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Title: The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120–5453

Abstract

We present new Atacama Large Millimeter/submillimeter Array Band 7 (∼340 GHz) observations of the dense gas tracers HCN, HCO{sup +}, and CS in the local, single-nucleus, ultraluminous infrared galaxy IRAS 13120–5453. We find centrally enhanced HCN (4–3) emission, relative to HCO{sup +} (4–3), but do not find evidence for radiative pumping of HCN. Considering the size of the starburst (0.5 kpc) and the estimated supernovae rate of ∼1.2 yr{sup −1}, the high HCN/HCO{sup +} ratio can be explained by an enhanced HCN abundance as a result of mechanical heating by the supernovae, though the active galactic nucleus and winds may also contribute additional mechanical heating. The starburst size implies a high Σ{sub IR} of 4.7 × 10{sup 12} L {sub ⊙} kpc{sup −2}, slightly below predictions of radiation-pressure limited starbursts. The HCN line profile has low-level wings, which we tentatively interpret as evidence for outflowing dense molecular gas. However, the dense molecular outflow seen in the HCN line wings is unlikely to escape the Galaxy and is destined to return to the nucleus and fuel future star formation. We also present modeling of Herschel observations of the H{sub 2}O lines and find a nuclear dust temperature of ∼40 K. IRASmore » 13120–5453 has a lower dust temperature and Σ{sub IR} than is inferred for the systems termed “compact obscured nuclei (CONs)” (such as Arp 220 and Mrk 231). If IRAS 13120–5453 has undergone a CON phase, we are likely witnessing it at a time when the feedback has already inflated the nuclear ISM and diluted star formation in the starburst/active galactic nucleus core.« less

Authors:
;  [1]; ; ; ;  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [9];  [10];  [11]
  1. Instituto de Astrofśica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile)
  2. Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 94 Onsala (Sweden)
  3. Universidad de Alcalá, Departamento de Física y Matemáticas, Campus Universitario, E-28871 Alcalá de Henares, Madrid (Spain)
  4. Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)
  5. Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA, 91125 (United States)
  6. Department of Astronomy, University of Virginia, Charlottesville, VA 22903 (United States)
  7. Observatorio de Madrid, OAN-IGN, Alfonso XII, 3, E-28014-Madrid (Spain)
  8. Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
  9. Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, 10617, Taipei, Taiwan (China)
  10. Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)
  11. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
Publication Date:
OSTI Identifier:
22663149
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; 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; COMPACTS; DUSTS; EMISSION; FEEDBACK; FORECASTING; GALAXIES; HEATING; HYDROCYANIC ACID; INTERACTIONS; NUCLEI; RADIATION PRESSURE; SIMULATION; STELLAR WINDS; SUPERNOVAE; WATER

