Eliminating error in the chemical abundance scale for extragalactic H <scp>ii</scp>regions

López-Sánchez, Ángel R.; Dopita, Michael A.; Kewley, Lisa J.; Zahid, H. Jabran; Nicholls, David C.; Scharwächter, J.

doi:10.1111/j.1365-2966.2012.21145.x

Cited by 180 publications

(206 citation statements)

References 90 publications

(310 reference statements)

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“…In our sample, 19 galaxies (∼12%) at z < 0.48 fall into this category. For these galaxies, however, we can derive a semidirect metallicity taking advantage of the tight relation between t e [O iii] and Z expected for high-excitation environments -like those present in EELGs -from both observations and models (e.g., Masegosa et al 1994;López-Sánchez et al 2012). Thus, we calibrate the relation between t e [O iii] and Z for EELGs (dubbed hereafter the t e [O iii]−Z calibration) using a combination of two independent datasets.…”

Section: Metallicity Derived Through the Direct Methodsmentioning

confidence: 99%

Extreme emission-line galaxies out toz~ 1 in zCOSMOS

Amorín

Pérez-Montero

Contini

et al. 2015

A&A

113

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Context. The study of large and representative samples of low-metallicity star-forming galaxies at different cosmic epochs is of great interest to the detailed understanding of the assembly history and evolution of low-mass galaxies. Aims. We present a thorough characterization of a large sample of 183 extreme emission-line galaxies (EELGs) at redshift 0.11 ≤ z ≤ 0.93 selected from the 20k zCOSMOS bright survey because of their unusually large emission line equivalent widths. Methods. We use multiwavelength COSMOS photometry, HST-ACS I-band imaging, and optical zCOSMOS spectroscopy to derive the main global properties of star-forming EELGs, such as sizes, stellar masses, star formation rates (SFR), and reliable oxygen abundances using both "direct" and "strong-line" methods. Results. The EELGs are extremely compact (r 50 ∼ 1.3 kpc), low-mass (M * ∼ 10 7 −10 10 M ) galaxies forming stars at unusually high specific star formation rates (sSFR ≡ SFR/M up to 10 −7 yr −1 ) compared to main sequence star-forming galaxies of the same stellar mass and redshift. At rest-frame UV wavelengths, the EELGs are luminous and show high surface brightness and include strong Lyα emitters, as revealed by GALEX spectroscopy. We show that zCOSMOS EELGs are high-ionization, low-metallicity systems, with median 12+ log(O/H) = 8.16 ± 0.21 (0.2 Z ) including a handful of extremely metal-deficient (<0.1 Z ) EELGs. While ∼80% of the EELGs show non-axisymmetric morphologies, including clumpy and cometary or tadpole galaxies, we find that ∼29% of them show additional low-surface-brightness features, which strongly suggests recent or ongoing interactions. As star-forming dwarfs in the local Universe, EELGs are most often found in relative isolation. While only very few EELGs belong to compact groups, almost one third of them are found in spectroscopically confirmed loose pairs or triplets. Conclusions. The zCOSMOS EELGs are galaxies caught in a transient and probably early period of their evolution, where they are efficiently building up a significant fraction of their present-day stellar mass in an ongoing, galaxy-wide starburst. Therefore, the EELGs constitute an ideal benchmark for comparison studies between low-and high-redshift low-mass star-forming galaxies.

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Section: Metallicity Derived Through the Direct Methodsmentioning

confidence: 99%

Extreme emission-line galaxies out toz~ 1 in zCOSMOS

Amorín

Pérez-Montero

Contini

et al. 2015

A&A

113

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“…One important problem is that many of the most widely used calibrations based on photoionization models (e.g., McGaugh 1991; Kewley & Dopita 2002) also give systematic overabundances with respect to the direct method. These differences can be up to 0.7 dex depending on the models and the Z range (Kewley & Ellison 2008;Moustakas et al 2010;Stasińska 2010;López-Sánchez et al 2012).…”

Section: From the Three Fields Of Vuds Survey (Cosmos Ecdfsmentioning

confidence: 99%

Characterization of star-forming dwarf galaxies at 0.1 ≲z ≲ 0.9 in VUDS: probing the low-mass end of the mass-metallicity relation

