co-evolutionary models. Finally, we consider the qualitative effects on mean SFR trends from different assumptions about the SF properties of QSO hosts and from redshift evolution of the SMBH-galaxy relationship. While currently limited by uncertainties, valuable constraints on AGN-galaxy co-evolution can emerge from our approach.

  14. 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.

  15. Active region coronal evolution

    NASA Technical Reports Server (NTRS)

    Golub, L.; Noci, G.; Poletto, G.; Vaiana, G. S.

    1982-01-01

    Scaling relations between coronal base pressure and longitudinal photospheric magnetic field strength are tested for the case of a single active region observed for five solar rotations from Skylab. The evolution of measureable quantities, such as coronal thermal energy content, total longitudinal photospheric magnetic flux, region scale size, and peak energy density, is traced throughout the five rotations observed. The theoretically derived scaling law of Golub et al. (1980) is found to provide an acceptable fit to the data throughout the entire evolutionary history of the region from an age of about 3 days to the fully evolved state in which the mature active region merges into the general large-scale structure of the quiet corona. An alternative scaling law obtained by including the results of Galeev et al. (1981), however, is found to provide a somewhat better fit to the data. The study is seen as providing additional justification for the belief that magnetic field-related heating is the operative mechanism in the solar corona.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. The star-forming history of the young cluster NGC 2264

    NASA Technical Reports Server (NTRS)

    Adams, M. T.; Strom, K. M.; Strom, S. E.

    1983-01-01

    UBVRI H-alpha photographic photometry was obtained for a sample of low-mass stars in the young open cluster NGC 2264 in order to investigate the star-forming history of this region. A theoretical H-R diagram was constructed for the sample of probable cluster members. Isochrones and evolutionary tracks were adopted from Cohen and Kuhi (1979). Evidence for a significant age spread in the cluster was found amounting to over ten million yr. In addition, the derived star formation rate as a function of stellar mass suggests that the principal star-forming mass range in NGC 2264 has proceeded sequentially in time from the lowest to the highest masses. The low-mass cluster stars were the first cluster members to form in significant numbers, although their present birth rate is much lower now than it was about ten million yr ago. The star-formation rate has risen to a peak at successively higher masses and then declined.

  1. 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.

  2. 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.

  3. VLBA Provides Best Detail Yet of Star-Forming Cloud's Magnetic Field

    NASA Astrophysics Data System (ADS)

    2001-07-01

    Astronomers have used the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope to do a very detailed map of the magnetic field within a star-forming cloud, an achievement that will help scientists unravel the mysterious first steps of the stellar birth process. "This study provides new and important data needed by theorists to understand how magnetic fields affect the early stages of star formation," said Anuj Sarma, an astronomer at the University of Illinois at Urbana-Champaign. Sarma worked with Thomas Troland of the University of Kentucky and Jonathan Romney of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. Their research results were published in the Astrophysical Journal Letters. Stars are formed when gas in giant interstellar clouds collapses gravitationally. Magnetic fields are believed to support such gas clouds, helping them resist gravitational collapse, so the beginning stages of star formation arise from a complex interplay of the magnetic fields and gravity that is not yet well understood. "In order to understand how star formation gets started, we need to know in detail the structure of the magnetic fields in a star-forming cloud," Sarma said. "Our observations with the VLBA have provided one more big step in this direction," he added. The astronomers studied a cloud of molecular gas more than 5,000 light- years from Earth in a spiral arm of our own Milky Way Galaxy. The cloud, known as W3 IRS5, contains seven newly-formed stars. In addition, it contains a number of regions, somewhat smaller than the diameter of Earth's orbit, in which water vapor molecules act to amplify, or strengthen, radio emission. Such regions, called masers, are a radio- wave parallel to lasers, which amplify light. The scientists used the VLBA to make a detailed study of the radio waves coming from these maser regions in the gas cloud. They detected a phenomenon called the Zeeman effect, in which a very precise frequency

  4. 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.

  5. Numerical Simulations of Self-Regulated, Star Forming Galactic Disks

    NASA Astrophysics Data System (ADS)

    Smith, D. C.; Struck, C.

    2000-12-01

    While star formation feedback models have been used in the study of galaxy formation, the effects of these processes on the global structure of disks have received less attention. We have adapted Hydra, the adaptive particle-particle, particle-mesh with smoothed particle hydrodynamics code by Couchman et al., to include heating processes deriving from star formation in order to study the effects of this heating on the structure of the disk and on the star formation itself. These processes include mechanical heating from strong stellar winds and supernovae, as well as heating due to photoelectric removal of electrons from grains by UV flux from young OB stars. Mechanisms of this type can be implemented in a simple way within the Hydra code, allowing us to study the density and temperature profiles of the gas, the balance among the multiple thermal phases generated in the disk, and the kinematics of the disk. Preliminary results from numerical simulations of star-forming gas disks of late type spirals are presented. Self-regulating effects of star formation on the global structure of the disk are discussed. We describe and compare the results of different star formation criteria and discuss the effects of particle resolution. This study was funded, in part, by a grant from the George Washington Carver Charitable Trust.

  6. 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'.

  7. 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.

  8. Star-forming filaments in warm dark matter models

    NASA Astrophysics Data System (ADS)

    Gao, Liang; Theuns, Tom; Springel, Volker

    2015-06-01

    We performed a hydrodynamical cosmological simulation of the formation of a Milky Way-like galaxy in a warm dark matter (WDM) cosmology. Smooth and dense filaments, several comoving mega parsec long, form generically above z ˜ 2 in this model. Atomic line cooling allows gas in the centres of these filaments to cool to the base of the cooling function, resulting in a very striking pattern of extended Lyman-limit systems (LLSs). Observations of the correlation function of LLSs might hence provide useful limits on the nature of the dark matter. We argue that the self-shielding of filaments may lead to a thermal instability resulting in star formation. We implement a sub-grid model for this, and find that filaments rather than haloes dominate star formation until z ˜ 6, although this depends on how stars form in WDM. Reionization decreases the gas density in filaments, and the more usual star formation in haloes dominates below z ˜ 6, although star formation in filaments continues until z = 2. 15 per cent of the stars of the z = 0 galaxy formed in filaments. At higher redshift, these stars give galaxies a stringy appearance, which, if observed, might be a strong indication that the dark matter is warm.

  9. Evolution of Active Regions

    NASA Astrophysics Data System (ADS)

    van Driel-Gesztelyi, Lidia; Green, Lucie May

    2015-09-01

    The evolution of active regions (AR) from their emergence through their long decay process is of fundamental importance in solar physics. Since large-scale flux is generated by the deep-seated dynamo, the observed characteristics of flux emergence and that of the subsequent decay provide vital clues as well as boundary conditions for dynamo models. Throughout their evolution, ARs are centres of magnetic activity, with the level and type of activity phenomena being dependent on the evolutionary stage of the AR. As new flux emerges into a pre-existing magnetic environment, its evolution leads to re-configuration of small-and large-scale magnetic connectivities. The decay process of ARs spreads the once-concentrated magnetic flux over an ever-increasing area. Though most of the flux disappears through small-scale cancellation processes, it is the remnant of large-scale AR fields that is able to reverse the polarity of the poles and build up new polar fields. In this Living Review the emphasis is put on what we have learned from observations, which is put in the context of modelling and simulation efforts when interpreting them. For another, modelling-focused Living Review on the sub-surface evolution and emergence of magnetic flux see Fan (2009). In this first version we focus on the evolution of dominantly bipolar ARs.

  10. 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.

  11. 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.

  12. Popularizing a scientific project: star forming rate in different ages of the Universe

    NASA Astrophysics Data System (ADS)

    Zamorano, J.; Jáuregui, F.; Fernández-Castro, T.; Gallego, J.; Armentia, J.

