302 research outputs found

    Physical properties and morphology of a newly identified compact z=4.04 lensed submillimeter galaxy in Abell 2218

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    We present the identification of a bright submm source, SMMJ163555.5+661300, detected in the lensing cluster Abell2218, for which we have accurately determined the position using observations from the Submillimeter Array (SMA). The identified optical counterpart has a spectroscopic redshift of z=4.044+-0.001 if we attribute the single emission line detected at lambda=6140AA to Lyman-alpha. This redshift identification is in good agreement with the optical/near-infrared photometric redshift as well as the submm flux ratio S_450/S_850~1.6, the radio-submm flux ratio S_1.4/S_850 < 0.004, and the 24um to 850um flux ratio S_24/S_850 < 0.005. Correcting for the gravitational lensing amplification of ~5.5, we find that the source has a far-infrared luminosity of 1.3x10^12 Lsun, which implies a star formation rate of 230 Msun/yr. This makes it the lowest-luminosity SMG known at z>4 to date. Previous CO(4-3) emission line obserations yielded a non-detection, for which we derived an upper limit of the CO line luminosity of L'_CO = 0.3x10^10 K km/s/pc^2, which is not inconsistent with the L'_CO - L_FIR relation for starburst galaxies. The best fit model to the optical and near-infrared photometry give a stellar population with an age of 1.4 Gyr and a stellar mass of 1.6x10^10 Msun. The optical morphology is compact and in the source plane the galaxy has an extent of ~6kpc x 3kpc with individual star forming knots of <500 pc in size. J163556 is not resolved in the SMA data and we place a strict upper limit on the size of the starburst region of 8kpc x 3kpc, which implies a lower limit on the star formation rate surface density of 12 Msun/yr/kpc^2. The redshift of J163556 extends the redshift distribution of faint, lensed SMGs, and we find no evidence that these have a different redshift distribution than bright SMGs.Comment: Accepted for publication in ApJ. 11 pages, 7 figure

    Unveiling Palomar 2: The Most Obscure Globular Cluster in the Outer Halo

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    We present the first color-magnitude study for Palomar 2, a distant and heavily obscured globular cluster near the Galactic anticenter. Our (V,V-I) color-magnitude diagram (CMD), obtained with the UH8K camera at the CFHT, reaches V(lim) = 24 and clearly shows the principal sequences of the cluster, though with substantial overall foreground absorption and differential reddening. The CMD morphology shows a well populated red horizontal branch with a sparser extension to the blue, similar to clusters such as NGC 1261, 1851, or 6229 with metallicities near [Fe/H] = -1.3.Fromanaverageofseveralindicators,weestimatetheforegroundreddeningatE(B−V)=1.24+−0.07andobtainatruedistancemodulus(m−M)0=17.1+−0.3. From an average of several indicators, we estimate the foreground reddening at E(B-V) = 1.24 +- 0.07 and obtain a true distance modulus (m-M)_0 = 17.1 +- 0.3, placing it about 34 kpc from the Galactic center. We use starcounts of the bright stars to measure the core radius, half-mass radius, and central concentration of the cluster. Its integrated luminosity is M_V = -7.9, making it clearly brighter and more massive than most other clusters in the outer halo.Comment: 25 pages, aastex, with 8 postscript figures; accepted for publication in AJ, September 1997. Also available by e-mail from [email protected]. Please consult Harris directly for (big) postscript files of Figures 1a,b (the images of the cluster

    The Effect of Star Formation on Molecular Clouds in Dwarf Irregular Galaxies: IC 10 and NGC 6822

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    We have observed the 13CO J=2-1, 12CO J=2-1 and 12CO J=3-2 lines at a few locations in the dwarf irregular galaxies IC 10 and NGC 6822 using the James Clerk Maxwell Telescope. In addition, we report the first detection of the 13CO J=3-2 transition in a Local Group galaxy. These low metallicity environments appear to be porous to UV radiation and allow for more efficient heating of molecular gas by nearby HII regions. The high 12CO J=3-2/J=2-1 ratio in NGC 6822 suggests that the 12CO emission is optically thin in this region. This high line ratio is likely the result of its location inside a large HII region with low metallicity and low gas content. In IC 10 we observe structures on a variety of size scales that all appear to be gravitationally bound. This effect may help explain the rather high star formation rate in IC 10.Comment: 20 pages with 6 ps figures, accepted for publication in The Astrophysical Journa

