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Title: SUBMILLIMETER LINE SPECTRUM OF THE SEYFERT GALAXY NGC 1068 FROM THE HERSCHEL-SPIRE FOURIER TRANSFORM SPECTROMETER

Abstract

The first complete submillimeter spectrum (190-670 {mu}m) of the Seyfert 2 galaxy NGC 1068 has been observed with the SPIRE Fourier transform spectrometer on board the Herschel Space Observatory. The sequence of CO lines (J {sub up} = 4-13), lines from H{sub 2}O, the fundamental rotational transition of hydrogen fluoride, two o-H{sub 2}O{sup +} lines, and one line each from CH{sup +} and OH{sup +} have been detected, together with the two [C I] lines and the [N II] 205 {mu}m line. The observations in both single pointing mode with sparse image sampling and in mapping mode with full image sampling allow us to disentangle two molecular emission components, one due to the compact circumnuclear disk (CND) and one from the extended region encompassing the star-forming ring (SF-ring). Radiative transfer models show that the two CO components are characterized by densities of n(H{sub 2}) = 10{sup 4.5} and 10{sup 2.9} cm{sup -3} and temperatures of T {sub kin} = 100 K and 127 K, respectively. A comparison of the CO line intensities with the photodissociation region (PDR) and X-ray-dominated region (XDR) models, together with the other observational constraints, such as the observed CO surface brightness and the radiation field, indicatesmore » that the best explanation for the CO excitation of the CND is an XDR with a density of n(H{sub 2}) {approx} 10{sup 4} cm{sup -3} and an X-ray flux of 9 erg s{sup -1} cm{sup -2}, consistent with illumination by the active galactic nucleus, while the CO lines in the SF-ring are better modeled by a PDR. The detected water transitions, together with those observed with the Herschel PACS spectrometer, can be modeled by a large velocity gradient model with low temperature (T {sub kin} {approx} 40 K) and high density (n(H{sub 2}) in the range 10{sup 6.7}-10{sup 7.9} cm{sup -3}). The emission of H{sub 2}O{sup +} and OH{sup +} are in agreement with PDR models with cosmic-ray ionization. The diffuse ionized atomic component observed through the [N II] 205 {mu}m line is consistent with previous photoionization models of the starburst.« less

Authors:
; ;  [1]; ; ;  [2]; ; ; ;  [3];  [4];  [5];  [6];  [7];  [8];  [9]
  1. Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via Fosso del Cavaliere 100, I-00133 Roma (Italy)
  2. Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada)
  3. Center for Astrophysics and Space Astronomy, 389-UCB, University of Colorado, Boulder, CO 80303 (United States)
  4. UK ALMA Regional Centre Node, Jordell Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)
  5. CEA, Laboratoire AIM, Irfu/SAp, Orme des Merisiers, F-91191 Gif-sur-Yvette (France)
  6. Astronomy Department, University of Maryland, College Park, MD 20742 (United States)
  7. Laboratoire d'Astrophysique de Marseille-LAM, Universite d'Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France)
  8. Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
  9. Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)
Publication Date:
OSTI Identifier:
22086519
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 758; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; CARBON MONOXIDE; COSMIC RADIATION; EMISSION SPECTRA; EMISSION SPECTROSCOPY; EXCITATION; FOURIER TRANSFORM SPECTROMETERS; GALAXY NUCLEI; HYDROGEN; HYDROGEN FLUORIDES; HYDROXIDES; ION EMISSION; PHOTOIONIZATION; RADIANT HEAT TRANSFER; RADIOASTRONOMY; SEYFERT GALAXIES; STARS; X RADIATION

Citation Formats

Spinoglio, Luigi, Pereira-Santaella, Miguel, Busquet, Gemma, Schirm, Maximilien R. P., Wilson, Christine D., Parkin, Tara J., Glenn, Jason, Kamenetzky, Julia, Rangwala, Naseem, Maloney, Philip R., Bendo, George J., Madden, Suzanne C., Wolfire, Mark G., Boselli, Alessandro, Cooray, Asantha, and Page, Mathew J., E-mail: luigi.spinoglio@iaps.inaf.it. SUBMILLIMETER LINE SPECTRUM OF THE SEYFERT GALAXY NGC 1068 FROM THE HERSCHEL-SPIRE FOURIER TRANSFORM SPECTROMETER. United States: N. p., 2012. Web. doi:10.1088/0004-637X/758/2/108.
