Millimeter-wave Emission Lines Research Articles

Spatially Resolved Water Emission from Gravitationally Lensed Dusty Star-forming Galaxies at z ∼ 3

Abstract Water (H2O), one of the most ubiquitous molecules in the universe, has bright millimeter-wave emission lines that are easily observed at high redshift with the current generation of instruments. The low-excitation transition of H2O, (ν rest = 987.927 GHz), is known to trace the far-infrared (FIR) radiation field independent of the presence of active galactic nuclei (AGNs) over many orders of magnitude in FIR luminosity ( ). This indicates that this transition arises mainly due to star formation. In this paper, we present spatially (∼0.″5 corresponding to ∼1 kiloparsec) and spectrally resolved (∼100 kms−1) observations of in a sample of four strong gravitationally lensed high-redshift galaxies with the Atacama Large Millimeter/submillimeter Array. In addition to increasing the sample of luminous (>1012 L ⊙) galaxies observed with H2O, this paper examines the relation on resolved scales for the first time at high redshift. We find that is correlated with on both global and resolved kiloparsec scales within the galaxy in starbursts and AGN with average . We find that the scatter in the observed relation does not obviously correlate with the effective temperature of the dust spectral energy distribution or the molecular gas surface density. This is a first step in developing as a resolved star formation rate calibrator.

Millimeter-wave Observations of Gaseous Species in Disks

The role of high spectral and spatial resolution spectroscopy in understanding the evolution of the gaseous component of circumstellar accretion disks is described. Millimeter-wave emission lines from trace constituents such as CO, CN, HCO+, and HCN can be used to probe the kinematic and physico-chemical properties in the near-surface regions of disks beyond 50–100 AU, but, thanks to extensive depletion in the midplane, they are not a reliable proxy for the disk mass. For the special case of nearly edge-on circumstellar disks, the resulting ices can be directly observed through mid-infrared spectroscopy, using ground based facilities or spacecraft (cf. Najita, this volume). Emerging and planned millimeter-wave → THz arrays will possess sufficient sensitivity and resolution to probe much closer to the central star and to search for prebiotic compounds such as those detected in comets, meteorites and interplanetary dust particles.

High‐Resolution 4.7 Micron Keck/NIRSPEC Spectra of Protostars. I. Ices and Infalling Gas in the Disk of L1489 IRS

We explore the infrared M-band (4.7 μm) spectrum of the Class I protostar L1489 IRS in the Taurus molecular cloud. This is the highest-resolution wide-coverage spectrum at this wavelength of a low-mass protostar observed to date (R = 25,000; Δv = 12 km s^(-1)). A large number of narrow absorption lines of gas-phase ^(12)CO, ^(13)CO, and C^(18)O are detected, as well as a prominent band of solid ^(12)CO. The gas-phase ^(12)CO lines have redshifted absorption wings (up to 100 km s^(-1)), which likely originate from warm disk material falling toward the central object. Both the isotopes and the extent of the ^(12)CO line wings are successfully fitted with a contracting-disk model of this evolutionary transitional object. This shows that the inward motions seen in millimeter-wave emission lines continue to within ~0.1 AU of the star. The amount of high-velocity infalling gas is, however, overestimated by this model, suggesting that only part of the disk is infalling, e.g., a hot surface layer or hot gas in magnetic field tubes. The colder parts of the disk are traced by the prominent CO-ice band. The band profile results from CO in polar ices (CO mixed with H_2O) and CO in apolar ices. At high spectral resolution, the apolar component is, for the first time, resolved into two distinct components, likely due to pure CO and CO mixed with CO_2, O_2, and/or N_2. The ices have probably undergone thermal processing in the upper disk layer traced by our pencil absorption beam: much of the volatile apolar ices has evaporated, the depletion factor of CO onto grains is remarkably low (~7%), and the CO_2 traced in the CO-band profile was possibly formed energetically. This study shows that high spectral resolution 4.7 μm observations provide important and unique information on the dynamics and structure of protostellar disks and on the origin and evolution of ices in these disks.

Excitation Analysis of SO and SO2in the Proto–Planetary Nebula OH 231.8+4.2

In the nebula OH 231.8+4.2 we have observed SO and SO2 millimeter-wave emission lines having a wide range of excitation energy. The extent of the SO emission was also mapped. Rotation diagrams were derived from these observations, and we deduced the rotation temperatures and relative abundances of SO and SO2 for three different velocity ranges corresponding to the spherical mass-loss envelope and the blue and red lobes of the bipolar outflow. The rotation temperatures for SO and SO2 are higher in the expanding envelope than in the outflow lobes. Subject to modeling uncertainties, the relative abundances of both molecules in the lobes are slightly enhanced by factors 2-5 times relative to the values in the envelope.

Electron densities and the excitation of CN in molecular clouds

In molecular clouds of modest density and relatively high fractional ionization, the rotational excitation of CN is controlled by a competition among electron impact, neutral impact and the interaction with the cosmic background radiation. The degree of excitation can be measured through optical absorption lines and millimeter-wave emission lines. The available, accurate data on CN in diffuse and translucent molecular clouds are assembled and used to determine electron densities. The derived values, n(e) = roughly 0.02 - 0.5/cu cm, imply modest neutral densities, which generally agree well with determinations by other techniques. The absorption- and emission-line measurements of CN both exclude densities higher than n(H2) = roughly 10 exp 3.5/cu cm on scales varying from 0.001 to 60 arcsec in these clouds.