    The Physical Conditions and Dynamics of the Interstellar Medium in the Nucleus of M83: Observations of CO and CI

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    This paper presents CI, CO J=4-3, and CO J=3-2 maps of the barred spiral galaxy M83 taken at the James Clerk Maxwell Telescope. Observations indicate a double peaked structure which is consistent with gas inflow along the bar collecting at the inner Lindblad resonance. This structure suggests that nuclear starbursts can occur even in galaxies where this inflow/collection occurs, in contrast to previous studies of barred spiral galaxies. However, the observations also suggest that the double peaked emission may be the result of a rotating molecular ring oriented nearly perpendicular to the main disk of the galaxy. The CO J=4-3 data indicate the presence of warm gas in the nucleus that is not apparent in the lower-J CO observations, which suggests that CO J=1-0 emission may not be a reliable tracer of molecular gas in starburst galaxies. The twelve CI/CO J=4-3 line ratios in the inner 24'' x 24'' are uniform at the 2 sigma level, which indicates that the CO J=4-3 emission is originating in the same hot photon-dominated regions as the CI emission. The CO J=4-3/J=3-2 line ratios vary significantly within the nucleus with the higher line ratios occurring away from peaks of emission along an arc of active star forming regions. These high line ratios (>1) likely indicate optically thin gas created by the high temperatures caused by star forming regions in the nucleus of this starburst galaxy.Comment: 15 pages with 10 figures. To appear in the August 10 1998 issue of The Astrophysical Journa

    The obscured hyper-energetic GRB 120624B hosted by a luminous compact galaxy at z = 2.20

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    Gamma-ray bursts are the most luminous explosions that we can witness in the Universe. Studying the most extreme cases of these phenomena allows us to constrain the limits for the progenitor models. In this Letter, we study the prompt emission, afterglow, and host galaxy of GRB 120624B, one of the brightest GRBs detected by Fermi, to derive the energetics of the event and characterise the host galaxy in which it was produced. Following the high-energy detection we conducted a multi-wavelength follow-up campaign, including near-infrared imaging from HAWKI/VLT, optical from OSIRIS/GTC, X-ray observations from the Chandra X-ray Observatory and at sub-millimetre/millimetre wavelengths from SMA. Optical/nIR spectroscopy was performed with X-shooter/VLT. We detect the X-ray and nIR afterglow of the burst and determine a redshift of z = 2.1974 +/- 0.0002 through the identification of emission lines of [OII], [OIII] and H-alpha from the host galaxy of the GRB. This implies an energy release of Eiso = (3.0+/-0.2)x10^54 erg, amongst the most luminous ever detected. The observations of the afterglow indicate high obscuration with AV > 1.5. The host galaxy is compact, with R1/2 < 1.6 kpc, but luminous, at L ~ 1.5 L* and has a star formation rate of 91 +/- 6 Msol/yr as derived from H-alpha. As other highly obscured GRBs, GRB 120624B is hosted by a luminous galaxy, which we also proof to be compact, with a very intense star formation. It is one of the most luminous host galaxies associated with a GRB, showing that the host galaxies of long GRBs are not always blue dwarf galaxies, as previously thought.Comment: 6 pages, 4 figures, 4 tables; accepted for publication in A&

    SMA Imaging of CO(3-2) Line and 860 micron Continuum of Arp 220 : Tracing the Spatial Distribution of Luminosity

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    We used the Submillimeter Array (SMA) to image 860 micron continuum and CO(3-2) line emission in the ultraluminous merging galaxy Arp 220, achieving a resolution of 0.23" (80 pc) for the continuum and 0.33" (120 pc) for the line. The CO emission peaks around the two merger nuclei with a velocity signature of gas rotation around each nucleus, and is also detected in a kpc-size disk encompassing the binary nucleus. The dust continuum, in contrast, is mostly from the two nuclei. The beam-averaged brightness temperature of both line and continuum emission exceeds 50 K at and around the nuclei, revealing the presence of warm molecular gas and dust. The dust emission morphologically agrees with the distribution of radio supernova features in the east nucleus, as expected when a starburst heats the nucleus. In the brighter west nucleus, however, the submillimeter dust emission is more compact than the supernova distribution. The 860 micron core, after deconvolution, has a size of 50-80 pc, consistent with recent 1.3 mm observations, and a peak brightness temperature of (0.9-1.6)x10^2 K. Its bolometric luminosity is at least 2x10^{11} Lsun and could be ~10^{12} Lsun depending on source structure and 860 micron opacity, which we estimate to be of the order of tau_{860} ~ 1 (i.e., N_{H_2} ~ 10^{25} cm^{-2}). The starbursting west nuclear disk must have in its center a dust enshrouded AGN or a very young starburst equivalent to hundreds of super star clusters. Further spatial mapping of bolometric luminosity through submillimeter imaging is a promising way to identify the heavily obscured heating sources in Arp 220 and other luminous infrared galaxies.Comment: ApJ. in press. 26 pages, 10 figure

