Hidden or missing outflows in highly obscured galaxy nuclei?

N. Falstad*, F. Hallqvist, S. Aalto, S. Konig, S Muller, R. Aladro, F. Combes, A. S. Evans, G. A. Fuller, J. S. Gallagher, S. Garcia-Burillo, E. Gonzalez-Alfonso, T. R. Greve, C. Henkel, M. Imanishi, T. Izumi, J. G. Mangum, S. Martin, G. C. Privon, K. Sakamoto & 2 others S. Veilleux, P. P. van der Werf

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

121 Downloads (Pure)

Abstract

Context. Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed.
Aims
. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs).
Methods
. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs.
Results
. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH.
Conclusions
. We conclude that the galaxy nuclei with the highest LHCN − vib/LIR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.

Original languageEnglish
Article numberA29
JournalAstronomy and Astrophysics
Volume623
ISSN0004-6361
DOIs
Publication statusPublished - 2019

Keywords

  • Galaxies: evolution
  • Galaxies: nuclei
  • Galaxies: ISM
  • ISM: molecules
  • ISM: jets and outflows

Cite this

Falstad, N., Hallqvist, F., Aalto, S., Konig, S., Muller, S., Aladro, R., ... van der Werf, P. P. (2019). Hidden or missing outflows in highly obscured galaxy nuclei? Astronomy and Astrophysics, 623, [A29]. https://doi.org/10.1051/0004-6361/201834586
Falstad, N. ; Hallqvist, F. ; Aalto, S. ; Konig, S. ; Muller, S ; Aladro, R. ; Combes, F. ; Evans, A. S. ; Fuller, G. A. ; Gallagher, J. S. ; Garcia-Burillo, S. ; Gonzalez-Alfonso, E. ; Greve, T. R. ; Henkel, C. ; Imanishi, M. ; Izumi, T. ; Mangum, J. G. ; Martin, S. ; Privon, G. C. ; Sakamoto, K. ; Veilleux, S. ; van der Werf, P. P. / Hidden or missing outflows in highly obscured galaxy nuclei?. In: Astronomy and Astrophysics. 2019 ; Vol. 623.
@article{d0d7811a461e4c688741e1358be5b702,
title = "Hidden or missing outflows in highly obscured galaxy nuclei?",
abstract = "Context. Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed.Aims. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs).Methods. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs.Results. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH.Conclusions. We conclude that the galaxy nuclei with the highest LHCN − vib/LIR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.",
keywords = "Galaxies: evolution, Galaxies: nuclei, Galaxies: ISM, ISM: molecules, ISM: jets and outflows",
author = "N. Falstad and F. Hallqvist and S. Aalto and S. Konig and S Muller and R. Aladro and F. Combes and Evans, {A. S.} and Fuller, {G. A.} and Gallagher, {J. S.} and S. Garcia-Burillo and E. Gonzalez-Alfonso and Greve, {T. R.} and C. Henkel and M. Imanishi and T. Izumi and Mangum, {J. G.} and S. Martin and Privon, {G. C.} and K. Sakamoto and S. Veilleux and {van der Werf}, {P. P.}",
year = "2019",
doi = "10.1051/0004-6361/201834586",
language = "English",
volume = "623",
journal = "Astronomy & Astrophysics",
issn = "0004-6361",
publisher = "E D P Sciences",

}

Falstad, N, Hallqvist, F, Aalto, S, Konig, S, Muller, S, Aladro, R, Combes, F, Evans, AS, Fuller, GA, Gallagher, JS, Garcia-Burillo, S, Gonzalez-Alfonso, E, Greve, TR, Henkel, C, Imanishi, M, Izumi, T, Mangum, JG, Martin, S, Privon, GC, Sakamoto, K, Veilleux, S & van der Werf, PP 2019, 'Hidden or missing outflows in highly obscured galaxy nuclei?', Astronomy and Astrophysics, vol. 623, A29. https://doi.org/10.1051/0004-6361/201834586

Hidden or missing outflows in highly obscured galaxy nuclei? / Falstad, N.; Hallqvist, F.; Aalto, S.; Konig, S.; Muller, S; Aladro, R.; Combes, F.; Evans, A. S.; Fuller, G. A.; Gallagher, J. S.; Garcia-Burillo, S.; Gonzalez-Alfonso, E.; Greve, T. R.; Henkel, C.; Imanishi, M.; Izumi, T.; Mangum, J. G.; Martin, S.; Privon, G. C.; Sakamoto, K.; Veilleux, S.; van der Werf, P. P.

In: Astronomy and Astrophysics, Vol. 623, A29, 2019.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Hidden or missing outflows in highly obscured galaxy nuclei?

AU - Falstad, N.

AU - Hallqvist, F.

AU - Aalto, S.

AU - Konig, S.

AU - Muller, S

AU - Aladro, R.

AU - Combes, F.

AU - Evans, A. S.

AU - Fuller, G. A.

AU - Gallagher, J. S.

AU - Garcia-Burillo, S.

AU - Gonzalez-Alfonso, E.

AU - Greve, T. R.

AU - Henkel, C.

AU - Imanishi, M.

AU - Izumi, T.

AU - Mangum, J. G.

AU - Martin, S.

AU - Privon, G. C.

AU - Sakamoto, K.

AU - Veilleux, S.

AU - van der Werf, P. P.

PY - 2019

Y1 - 2019

N2 - Context. Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed.Aims. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs).Methods. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs.Results. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH.Conclusions. We conclude that the galaxy nuclei with the highest LHCN − vib/LIR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.

AB - Context. Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed.Aims. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs).Methods. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs.Results. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH.Conclusions. We conclude that the galaxy nuclei with the highest LHCN − vib/LIR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.

KW - Galaxies: evolution

KW - Galaxies: nuclei

KW - Galaxies: ISM

KW - ISM: molecules

KW - ISM: jets and outflows

U2 - 10.1051/0004-6361/201834586

DO - 10.1051/0004-6361/201834586

M3 - Journal article

VL - 623

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - A29

ER -

Falstad N, Hallqvist F, Aalto S, Konig S, Muller S, Aladro R et al. Hidden or missing outflows in highly obscured galaxy nuclei? Astronomy and Astrophysics. 2019;623. A29. https://doi.org/10.1051/0004-6361/201834586