Far-infrared emission lines of CO and OH in the Orion-KL molecular shock
TL;DR: In this article, the far infrared rotational emission lines are observed to have velocity widths of Del V approx. 20 to 30 km/sec, somewhat less than either the 2 micro H sub 2 lines or the high velocity plateau component of the millimeter wave CO lines seen in this object.
Abstract: Observations of far infrared rotational emission lines which arise in the shocked gas associted with Orion-Kl are presented, including detections of the CO J = 34 yields 33, J = 31 yields 30, J = 26 yields 25, and OH sup 2 PI sub (3/2) J sup P = 7/2(-) yields 5/2(+) emission lines, as well as improved measurements of the CO J = 22 yields 21 and OH sup 2 PI sub (3/2) J = 5/2 yields 3/2 lines. These lines are observed to have velocity widths of Del V approx. 20 to 30 km/sec, somewhat less than either the 2 micro H sub 2 lines or the high velocity plateau component of the millimeter wave CO lines seen in this object. An H sub 2 column density of aprox. 3 x 10 to the 21st power, a total mass of approx. 1 solar mass and characteristic temperature and density T approx. 750 K and approx. 2 x 10 to the 6th power per cu cm can be derived from the CO intensities. The density is too low by at least an order of magnitude for the observed infrared H sub 2 and far infrared CO emission to bemore » accounted for by a purely hydrodynamic shock, and support is lent to hydromagnetic shock models. From the present measurements, the relative abundance of CO is estimated to be CO H sub 2 = 1.2 x .0001, corresponding to 20 percent of the cosmic abundance of C existing in the form of CO. The average relative abundance of OH in the shocked gas is O/H sub 2 or = 5 x 10 to the -7th power. An upper limit to the intensity of the HD J - 1 yields 0 line is used to derive an upper limit of tau or = 3 for the D/H relative abundance in the Orion cloud core. 61 references.« less
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TL;DR: In this paper, the authors reported the detection of massive molecular outflows, traced by the hydroxyl molecule (OH), in far-infrared spectra of ULIRGs obtained with Herschel-PACS as part of the SHINING key project.
Abstract: Mass outflows driven by stars and active galactic nuclei (AGNs) are a key element in many current models of galaxy evolution. They may produce the observed black-hole-galaxy mass relation and regulate and quench both star formation in the host galaxy and black hole accretion. However, observational evidence of such feedback processes through outflows of the bulk of the star-forming molecular gas is still scarce. Here we report the detection of massive molecular outflows, traced by the hydroxyl molecule (OH), in far-infrared spectra of ULIRGs obtained with Herschel-PACS as part of the SHINING key project. In some of these objects the (terminal) outflow velocities exceed 1000?km?s?1, and their outflow rates (up to ~1200 M ? yr?1) are several times larger than their star formation rates. We compare the outflow signatures in different types of ULIRGs and in starburst galaxies to address the issue of the energy source (AGN or starburst) of these outflows. We report preliminary evidence that ULIRGs with a higher AGN luminosity (and higher AGN contribution to L IR) have higher terminal velocities and shorter gas depletion timescales. The outflows in the observed ULIRGs are able to expel the cold gas reservoirs from the centers of these objects within ~106-108 years.
606 citations
TL;DR: In this article, a review of the measurement processes and the interpretations needed to obtain actual isotope and element abundances from measurements is presented, with emphasis placed on descriptions of the measurements.