    A High Resolution Mosaic of Molecular Gas in Stephan's Quintet

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    We present high resolution CO J=1-0 observations of the molecular gas in the Hickson Compact Group Stephan's Quintet (HCG92). Our observations consist of multiple pointing and mosaics covering all the regions where CO and star formation has been detected. Within the 100'' field of view centered on the eastern-most tidal tail, we detect three clumps of emission that may be partially resolved at our resolution of 8''; two of these are new detections not previously seen in ISM studies of this region. Two of these clumps lie in the optical tidal tail, while the third lies to the southeast and is coincident with a large HI feature, but does not correspond to any features at other wavelengths. We also tentatively detect CO emission from the star forming regions in the ``Old Tail'' corresponding to recent star formation activity detected in recent UV and Hα\alpha observations. Observations of the rest of the compact group do not show detections even though strong emission was detected with single dish telescopes, which suggests the CO emission originates from a diffuse molecular gas cloud or from more at least three separate clumps with separations of greater than around 3 kpc.Comment: 23 pages, 6 figures, to appear in the ApJ 1 November 2005, v633, 1 issue. Full resolution versions of figures available at http://cfa-www.harvard.edu/~gpetitpas/hcg92

    A psycho-educational curriculum for sport career transition practitioners: Development and evaluation

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    Research question: This paper is an integration of three studies. Study 1 investigates sport career transition organisational intervention programmes for high performance athletes and training and development programmes for sport career transition practitioners in order to find a research gap with regard to sport career transition supporting services. A psycho-educational curriculum was developed for sport career transition practitioner in Study 2 to fill the research gap. In Study 3, the curriculum was examined to see if the curriculum contributed to enhancing practitioners’ confidence in key competences.  Research methods: A range of methods were applied to the studies including One Group Pre- and Post-test design, Case Study, Focus Group, Semi-Structured Interview, two-round Delphi-Method and Questionnaires. The data for Study 1 collected from 19 countries worldwide and total 16 participants based in seven different countries were invited to development and evaluation of the curriculum.  Results and Findings: A novel psycho-educational curriculum for sport career transition practitioner was developed and evaluated concerning four competences as a form of curriculum package. The findings revealed that the curriculum package increased the participants’ confidence in key competences concerning sport career transition.  Implications: The findings deepen the knowledge of sport career transition in the areas of organisational intervention programmes focusing on high performance athletes and sport career transition practitioners. These findings contribute to modifying the Conceptual Model of Adaptation to Career Transition (Lavallee, Park, & Taylor, 2014) by strengthening the organisational intervention perspective and applied work in respect of sporting organisation management strategie

    Forming double-barred galaxies from dynamically cool inner disks

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    About one-third of early-type barred galaxies host small-scale secondary bars. The formation and evolution of such double-barred (S2B) galaxies remain far from being well understood. In order to understand the formation of such systems, we explore a large parameter space of isolated pure-disk simulations. We show that a dynamically cool inner disk embedded in a hotter outer disk can naturally generate a steady secondary bar while the outer disk forms a large-scale primary bar. The independent bar instabilities of inner and outer disks result in long-lived double-barred structures whose dynamical properties are comparable to those in observations. This formation scenario indicates that the secondary bar might form from the general bar instability, the same as the primary bar. Under some circumstances, the interaction of the bars and the disk leads to the two bars aligning or single, nuclear, bars only. Simulations that are cool enough of the center to experience clump instabilities may also generate steady S2B galaxies. In this case, the secondary bars are “fast,” i.e., the bar length is close to the co-rotation radius. This is the first time that S2B galaxies containing a fast secondary bar are reported. Previous orbit-based studies had suggested that fast secondary bars were not dynamically possibl
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