Citation Formats

Privon, G. C., Treister, E., Aalto, S., Falstad, N., Muller, S., Costagliola, F., González-Alfonso, E., Sliwa, K., Armus, L., Evans, A. S., Garcia-Burillo, S., Izumi, T., Sakamoto, K., Werf, P. van der, and Chu, J. K. The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120–5453. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/213.
Privon, G. C., Treister, E., Aalto, S., Falstad, N., Muller, S., Costagliola, F., González-Alfonso, E., Sliwa, K., Armus, L., Evans, A. S., Garcia-Burillo, S., Izumi, T., Sakamoto, K., Werf, P. van der, & Chu, J. K. The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120–5453. United States. doi:10.3847/1538-4357/835/2/213.
Privon, G. C., Treister, E., Aalto, S., Falstad, N., Muller, S., Costagliola, F., González-Alfonso, E., Sliwa, K., Armus, L., Evans, A. S., Garcia-Burillo, S., Izumi, T., Sakamoto, K., Werf, P. van der, and Chu, J. K. Wed . "The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120–5453". United States. doi:10.3847/1538-4357/835/2/213.
@article{osti_22663149,
title = {The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120–5453},
author = {Privon, G. C. and Treister, E. and Aalto, S. and Falstad, N. and Muller, S. and Costagliola, F. and González-Alfonso, E. and Sliwa, K. and Armus, L. and Evans, A. S. and Garcia-Burillo, S. and Izumi, T. and Sakamoto, K. and Werf, P. van der and Chu, J. K.},
abstractNote = {We present new Atacama Large Millimeter/submillimeter Array Band 7 (∼340 GHz) observations of the dense gas tracers HCN, HCO{sup +}, and CS in the local, single-nucleus, ultraluminous infrared galaxy IRAS 13120–5453. We find centrally enhanced HCN (4–3) emission, relative to HCO{sup +} (4–3), but do not find evidence for radiative pumping of HCN. Considering the size of the starburst (0.5 kpc) and the estimated supernovae rate of ∼1.2 yr{sup −1}, the high HCN/HCO{sup +} ratio can be explained by an enhanced HCN abundance as a result of mechanical heating by the supernovae, though the active galactic nucleus and winds may also contribute additional mechanical heating. The starburst size implies a high Σ{sub IR} of 4.7 × 10{sup 12} L {sub ⊙} kpc{sup −2}, slightly below predictions of radiation-pressure limited starbursts. The HCN line profile has low-level wings, which we tentatively interpret as evidence for outflowing dense molecular gas. However, the dense molecular outflow seen in the HCN line wings is unlikely to escape the Galaxy and is destined to return to the nucleus and fuel future star formation. We also present modeling of Herschel observations of the H{sub 2}O lines and find a nuclear dust temperature of ∼40 K. IRAS 13120–5453 has a lower dust temperature and Σ{sub IR} than is inferred for the systems termed “compact obscured nuclei (CONs)” (such as Arp 220 and Mrk 231). If IRAS 13120–5453 has undergone a CON phase, we are likely witnessing it at a time when the feedback has already inflated the nuclear ISM and diluted star formation in the starburst/active galactic nucleus core.},
doi = {10.3847/1538-4357/835/2/213},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}
  • We present a survey of 3 mm molecular lines in IRAS 04296+2923, one of the brightest known molecular-line emitting galaxies, and one of the closest luminous infrared galaxies (LIRGs). Data are from the Owens Valley and CARMA millimeter interferometers. Species detected at ≲ 4'' resolution include C{sup 18}O, HCN, HCO{sup +}, HNC, CN, CH{sub 3}OH, and, tentatively, HNCO. Along with existing CO, {sup 13}CO, and radio continuum data, these lines constrain the chemical properties of the inner disk. Dense molecular gas in the nucleus fuels a star formation rate ≳10 M {sub ☉} yr{sup –1} and is traced by linesmore » of HCN, HCO{sup +}, HNC, and CN. A correlation between HCN and star formation rate is observed on sub-kiloparsec scales, consistent with global relations. Toward the nucleus, CN abundances are similar to those of HCN, indicating emission comes from a collection (∼40-50) of moderate visual extinction, photon-dominated-region clouds. The CO isotopic line ratios are unusual: CO(1-0)/{sup 13}CO(1-0) and CO(1-0)/C{sup 18}O(1-0) line ratios are large toward the starburst, as is commonly observed in LIRGs, but farther out in the disk these ratios are remarkably low (≲ 3). {sup 13}CO/C{sup 18}O abundance ratios are lower than in Galactic clouds, possibly because the C{sup 18}O is enriched by massive star ejecta from the starburst. {sup 13}CO is underabundant relative to CO. Extended emission from CH{sub 3}OH indicates that dynamical shocks pervade both the nucleus and the inner disk. The unusual CO isotopologue ratios, the CO/HCN intensity ratio versus L {sub IR}, the HCN/CN abundance ratio, and the gas consumption time versus inflow rate all indicate that the starburst in IRAS 04296+2923 is in an early stage of development.« less
  • We present ALMA {sup 12}CO (J = 1-0, 3-2 and 6-5), {sup 13}CO (J = 1-0), and C{sup 18}O (J = 1-0) observations of the local ultraluminous infrared galaxy (ULIRG) IRAS 13120-5453. The morphologies of the three isotopic species differ, as {sup 13}CO shows a hole in emission toward the center. We measure integrated brightness temperature line ratios of {sup 12}CO/{sup 13}CO ≥ 60 (exceeding 200) and {sup 13}CO/C{sup 18}O ≤ 1 in the central region. Assuming optical thin emission, C{sup 18}O is more abundant than {sup 13}CO in several regions. The abundances within the central 500 pc are consistentmore » with the enrichment of the interstellar medium via a young starburst (<7 Myr), a top-heavy initial mass function, or a combination of both.« less