Abstract: Measurements of the present-day abundances of elements and isotopes, combined with model calculations, allow us to trace the history of nucleosynthesis in the universe. Throughout this review, emphasis will be placed on descriptions of the measurement processes and the interpretations needed to obtain actual isotope and element abundances from measurements. Comparisons of the abundances of isotopomers of a given element are less affected by systematic effects than are comparisons of the abundances of different elements. Thus ratios of isotopomers should be given a greater weight when data and models are compared. As is generally accepted, the universe began with an explosive event, the Big Bang. The nucleosynthesis associated with this event produced `primordial' abundances of the `light elements', deuterium, , , and . Subsequent stellar processing of the light elements has altered the relative abundances, and also produced heavier elements such as carbon, nitrogen and oxygen. Stellar nucleosynthesis products from solar and larger mass stars are expelled into the interstellar medium (ISM). The goal of studies of the abundances of the light elements is to estimate the primordial abundances, that is, the abundances produced in the Big Bang. It is believed that D is always net destroyed in stars; and may be net produced, is certainly net produced. In the Solar System itself, results are obtained from in situ measurements with space probes to Jupiter, measurements of solar wind constituents, the analysis of the content of meteorites, and spectral line measurements of the solar photosphere. For sources outside the Solar System, these data are based on spectral line measurements of gas-phase species. The ratio of gas-phase abundances of elements, such as carbon to lithium may be affected by differing amounts of condensation onto dust grains; however such a process will not affect the ratio of isotopes such as . The most reliable measurements of D to H ratios are based on spectroscopic measurements of Lyman series ultraviolet absorption lines from foreground interstellar gas. Measurements of clouds in our galaxy have been obtained with satellites such as the International Ultraviolet Observatory, Copernicus, and the Hubble Space Telescope. The most interesting new development is the measurement of distant clouds with large redshifted velocities. Such data can be taken with Earth-bound optical telescopes. In the near future the Far Ultra Violet Explorer will refine and extend measurements of D/H ratios in relatively nearby regions. Abundances of in the ISM have been measured using the hyperfine transition of , in galactic H II regions which are ionized by high-mass stars. is the most abundant of the light elements. The primordial abundance must be very accurately determined if one wishes to use this quantity to estimate the baryon density in the early universe. Recently /H ratios have been measured in a number of metal-poor compact blue galaxies. These sources seem to have had little stellar evolution, so the ratio should be close to the primordial value. Estimates of the primordial abundance of are made for a population of old stars found far from the plane of our galaxy. A refinement of Li abundance estimates requires a more detailed understanding of the Li destruction processes in stars.
323 citations
TL;DR: In this paper, a case-by-case analysis of results for D, He, Li and CNO isotope data in the disk and center of our galaxy is presented; previous results for element gradients are also summarized.
Abstract: Recent developments in the theory of element production and the chemical evolution of the galaxy are presented. Following this, observational data and their interpretation are given. A case by case analysis of results for D, He, Li and CNO isotope data in the disk and center of our galaxy is presented; previous results for element gradients are also summarized. The primordial abundances of D and He cannot be directly obtained from observations; corrections for stellar processing are discussed. From these data and the Li abundances, it appears that the abundance of the light elements is consistent with the standard big bang. In agreement with previous results, the range ofη, the baryon to photon ratio, is 5–8 10−10. If the amount of non-baryonic matter is small, these results indicate an open universe, in the standard big bang model. New data show a gradient in the (12C/13C) and (16O/18O) ratios with galactocentric distance, DGC. The presence of a gradient in the (14N/15N) ratio is less clear and there is no measurable gradient in the (32S/34S) ratio. In the interstellar medium near the sun, the carbon isotope ratio is −20 percent lower than the solar system ratio. This indicates that there has been only a moderate amount of enrichment of the nearby interstellar medium since the formation of the solar system. These results and previously determined galactic element gradients are interpreted in the framework of chemical evolution models. Delayed recycling of nucleosynthesis products is essential for the correct interpretation of the results. Comparisons of data with galactic evolution models are discussed.
153 citations
University of Rochester1, Johns Hopkins University2, University of Toledo3, European Space Agency4, University of Michigan5, National Radio Astronomy Observatory6, Max Planck Society7, University of Arizona8, California Institute of Technology9, United States Naval Research Laboratory10, Herzberg Institute of Astrophysics11, Spanish National Research Council12, Joseph Fourier University13
TL;DR: In this article, the authors analyzed the emission lines from rotational transitions of CO, involving rotational quantum numbers in the range J_(up) = 14-46, using PACS spectra extracted within a projected distance of ≾2000 AU centered on the protostar.