    In Spain we have to make a big effort in order to produce more activities dedicated to the popularization of Science. In this paper we show the activities we have developped, and others that will be done soon, in order to show to the general public, an example of how science is made. The project Star Forming Rate at Different z's is paid with public founds and included in its objectives, are some actions directed to the popularization of the science made in it. Exhibitions, public talks and planetarium shows are part of these activities presented to the general public in two of the main Science Centers of Spain, the Madrid and Pamplona planetaria.

  13. 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.

  14. 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.

  15. 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.

  16. Hα Surface Brightness Profiles of Star-Forming Galaxies and Dependence on Halo Mass Using the HAGGIS Survey

    NASA Astrophysics Data System (ADS)

    Kulkarni, S.; Wilman, D.; Erwin, P.; Koppenhöfer, J.; Gutierrez, L.; Beckman, J.; Saglia, R.; Bender, R.

    2014-03-01

    We present the first results from the Hα Galaxy Groups Imaging Survey (HAGGIS), a narrow-band imaging survey of SDSS groups at z < 0.05 conducted using the Wide Field Imager (WFI) on the ESO/MPG 2.2-meter telescope and the Wide Field Camera (WFC) on the Issac Newton Telescope (INT). In total, we observed 100 galaxy groups with a wide range of halo mass (1012 - 1014 M⊙) in pairs of narrow-band filters selected to get continuum subtracted rest-frame Hα images for each galaxy. The excellent data allows us to detect Hα down to the 10-18 ergs/s/cm2/arcsec2 level. Here, we examine the role played by halo mass and galaxy stellar mass in deciding the overall star formation activity in star forming disks by comparing stacked Hα profiles of galaxies in different halo mass and stellar mass bins. With this preliminary study, we have found that the star-formation activity in star-forming galaxies decreases in larger halos compared to the field galaxies. Using median equivalent width profiles, we can infer how environmental processes affect star-forming galaxies differently at different radii.

  17. Star-forming compact groups (SFCGs): an ultraviolet search for a local sample

    NASA Astrophysics Data System (ADS)

    Hernández-Fernández, Jonathan D.; Mendes de Oliveira, C.

    2015-10-01

    We present a local sample (z < 0.15) of 280 star-forming compact groups (SFCGs) of galaxies identified in the ultraviolet Galaxy Evolution EXplorer (GALEX) All-sky Imaging Survey (AIS). So far, just one prototypical example of SFCG, the Blue Infalling Group, has been studied in detail in the Local Universe. The sample of SFCGs is mainly the result of applying a Friends-of-Friends group finder in the space of celestial coordinates with a maximum linking-length of 1.5 arcmin and choosing groups with a minimum number of four members of bright UV-emitting 17regions of clusters with known redshift. The SFCG sample presents a combination of properties different from the group samples studied up to now, such as low-velocity dispersions (σ _{l-o-s} ˜ 120 km s-1), small crossing-times (H0tc ˜ 0.05) and high star formation content (95 per cent of star-forming galaxies). This points to the SFCGs being in an evolutionary stage distinct from those groups selected in the optical and near-infrared ranges. Once redshifts are obtained to discard interlopers, SFCGs will constitute a unique sample of SFCGs.

  18. 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.

  19. DUST EXTINCTION AND METALLICITIES OF STAR-FORMING Ly{alpha} EMITTING GALAXIES AT LOW REDSHIFT

    SciTech Connect

    Finkelstein, Steven L.; Papovich, Casey; Cohen, Seth H.; Malhotra, Sangeeta; Rhoads, James E.; Moustakas, John

    2011-06-01

    We present the results of an optical spectroscopic study of 12 GALEX-discovered star-forming Ly{alpha} emitting galaxies (LAEs) at z {approx} 0.3. We measure the emission-line fluxes from these galaxies by fitting their observed spectra to stellar population models in order to correct for underlying stellar absorption. We revisit earlier stellar population model fitting results, finding that excluding now-known active galactic nuclei lowers the typical stellar population age and stellar mass of this sample to {approx}300 Myr and {approx}4 x 10{sup 9} M{sub sun}, respectively. We calculate their dust extinction using the Balmer decrement, and find a typical visual attenuation of A{sub V} {approx} 0.3 mag, similar to that seen in some high-redshift LAEs. Comparing the ratios of Ly{alpha}/H{alpha} and the Ly{alpha} equivalent widths to the measured dust extinction, we find that the interstellar media (ISMs) in these objects appear to be neither enhancing nor seriously attenuating the Ly{alpha} equivalent widths, as would be the case in a quasi-clumpy ISM. Lastly, we perform a detailed analysis of the gas-phase metallicities of these galaxies, and we find that most galaxies in our sample have Z {approx}< 0.4 Z{sub sun}. We find that at a fixed stellar mass, these low-redshift LAE analogs are offset by {approx}0.3-0.6 dex lower metallicity from the general galaxy population at similar redshifts based on the local mass-metallicity relationship. This implies that galaxies with Ly{alpha} in emission may be systematically more metal-poor than star-forming galaxies at the same stellar mass and redshift, similar to preliminary results at z {approx} 2.

  20. MID-INFRARED SPECTROSCOPY OF TWO LENSED STAR-FORMING GALAXIES

    SciTech Connect

    Fadely, Ross; Baker, Andrew J.; Allam, Sahar S.; Lin Huan; Tucker, Douglas L.; Lutz, Dieter; Shapley, Alice E.; Shin, Min-Su; Smith, J. Allyn; Strauss, Michael A. E-mail: ajbaker@physics.rutgers.ed E-mail: hlin@fnal.go E-mail: lutz@mpe.mpg.d E-mail: msshin@umich.ed E-mail: strauss@astro.princeton.ed

    2010-11-01

    We present low-resolution, rest-frame {approx}5-12 {mu}m Spitzer/IRS spectra of two lensed z {approx} 2 UV-bright star-forming galaxies, SDSS J120602.09+514229.5 and SDSS J090122.37+181432.3. Using the magnification boost from lensing, we are able to study the physical properties of these objects in greater detail than is possible for unlensed systems. In both targets, we detect strong polycyclic aromatic hydrocarbon (PAH) emission at 6.2, 7.7, and 11.3 {mu}m, indicating the presence of vigorous star formation. For J1206, we find a steeply rising continuum and significant [S IV] emission, suggesting that a moderately hard radiation field is powering continuum emission from small dust grains. The strength of the [S IV] emission also implies a sub-solar metallicity of {approx}0.5 Z{sub sun}, confirming published rest-frame optical measurements. In J0901, the PAH lines have large rest-frame equivalent widths (>1 {mu}m) and the continuum rises slowly with wavelength, suggesting that any active galactic nucleus (AGN) contribution to L{sub IR} is insignificant, in contrast to the implications of optical emission-line diagnostics. Using [O III] line flux as a proxy for AGN strength, we estimate that the AGN in J0901 provides only a small fraction of its mid-infrared continuum flux. By combining the detection of [Ar II] with an upper limit on [Ar III] emission, we infer a metallicity of {approx}>1.3 Z{sub sun}. This work highlights the importance of combining rest-frame optical and mid-IR spectroscopy in order to understand the detailed properties of star-forming galaxies at high redshift.

