Gemini Telescope

Hilo, HI, United States

Gemini Telescope

Hilo, HI, United States

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Persson C.M.,Chalmers University of Technology | Black J.H.,Chalmers University of Technology | Cernicharo J.,CSIC - National Institute of Aerospace Technology | Goicoechea J.R.,CSIC - National Institute of Aerospace Technology | And 55 more authors.
Astronomy and Astrophysics | Year: 2010

The HIFI instrument on board the Herschel Space Observatory has been used to observe interstellar nitrogen hydrides along the sight-line towards G10.6-0.4 in order to improve our understanding of the interstellar chemistry of nitrogen. We report observations of absorption in NH N = 1 le 0, J = 2 leftarrow 1 and ortho-NH2 11,1 ← 00,0. We also observed ortho-NH3 10 ←00, and 2 0 ← 10, para-NH3 21 ← 11, and searched unsuccessfully for NH+. All detections show emission and absorption associated directly with the hot-core source itself as well as absorption by foreground material over a wide range of velocities. All spectra show similar, non-saturated, absorption features, which we attribute to diffuse molecular gas. Total column densities over the velocity range 11-54 km s-1 are estimated. The similar profiles suggest fairly uniform abundances relative to hydrogen, approximately 6 × 10-9, 3 × 10-9, and 3 × 10-9 for NH, NH2, and NH3, respectively. These abundances are discussed with reference to models of gas-phase and surface chemistry. © 2010 ESO.


News Article | April 8, 2016
Site: www.techtimes.com

Scientists are astonished by their discovery of a supermassive black hole in a “relative desert,” a location unlike the usual dense galaxy clusters they are found in. Part of the realization is that there may be bigger populations of these monstrous black holes than commonly thought. The newly detected supermassive black hole contains 17 billion solar masses. It sits smack in the center of Galaxy NGC 1600, situated 200 million light years away from Earth and was an unlikely home for this gigantic black hole since it belongs to an average-sized galaxy group. The stars surrounding NGC 1600 also behave as if the black hole were a binary black hole, something expected to more commonly occur in large galaxies and not its unusual location. After stumbling on these monster black holes in unlikely places, the researchers – discussing their findings in the journal Nature – speculated that the population of black holes in the universe may then be much bigger than thought. Black holes form with matter becoming so dense that not even light can escape the pull of gravity. In the early days of the universe, gas was so abundant that many black holes grew to an extremely massive size by swallowing it up, giving off intense amounts of energy. These supermassive black holes appear as ultra-bright quasars when one looks back in time at the far universe, but as one looks closer to Earth, the view is of galaxies with little gas (already turning into stars) and no quasars. The most gigantic of the local galaxies, however, shelter old quasars at the core. NGC 1600, an old galaxy with little new star formation, is in a lesser populated part of the universe. Since barely inhabited regions like these are far more common than the superdense ones where the largest black holes are typically found, then finding a supermassive black hole in it may just be “the tip of an iceberg,” according to lead scientist Chung-Pei Ma. Seeking an answer for just how common these huge bodies are is the Massive Survey, a multi-telescope venture founded in 2014 for weighing the stars, dark matter, as well as central black holes of the 100 largest nearby galaxies – particularly bigger than 300 billion solar masses and within 350 million light-years of our planet. One of its early triumphs is NGC 1600’s supermassive black hole. "I'm confident we're going to find black holes – if we don't, that would be really, really strange,” says Ma. The question, she points out, is how massive the black holes could get. Will they, for instance, stop growing at 20 billion solar masses or assert themselves as even bigger monsters? The largest known black hole weighs 21 billion suns and is found in the Coma galaxy cluster, where there are over a thousand galaxies. These rich galaxy clusters are very rare, but with observations of NASA’s Hubble Space Telescope and the Gemini Telescope in Hawaii of a gigantic black hole in a sparsely populated galaxy region, there are potentially more outside of the Coma cluster types. “What this is saying is that you don’t need these galaxy clusters to grow very massive black holes,” says University of Southampton's Professor Poshak Gandhi, who was not involved in the study. Now, University of California Berkeley researchers continue to scour the Earth’s vicinity for more of these black hole wonders. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.


Gerin M.,French National Center for Scientific Research | De Luca M.,French National Center for Scientific Research | Black J.,Chalmers University of Technology | Goicoechea J.R.,CSIC - National Institute of Aerospace Technology | And 55 more authors.
Astronomy and Astrophysics | Year: 2010

We report the detection of absorption lines by the reactive ions OH +, H2O+and H3O+ along the line of sight to the submillimeter continuum source G10.6-0.4 (W31C). We used the Herschel HIFI instrument in dual beam switch mode to observe the ground state rotational transitions of OH+ at 971 GHz, H2O + at 1115 and 607 GHz, and H3O+ at 984 GHz. The resultant spectra show deep absorption over a broad velocity range that originates in the interstellar matter along the line of sight to G10.6-0.4 as well as in the molecular gas directly associated with that source. The OH + spectrum reaches saturation over most velocities corresponding to the foreground gas, while the opacity of the H2O+ lines remains lower than 1 in the same velocity range, and the H3O+line shows only weak absorption. For LSR velocities between 7 and 50 kms-1 we estimate total column densities of N(OH+) = 2.5 × 1014 cm-2, N(H 2O+) ∼6 × 1013 cm-2 and N(H3O+) ∼4.0 × 1013 cm-2. These detections confirm the role of O+ and OH+ in initiating the oxygen chemistry in diffuse molecular gas and strengthen our understanding of the gas phase production of water. The high ratio of the OH+ by the H2O+ column density implies that these species predominantly trace low-density gas with a small fraction of hydrogen in molecular form. © 2010 ESO.