Hot water around late-type stars - Detection of two millimeter-wave emission lines from the nu2 vibrationally excited state

view Abstract Citations (48) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hot Water around Late-Type Stars: Detection of Two Millimeter-Wave Emission Lines from the nu 2 Vibrationally Excited State Menten, Karl M. ; Melnick, Gary J. Abstract The first astronomical detection of two millimeter-wave emission lines from vibrationally excited water is reported. The 96 GHz 4(40)-5(33) and the 232 GHz 5(50)-6(43) rotational transitions within the nu2 vibrationally excited state of H2O have been discovered toward the supergiant star VY CMa. The latter transition was also detected toward the semiregular variable W Hya. The 4(40)-5(33) transition shows definite signs of maser action while the 5(50)-6(43) emission may be of (quasi-)thermal nature. Based on a comparison of the line profiles of the 22 GHz H2O masers, various SiO maser lines, and the nu2 H2O emission, it is concluded that the vibrationally excited H2O and the SiO masers probably arise from a region in which the expansion of the circumstellar envelope has not yet begun and some infalling motions are present. This region is closer to the star than the part of the envelope that gives rise to the 22 GHz H2O masers. Publication: The Astrophysical Journal Pub Date: June 1989 DOI: 10.1086/185465 Bibcode: 1989ApJ...341L..91M Keywords: Interstellar Masers; Late Stars; Molecular Excitation; Stellar Envelopes; Water Masers; Electron Transitions; Molecular Rotation; Radio Emission; Silicon Oxides; Vibrational Spectra; Astrophysics; MASERS; STARS: CIRCUMSTELLAR SHELLS; STARS: LATE-TYPE full text sources ADS | data products SIMBAD (8)

Linear polarization of millimeter-wave emission lines in clouds without large velocity gradients

view Abstract Citations (14) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Linear Polarization of Millimeter-Wave Emission Lines in Clouds without Large Velocity Gradients Lis, D. C. ; Goldsmith, P. F. ; Dickman, R. L. ; Predmore, C. R. ; Omont, A. ; Cernicharo, J. Abstract An equivalent model for linearly polarized emission of optically thin lines in dark clouds without embedded infrared sources which discards the large velocity gradient assumption is presented. Molecular clouds generally consist of a high-density core surrounded by an envelope with density decreasing with distance from the core. If the density contrast between the core and the outer portion of the envelope is large, the excitation temperature can drop rapidly with radius. Gradients in the excitation temperature through the cloud can be expected to produce an anisotropic radiation field away from the cloud center. If the excitation temperature is large enough, this anisotropy may produce significant differences in the population of different Zeeman sublevels of a given rotational level, resulting in the polarization of emergent radiation. Observations of (H-13)CO(+) and HCO(+) in four dark clouds show no linear polarizations. The significance of the achieved upper limits is discussed. Publication: The Astrophysical Journal Pub Date: May 1988 DOI: 10.1086/166293 Bibcode: 1988ApJ...328..304L Keywords: Emission Spectra; Interstellar Magnetic Fields; Line Spectra; Linear Polarization; Millimeter Waves; Molecular Clouds; Computational Astrophysics; Fine Structure; Formyl Ions; Molecular Ions; Velocity Distribution; Astrophysics; INTERSTELLAR: MAGNETIC FIELDS; INTERSTELLAR: MOLECULES; POLARIZATION full text sources ADS | data products SIMBAD (11)

The polarization of millimeter-wave emission lines in dense interstellar clouds

Measurements of linear polarization are reported for thermally excited CO, /sup 13/CO, HCN, and CS in 14 dense clouds which encompass a broad range of physical conditions, gas dynamics, and possible magnetic field structure. Observing techniques are described which are sensitive to polarizations as small as 0.5%, and upper limits this small were derived in some cases. In clouds with magnetic fields, significant linear polarization has been predicted due to non-LTE population of the magnetic sublevels in each rotational state. No definite linear polarization was detected in any source. Assuming that the photon escape probability is generally anisotropic in these clouds, the lack of polarization could be the effect of unresolved kinematic or magnetic field structure.

Detection of interstellar ethyl cyanide

Twenty-four millimeter-wave emission lines of ethyl cyanide (CH3CH2CN) have been detected in the Orion Nebula (OMC-1) and seven in Sgr B2. To derive precise radial velocities from the astronomical data, a laboratory measurement of the rotational spectrum of ethyl cyanide has been made at frequencies above 41 GHz. In OMC-1, the rotational temperature of ethyl cyanide is 90 K (in good agreement with other molecules), the local-standard-of-rest radial velocity is 4.5 + or - 1.0 km/s (versus 8.5 km/s for most molecules), and the column density is 1.8 by 10 to the 14th power per sq cm (a surprisingly high figure for a complicated molecule). The high abundance of ethyl cyanide in the Orion Nebula suggests that ethane and perhaps larger saturated hydrocarbons may be common constituents of molecular clouds and have escaped detection only because they are nonpolar or only weakly polar.

HCN, X-ogen /HCO+/, and U90.66 emission spectra from L134

Millimeter-wave emission lines from HCN, X-ogen (HCO/sup +/), and U90.66 from the direction of the cool dust cloud L134 have been detected. This is the first reported detection of HCN and U90.66 in a dark nebula, and the lines are the narrowest reported to date for all three species. The HCN radial velocity was used to decrease the uncertainties of the previously measured X-ogen (HCO/sup +/) and U90.66 rest frequencies. The emission profile of U90.66 was found to be consistent with the expected profile for hydrogen isocyanide (HNC). Observations suggest that L134 and other cool dust clouds should be superb objects for future high-resolution measurements of other interstellar molecules which have never been detected spectroscopically in the laboratory. (AIP)