Dissecting galaxies: Separating star formation, shock excitation and AGN activity in the central region of NGC 613

Rebecca L. Davies; Brent Groves; Lisa J. Kewley; Anne M. Medling; Prajval Shastri; Jaya Maithil; Preeti Kharb; Julie Banfield; Fergus Longbottom; Michael A. Dopita; Elise J. Hampton; Julia Scharwächter; Ralph Sutherland; Chichuan Jin; Ingyin Zaw; Bethan James; Stéphanie Juneau

doi:10.1093/mnras/stx1559

Dissecting galaxies: Separating star formation, shock excitation and AGN activity in the central region of NGC 613

Rebecca L. Davies, Brent Groves, Lisa J. Kewley, Anne M. Medling, Prajval Shastri, Jaya Maithil, Preeti Kharb, Julie Banfield, Fergus Longbottom, Michael A. Dopita, Elise J. Hampton, Julia Scharwächter, Ralph Sutherland, Chichuan Jin, Ingyin Zaw, Bethan James, Stéphanie Juneau

Physics

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Abstract

The most rapidly evolving regions of galaxies often display complex optical spectra with emission lines excited by massive stars, shocks and accretion on to supermassive black holes. Standard calibrations (such as for the star formation rate) cannot be applied to such mixed spectra. In this paper, we isolate the contributions of star formation, shock excitation and active galactic nucleus (AGN) activity to the emission line luminosities of individual spatially resolved regions across the central 3 × 3 kpc² region of the active barred spiral galaxy NGC 613. The star formation rate and AGN luminosity calculated from the decomposed emission line maps are in close agreement with independent estimates from data at other wavelengths. The star formation component traces the B-band stellar continuum emission, and the AGN component forms an ionization cone which is aligned with the nuclear radio jet. The optical line emission associated with shock excitation is cospatial with strong H₂ and [Fe II] emission and with regions of high ionized gas velocity dispersion (σ ≳ 100 km s^-1). The shock component also traces the outer boundary of the AGN ionization cone and may therefore be produced by outflowing material interacting with the surrounding interstellar medium. Our decomposition method makes it possible to determine the properties of star formation, shock excitation and AGN activity from optical spectra, without contamination from other ionization mechanisms.

Original language	English (US)
Pages (from-to)	4974-4988
Number of pages	15
Journal	Monthly Notices of the Royal Astronomical Society
Volume	470
Issue number	4
DOIs	https://doi.org/10.1093/mnras/stx1559
State	Published - Oct 2017

Keywords

Galaxies: ISM
Galaxies: Seyfert
Galaxies: evolution

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1093/mnras/stx1559

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Davies, R. L., Groves, B., Kewley, L. J., Medling, A. M., Shastri, P., Maithil, J., Kharb, P., Banfield, J., Longbottom, F., Dopita, M. A., Hampton, E. J., Scharwächter, J., Sutherland, R., Jin, C., Zaw, I., James, B., & Juneau, S. (2017). Dissecting galaxies: Separating star formation, shock excitation and AGN activity in the central region of NGC 613. Monthly Notices of the Royal Astronomical Society, 470(4), 4974-4988. https://doi.org/10.1093/mnras/stx1559

Davies, RL, Groves, B, Kewley, LJ, Medling, AM, Shastri, P, Maithil, J, Kharb, P, Banfield, J, Longbottom, F, Dopita, MA, Hampton, EJ, Scharwächter, J, Sutherland, R, Jin, C, Zaw, I, James, B & Juneau, S 2017, 'Dissecting galaxies: Separating star formation, shock excitation and AGN activity in the central region of NGC 613', Monthly Notices of the Royal Astronomical Society, vol. 470, no. 4, pp. 4974-4988. https://doi.org/10.1093/mnras/stx1559

@article{c483fc0851e142f788ae9fdcd03e4aa8,

title = "Dissecting galaxies: Separating star formation, shock excitation and AGN activity in the central region of NGC 613",

abstract = "The most rapidly evolving regions of galaxies often display complex optical spectra with emission lines excited by massive stars, shocks and accretion on to supermassive black holes. Standard calibrations (such as for the star formation rate) cannot be applied to such mixed spectra. In this paper, we isolate the contributions of star formation, shock excitation and active galactic nucleus (AGN) activity to the emission line luminosities of individual spatially resolved regions across the central 3 × 3 kpc2 region of the active barred spiral galaxy NGC 613. The star formation rate and AGN luminosity calculated from the decomposed emission line maps are in close agreement with independent estimates from data at other wavelengths. The star formation component traces the B-band stellar continuum emission, and the AGN component forms an ionization cone which is aligned with the nuclear radio jet. The optical line emission associated with shock excitation is cospatial with strong H2 and [Fe II] emission and with regions of high ionized gas velocity dispersion (σ ≳ 100 km s-1). The shock component also traces the outer boundary of the AGN ionization cone and may therefore be produced by outflowing material interacting with the surrounding interstellar medium. Our decomposition method makes it possible to determine the properties of star formation, shock excitation and AGN activity from optical spectra, without contamination from other ionization mechanisms.",

