LINER‐like Extended Nebulae in ULIRGs: Shocks Generated by Merger‐Induced Flows

Monreal-Ibero, A.; Arribas, S.; Colina, L.

doi:10.1086/498257

Cited by 106 publications

(114 citation statements)

References 43 publications

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“…We should note that, this ratio might also be affected by the presence of an AGN and by shock excitation as found in local (e.g. Veilleux et al 1995Veilleux et al , 1999Yuan et al 2010;Monreal Ibero et al 2006 and distant (Shapiro et al 2009) samples. However, according to the diagnostic diagram proposed by Veilleux & Osterbrock (1987) noted that [NII]/Hα values are available for only a fraction of the SINS sample and these are strongly biased towards the BX (i.e.…”

Section: Ifs Based Hα Emission Size Of Local and High-z Sfgs Samplesmentioning

confidence: 79%

Integral field spectroscopy based Hαsizes of local luminous and ultraluminous infrared galaxies

Arribas

Colina

Alonso‐Herrero

et al. 2012

A&A

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Aims. We study the analogy between local luminous and ultraluminous infrared galaxies (U/LIRGs) and high-z massive star forming galaxies (SFGs) by comparing their basic Hα structural characteristics, such as size and luminosity surface density, in an homogeneous way (i.e. same tracer, size definition, and similar physical scales). Methods. We use integral field spectroscopy (IFS) based Hα emission maps for a representative sample of 54 local U/LIRGs (66 galaxies) observed with INTEGRAL/WHT and VIMOS/VLT. From this initial sample, we select 26 objects with similar Hα luminosities (L(Hα)) to those of massive (i.e. M ∼ 10 10 M or larger) SFGs at z ∼ 2, and observed on similar physical scales. We then directly compare the sizes, and luminosity (and SFR) surface densities of these local and high-z samples.Results. The size of the Hα emitting region in the local U/LIRGs that we study has a wide range of values, with r 1/2 (Hα) from 0.2 kpc to 7 kpc. However, about two-thirds of local U/LIRGs with L ir > 10 11.4 L have compact Hα emission (i.e. r 1/2 < 2 kpc). The comparison sample of local U/LIRGs also contains a larger fraction (59%) of objects with compact Hα emission than the high-z sample (25%). This gives further support to the idea that for this luminosity range the size of the star forming region is a distinctive factor when comparing local and distant galaxies of similar SFRs. However, when using Hα as a tracer for both local and high-z samples, the differences are smaller than those reported using a variety of other tracers. In the L(Hα) -L(Hα) surface density (Σ Hα ) plane, most of the local U/LIRGs and high-z SF galaxies follow the same trend (i.e. higher luminosity for higher surface density) and cover a similar range, except for about 20-40% of local U/LIRGs, which have a higher Σ Hα by a factor of about 10. This is considerably smaller than the factors of 1000 or more reported in similar planes (i.e. L(TIR) versus Σ TIR ). Despite of the higher fraction of galaxies with compact Hα emission, a sizable group (about one-third) of local U/LIRGs are large (i.e. r 1/2 > 2 kpc). These are systems that show evidence of pre-coalescence merger activity and are indistinguishable from the massive high-z SFGs galaxies in terms of their Hα sizes, and luminosity and SFR surface densities.

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Section: Ifs Based Hα Emission Size Of Local and High-z Sfgs Samplesmentioning

confidence: 79%

Integral field spectroscopy based Hαsizes of local luminous and ultraluminous infrared galaxies

Arribas

Colina

Alonso‐Herrero

et al. 2012

A&A

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“…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%