Spinoglio, Luigi, Pereira-Santaella, Miguel, Busquet, Gemma, Schirm, Maximilien R. P., Wilson, Christine D., Parkin, Tara J., Glenn, Jason, Kamenetzky, Julia, Rangwala, Naseem, Maloney, Philip R., Bendo, George J., Madden, Suzanne C., Wolfire, Mark G., Boselli, Alessandro, Cooray, Asantha, & Page, Mathew J., E-mail: luigi.spinoglio@iaps.inaf.it. SUBMILLIMETER LINE SPECTRUM OF THE SEYFERT GALAXY NGC 1068 FROM THE HERSCHEL-SPIRE FOURIER TRANSFORM SPECTROMETER. United States. doi:10.1088/0004-637X/758/2/108.
Spinoglio, Luigi, Pereira-Santaella, Miguel, Busquet, Gemma, Schirm, Maximilien R. P., Wilson, Christine D., Parkin, Tara J., Glenn, Jason, Kamenetzky, Julia, Rangwala, Naseem, Maloney, Philip R., Bendo, George J., Madden, Suzanne C., Wolfire, Mark G., Boselli, Alessandro, Cooray, Asantha, and Page, Mathew J., E-mail: luigi.spinoglio@iaps.inaf.it. 2012. "SUBMILLIMETER LINE SPECTRUM OF THE SEYFERT GALAXY NGC 1068 FROM THE HERSCHEL-SPIRE FOURIER TRANSFORM SPECTROMETER". United States. doi:10.1088/0004-637X/758/2/108.
@article{osti_22086519,
title = {SUBMILLIMETER LINE SPECTRUM OF THE SEYFERT GALAXY NGC 1068 FROM THE HERSCHEL-SPIRE FOURIER TRANSFORM SPECTROMETER},
author = {Spinoglio, Luigi and Pereira-Santaella, Miguel and Busquet, Gemma and Schirm, Maximilien R. P. and Wilson, Christine D. and Parkin, Tara J. and Glenn, Jason and Kamenetzky, Julia and Rangwala, Naseem and Maloney, Philip R. and Bendo, George J. and Madden, Suzanne C. and Wolfire, Mark G. and Boselli, Alessandro and Cooray, Asantha and Page, Mathew J., E-mail: luigi.spinoglio@iaps.inaf.it},
abstractNote = {The first complete submillimeter spectrum (190-670 {mu}m) of the Seyfert 2 galaxy NGC 1068 has been observed with the SPIRE Fourier transform spectrometer on board the Herschel Space Observatory. The sequence of CO lines (J {sub up} = 4-13), lines from H{sub 2}O, the fundamental rotational transition of hydrogen fluoride, two o-H{sub 2}O{sup +} lines, and one line each from CH{sup +} and OH{sup +} have been detected, together with the two [C I] lines and the [N II] 205 {mu}m line. The observations in both single pointing mode with sparse image sampling and in mapping mode with full image sampling allow us to disentangle two molecular emission components, one due to the compact circumnuclear disk (CND) and one from the extended region encompassing the star-forming ring (SF-ring). Radiative transfer models show that the two CO components are characterized by densities of n(H{sub 2}) = 10{sup 4.5} and 10{sup 2.9} cm{sup -3} and temperatures of T {sub kin} = 100 K and 127 K, respectively. A comparison of the CO line intensities with the photodissociation region (PDR) and X-ray-dominated region (XDR) models, together with the other observational constraints, such as the observed CO surface brightness and the radiation field, indicates that the best explanation for the CO excitation of the CND is an XDR with a density of n(H{sub 2}) {approx} 10{sup 4} cm{sup -3} and an X-ray flux of 9 erg s{sup -1} cm{sup -2}, consistent with illumination by the active galactic nucleus, while the CO lines in the SF-ring are better modeled by a PDR. The detected water transitions, together with those observed with the Herschel PACS spectrometer, can be modeled by a large velocity gradient model with low temperature (T {sub kin} {approx} 40 K) and high density (n(H{sub 2}) in the range 10{sup 6.7}-10{sup 7.9} cm{sup -3}). The emission of H{sub 2}O{sup +} and OH{sup +} are in agreement with PDR models with cosmic-ray ionization. The diffuse ionized atomic component observed through the [N II] 205 {mu}m line is consistent with previous photoionization models of the starburst.},
doi = {10.1088/0004-637X/758/2/108},
journal = {Astrophysical Journal},
number = 2,
volume = 758,
place = {United States},
year = 2012,
month =
}