  1. Physical Properties of Compact Star-forming Galaxies at z ˜ 2-3

    NASA Astrophysics Data System (ADS)

    Fang, Guanwen; Ma, Zhongyang; Kong, Xu; Fan, Lulu

    2015-07-01

    We present a study on the physical properties of compact star-forming galaxies (cSFGs) with M* ≥ 1010M⊙ and 2 ≤ z ≤ 3 in the COSMOS (Cosmic Evolution Survey) and GOODS-S (Great Observatories Origins Deep Survey South) fields. We find that massive cSFGs have a comoving number density of (1.0 ± 0.1) × 10-4 Mpc-3. The cSFGs are distributed at nearly the same locus on the main sequence as extended star-forming galaxies (eSFGs) and dominate the high-mass end. On the rest-frame U - V versus V-J and U-B versus {M}{{B}} diagrams, cSFGs are mainly distributed at the middle of eSFGs and compact quiescent galaxies (cQGs) in all colors, but are more inclined to “red sequence” than “green valley” galaxies. We also find that cSFGs have distributions similar to cQGs on the nonparametric morphology diagrams. The cQGs and cSFGs have larger Gini and smaller M20, while eSFGs have the reverse. About one-third of cSFGs show signatures of postmergers, and almost none of them can be recognized as disks. Moreover, those visually extended cSFGs all have lower Gini coefficients (Gini < 0.4), indicating that the Gini coefficient could be used to clean out noncompact galaxies in a sample of candidate cSFGs. The X-ray-detected counterparts are more frequent among cSFGs than in eSFGs and cQGs, implying that cSFGs have previously experienced violent gas-rich interactions (such as major mergers or disk instabilities), which could trigger both star formation and black hole growth in an active phase.

  2. Star-forming Galaxies as the Origin of the IceCube PeV Neutrinos

    NASA Astrophysics Data System (ADS)

    Chang, Xiao-Chuan; Liu, Ruo-Yu; Wang, Xiang-Yu

    2015-06-01

    Star-forming galaxies, due to their high star formation rates, and hence large number of supernova remnants (SNRs) therein, are huge reservoirs of cosmic rays (CRs). These CRs collide with gases in galaxies and produce high-energy neutrinos through proton-proton collisions. In this paper, we calculate the neutrino production efficiency in star-forming galaxies by considering realistic galaxy properties, such as the gas density and galactic wind in star-forming galaxies. To calculate the accumulated neutrino flux, we use the infrared luminosity function of star-forming galaxies recently obtained by the Herschel PEP/HerMES survey. The intensity of CRs producing PeV neutrinos in star-forming galaxies is normalized with the observed CR flux at EeV (1 EeV = {{10}18} eV), assuming that SNR or hypernova remnants in star-forming galaxies can accelerate protons to EeV energies. Our calculations show that the accumulated neutrino emission produced by CRs in star-forming galaxies can account for the flux and spectrum of the sub-PeV/PeV neutrinos under reasonable assumptions on the CR confinement time in these galaxies.

  3. 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.

  4. 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…

  5. 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

  6. The Spatially Resolved NUV-r Color of Local Star-forming Galaxies and Clues for Quenching

    NASA Astrophysics Data System (ADS)

    Pan, Zhizheng; Zheng, Xianzhong; Lin, Weipeng; Li, Jinrong; Wang, Jing; Fan, Lulu; Kong, Xu

    2016-03-01

    Using a sample of ˜6000 local face-on star-forming galaxies (SFGs) we examine the correlations between the NUV-r colors both inside and outside the half-light radius, stellar mass M*, and Sérsic index n to understand how the quenching of star formation is linked to galaxy structure. For these less dust-attenuated galaxies, NUV-r is found to be linearly correlated with {D}n4000, supporting NUV-r as a good photometric indicator of stellar age (or specific star formation rate). First, we find that at {M}*\\lt {10}10.2{M}⊙ the central NUV-r is on average only ˜0.25 mag redder than the outer NUV-r the intrinsic value would be even smaller after accounting for dust correction. However, the central NUV-r becomes systematically much redder than the outer NUV-r for more massive galaxies at {M}*\\gt {10}10.2{M}⊙ . Second, the central NUV-r shows no dependence on Sérsic index n at {M}*\\lt {10}10.2{M}⊙ , while above this mass galaxies with a higher n tend to be redder in the central NUV-r color. These results suggest that galaxies with {M}*\\lt {10}10.2{M}⊙ exhibit similar star formation activity from the inner R\\lt {R}50 region to the R\\gt {R}50 region. In contrast, a considerable fraction of the {M}*\\gt {10}10.2{M}⊙ galaxies, especially those with a high n, have harbored a relatively inactive bulge component.

  7. Massive star clusters in a z=1 star-forming galaxy seen at a 100 pc scale thanks to strong gravitational lensing

    NASA Astrophysics Data System (ADS)

    Dessauges-Zavadsky, Miroslava; Cava, Antonio; Richard, Johan; Schaerer, Daniel; Egami, Eiichi

    2015-08-01

    Deep and high-resolution imaging has revealed clumpy, rest-frame UV morphologies among z=1-3 galaxies. The majority of these galaxies has been shown to be dominated by ordered disk rotation, which led to the conclusion that the observed giant clumps, resolved on kpc-scales, are generated from disk fragmentation due to gravitational instability. State-of-the-art numerical simulations show that they may occupy a relevant role in galaxy evolution, contributing to the galactic bulge formation. Despite the high resolution attained by the most advanced ground- and space-based facilities, as well as in numerical simulations, the intrinsic typical masses and scale sizes of these star-forming clumps remain unconstrained, since they are barely resolved at z=1-3.Thanks to the amplification and stretching power provided by strong gravitational lensing, we are likely to reach the spatial resolving power for unveiling the physics of these star-forming regions. We report on the study of clumpy star formation observed in the Cosmic Snake, a strongly lensed galaxy at z=1, representative of the typical star-forming population close to the peak of Universe activity. About 20 clumps are identified in the HST images. Benefiting from extreme amplification factors up to 100, they are resolved down to an intrinsic scale of 100 pc, never reached before at z=1.The HST multi-wavelength analysis of these individual star clusters allows us to determine their intrinsic physical properties, showing stellar masses (Ms) from 106 to 108.3 Msun, sizes from 100 to 400 pc, and ages from 106 to 108.5 yr. The masses we find are in line with the new, very high resolution numerical simulations, which also suggest that the massive giant clumps previously observed at high redshift with Ms as high as 109-10 Msun may suffer from low resolution effects, being unresolved conglomerates of less massive star clusters. We also compare our results with those of massive young clusters in nearby galaxies. Our approved

  8. THE FRAGMENTATION OF MAGNETIZED, MASSIVE STAR-FORMING CORES WITH RADIATIVE FEEDBACK

    SciTech Connect

    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{sub Sun }), 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 {approx}100 M{sub Sun} cores with many thermal Jeans masses of material. We also demonstrate that a {approx}40 AU Keplerian disk is able to form in our simulations, despite the braking effect caused by the strong magnetic field.

  9. 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).

  10. 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 ...

  11. 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

  12. [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.

  13. The G305 star-forming complex: the central star clusters Danks 1 and Danks 2

    NASA Astrophysics Data System (ADS)

    Davies, Ben; Clark, J. S.; Trombley, Christine; Figer, Donald F.; Najarro, Francisco; Crowther, Paul A.; Kudritzki, Rolf-Peter; Thompson, Mark; Urquhart, James S.; Hindson, Luke

    2012-01-01

    The G305 H II complex (G305.4+0.1) is one of the most massive star-forming structures yet identified within the Galaxy. It is host to many massive stars at all stages of formation and evolution, from embedded molecular cores to post-main-sequence stars. Here, we present a detailed near-infrared analysis of the two central star clusters Danks 1 and Danks 2, using Hubble Space Telescope+NICMOS imaging and Very Large Telescope+ISAAC spectroscopy. We find that the spectrophotometric distance to the clusters is consistent with the kinematic distance to the G305 complex, an average of all measurements giving a distance of 3.8 ± 0.6 kpc. From analysis of the stellar populations and the pre-main-sequence stars, we find that Danks 2 is the elder of the two clusters, with an age of 3+3- 1 Myr. Danks 1 is clearly younger with an age of 1.5+1.5- 0.5 Myr, and is dominated by three very luminous H-rich Wolf-Rayet stars which may have masses ≳100 M⊙. The two clusters have mass functions consistent with the Salpeter slope, and total cluster masses of 8000 ± 1500 and 3000 ± 800 M⊙ for Danks 1 and Danks 2, respectively. Danks 1 is significantly the more compact cluster of the two, and is one of the densest clusters in the Galaxy with log (ρ/M⊙ pc-3) = 5.5+0.5- 0.4. In addition to the clusters, there is a population of apparently isolated Wolf-Rayet stars within the molecular cloud's cavity. Our results suggest that the star-forming history of G305 began with the formation of Danks 2, and subsequently Danks 1, with the origin of the diffuse evolved population currently uncertain. Together, the massive stars at the centre of the G305 region appear to be clearing away what is left of the natal cloud, triggering a further generation of star formation at the cloud's periphery.