  • The feedback from galactic outflows is thought to play an important role in shaping the gas content, star formation history, and ultimately the stellar mass function of galaxies. Here we present evidence for massive molecular outflows associated with ultra-luminous infrared galaxies (ULIRGs) in the co-added Redshift Search Receiver {sup 12}CO (1-0) spectrum. Our stacked spectrum of 27 ULIRGs at z = 0.043-0.11 ({nu}{sub rest} = 110-120 GHz) shows broad wings around the CO line with {Delta}V(FWZI) {approx} 2000 km s{sup -1}. Its integrated line flux accounts for up to 25% {+-} 5% of the total CO line luminosity. When interpretedmore » as a massive molecular outflow wind, the associated mechanical energy can be explained by a concentrated starburst with star formation rate (SFR) {>=}100 M{sub sun} yr{sup -1}, which agrees well with their SFR derived from the FIR luminosity. Using the high signal-to-noise stacked composite spectrum, we also probe {sup 13}CO and {sup 12}CN emission in the sample and discuss how the chemical abundance of molecular gas may vary depending on the physical conditions of the nuclear region.« less
  • We report the detection of surprisingly strong HCN(J = 6{yields}5), HNC(J = 6{yields}5), and HCO{sup +}(J = 6{yields}5) emission in the host galaxy of the z = 3.91 quasar APM 08279+5255 through observations with the Combined Array for Research in Millimeter-wave Astronomy. HCN, HNC, and HCO{sup +} are typically used as star formation indicators, tracing dense molecular hydrogen gas [n(H{sub 2}) >10{sup 5} cm{sup -3}] within star-forming molecular clouds. However, the strength of their respective line emission in the J = 6{yields}5 transitions in APM 08279+5255 is extremely high, suggesting that they are excited by another mechanism besides collisions inmore » the dense molecular gas phase alone. We derive J = 6{yields}5 line luminosities of L'{sub HCN} = (4.9 {+-} 0.6), L'{sub HNC} = (2.4 {+-} 0.7), and L{sup '}{sub HCO}{sup +}= (3.0{+-}0.6)x10{sup 10} {mu}{sup -1}{sub L} K km s{sup -1} pc{sup 2} (where {mu}{sub L} is the lensing magnification factor), corresponding to L' ratios of {approx}0.23-0.46 relative to CO(J = 1{yields}0). Such high line ratios would be unusual even in the respective ground-state (J = 1{yields}0) transitions, and indicate exceptional, collisionally and radiatively driven excitation conditions in the dense, star-forming molecular gas in APM 08279+5255. Through an expansion of our previous modeling of the HCN line excitation in this source, we show that the high rotational line fluxes are caused by substantial infrared pumping at moderate opacities in a {approx}220 K warm gas and dust component. This implies that standard M{sub dense}/L' conversion factors would substantially overpredict the dense molecular gas mass M{sub dense}. We also find a HCN(J = 6{yields}5)/HCN(J = 5{yields}4) L' ratio greater than 1 (1.36 {+-} 0.31)-however, our models show that the excitation is likely not 'super-thermal', but that the high line ratio is due to a rising optical depth between both transitions. These findings are consistent with the picture that the bulk of the gas and dust in this source is situated in a compact, nuclear starburst, where both the highly active galactic nucleus and star formation contribute to the heating.« less
  • We report the detection of the {sup 12}CO J = 1-0 emission line in [H89]1821+643, one of the most optically luminous quasi-stellar objects (QSOs) in the local universe, and a template ULIRG-to-QSO transition object, located in a rich, cool-core cluster at z = 0.297. The CO emission is likely to be extended, highly asymmetric with respect to the center of the host elliptical where the QSO resides, and correspond with a molecular gas mass of {approx}8.0 x 10{sup 9} M{sub sun}. The dynamical mass enclosed by the CO emission-line region could amount to {approx}1.7 x 10{sup 12} M{sub sun} (80%more » of the total mass of the elliptical host). The bulk of the CO emission is located at {approx}9 kpc southeast from the nuclei position, close to a faint optical structure, suggesting that the CO emission could either represent a gas-rich companion galaxy merging with the elliptical host or a tail-like structure reminiscent of a previous interaction. We argue that the first scenario is more likely given the large masses implied by the CO source, which would imply a highly asymmetric elliptical host. The close alignment between the CO emission's major axis and the radio plume suggests a possible role in the excitation of the ambient gas reservoir by the latter. The stacking technique was used to search for CO emission and 3-mm continuum emission from galaxies in the surrounding cluster. However, no detection was found toward individual galaxies or the stacked ensemble of galaxies, with a 3{sigma} limit of <1.1 x 10{sup 9} M{sub sun} for the molecular gas.« less