  • We present Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer (FTS) observations of the Antennae (NGC 4038/39), a well-studied, nearby (22 Mpc), ongoing merger between two gas-rich spiral galaxies. The SPIRE-FTS is a low spatial ( FWHM ∼ 19''-43'') and spectral (∼1.2 GHz) resolution mapping spectrometer covering a large spectral range (194-671 μm, 450-1545 GHz). We detect five CO transitions (J = 4-3 to J = 8-7), both [C I] transitions, and the [N II] 205 μm transition across the entire system, which we supplement with ground-based observations of the CO J = 1-0, J = 2-1, andmore » J = 3-2 transitions and Herschel Photodetecting Array Camera and Spectrometer (PACS) observations of [C II] and [O I] 63 μm. Using the CO and [C I] transitions, we perform both a local thermodynamic equilibrium (LTE) analysis of [C I] and a non-LTE radiative transfer analysis of CO and [C I] using the radiative transfer code RADEX along with a Bayesian likelihood analysis. We find that there are two components to the molecular gas: a cold (T {sub kin} ∼ 10-30 K) and a warm (T {sub kin} ≳ 100 K) component. By comparing the warm gas mass to previously observed values, we determine a CO abundance in the warm gas of x {sub CO} ∼ 5 × 10{sup –5}. If the CO abundance is the same in the warm and cold gas phases, this abundance corresponds to a CO J = 1-0 luminosity-to-mass conversion factor of α{sub CO} ∼ 7 M {sub ☉} pc{sup –2} (K km s{sup –1}){sup –1} in the cold component, similar to the value for normal spiral galaxies. We estimate the cooling from H{sub 2}, [C II], CO, and [O I] 63 μm to be ∼0.01 L {sub ☉}/M {sub ☉}. We compare photon-dominated region models to the ratio of the flux of various CO transitions, along with the ratio of the CO flux to the far-infrared flux in NGC 4038, NGC 4039, and the overlap region. We find that the densities recovered from our non-LTE analysis are consistent with a background far-ultraviolet field of strength G {sub 0} ∼ 1000. Finally, we find that a combination of turbulent heating, due to the ongoing merger, and supernova and stellar winds are sufficient to heat the molecular gas.« less
  • We present high angular resolution (0.''5-2.''0) observations of the millimeter continuum and the {sup 12}CO(J = 3-2), {sup 13}CO(J = 3-2), {sup 13}CO(J = 2-1), C{sup 18}O(J = 2-1), HCN(J = 3-2), HCO{sup +}(J = 4-3), and HCO{sup +}(J = 3-2) line emission in the circumnuclear disk (r {approx}< 100 pc) of the prototypical Seyfert 2 galaxy NGC 1068, carried out with the Submillimeter Array. We also include in our analysis new {sup 13}CO(J = 1-0) and improved {sup 12}CO(J = 2-1) observations of NGC 1068 at high angular resolution (1.''0-2.''0) and sensitivity, conducted with the Institute de Radioastronomie Millimetriquemore » Plateau de Bure Interferometer. Based on the complex dynamics of the molecular gas emission indicating non-circular motions in the central {approx}100 pc, we propose a scenario in which part of the molecular gas in the circumnuclear disk of NGC 1068 is blown radially outward as a result of shocks. This shock scenario is further supported by quite warm (T{sub kin} {>=} 200 K) and dense (n(H{sub 2}) {approx_equal} 10{sup 4} cm{sup -3}) gas constrained from observed molecular line ratios. The HCN abundance in the circumnuclear disk is found to be [HCN]/[{sup 12}CO] {approx} 10{sup -3.5}. This is slightly higher than the abundances derived for Galactic and extragalactic star-forming/starbursting regions. This result lends further support to X-ray-enhanced HCN formation in the circumnuclear disk of NGC 1068 as suggested by earlier studies. The HCO{sup +} abundance ([HCO{sup +}]/[{sup 12}CO] {approx} 10{sup -5}) appears to be somewhat lower than that of Galactic and extragalactic star-forming/starbursting regions. When trying to fit the centimeter-to-millimeter continuum emission by different thermal and non-thermal processes, it appears that electron-scattered synchrotron emission yields the best results while thermal free-free emission seems to overpredict the millimeter continuum emission.« less