  14. Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC 6334I

    NASA Astrophysics Data System (ADS)

    van der Wiel, M. H. D.; van der Tak, F. F. S.; Lis, D. C.; Bell, T.; Bergin, E. A.; Comito, C.; Emprechtinger, M.; Schilke, P.; Caux, E.; Ceccarelli, C.; Baudry, A.; Goldsmith, P. F.; Herbst, E.; Langer, W.; Lord, S.; Neufeld, D.; Pearson, J.; Phillips, T.; Rolffs, R.; Yorke, H.; Bacmann, A.; Benedettini, M.; Blake, G. A.; Boogert, A.; Bottinelli, S.; Cabrit, S.; Caselli, P.; Castets, A.; Cernicharo, J.; Codella, C.; Coutens, A.; Crimier, N.; Demyk, K.; Dominik, C.; Encrenaz, P.; Falgarone, E.; Fuente, A.; Gerin, M.; Helmich, F.; Hennebelle, P.; Henning, T.; Hily-Blant, P.; Jacq, T.; Kahane, C.; Kama, M.; Klotz, A.; Lefloch, B.; Lorenzani, A.; Maret, S.; Melnick, G.; Nisini, B.; Pacheco, S.; Pagani, L.; Parise, B.; Salez, M.; Saraceno, P.; Schuster, K.; Tielens, A. G. G. M.; Vastel, C.; Viti, S.; Wakelam, V.; Walters, A.; Wyrowski, F.; Edwards, K.; Zmuidzinas, J.; Morris, P.; Samoska, L. A.; Teyssier, D.

    2010-10-01

    Context. In contrast to the more extensively studied dense star-forming cores, little is known about diffuse gas surrounding star-forming regions. Aims: We study the molecular gas in the Galactic high-mass star-forming region NGC 6334I, which contains diffuse, quiescent components that are inconspicuous in widely used molecular tracers such as CO. Methods: We present Herschel/HIFI observations of methylidyne (CH) toward NGC 6334I observed as part of the “Chemical HErschel Survey of Star forming regions” (CHESS) key program. HIFI resolves each of the six hyperfine components of the lowest rotational transition (J = 3/2 - 1/2) of CH, observed in both emission and absorption. Results: The CH emission features appear close to the systemic velocity of NGC 6334I, while its measured FWHM linewidth of 3 km s-1 is smaller than previously observed in dense gas tracers such as NH3 and SiO. The CH abundance in the hot core is ~7 × 10-11, two to three orders of magnitude lower than in diffuse clouds. While other studies find distinct outflows in, e.g., CO and H2O toward NGC 6334I, we do not detect any outflow signatures in CH. At least two redshifted components of cold absorbing material must be present at -3.0 and +6.5 km s-1 to explain the absorption signatures. We derive a CH column density (NCH) of 7 × 1013 and 3 × 1013 cm-2 for these two absorbing clouds. We find evidence of two additional absorbing clouds at +8.0 and 0.0 km s-1, both with NCH ≈ 2 × 1013 cm-2. Turbulent linewidths for the four absorption components vary between 1.5 and 5.0 km s-1 in FWHM. We constrain the physical properties and locations of the clouds by matching our CH absorbers with the absorption signatures seen in other molecular tracers. Conclusions: In the hot core, molecules such as H2O and CO trace gas that is heated and dynamically influenced by outflow activity, whereas the CH molecule traces more quiescent material. The four CH absorbing clouds have column densities and turbulent

  15. Chemo-population multizone models for emission line evolution of star forming galaxies

    NASA Astrophysics Data System (ADS)

    Valle, G.; Shore, S. N.

    2007-02-01

    Aims:We apply the nonlinear chemo-population (CP) models for galactic star formation and abundance evolution to the prediction of emission line diagnostics. Methods: We interfaced the CP code with the photoionization code Cloudy. Using the self-consistently generated star forming rates and abundance histories we predict the time dependences of the nebular line emissivities from model H II regions. We also simulated some effects of collisions, stripping, and accretion events on the emission line diagnostics. Results: We find, despite using extremely simplified input fluxes (i.e. blackbodies scaled to a range of effective temperatures but without detailed model atmospheres or population synthesis), the models reproduce many features of the observations. In particular, we suggest that the line ratios for highly ionized species (e.g. [O III] vs. [N II]) are more sensitive to the galactic history, while the exclusively ionization diagnostics (e.g. [O II] vs. [O I]) are more sensitive to the underlying stellar population and the composite ultraviolet flux distribution. We discuss some reasons for this and conclude that a coupled treatment of the galactic population and chemical evolution is essential for interpretation of the data. We also find that collisional and stripped models cover a wider range in the diagnostic diagrams that provide clues to the environmental effects.

  16. How does the far-IR properties of star-forming galaxies depend on environment?

    NASA Astrophysics Data System (ADS)

    Guo, Qi

    2015-08-01

    Traditionally, most observational studies estimate SFRs using rest-frame UV luminosities or emission lines, which are subject to uncertain corrections for dust extinction. In star-forming regions, UV photons heat the dust, and their energy is re-emitted in the mid- and far-IR range. About half of the starlight is absorbed and re-emitted over the history of the Universe. Observations at IR wavelengths are thus an essential complement to UV and optical tracers of star formation. We use far-IR selected galaxies from the Herschel ATLAS (H-ATLAS) survey and optically selected galaxies from the Galaxy and Mass Assembly (GAMA) redshift survey to study the environmental effects on far-IR properties. It includes the following aspects. What is the typical halo mass of the low-redshift H-ATLAS sources? How does far-IR luminosity depend on host halo mass? How do the far-IR conditional luminosity functions depend on group masses and redshifts? How is the total far-IR light-to-mass ratio in groups of different masses at different redshifts? How much of the far-IR luminosity is contributed by galaxies in groups? Are there any environmental effects on the far-IR-to-optical colour? How does the far-IR properties depend on large-scale environments? Can we pose constrains on current galaxy formation models?

  17. Relation between Starlight and Nebular Emission Lines of Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Lu, Hong-Lin; Zhou, Hong-Yan; Wang, Ting-Gui; Zhuang, Zhen-Quan; Dong, Xiao-Bo; Wang, Jun-Xian; Li, Cheng

    2005-06-01

    We present an exercise that intends to establish a relationship between the strength of nebular emission lines and optical stellar features in the spectrum of a galaxy. After accurately subtracting the stellar continuum and the underlying stellar absorption, we made reliable measurements of the emission lines of all the galaxies in the Sloan Digital Sky Survey Data Release 2 (SDSS DR2). More than 4000 star-forming galaxies with high S/N ratio of both the stellar spectrum and the emission lines are selected. These galaxy spectra are fitted with the 10 PCs of Yip et al., after all the emission line regions have been filtered out. We find that the flux of hydrogen Balmer emission lines, Hα and Hβ can be well recovered from the PCs, while the metal lines are not well reproduced. The fluxes of Hα and Hβ measured from the PC-reconstructed spectra and from the observed spectra agree well with an rms scatter of only ~0.1 dex. This result suggests that, with moderate spectral resolution and S/N ratio, the optical stellar spectrum of a galaxy can serve as an indicator of star formation rate.

