Modeling the Pan‐Spectral Energy Distribution of Starburst Galaxies. III. Emission Line Diagnostics of Ensembles of Evolving H
                    <scp>ii</scp>
                    Regions

Dopita, Michael A.; Fischera, Joerg; Sutherland, Ralph S.; Kewley, Lisa J.; Leitherer, Claus; Tuffs, R.; Popescu, Cristina; Breugel, Wil van; Groves, Brent

doi:10.1086/508261

Cited by 183 publications

(217 citation statements)

References 66 publications

(75 reference statements)

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“…Thus, two families of calibrators have been developed and are widely used today: empirical calibrators based on direct estimations of oxygen abundances (Zaritsky et al 1994 Dopita et al 2006Dopita et al , 2013Pérez-Montero 2014;Dopita et al 2016). It is important to note that T e -based empirical calibrations provide results that are at least 0.2 − 0.4 dex lower than strong-line methods based on photoionisation models (see López-Sánchez 2010;López-Sánchez et al 2012 for extended discussion of these issues).…”

Section: Measurement Of the Oxygen Abundancesmentioning

confidence: 99%

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

Sánchez-Menguiano

Sanchez

Pérez

et al. 2018

A&A

146

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We characterised the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high spatial resolution of the data allowed us to detect 14345 H ii regions with the same image quality as with photometric data, avoiding any dilution effect. We developed a new methodology to automatically fit the abundance radial profiles, finding that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10), or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence in the case of the outer flattening. We find that the inner drop appears always around 0.5 r e , while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope in the sample of α O/H = − 0.10 ± 0.03 dex/r e . This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale ('the abundance scale length', r O/H ) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop (∼ 0.5 r O/H ) and the outer flattening (∼ 1.5 r O/H ). Finally, we find no significant dependence of the dispersion around the negative gradient with any property of the galaxies, with values compatible with the uncertainties associated with the derivation of the abundances.

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Section: Measurement Of the Oxygen Abundancesmentioning

confidence: 99%

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

Sánchez-Menguiano

Sanchez

Pérez

et al. 2018

A&A

146

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“…In the next section we will explore the role of these different ionization mechanisms by comparing our measured line ratios with the predictions of the models. (Dopita et al 2006), shocks (Allen et al 2008), TML (Slavin et al 1993) and dusty AGNs (Groves et al 2004) covering a wide range of physical parameters (ionization, density, stellar ages, shock velocity, etc.) and metallicities were considered.…”

Section: Anti-correlation Between Excitation and Hα Luminositymentioning

confidence: 99%

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

Monreal-Ibero

Arribas

Colina

et al. 2010

A&A

101

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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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“…We inputted the different continua into the photoionization code Cloudy (Ferland et al 1998, version C08). In addition, we assumed a rather simple description of the gaseous component: an expanding radiation-limited nebula with a 1 pc inner radio, density equal to 100 cm −3 , and the same solar metallicity mixture as in Table 1 from Dopita et al (2006), although without taking into account any depletion of metals.…”

Section: Effects On the Emission Line Spectrummentioning

confidence: 99%

“…To analyse easily the results obtained, we used diagnostic diagrams and compared with the grids by Dopita et al (2006). These grids were parametrized as a function of a parameter R, which is the logarithm of the ratio of the cluster mass to the ambient pressure.…”

Section: Effects On the Emission Line Spectrummentioning

confidence: 99%

“…For the evolutionary status of the stellar component, there are common simplifying hypotheses for the description of the ionizing continuum produced by the cluster. Examples are methods using either individual stars, such as the use of a cluster effective temperature (e.g., Stasińska 1990;Stasińska & Schaerer 1997;Bresolin et al 1999;Bresolin & Kenicutt 2002) or a stellar ensemble where the different stellar components are mixed according to some specific prescriptions, as in evolutionary synthesis models (Olofsson 1989;García Vargas & Díaz 1994 are examples of pioneering works; and Dopita et al 2006 a more recent one).…”

Section: Introductionmentioning

confidence: 99%

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Modeling the ionizing spectra of H II regions: individual stars versus stellar ensembles

Villaverde

Cerviño

Luridiana

2010

A&A

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Aims. We study how IMF sampling affects the ionizing flux and emission line spectra of low mass stellar clusters. Methods. We performed 2 × 10 6 Monte Carlo simulations of zero-age solar-metallicity stellar clusters covering the 20−10 6 M mass range. We study the distribution of cluster stellar masses, M clus , ionizing fluxes, Q(H 0 ), and effective temperatures, T clus eff . We compute photoionization models that broadly describe the results of the simulations and compare them with photoionization grids.Results. Our main results are: (a) a large number of low mass clusters (80% for M clus = 100 M ) are unable to form an H ii region. (b) There are a few overluminous stellar clusters that form H ii regions. These overluminous clusters preserve statistically the mean value of Q(H 0 ) obtained by synthesis models, but the mean value cannot be used as a description of particular clusters. (c) The ionizing continuum of clusters with M clus < ∼ 10 4 M is more accurately described by an individual star with self-consistent effective temperature (T * eff ) and Q(H 0 ) than by the ensemble of stars (or a cluster T clus eff ) produced by synthesis models. (d) Photoionization grids of stellar clusters cannot be used to derive the global properties of low mass clusters. Conclusions. Although variations in the upper mass limit, m up , of the IMF would reproduce the effects of IMF sampling, we find that an ad hoc law that relates m up to M clus in the modeling of stellar clusters is useless, since: (a) it does not cover the whole range of possible cases; and (b) the modeling of stellar clusters with an IMF is motivated by the need to derive the global properties of the cluster: however, in clusters affected by sampling effects we have no access to global information of the cluster but only particular information about a few individual stars.

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Modeling the Pan‐Spectral Energy Distribution of Starburst Galaxies. III. Emission Line Diagnostics of Ensembles of Evolving H ii Regions

Cited by 183 publications

References 66 publications

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

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

Modeling the ionizing spectra of H II regions: individual stars versus stellar ensembles

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