keywords = "Galaxies: ISM, Galaxies: Seyfert, Galaxies: evolution",

author = "Davies, {Rebecca L.} and Brent Groves and Kewley, {Lisa J.} and Medling, {Anne M.} and Prajval Shastri and Jaya Maithil and Preeti Kharb and Julie Banfield and Fergus Longbottom and Dopita, {Michael A.} and Hampton, {Elise J.} and Julia Scharw{\"a}chter and Ralph Sutherland and Chichuan Jin and Ingyin Zaw and Bethan James and St{\'e}phanie Juneau",

note = "Funding Information: BG gratefully acknowledges the support of the Australian Research Council as the recipient of a Future Fellowship (FT140101202). LK and MD acknowledge the support of the Australian Research Council (ARC) through Discovery project DP130103925. Support for AMM is provided by NASA through Hubble Fellowship grant #HST-HF2-51377 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. JKB acknowledges support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. The Australia Telescope Compact Array is part of the Australia Telescope, which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Publisher Copyright: {\textcopyright} 2018 The Author(s).",

year = "2017",

month = oct,

doi = "10.1093/mnras/stx1559",

language = "English (US)",

volume = "470",

pages = "4974--4988",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

number = "4",

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T1 - Dissecting galaxies

T2 - Separating star formation, shock excitation and AGN activity in the central region of NGC 613

AU - Davies, Rebecca L.

AU - Groves, Brent

AU - Kewley, Lisa J.

AU - Medling, Anne M.

AU - Shastri, Prajval

AU - Maithil, Jaya

AU - Kharb, Preeti

AU - Banfield, Julie

AU - Longbottom, Fergus

AU - Dopita, Michael A.

AU - Hampton, Elise J.

AU - Scharwächter, Julia

AU - Sutherland, Ralph

AU - Jin, Chichuan

AU - Zaw, Ingyin

AU - James, Bethan

AU - Juneau, Stéphanie

N1 - Funding Information: BG gratefully acknowledges the support of the Australian Research Council as the recipient of a Future Fellowship (FT140101202). LK and MD acknowledge the support of the Australian Research Council (ARC) through Discovery project DP130103925. Support for AMM is provided by NASA through Hubble Fellowship grant #HST-HF2-51377 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. JKB acknowledges support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. The Australia Telescope Compact Array is part of the Australia Telescope, which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Publisher Copyright: © 2018 The Author(s).

PY - 2017/10

Y1 - 2017/10

N2 - The most rapidly evolving regions of galaxies often display complex optical spectra with emission lines excited by massive stars, shocks and accretion on to supermassive black holes. Standard calibrations (such as for the star formation rate) cannot be applied to such mixed spectra. In this paper, we isolate the contributions of star formation, shock excitation and active galactic nucleus (AGN) activity to the emission line luminosities of individual spatially resolved regions across the central 3 × 3 kpc2 region of the active barred spiral galaxy NGC 613. The star formation rate and AGN luminosity calculated from the decomposed emission line maps are in close agreement with independent estimates from data at other wavelengths. The star formation component traces the B-band stellar continuum emission, and the AGN component forms an ionization cone which is aligned with the nuclear radio jet. The optical line emission associated with shock excitation is cospatial with strong H2 and [Fe II] emission and with regions of high ionized gas velocity dispersion (σ ≳ 100 km s-1). The shock component also traces the outer boundary of the AGN ionization cone and may therefore be produced by outflowing material interacting with the surrounding interstellar medium. Our decomposition method makes it possible to determine the properties of star formation, shock excitation and AGN activity from optical spectra, without contamination from other ionization mechanisms.

AB - The most rapidly evolving regions of galaxies often display complex optical spectra with emission lines excited by massive stars, shocks and accretion on to supermassive black holes. Standard calibrations (such as for the star formation rate) cannot be applied to such mixed spectra. In this paper, we isolate the contributions of star formation, shock excitation and active galactic nucleus (AGN) activity to the emission line luminosities of individual spatially resolved regions across the central 3 × 3 kpc2 region of the active barred spiral galaxy NGC 613. The star formation rate and AGN luminosity calculated from the decomposed emission line maps are in close agreement with independent estimates from data at other wavelengths. The star formation component traces the B-band stellar continuum emission, and the AGN component forms an ionization cone which is aligned with the nuclear radio jet. The optical line emission associated with shock excitation is cospatial with strong H2 and [Fe II] emission and with regions of high ionized gas velocity dispersion (σ ≳ 100 km s-1). The shock component also traces the outer boundary of the AGN ionization cone and may therefore be produced by outflowing material interacting with the surrounding interstellar medium. Our decomposition method makes it possible to determine the properties of star formation, shock excitation and AGN activity from optical spectra, without contamination from other ionization mechanisms.

KW - Galaxies: ISM

KW - Galaxies: Seyfert

KW - Galaxies: evolution

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Dissecting galaxies: Separating star formation, shock excitation and AGN activity in the central region of NGC 613

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