Falgarone E.,French National Center for Scientific Research | Godard B.,French National Center for Scientific Research | Godard B.,Institute dAstrophysique Spatiale IAS | Cernicharo J.,CSIC - National Institute of Aerospace Technology | And 61 more authors.
Astronomy and Astrophysics | Year: 2010

We report the detection of the ground-state rotational transition of the methylidyne cation CH+ and its isotopologue 13CH + toward the remote massive star-forming regions W33A, W49N, and W51 with the HIFI instrument onboard the Herschel satellite. Both lines are seen only in absorption against the dust continuum emission of the star-forming regions. The CH+ absorption is saturated over almost the entire velocity ranges sampled by the lines-of-sight that include gas associated with the star-forming regions (SFR) and Galactic foreground material. The CH + column densities are inferred from the optically thin components. A lower limit of the isotopic ratio [12CH+]/[ 13CH+] > 35.5 is derived from the absorptions of foreground material toward W49N. The column density ratio, N(CH +)/N(HCO+), is found to vary by at least a factor 10, between 4 and >40, in the Galactic foreground material. Line-of-sight 12CH+ average abundances relative to total hydrogen are estimated. Their average value, N(CH+)/NH > 2.6×10-8, is higher than that observed in the solar neighborhood and confirms the high abundances of CH+ in the Galactic interstellar medium. We compare this result to the predictions of turbulent dissipation regions (TDR) models and find that these high abundances can be reproduced for the inner Galaxy conditions. It is remarkable that the range of predicted N(CH+)/N(HCO+) ratios, from 1 to ∼50, is comparable to that observed. © 2010 ESO.


Neufeld D.A.,Johns Hopkins University | Goicoechea J.R.,CSIC - National Institute of Aerospace Technology | Sonnentrucker P.,Johns Hopkins University | Black J.H.,Chalmers University of Technology | And 49 more authors.
Astronomy and Astrophysics | Year: 2010

We report the detection of absorption by interstellar hydroxyl cations and water cations, along the sight-line to the bright continuum source W49N. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 972 GHz N = 1-0 transition of OH+ and the 1115 GHz 111-0 00 transition of ortho-H2O+. The resultant spectra show absorption by ortho-H2O+, and strong absorption by OH+, in foreground material at velocities in the range 0 to 70 km s-1 with respect to the local standard of rest. The inferred OH+/H2O+ abundance ratio ranges from ∼3 to ∼15, implying that the observed OH+ arises in clouds of small molecular fraction, in the 2-8% range. This conclusion is confirmed by the distribution of OH+ and H2O+ in Doppler velocity space, which is similar to that of atomic hydrogen, as observed by means of 21 cm absorption measurements, and dissimilar from that typical of other molecular tracers. The observed OH+/H abundance ratio of a few × 10-8 suggests a cosmic ray ionization rate for atomic hydrogen of 0.6-2.4×10-16 s-1, in good agreement with estimates inferred previously for diffuse clouds in the Galactic disk from observations of interstellar H3+ and other species. © 2010 ESO.


Gerin M.,French National Center for Scientific Research | De Luca M.,French National Center for Scientific Research | Goicoechea J.R.,CSIC - National Institute of Aerospace Technology | Herbst E.,Ohio State University | And 59 more authors.
Astronomy and Astrophysics | Year: 2010

We report the detection of the ground state N,J = 1,3/2 rightarrow 1,1/2 doublet of the methylidyne radical CH at ∼532 GHz and ∼536 GHz with the Herschel/HIFI instrument along the sight-line to the massive star-forming regions G10.6-0.4 (W31C), W49N, and W51. While the molecular cores associated with these massive star-forming regions show emission lines, clouds in the diffuse interstellar medium are detected in absorption against the strong submillimeter background. The combination of hyperfine structure with emission and absorption results in complex profiles, with overlap of the different hyperfine components. The opacities of most of the CH absorption features are linearly correlated with those of CCH, CN, and HCO+ in the same velocity intervals. In specific narrow velocity intervals, the opacities of CN and HCO+ deviate from the mean trends, giving rise to more opaque absorption features. We propose that CCH can be used as another tracer of the molecular gas in the absence of better tracers, with [CCH]/[H2] ∼ 3.2±1.1×10-8. The observed [CN]/[CH], [CCH]/[CH] abundance ratios suggest that the bulk of the diffuse matter along the lines of sight has gas densities nH = n(H) + 2n(H2) ranging between 100 and 1000 cm-3. © 2010 ESO.