  18. Dusty, Intensively Star Forming Hα Emitters (HAEs) in Protocluster 4C23.56

    NASA Astrophysics Data System (ADS)

    Lee, M.; Suzuki, K.; Kohno, K.; Tamura, Y.; Iono, D.; Hatsukade, B.; Nakanishi, K.; Tanaka, I.; Kodama, T.; Tadaki, K.; Ikarashi, S.; Ueda, J.; Umehata, H.; Saito, T.; Kawabe, R.

    2015-12-01

    We report on the measurements of physical properties of HAEs in protocluster 4C23.56 at z = 2.49 using deep and high resolution observations with ALMA at Band 6 (270 GHz) and JVLA at S-band (3 GHz). We detect four and seven out of 24 HAEs from ALMA and JVLA, and we find that the detected samples are in massive-end (log M★(M⊙)≳10.1) . We derive extinction-free SFRs and the amount of dust attenuation based on JVLA detections for those without AGN features. The detected HAEs are massive and heavily dust-obscured star forming galaxies. The majority of these HAEs are experiencing burst-like phase. We derive interstellar medium (ISM) masses from the single band ALMA observation and all but one of ALMA detections have ISM mass fractions of ˜ 25% which is a tentatively low value compared to the samples of the general field. This suggests that an accelerated galaxy evolution may have occurred in the over-dense region at this high redshift, though the uncertainty is large.

  19. 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.

  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. 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.

  2. 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.

  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. HerMES: Cosmic Infrared Background Anisotropies and the Clustering of Dusty Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Viero, M. P.; Wang, L.; Zemcov, M.; Addison, G.; Amblard, A.; Arumugam, V.; Aussel, H.; Béthermin, M.; Bock, J.; Boselli, A.; Buat, V.; Burgarella, D.; Casey, C. M.; Clements, D. L.; Conley, A.; Conversi, L.; Cooray, A.; De Zotti, G.; Dowell, C. D.; Farrah, D.; Franceschini, A.; Glenn, J.; Griffin, M.; Hatziminaoglou, E.; Heinis, S.; Ibar, E.; Ivison, R. J.; Lagache, G.; Levenson, L.; Marchetti, L.; Marsden, G.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Omont, A.; Page, M. J.; Papageorgiou, A.; Pearson, C. P.; Pérez-Fournon, I.; Pohlen, M.; Rigopoulou, D.; Roseboom, I. G.; Rowan-Robinson, M.; Schulz, B.; Scott, D.; Seymour, N.; Shupe, D. L.; Smith, A. J.; Symeonidis, M.; Vaccari, M.; Valtchanov, I.; Vieira, J. D.; Wardlow, J.; Xu, C. K.

    2013-07-01

    We present measurements of the auto- and cross-frequency power spectra of the cosmic infrared background (CIB) at 250, 350, and 500 μm (1200, 860, and 600 GHz) from observations totaling ~70 deg2 made with the SPIRE instrument aboard the Herschel Space Observatory. We measure a fractional anisotropy δI/I = 14% ± 4%, detecting signatures arising from the clustering of dusty star-forming galaxies in both the linear (2-halo) and nonlinear (1-halo) regimes; and that the transition from the 2- to 1-halo terms, below which power originates predominantly from multiple galaxies within dark matter halos, occurs at k θ ~ 0.10-0.12 arcmin-1 (l ~ 2160-2380), from 250 to 500 μm. New to this paper is clear evidence of a dependence of the Poisson and 1-halo power on the flux-cut level of masked sources—suggesting that some fraction of the more luminous sources occupy more massive halos as satellites, or are possibly close pairs. We measure the cross-correlation power spectra between bands, finding that bands which are farthest apart are the least correlated, as well as hints of a reduction in the correlation between bands when resolved sources are more aggressively masked. In the second part of the paper, we attempt to interpret the measurements in the framework of the halo model. With the aim of fitting simultaneously with one model the power spectra, number counts, and absolute CIB level in all bands, we find that this is achievable by invoking a luminosity-mass relationship, such that the luminosity-to-mass ratio peaks at a particular halo mass scale and declines toward lower and higher mass halos. Our best-fit model finds that the halo mass which is most efficient at hosting star formation in the redshift range of peak star-forming activity, z ~ 1-3, is log(M peak/M ⊙) ~ 12.1 ± 0.5, and that the minimum halo mass to host infrared galaxies is log(M min/M ⊙) ~ 10.1 ± 0.6. Herschel is an ESA space observatory with science instruments provided by European

  5. HerMES: COSMIC INFRARED BACKGROUND ANISOTROPIES AND THE CLUSTERING OF DUSTY STAR-FORMING GALAXIES

    SciTech Connect

    Viero, M. P.; Zemcov, M.; Bock, J.; Cooray, A.; Dowell, C. D.; Wang, L.; Addison, G.; Amblard, A.; Arumugam, V.; Aussel, H.; Bethermin, M.; Casey, C. M.; Clements, D. L.; Conley, A.; Conversi, L.; De Zotti, G.; Farrah, D.; and others

    2013-07-20

    We present measurements of the auto- and cross-frequency power spectra of the cosmic infrared background (CIB) at 250, 350, and 500 {mu}m (1200, 860, and 600 GHz) from observations totaling {approx}70 deg{sup 2} made with the SPIRE instrument aboard the Herschel Space Observatory. We measure a fractional anisotropy {delta}I/I = 14% {+-} 4%, detecting signatures arising from the clustering of dusty star-forming galaxies in both the linear (2-halo) and nonlinear (1-halo) regimes; and that the transition from the 2- to 1-halo terms, below which power originates predominantly from multiple galaxies within dark matter halos, occurs at k{sub {theta}} {approx} 0.10-0.12 arcmin{sup -1} (l {approx} 2160-2380), from 250 to 500 {mu}m. New to this paper is clear evidence of a dependence of the Poisson and 1-halo power on the flux-cut level of masked sources-suggesting that some fraction of the more luminous sources occupy more massive halos as satellites, or are possibly close pairs. We measure the cross-correlation power spectra between bands, finding that bands which are farthest apart are the least correlated, as well as hints of a reduction in the correlation between bands when resolved sources are more aggressively masked. In the second part of the paper, we attempt to interpret the measurements in the framework of the halo model. With the aim of fitting simultaneously with one model the power spectra, number counts, and absolute CIB level in all bands, we find that this is achievable by invoking a luminosity-mass relationship, such that the luminosity-to-mass ratio peaks at a particular halo mass scale and declines toward lower and higher mass halos. Our best-fit model finds that the halo mass which is most efficient at hosting star formation in the redshift range of peak star-forming activity, z {approx} 1-3, is log(M{sub peak}/M{sub Sun }) {approx} 12.1 {+-} 0.5, and that the minimum halo mass to host infrared galaxies is log(M{sub min}/M{sub Sun }) {approx} 10

  6. LOOKING INTO THE HEARTS OF BOK GLOBULES: MILLIMETER AND SUBMILLIMETER CONTINUUM IMAGES OF ISOLATED STAR-FORMING CORES

    SciTech Connect

    Launhardt, R.; Henning, Th.; Khanzadyan, T.; Schmalzl, M.; Wolf, S.; Nutter, D.; Ward-Thompson, D.; Bourke, T. L.; Zylka, R.

