Galaxy-Wide Shocks in Late-Merger Stage Luminous Infrared Galaxies

Rich, Jeffrey A.; Kewley, Lisa J.; Dopita, Michael A.

doi:10.1088/0004-637x/734/2/87

Cited by 257 publications

(380 citation statements)

References 75 publications

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“…Rich et al 2010Rich et al , 2011Ho et al 2014), but we see no such trend here. It is possible that the lack of a correlation simply means that the shock velocity is not related to the turbulent velocity of the gas.…”

Section: Shocks Caused By Outflows Driven By Star Formationcontrasting

confidence: 53%

“…Mixing between AGN and star formation can also exist (Davies et al 2014b), but such mixing increases the [O III]/Hβ ratio more strongly, shifting points towards the Seyfert region of the diagnostic diagrams. By comparing these ionization line ratios in spatially-resolved spectroscopy to photoionization and shock models, it is thus possible to map out the shocked regions and identify the relative contribution to the luminosity from shocks, star formation, and AGN (Monreal-Ibero et al 2006, 2010Sharp & Bland-Hawthorn 2010;Rich et al 2010Rich et al , 2011Westmoquette et al 2011;Freeland et al 2011;Davis et al 2012;Fogarty et al 2012;Yuan et al 2012;Vogt et al 2013;Ho et al 2014).…”

Section: Shock Modelsmentioning

confidence: 99%

“…Comparisons of these line ratios and [O III]/Hβ, used as diagnostics of the energy source (as in the BPT/VO87 diagrams; Baldwin, Phillips & Terlevich 1981;Veilleux & Osterbrock 1987), would misidentify a starburst galaxy with shocks as a LINER or composite galaxy (e.g. Armus et al 1989;Veilleux et al 1995;Martin 1997;Dopita et al 1997;Kim et al 1998;Allen et al 1999;Veilleux et al 1999;Sharp & Bland-Hawthorn 2010;Rich et al 2010Rich et al , 2011Rich et al , 2014. Measurements that rely on emission line fluxes or ratios, such as star formation rate and metallicity, can also be affected unless shocks are identified and removed from the calculation.…”

Section: Introductionmentioning

confidence: 99%

“…Outflows are commonly observed in local U/LIRGs Rupke & Veilleux 2005;Rupke et al 2005a,b,c;Martin 2006;Sturm et al 2011;Rupke & Veilleux 2013;Veilleux et al 2013;Teng et al 2013;Spoon et al 2013;Rodríguez Zaurín et al 2013;Arribas et al 2014;Cicone et al 2014), and are likely a common cause of shocks. Several studies of shocks in nearby galaxies have linked them to superwinds produced by stellar feedback (Heckman et al 1990;Grimes et al 2005;Rich et al 2011;Hopkins et al 2012;Hong et al 2013) and AGN-driven outflows (Mazzarella et al 2012). Although these systems are relatively rare in the local universe, Le Floc'h et al (2005) have shown that high infrared luminosities may have been the norm at redshifts beyond 0.7.…”

Section: Introductionmentioning

confidence: 99%

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Shocked gas in IRAS F17207-0014: ISM collisions and outflows

Medling

Vivian

Kewley

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We combine optical and near-infrared AO-assisted integral field observations of the merging ULIRG IRAS F17207-0014 from the Wide-Field Spectrograph (WiFeS) and Keck/OSIRIS. The optical emission line ratios [N II]/Hα, [S II]/Hα, and [O I]/Hα reveal a mixing sequence of shocks present throughout the galaxy, with the strongest contributions coming from large radii (up to 100% at ∼5 kpc in some directions), suggesting galactic-scale winds. The nearinfrared observations, which have approximately 30 times higher spatial resolution, show that two sorts of shocks are present in the vicinity of the merging nuclei: low-level shocks distributed throughout our field-of-view evidenced by an H 2 /Brγ line ratio of ∼0.6-4, and strong collimated shocks with a high H 2 /Brγ line ratio of ∼4-8, extending south from the two nuclear disks approximately 400 pc (∼0. ′′ 5). Our data suggest that the diffuse shocks are caused by the collision of the interstellar media associated with the two progenitor galaxies and the strong shocks trace the base of a collimated outflow coming from the nucleus of one of the two disks.