  • We report the discovery of a bright (f(250 {mu}m)>400 mJy), multiply lensed submillimeter galaxy HERMES J105751.1+573027 in Herschel/SPIRE Science Demonstration Phase data from the HerMES project. Interferometric 880 {mu}m Submillimeter Array observations resolve at least four images with a large separation of {approx}9''. A high-resolution adaptive optics K{sub p} image with Keck/NIRC2 clearly shows strong lensing arcs. Follow-up spectroscopy gives a redshift of z = 2.9575, and the lensing model gives a total magnification of {mu} {approx} 11 {+-} 1. The large image separation allows us to study the multi-wavelength spectral energy distribution (SED) of the lensed source unobscured bymore » the central lensing mass. The far-IR/millimeter-wave SED is well described by a modified blackbody fit with an unusually warm dust temperature, 88 {+-} 3 K. We derive a lensing-corrected total IR luminosity of (1.43 {+-} 0.09) x 10{sup 13} L{sub sun}, implying a star formation rate of {approx}2500 M{sub sun} yr{sup -1}. However, models primarily developed from brighter galaxies selected at longer wavelengths are a poor fit to the full optical-to-millimeter SED. A number of other strongly lensed systems have already been discovered in early Herschel data, and many more are expected as additional data are collected.« less
  • We observed the far-IR fine-structure lines of 26 Seyfert galaxies with the Herschel-PACS spectrometer. These observations are complemented with Spitzer Infrared Spectrograph and Herschel SPIRE spectroscopy. We used the ionic lines to determine electron densities in the ionized gas and the [C I] lines, observed with SPIRE, to measure the neutral gas densities, while the [O I] lines measure the gas temperature, at densities below ∼10{sup 4} cm{sup –3}. Using the [O I]145 μm/63 μm and [S III]33/18 μm line ratios, we find an anti-correlation of the temperature with the gas density. Various fine-structure line ratios show density stratifications in these active galaxies. Onmore » average, electron densities increase with the ionization potential of the ions. The infrared lines arise partly in the narrow line region, photoionized by the active galactic nucleus (AGN), partly in H II regions photoionized by hot stars, and partly in photo-dissociated regions. We attempt to separate the contributions to the line emission produced in these different regions by comparing our observed emission line ratios to theoretical values. In particular, we tried to separate the contribution of AGNs and star formation by using a combination of Spitzer and Herschel lines, and we found that besides the well-known mid-IR line ratios, the line ratio of [O III]88 μm/[O IV]26 μm can reliably discriminate the two emission regions, while the far-IR line ratio of [C II]157 μm/[O I]63 μm is only able to mildly separate the two regimes. By comparing the observed [C II]157 μm/[N II]205 μm ratio with photoionization models, we also found that most of the [C II] emission in the galaxies we examined is due to photodissociation regions.« less
  • Measurements of several infrared lines in NGC 1068 are presented, including the forbidden Si VI transition at 1.962 microns which is detected for the first time in an extragalactic object. This line is among the brightest IR features (about 5 times stronger than H2 2.121 microns), is broad (Delta-v of about 1100 km/s), and has a profile similar to He I 1.083 microns. The possibility of using the forbidden Si VI line to trace Seyfert activity and the origin of the H, forbidden Fe II, and H2 lines are briefly discussed. 23 refs.