    2010-05-15

    We present the results of a comprehensive infrared, submillimeter, and millimeter continuum emission study of isolated low-mass star-forming cores in 32 Bok globules, with the aim to investigate the process of star formation in these regions. The submillimeter and millimeter dust continuum emission maps together with the spectral energy distributions are used to model and derive the physical properties of the star-forming cores, such as luminosities, sizes, masses, densities, etc. Comparisons with ground-based near-infrared and space-based mid- and far-infrared images from Spitzer are used to reveal the stellar content of the Bok globules, association of embedded young stellar objects (YSOs) with the submillimeter dust cores, and the evolutionary stages of the individual sources. Submillimeter dust continuum emission was detected in 26 out of the 32 globule cores observed. For 18 globules with detected (sub)millimeter cores, we derive evolutionary stages and physical parameters of the embedded sources. We identify nine starless cores, most of which are presumably prestellar, nine Class 0 protostars, and twelve Class I YSOs. Specific source properties like bolometric temperature, core size, and central densities are discussed as a function of evolutionary stage. We find that at least two thirds (16 out of 24) of the star-forming globules studied here show evidence of forming multiple stars on scales between 1000 and 50,000 AU. However, we also find that most of these small prototstar and star groups are comprised of sources with different evolutionary stages, suggesting a picture of slow and sequential star formation in isolated globules.

  7. A CHANDRA OBSERVATION OF THE OBSCURED STAR-FORMING COMPLEX W40

    SciTech Connect

    Kuhn, Michael A.; Getman, Konstantin V.; Feigelson, Eric D.; Garmire, Gordon P.; Bo Reipurth; Rodney, Steven A.

    2010-12-20

    The young stellar cluster illuminating the W40 H II region, one of the nearest massive star-forming regions, has been observed with the ACIS detector on board the Chandra X-ray Observatory. Due to its high obscuration, this is a poorly studied stellar cluster with only a handful of bright stars visible in the optical band, including three OB stars identified as primary excitation sources. We detect 225 X-ray sources, of which 85% are confidently identified as young stellar members of the region. Two potential distances of the cluster, 260 pc and 600 pc, are used in the paper. Supposing the X-ray luminosity function to be universal, it supports a 600 pc distance as a lower limit for W40 and a total population of at least 600 stars down to 0.1 M{sub sun} under the assumption of a coeval population with a uniform obscuration. In fact, there is strong spatial variation in K{sub s} -band-excess disk fraction and non-uniform obscuration due to a dust lane that is identified in absorption in optical, infrared, and X-ray. The dust lane is likely part of a ring of material which includes the molecular core within W40. In contrast to the likely ongoing star formation in the dust lane, the molecular core is inactive. The star cluster has a spherical morphology, an isothermal sphere density profile, and mass segregation down to 1.5 M{sub sun}. However, other cluster properties, including a {approx}<1 Myr age estimate and ongoing star formation, indicate that the cluster is not dynamically relaxed. X-ray diffuse emission and a powerful flare from a young stellar object are also reported.

  8. 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. PMID:15815623

  9. The Dawes Review 1: Kinematic Studies of Star-Forming Galaxies Across Cosmic Time

    NASA Astrophysics Data System (ADS)

    Glazebrook, Karl

    2013-11-01

    The last seven years have seen an explosion in the number of Integral Field galaxy surveys, obtaining resolved 2D spectroscopy, especially at high-redshift. These have taken advantage of the mature capabilities of 8-10 m class telescopes and the development of associated technology such as AO. Surveys have leveraged both high spectroscopic resolution enabling internal velocity measurements and high spatial resolution from AO techniques and sites with excellent natural seeing. For the first time, we have been able to glimpse the kinematic state of matter in young, assembling star-forming galaxies and learn detailed astrophysical information about the physical processes and compare their kinematic scaling relations with those in the local Universe. Observers have measured disc galaxy rotation, merger signatures, and turbulence-enhanced velocity dispersions of gas-rich discs. Theorists have interpreted kinematic signatures of galaxies in a variety of ways (rotation, merging, outflows, and feedback) and attempted to discuss evolution vs. theoretical models and relate it to the evolution in galaxy morphology. A key point that has emerged from this activity is that substantial fractions of high-redshift galaxies have regular kinematic morphologies despite irregular photometric morphologies and this is likely due to the presence of a large number of highly gas-rich discs. There has not yet been a review of this burgeoning topic. In this first Dawes review, I will discuss the extensive kinematic surveys that have been done and the physical models that have arisen for young galaxies at high-redshift.

  10. 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.

  11. Detection of a large fraction of atomic gas not associated with star-forming material in M17 SW⋆

    NASA Astrophysics Data System (ADS)

    Pérez-Beaupuits, J. P.; Stutzki, J.; Ossenkopf, V.; Spaans, M.; Güsten, R.; Wiesemeyer, H.

    2015-03-01

    Context. The [C II] 158 μm line is one of the dominant coolants of the ISM, and an important probe with which to study the star formation process. Recent Herschel/HIFI and SOFIA/GREAT observations showed that assuming the total velocity-integrated intensity of this line is directly associated with the star-forming material is inadequate. Aims: We probe the column densities and masses traced by the ionized and neutral atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [C I] and low-J CO lines toward the star-forming region M17 SW. Methods: We mapped a 4.1 pc × 4.7 pc region in the [C I] 609 μm line using the APEX telescope, as well as the CO isotopologues with the IRAM 30 m telescope. Because of the velocity-resolved spectra, we analyze the data based on velocity channel maps that are 1 km s-1 wide. We correlate their spatial distribution with that of the [C II] map obtained with SOFIA/GREAT. Optically thin approximations were used to estimate the column densities of [C I] and [C II] in each velocity channel. Results: The distribution of the emission from the isotopologues 13CO, C17O, and C18O resembles more closely that of the [C I] emission than that of the 12CO emission. The spatial distribution of the [C I] and all CO isotopologues emission was found to be associated with that of [C II] in about 20%-80% of the mapped region, with the high correlation found in the central (15-23 km s-1) velocity channels. Conclusions: The excitation temperature of [C I] ranges between 40 K and 100 K in the inner molecular region of M17 SW. Excitation temperatures up to 200 K are found along the ridge. Column densities in 1 km s-1 channels between ~1015 cm-2 and ~1017 cm-2 were found for [C I]. Just ~20 % of the velocity range (~40 km s-1) that the [C II] line spans is associated with the star-forming material traced by [C I] and CO. The total (integrated over the 0-40 km s-1 velocity range) gas mass estimated from the

  12. 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).

  13. 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.

    2016-06-01

    In this work, we aim to characterise high-mass clumps with infall motions. We selected 327 clumps from the Millimetre Astronomy Legacy Team 90-GHz (MALT90) survey, and identified 100 infall candidates. Combined with the results of He et al. (2015), 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, HII or photo-dissociation region (PDR). The detection rates of the infall candidates in the pre-stellar, proto-stellar, HII and PDR stages are 41.2%, 36.6%, 30.6% and 12.7%, 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, HII 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 HII stages. The power indices of the clump mass function (ClMF) 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).

  14. Multithermal emission in active regions

    NASA Astrophysics Data System (ADS)

    Del Zanna, Giulio

    High-resolution EUV observations from SDO/AIA, Hi-C and Hinode/EIS are used, together with updated new atomic data, to study the multi-thermal emission in active region structures. Previous observations are largely confirmed, with most structures being not co-spatial and having nearly isothermal cross-sections. Those at temperatures below 1 MK appear as nearly resolved but those at 1-3 MK are still largely unresolved even at the Hi-C resolution. Very little emission above 3 MK is present in quiescent active regions. Elemental abundances vary in different structures. The active region cores show FIP enhancements of about a factor of three. X-ray spectroscopy confirms the results of the EUV observations for the hot cores.