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Section: Shocks Caused By Outflows Driven By Star Formationcontrasting

confidence: 53%

Section: Shock Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Shocked gas in IRAS F17207-0014: ISM collisions and outflows

Medling

Vivian

Kewley

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…The nature of LINERs in U/LIRGs has been explained as the consequence of galaxy-wide merger-driven shocks (Monreal-Ibero et al 2006Rich et al 2011Rich et al , 2013, but other alternatives like a mixture of starbursts and AGN have also been invoked (Kewley et al 2001;Yuan et al 2010;Kewley et al 2013). The study of U/LIRGs in the optical includes additional complications derived by the amount and clumpy nature of their dust distribution, and by the presence of additional heating mechanisms due to the tidal forces associated with the interactions and mergers involved mostly in ULIRGs.…”

Section: Introductionmentioning

confidence: 99%

Understanding the two-dimensional ionization structure in luminous infrared galaxies

Colina

López

Arribas

et al. 2015

A&A

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We investigate the two-dimensional excitation structure of the interstellar medium (ISM) in a sample of luminous infrared galaxies (LIRGs) and Seyferts using near-IR integral field spectroscopy. This study extends to the near infrared the well-known optical and mid-IR emission line diagnostics used to classify activity in galaxies. Based on the spatially resolved spectroscopy of prototypes, we identify in the [FeII]1.64 µm/Brγ − H 2 2.12 µm/Brγ plane regions dominated by the different heating sources, i.e. active galactic nuclei (AGNs), young main-sequence massive stars, and evolved stars i.e. supernovae. The ISM in LIRGs occupy a wide region in the near-IR diagnostic plane from −0.6 to +1.5 and from −1.2 to +0.8 (in log units) for the [FeII]/Brγ and H 2 /Brγ line ratios, respectively. The corresponding median(mode) ratios are +0.18(0.16) and +0.02(−0.04). Seyferts show on average larger values by factors ∼2.5 and ∼1.4 for the [FeII]/Brγ and H 2 /Brγ ratios, respectively. New areas and relations in the near-IR diagnostic plane are defined for the compact, high surface brightness regions dominated by AGN, young ionizing stars, and supernovae explosions, respectively. In addition to these high surface brightness regions, the diffuse regions affected by the AGN radiation field cover an area similar to that of Seyferts, but with high values in [FeII]/Brγ that are not as extreme. The extended, non-AGN diffuse regions cover a wide area in the near-IR diagnostic diagram that overlaps that of individual excitation mechanisms (i.e. AGN, young stars, and supernovae), but with its mode value to that of the young star-forming clumps. This indicates that the excitation conditions of the extended, diffuse ISM are likely due to a mixture of the different ionization sources, weighted by their spatial distribution and relative flux contribution. The integrated line ratios in LIRGs show higher excitation conditions i.e. towards AGNs, than those measured by the spatially resolved spectroscopy. If this behaviour is representative, it would have clear consequences when classifying high-z, star-forming galaxies based on their near-infrared integrated spectra.

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Spaxel analysis: probing the physics of star formation in ultraluminous infrared galaxies

Dopita

Vogt

Kewley

et al. 2013

Astrophys Space Sci

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This paper presents a detailed spectral pixel (spaxel) analysis of the ten Luminous Infrared Galaxies (LIRGs) previously observed with the Wide Field Spectrograph (WiFeS), an integral field spectrograph mounted on the ANU 2.3m telescope, and for which an abundance gradient analysis has already been presented by Rich et al. (2012). Here we use the strong emission line analysis techniques developed by Dopita et al. (2013) to measure the ionisation parameter and the oxygen abundance in each spaxel. In addition, we use the observed Hα flux to determine the surface rate of star formation (M yr −1 kpc −2 ) and use the [S II] λλ6717/6731 ratio to estimate the local pressure in the ionised plasma. We discuss the correlations discovered between these physical quantities, and use them to infer aspects of the physics of star formation in these extreme star forming environments. In particular, we find a correlation between the star formation rate and the inferred ionisation parameter. We examine the possible reasons for this correlation, and determine that the most likely explanation is that the more active star forming regions have a different distribution of molecular gas which favour higher ionisation parameters in the ionised plasma.

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Galaxy-Wide Shocks in Late-Merger Stage Luminous Infrared Galaxies

Cited by 257 publications

References 75 publications

Shocked gas in IRAS F17207-0014: ISM collisions and outflows

Shocked gas in IRAS F17207-0014: ISM collisions and outflows

Understanding the two-dimensional ionization structure in luminous infrared galaxies

Spaxel analysis: probing the physics of star formation in ultraluminous infrared galaxies

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