Calabró

Amorín

Fontana

et al. 2017

A&A

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Context. The study of statistically significant samples of star-forming dwarf galaxies (SFDGs) at different cosmic epochs is essential for the detailed understanding of galaxy assembly and chemical evolution. However, the main properties of this large population of galaxies at intermediate redshift are still poorly known. Aims. We present the discovery and spectrophotometric characterization of a large sample of 164 faint (i AB ∼ 23-25 mag) SFDGs at redshift 0.13 ≤ z ≤ 0.88 selected by the presence of bright optical emission lines in the VIMOS Ultra Deep Survey (VUDS). We investigate their integrated physical properties and ionization conditions, which are used to discuss the low-mass end of the mass-metallicity relation (MZR) and other key scaling relations. Methods. We use optical VUDS spectra in the COSMOS, VVDS-02h, and ECDF-S fields, as well as deep multi-wavelength photometry that includes HST-ACS F814W imaging, to derive stellar masses, extinction-corrected star-formation rates (SFR), and gas-phase metallicities of SFDGs. For the latter, we use the direct method and a T e -consistent approach based on the comparison of a set of observed emission lines ratios with the predictions of detailed photoionization models. Results. The VUDS SFDGs are compact (median r e ∼ 1.2 kpc), low-mass (M * ∼ 10 7 -10 9 M ) galaxies with a wide range of starformation rates (SFR(Hα) ∼ 10 −3 -10 1 M /yr) and morphologies. Overall, they show a broad range of subsolar metallicities (12 + log(O/H) = 7.26-8.7; 0.04 < ∼ Z/Z < ∼ 1). Nearly half of the sample are extreme emission-line galaxies (EELGs) characterized by high equivalent widths and emission line ratios indicative of higher excitation and ionization conditions. The MZR of SFDGs shows a flatter slope compared to previous studies of galaxies in the same mass range and redshift. We find the scatter of the MZR is partly explained in the low mass range by varying specific SFRs and gas fractions amongst the galaxies in our sample. In agreement with recent studies, we find the subclass of EELGs to be systematically offset to lower metallicity compared to SFDGs at a given stellar mass and SFR, suggesting a younger starburst phase. Compared with simple chemical evolution models we find that most SFDGs do not follow the predictions of a "closed-box" model, but those from a gas-regulating model in which gas flows are considered. While strong stellar feedback may produce large-scale outflows favoring the cessation of vigorous star formation and promoting the removal of metals, younger and more metal-poor dwarfs may have recently accreted large amounts of fresh, very metal-poor gas, that is used to fuel current star formation.

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“…5.3 and 7). We stress that different strong-line diagnostics and calibration methodologies (e.g., photoionization models versus empirical electronic temperature, T e , derivations) yield substantial systematic offsets in the inferred gas metallicities (e.g., Kennicutt et al 2003;Moustakas et al 2010;López-Sánchez et al 2012;Bresolin et al 2016), reaching values up to 0.7 dex (Kewley & Ellison 2008). Methods calibrated from T e measurements tend to occupy the bottom of the abundance scale.…”

Section: Metallicity Abundancesmentioning

confidence: 99%

Radial distribution of dust, stars, gas, and star-formation rate in DustPedia face-on galaxies

Casasola

Cassarà

Bianchi

et al. 2017

A&A

128

140

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Aims. The purpose of this work is the characterization of the radial distribution of dust, stars, gas, and star-formation rate (SFR) in a sub-sample of 18 face-on spiral galaxies extracted from the DustPedia sample. Methods. This study is performed by exploiting the multi-wavelength, from ultraviolet (UV) to sub-millimeter bands, DustPedia database, in addition to molecular ( 12 CO) and atomic (Hi) gas maps and metallicity abundance information available in the literature. We fitted the surface brightness profiles of the tracers of dust and stars, the mass surface density profiles of dust, stars, molecular gas, and total gas, and the SFR surface density profiles with an exponential curve and derived their scale-lengths. We also developed a method to solve for the CO-to-H 2 conversion factor (α CO ) per galaxy by using dust and gas mass profiles. Results. Although each galaxy has its own peculiar behaviour, we identified a common trend of the exponential scale-lengths vs. wavelength. On average, the scale-lengths normalized to the B-band 25 mag/arcsec 2 radius decrease from UV to 70 µm, from 0.4 to 0.2, and then increase back up to ∼0.3 at 500 microns. The main result is that, on average, the dust mass surface density scale-length is about 1.8 times the stellar one derived from IRAC data and the 3.6 µm surface brightness, and close to that in the UV. We found a mild dependence of the scale-lengths on the Hubble stage T: the scale-lengths of the Herschel bands and the 3.6 µm scale-length tend to increase from earlier to later types, the scale-length at 70 µm tends to be smaller than that at longer sub-mm wavelength with ratios between longer sub-mm wavelengths and 70 µm that decrease with increasing T. The scale-length ratio of SFR and stars shows a weak increasing trend towards later types. Our α CO determinations are in the range (0.3 − 9) M pc −2 (K km s −1 ) −1 , almost invariant by using a fixed dust-to-gas ratio mass (DGR) or a DGR depending on metallicity gradient.

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Eliminating error in the chemical abundance scale for extragalactic H iiregions

Cited by 180 publications

References 90 publications

Extreme emission-line galaxies out toz~ 1 in zCOSMOS

Extreme emission-line galaxies out toz~ 1 in zCOSMOS

Characterization of star-forming dwarf galaxies at 0.1 ≲z ≲ 0.9 in VUDS: probing the low-mass end of the mass-metallicity relation

Radial distribution of dust, stars, gas, and star-formation rate in DustPedia face-on galaxies

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