  15. 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.

  16. Obscuration of LY alpha Photons in Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Giavalisco, Mauro; Koratkar, Anuradha; Calzetti, Daniela

    1996-08-01

    We present a new study of the correlations between the Lyα emission, the UV extinction, and the metal content in a sample of 21 local, low-metallicity starburst galaxies from archival IUE spectra. We have consistently reextracted all the spectra using the optimal extraction algorithm by Kinney and coworkers, and we have also included galaxies not previously studied. In 40% of the cases our new measures of the Lyα equivalent width, Walpha_, differ from those reported in the literature by up to 50% of their value. The new measures show no significant correlation with either the obscuration of the UV continuum or the Balmer decrement, and only a very weak correlation with the metal index [O/H]. Using the flux ratio Lyα/Hβ instead of Walpha_ to take into account differences in the ionizing conditions of the nebular gas does not change these results. This shows that the extinction vicissitudes of the Lyα and nonresonant radiations have been decoupled during their propagations through the ISM. We interpret this as evidence that the ISM in the sample galaxies is, on average, highly inhomogeneous and that the transport of Lyα photons is primarily controlled by the ISM geometry rather than by the amount of dust. If the ISM geometry is mainly the result of the energy release from the star formation activity, we speculate that a similar phenomenology was also present at high redshifts. As the median of the absolute value of Walpha_ in our sample is relatively large, the line can be efficiently used to measure the redshifts of primeval galaxy candidates at redshifts 2 <~ z <~ 7 via optical spectroscopy with the 10 m class telescopes.

  17. The evolution of the star-forming sequence in hierarchical galaxy formation models

    NASA Astrophysics Data System (ADS)

    Mitchell, Peter D.; Lacey, Cedric G.; Cole, Shaun; Baugh, Carlton M.

    2014-11-01

    It has been argued that the specific star formation rates of star-forming galaxies inferred from observational data decline more rapidly below z = 2 than is predicted by hierarchical galaxy formation models. We present a detailed analysis of this problem by comparing predictions from the GALFORM semi-analytic model with an extensive compilation of data on the average star formation rates of star-forming galaxies. We also use this data to infer the form of the stellar mass assembly histories of star-forming galaxies. Our analysis reveals that the currently available data favour a scenario where the stellar mass assembly histories of star-forming galaxies rise at early times and then fall towards the present day. In contrast, our model predicts stellar mass assembly histories that are almost flat below z = 2 for star-forming galaxies, such that the predicted star formation rates can be offset with respect to the observational data by factors of up to 2-3. This disagreement can be explained by the level of coevolution between stellar and halo mass assembly that exists in contemporary galaxy formation models. In turn, this arises because the standard implementations of star formation and supernova feedback used in the models result in the efficiencies of these process remaining approximately constant over the lifetime of a given star-forming galaxy. We demonstrate how a modification to the time-scale for gas ejected by feedback to be reincorporated into galaxy haloes can help to reconcile the model predictions with the data.

  18. Predicting dust extinction properties of star-forming galaxies from Hα/UV ratio

    NASA Astrophysics Data System (ADS)

    Koyama, Yusei; Kodama, Tadayuki; Hayashi, Masao; Shimakawa, Rhythm; Yamamura, Issei; Egusa, Fumi; Oi, Nagisa; Tanaka, Ichi; Tadaki, Ken-ichi; Takita, Satoshi; Makiuti, Sin'itirou

    2015-10-01

    Using star-forming galaxies sample in the nearby Universe (0.02 < z < 0.10) selected from the Sloan Digital Sky Survey (DR7) and Galaxy Evolution Explorer all-sky survey (GR5), we present a new empirical calibration for predicting dust extinction of galaxies from the Hα-to-FUV flux ratio. We find that the Hα dust extinction (AHα) derived with Hα/Hβ ratio (Balmer decrement) increases with increasing Hα/UV ratio as expected, but there remains a considerable scatter around the relation, which is largely dependent on stellar mass and/or Hα equivalent width (EWHα). At fixed Hα/UV ratio, galaxies with higher stellar mass (or galaxies with lower EWHα) tend to be more highly obscured by dust. We quantify this trend and establish an empirical calibration for predicting AHα with a combination of Hα/UV ratio, stellar mass, and EWHα, with which we can successfully reduce the systematic uncertainties accompanying the simple Hα/UV approach by ˜15-30 per cent. The new recipes proposed in this study will provide a convenient tool for predicting dust extinction level of galaxies particularly when Balmer decrement is not available. By comparing AHα (derived with Balmer decrement) and AUV (derived with IR/UV luminosity ratio) for a subsample of galaxies for which AKARI far-infrared photometry is available, we demonstrate that more massive galaxies tend to have higher extra extinction towards the nebular regions compared to the stellar continuum light. Considering recent studies reporting smaller extra extinction towards nebular regions for high-redshift galaxies, we argue that the dust geometry within high-redshift galaxies resembles low-mass galaxies in the nearby Universe.

  19. 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.

  20. 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.

  1. 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).

  2. 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...

  3. A Comparative Study of Star-forming and Quiescent Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Simpson, Caroline E.; Gottesman, S. T.

    2000-12-01

    We present the results from a comparative study of the atomic hydrogen (H I) and optical properties of a sample of 16 dwarf galaxies, chosen to investigate the effects of star formation on the properties of low-mass systems. The violent star formation bursts believed to occur in these low-mass systems suggest a possible connection between the actively star-forming blue compact dwarfs (BCDs), and the quiescent low surface brightness dwarfs (LSBDs). It has been suggested that LSBDs, upon undergoing a burst of star formation, will evolve into BCDs and then back into LSBDs when the star formation slows or stops as the H I column density falls below the critical threshold necessary to support it. We have examined the location and kinematics of H I in eight BCDs and eight LSBDs of similar H I masses and a range of color indices to investigate this ``evolutionary'' sequence. The starburst episodes in these low-mass galaxies should lead to (1) a dispersal/depletion of the H I seen in the eight LSB dwarfs and (2) more centrally concentrated and agitated H I in the eight BCDs. The results of this project indicate that the quiescent LSBD galaxies have more diffuse H I distributions and often show a ringlike structure, while the active galaxies have more highly centrally concentrated H I reservoirs. The bluer, more recently active systems of both types also have higher internal H I velocity dispersions, indicating that energy has been pumped into the interstellar medium of these galaxies. These observations are consistent with an evolutionary scheme wherein the H I reservoirs in these galaxies take on different characteristics depending upon their star formation histories.

  4. 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).

  5. 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).

  6. 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.

  7. Characterizing Dust Attenuation in Local Star-forming Galaxies: UV and Optical Reddening

    NASA Astrophysics Data System (ADS)

    Battisti, A. J.; Calzetti, D.; Chary, R.-R.

    2016-02-01

    The dust attenuation for a sample of ∼10,000 local (z ≲ 0.1) star-forming galaxies is constrained as a function of their physical properties. We utilize aperture-matched multiwavelength data available from the Galaxy Evolution Explorer and the Sloan Digital Sky Survey to ensure that regions of comparable size in each galaxy are being analyzed. We follow the method of Calzetti et al. and characterize the dust attenuation through the UV power-law index, β, and the dust optical depth, which is quantified using the difference in Balmer emission line optical depth, {τ }Bl={τ }{{H}β }-{τ }{{H}α }. The observed linear relationship between β and {τ }Bl is similar to the local starburst relation, but the large scatter (σint = 0.44) suggests that there is significant variation in the local universe. We derive a selective attenuation curve over the range 1250 Å < λ < 8320 Å and find that a single attenuation curve is effective for characterizing the majority of galaxies in our sample. This curve has a slightly lower selective attenuation in the UV compared to previously determined curves. We do not see evidence to suggest that a 2175 Å feature is significant in the average attenuation curve. Significant positive correlations are seen between the amount of UV and optical reddening and galaxy metallicity, mass, star formation rate (SFR), and SFR surface density. This provides a potential tool for gauging attenuation where the stellar population is unresolved, such as at high z.