Abstract: We present far-infrared (57-196 μm) spectra of 21 protostars in the Orion molecular clouds. These were obtained with the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel Space observatory as part of the Herschel Orion Protostar Survey program. We analyzed the emission lines from rotational transitions of CO, involving rotational quantum numbers in the range J_(up) = 14-46, using PACS spectra extracted within a projected distance of ≾2000 AU centered on the protostar. The total luminosity of the CO lines observed with PACS (L_(CO)) is found to increase with increasing protostellar luminosity (L_(bol)). However, no significant correlation is found between L_(CO) and evolutionary indicators or envelope properties of the protostars such as bolometric temperature, T_(bol), or envelope density. The CO rotational (excitation) temperature implied by the line ratios increases with increasing rotational quantum number J, and at least 3–4 rotational temperature components are required to fit the observed rotational diagram in the PACS wavelength range. The rotational temperature components are remarkably invariant between protostars and show no dependence on L_(bol), T_(bol), or envelope density, implying that if the emitting gas is in local thermodynamic equilibrium, the CO emission must arise in multiple temperature components that remain independent of L_(bol) over two orders of magnitudes. The observed CO emission can also be modeled as arising from a single-temperature gas component or from a medium with a power-law temperature distribution; both of these require sub-thermally excited molecular gas at low densities (n(H_2) ≾ 10^6 cm^(–3)) and high temperatures (T≳2000 K). Our results suggest that the contribution from photodissociation regions, produced along the envelope cavity walls from UV-heating, is unlikely to be the dominant component of the CO emission observed with PACS. Instead, the "universality" of the rotational temperatures and the observed correlation between L_(CO) and L_(bol) can most easily be explained if the observed CO emission originates in shock-heated, hot (T≳2000 K), sub-thermally excited (n(H_2) ≾ 10^6 cm^(–3)) molecular gas. Post-shock gas at these densities is more likely to be found within the outflow cavities along the molecular outflow or along the cavity walls at radii ≳ several 100-1000 AU.
119 citations
TL;DR: In this article, a non-local radiative transfer code was used to model the spectrum of the ultraluminous infrared galaxy Arp 220 and the emission/absorption of all observed features.
Abstract: ISO/LWS grating observations of the ultraluminous infrared galaxy Arp 220 shows absorption in molecular lines of OH, H 2 0 , CH, NH, and "3, well as in the [0 I] 63 pm line and emission in the [C 111 158 pm line. We have modeled the continuum and the emission/absorption of all observed features by means of a non-local radiative transfer code. The continuum from 25 to 1300 pm is modeled AS A WARM (106 K) NUCLEAR REGION THAT IS OPTICALLY THICK IN THE FAR-INFRARED, attenuated by an extended region (size 2") that is heated mainly through absorption of nuclear infrared radiation. The molecular absorption in the nuclear region is characterized by high excitation due to the high infrared radiation density. The OH column densities are high toward the nucleus and the extended region (about 2 x 10 sup 17 cm sup-2). The H2O column density is also high toward the nucleus (2 - 10 x 1017 cm-2) and lower in the extended region. The column densities in a halo that accounts for the absorption by the lowest lying levels are similar to what are found in the diffuse clouds toward the star forming regions in the Sgr B2 molecular cloud complex near the Galactic Center. Most notable are the high column densities found for NH and NH3 toward the nucleus, with values of about 1.5 x 10supl6 cmsup-2 and about 3 x 10supl6 cmsup-2, respectively, whereas the NH2 column density is lower than about 2 x 10sup15 cmsup-2. A combination of PDRs in the extended region and hot cores with enhanced H20 photodissociation and a possible shock contribution in the nuclei may explain the relative column densities of OH and H20, whereas the nitrogen chemistry may be strongly affected by cosmic ray ionization. The [C II] 158 pm line is well reproduced by our models and its "deficit" relative to the CII/FIR ratio in normal and starburst galaxies is suggested to be mainly a consequence of the dominant non-PDR component of far- infrared radiation, ALTHOUGH OUR MODELS ALONE CANNOT RULE OUT EXTINCTION EFFECTS IN THE NUCLEI.
117 citations