“…For example, cloud-cloud collisions (e.g. Savedoff, Hovenier & van Leer 1967), tidally-induced gas streams (McDowell et al 2003;Colina et al 2004;Monreal-Ibero et al 2006, 2010Farage et al 2010;Zakamska 2010), and outflows and galactic winds from AGN or star formation (e.g. Heckman et al 1990; Lehnert & Heckman 1996;Lípari et al 2004;Sharp & Bland-Hawthorn 2010) can all produce radiative shocks to dissipate their kinetic energy (Allen et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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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“…Also, the slit was positioned along a given orientation and therefore the results of these studies do not necessarily represent the excitation and kinematics of the ionized gas in the extra-nuclear extended (several kpc) regions. Instead, for the detailed study of the excitation conditions in the extended regions it is more appropriate to use the two-dimensional information provided by IFS data once the nuclear regions are removed, as already discussed for a small sample of ULIRGs (Monreal-Ibero et al 2006). We performed a similar study with the present sample of LIRGs, limiting the analysis to the data with [N ii]λ6584/Hα, [S ii]λλ6717,6731/Hα, and [O i]λ6300/Hα higher than −0.7, −0.8, −1.8, respectively (i.e.…”

Section: Ionization Mechanisms In the Extra-nuclear Ionized Regions: mentioning

confidence: 99%

VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies

Monreal-Ibero

Arribas

Colina

et al. 2010

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Context. Luminous infrared galaxies (LIRGs) are an important class of objects in the low-z universe bridging the gap between normal spirals and the strongly interacting and starbursting ultraluminous infrared galaxies (ULIRGs). Since a large fraction of the stars in the Universe have been formed in these objects, LIRGs are also relevant in a high-z context. Studies of the two-dimensional physical properties of LIRGs are still lacking. Aims. We aim to understand the nature and origin of the ionization mechanisms operating in the extra-nuclear regions of LIRGs as a function of the interaction phase and infrared luminosity. Methods. This study uses optical integral field spectroscopy (IFS) data obtained with VIMOS. Our analysis is based on over 25 300 spectra of 32 LIRGs covering all types of morphologies (isolated galaxies, interacting pairs, and advanced mergers), and the entire 10 11 −10 12 L infrared luminosity range. Results. We found strong evidence for shock ionization, with a clear trend with the dynamical status of the system. Specifically, we quantified the variation with interaction phase of several line ratios indicative of the excitation degree. While the [N ii]λ6584/Hα ratio does not show any significant change, the [S ii]λλ6717,6731/Hα and [O i]λ6300/Hα ratios are higher for more advanced interaction stages. Velocity dispersions are higher than in normal spirals and increase with the interaction class (medians of 37, 46, and 51 km s −1 for class 0−2, respectively). We constrained the main mechanisms causing the ionization in the extra-nuclear regions (typically for distances ranging from ∼0.2−2.1 kpc to ∼0.9−13.2 kpc) using diagnostic diagrams. Isolated systems are mainly consistent with ionization caused by young stars. Large fractions of the extra-nuclear regions in interacting pairs and more advanced mergers are consistent with ionization caused by shocks of v s < ∼ 200 km s −1 . This is supported by the relation between the excitation degree and the velocity dispersion of the ionized gas, which we interpret as evidence for shock ionization in interacting galaxies and advanced mergers but not in isolated galaxies. This relation does not show any dependence with the infrared luminosity (i.e. the level of star formation). All this indicates that tidal forces play a key role in the origin of the ionizing shocks in the extra-nuclear regions. We also showed for the first time what appears to be a common log([O i]λ6300/Hα) − log(σ) relation for the extranuclear ionized gas in interacting (U)LIRGs (i.e. covering the entire 10 11.0 −10 12.3 L luminosity range). This preliminary result needs to be investigated further with a larger sample of ULIRGs.

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LINER‐like Extended Nebulae in ULIRGs: Shocks Generated by Merger‐Induced Flows

Cited by 106 publications

References 43 publications

Integral field spectroscopy based Hαsizes of local luminous and ultraluminous infrared galaxies

Integral field spectroscopy based Hαsizes of local luminous and ultraluminous infrared galaxies

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

VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies

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