  8. 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.

  9. 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.

  10. The Unresolved Star-Forming Galaxy Component of the Extragalactic Gamma Ray Background

    NASA Technical Reports Server (NTRS)

    Venters, Tonia M.; Stecker, F. W.

    2011-01-01

    We present new theoretical estimates of the contribution of unresolved star-forming galaxies to the extragalactic gamma-ray background (EGB) as measured by EGRET and the Fermi-LAT. We employ several methods for determining the star-forming galaxy contribution the the EGB, including a method positing a correlation between the gamma-ray luminosity of a galaxy and its rate of star formation as calculated from the total infrared luminosity, and a method that makes use of a model of the evolution of the galaxy gas mass with cosmic time. We find that depending on the model, unresolved star-forming galaxies could contribute significantly to the EGB as measured by the Fermi-LAT at energies between approx. 300 MeV and approx. few GeV. However, the overall spectrum of unresolved star-forming galaxies can explain neither the EGRET EGB spectrum at energies between 50 and 200 MeV nor the Fermi-LAT EGB spectrum at energies above approx. few GeV.

  11. INVERSE-COMPTON CONTRIBUTION TO THE STAR-FORMING EXTRAGALACTIC GAMMA-RAY BACKGROUND

    SciTech Connect

    Chakraborty, Nachiketa; Fields, Brian D.

    2013-08-20

    Fermi has resolved several star-forming galaxies, but the vast majority of the star-forming universe is unresolved, and thus contributes to the extragalactic gamma-ray background (EGB). Here, we calculate the contribution of star-forming galaxies to the EGB in the Fermi range from 100 MeV to 100 GeV due to inverse-Compton (IC) scattering of the interstellar photon field by cosmic-ray electrons. We first construct one-zone models for individual star-forming galaxies assuming that supernovae power the acceleration of cosmic rays. We develop templates for both normal and starburst galaxies, accounting for differences in the cosmic-ray electron propagation and in the interstellar radiation fields. For both types of star-forming galaxies, the same IC interactions leading to gamma rays also substantially contribute to the energy loss of the high-energy cosmic-ray electrons. Consequently, a galaxy's IC emission is determined by the relative importance of IC losses in the cosmic-ray electron energy budget ({sup p}artial calorimetry{sup )}. We calculate the cosmological contribution of star-forming galaxies to the EGB using our templates and the cosmic star formation rate distribution. For all of our models, we find that the IC EGB contribution is almost an order of magnitude less than the peak of the emission due to cosmic-ray ion interactions (mostly pionic p{sub cr} p{sub ism} {yields} {pi}{sup 0} {yields} {gamma}{gamma}); even at the highest Fermi energies, IC is subdominant. The flatter IC spectrum increases the high-energy signal of the pionic+IC sum, bringing it closer to the EGB spectral index observed by Fermi. Partial calorimetry ensures that the overall IC signal is relatively well constrained, with only uncertainties in the amplitude and spectral shape for plausible model choices. We conclude with a brief discussion on how the pionic spectral feature and other methods can be used to measure the star-forming component of the EGB.

  12. Global oscillations and active regions

    NASA Astrophysics Data System (ADS)

    Durrant, C. J.

    The author presents further estimates of the amplitude of the modulation of the solar global velocity signal caused by the passage of active regions across the solar disc. Using measurements of the profile of the K I λ769.9 nm line in the quiet sun and in plages he finds a global velocity variation of ≡2 m s-1 during the transit of a typical active region of area 3300 millionths of the hemisphere. However, during the period in which a velocity amplitude of 6 m s-1 was reported by Claverie et al. (1982), the sunspot areas were exceptionally large and the author confirms Schröter's (1984) result that the combination of spot and plage contributions is sufficient to account for the observed signal. The velocity modulation is thus attributable to surface inhomogeneities, not to the structure of the solar core.

  13. From star-forming galaxies to AGN: the global HI content from a stacking experiment

    NASA Astrophysics Data System (ADS)

    Geréb, K.; Morganti, R.; Oosterloo, T. A.; Hoppmann, L.; Staveley-Smith, L.

    2015-08-01

    We study the atomic neutral hydrogen (H I) content of ~1600 galaxies up to z ~ 0.1 using stacking techniques. The observations were carried out with the Westerbork Synthesis Radio Telescope (WSRT) in the area of the SDSS South Galactic Cap (SSGC), where we selected a galaxy sample from the SDSS spectroscopic catalog. Multi-wavelength information is provided by SDSS, NVSS, GALEX, and WISE. We use the collected information to study H I trends with color, star-forming, and active galactic nuclei (AGN) properties. Using near-UV (NUV) -r colors, galaxies are divided into blue cloud, green valley and red sequence galaxies. As expected based on previous observations, we detect H I in green valley objects with lower amounts of H I than blue galaxies, while stacking only produces a 3σ upper limit for red galaxies with MHI< (5 ± 1.5) × 108 M⊙ and MHI/Lr< 0.02 ± 0.006 M⊙/L⊙ (averaged over four redshift bins up to z ~ 0.1). We find that the H I content is more dependent on NUV -r color, and less on ionization properties, in the sense that regardless of the presence of an optical AGN (based on optical ionization line diagnostics), green-valley galaxies always show H I, whereas red galaxies only produce an upper limit. This suggests that feedback from optical AGN is not the (main) reason for depleting large-scale gas reservoirs. Low-level radio continuum emission in our galaxies can stem either from star formation, or from AGN. We use the WISE color-color plot to separate these phenomena by dividing the sample into IR late-type and IR early-type galaxies. We find that the radio emission in IR late-type galaxies stems from enhanced star formation, and this group is detected in H I. However, IR early-type galaxies lack any sign of H I gas and star formation activity, suggesting that radio AGN are likely to be the source of radio emission in this population. Future H I surveys will allow for extending our studies to higher redshift, and for testing any possible evolution

  14. The slow flow model of dust efflux in local star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Zahid, H. J.; Torrey, P.; Kudritzki, R. P.; Kewley, L. J.; Davé, R.; Geller, M. J.

    2013-12-01

    We develop a dust efflux model of radiation pressure acting on dust grains which successfully reproduces the relation between stellar mass, dust opacity and star formation rate observed in local star-forming galaxies. The dust content of local star-forming galaxies is set by the competition between the physical processes of dust production and dust loss in our model. The dust loss rate is proportional to the dust opacity and star formation rate. Observations of the relation between stellar mass and star formation rate at several epochs imply that the majority of local star-forming galaxies are best characterized as having continuous star formation histories. Dust loss is a consequence of sustained interaction of dust with the radiation field generated by continuous star formation. Dust efflux driven by radiation pressure rather than dust destruction offers a more consistent physical interpretation of the dust loss mechanism. By comparing our model results with the observed relation between stellar mass, dust extinction and star formation rate in local star-forming galaxies, we are able to constrain the time-scale and magnitude of dust loss. The time-scale of dust loss is long and therefore dust is effluxed in a `slow flow'. Dust loss is modest in low-mass galaxies but massive galaxies may lose up to 70-80 per cent of their dust over their lifetime. Our slow flow model shows that mass-loss driven by dust opacity and star formation may be an important physical process for understanding normal star-forming galaxy evolution.

  15. 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.

  16. Direct Measurement of Dust Attenuation in z approx. 1.5 Star-Forming Galaxies from 3D-HST: Implications for Dus