Neufeld D.A.,Johns Hopkins University | Sonnentrucker P.,Johns Hopkins University | Phillips T.G.,California Institute of Technology | Lis D.C.,California Institute of Technology | And 44 more authors.
Astronomy and Astrophysics | Year: 2010

We report the detection of strong absorption by interstellar hydrogen fluoride along the sight-line to the submillimeter continuum source G10.6-0.4 (W31C). We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 1232.4763 GHz J = 1-0 HF transition in the upper sideband of the Band 5a receiver. The resultant spectrum shows weak HF emission from G10.6-0.4 at LSR velocities in the range -10 to -3 km s-1, accompanied by strong absorption by foreground material at LSR velocities in the range 15 to 50 km s-1. The spectrum is similar to that of the 1113.3430 GHz 1 11-000 transition of para-water, although at some frequencies the HF (hydrogen fluoride) optical depth clearly exceeds that of para-H2O. The optically-thick HF absorption that we have observed places a conservative lower limit of 1.6×1014 cm-2 on the HF column density along the sight-line to G10.6-0.4. Our lower limit on the HF abundance, 6×10-9 relative to hydrogen nuclei, implies that hydrogen fluoride accounts for between ∼30% and 100% of the fluorine nuclei in the gas phase along this sight-line. This observation corroborates theoretical predictions that - because the unique thermochemistry of fluorine permits the exothermic reaction of F atoms with molecular hydrogen - HF will be the dominant reservoir of interstellar fluorine under a wide range of conditions. © ESO 2010.


Mookerjea B.,Tata Institute of Fundamental Research | Giesen T.,University of Cologne | Stutzki J.,University of Cologne | Cernicharo J.,CSIC - National Institute of Aerospace Technology | And 47 more authors.
Astronomy and Astrophysics | Year: 2010

We present spectrally resolved observations of triatomic carbon (C 3) in several ro-vibrational transitions between the vibrational ground state and the low-energy ν2 bending mode at frequencies between 1654-1897 GHz along the sight-lines to the submillimeter continuum sources W31C and W49N, using Herschel's HIFI instrument. We detect C3 in absorption arising from the warm envelope surrounding the hot core, as indicated by the velocity peak position and shape of the line profile. The sensitivity does not allow to detect C3 absorption due to diffuse foreground clouds. From the column densities of the rotational levels in the vibrational ground state probed by the absorption we derive a rotation temperature (Trot) of ∼50-70 K, which is a good measure of the kinetic temperature of the absorbing gas, as radiative transitions within the vibrational ground state are forbidden. It is also in good agreement with the dust temperatures for W31C and W49N. Applying the partition function correction based on the derived Trot, we get column densities N(C3) ∼ 7-9 × 1014 cm-2 and abundance x(C3) ∼ 10-8 with respect to H2. For W31C, using a radiative transfer model including far-infrared pumping by the dust continuum and a temperature gradient within the source along the line of sight we find that a model with x(C3) = 10-8, Tkin = 30-50 K, N(C3) = 1.5 × 1015 cm-2 fits the observations reasonably well and provides parameters in very good agreement with the simple excitation analysis. © 2010 ESO.


Sonnentrucker P.,Johns Hopkins University | Neufeld D.A.,Johns Hopkins University | Phillips T.G.,California Institute of Technology | Gerin M.,French National Center for Scientific Research | And 46 more authors.
Astronomy and Astrophysics | Year: 2010

We discuss the detection of absorption by interstellar hydrogen fluoride (HF) along the sight line to the submillimeter continuum sources W49N and W51. We have used Herschel's HIFI instrument in dual beam switch mode to observe the 1232.4762 GHz J = 1-0 HF transition in the upper sideband of the band 5a receiver. We detected foreground absorption by HF toward both sources over a wide range of velocities. Optically thin absorption components were detected on both sight lines, allowing us to measure-as opposed to obtain a lower limit on-the column density of HF for the first time. As in previous observations of HF toward the source G10.6-0.4, the derived HF column density is typically comparable to that of water vapor, even though the elemental abundance of oxygen is greater than that of fluorine by four orders of magnitude. We used the rather uncertain N(CH)-N(H2) relationship derived previously toward diffuse molecular clouds to infer the molecular hydrogen column density in the clouds exhibiting HF absorption. Within the uncertainties, we find that the abundance of HF with respect to H2 is consistent with the theoretical prediction that HF is the main reservoir of gas-phase fluorine for these clouds. Thus, hydrogen fluoride has the potential to become an excellent tracer of molecular hydrogen, and provides a sensitive probe of clouds of small H 2 column density. Indeed, the observations of hydrogen fluoride reported here reveal the presence of a low column density diffuse molecular cloud along the W51 sight line, at an LSR velocity of ∼24 km s-1, that had not been identified in molecular absorption line studies prior to the launch of Herschel. © 2010 ESO.

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