H<scp>ii</scp>Regions in Spiral Galaxies: Size Distribution, Luminosity Function, and New Isochrone Diagnostics of Density-Wave Kinematics

Oey, M. S.; Parker, Jeffrey S.; Mikles, V. J.; Zhang, Xiaolei

doi:10.1086/378163

Cited by 62 publications

(86 citation statements)

References 40 publications

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“…The derived scale can be compared to the physical diameter of a well-known H ii region in our Galaxy, i.e. the Orion nebula (D ∼ 8 pc), or to the extent of those which are considered prototypes of extragalactic giant H ii regions, such as 30 Doradus (D ∼ 200 pc), NGC 604 (D ∼ 460 pc) or NGC 5471 (D ∼ 1 kpc) as reported by Oey et al (2003) and García-Benito et al (2011). Thus, given the undersampling in the physical size of the H ii regions in our data, we cannot use it to derive direct estimates of the optical extension of these regions.…”

Section: Sample Of Galaxiesmentioning

confidence: 96%

“…The procedure is based on some basic assumptions: (a) H ii regions are peaky/isolated structures with a strong ionized gas emission, clearly above the continuum emission and the average ionized gas emission across the galaxy; (b) H ii regions have a typical physical size of about a hundred or a few hundreds of parsecs (e.g. Gonzalez Delgado & Perez 1997;Lopez et al 2011;Oey et al 2003), which corresponds to a typical projected size at the distance of the galaxies of a few arcsec.…”

Section: Extraction Of the H II Regionsmentioning

confidence: 99%

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Integral field spectroscopy of a sample of nearby galaxies

Sánchez

Rosales-Ortega

Marino

et al. 2012

A&A

186

189

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We analyse the spectroscopic properties of thousands of H ii regions identified in 38 face-on spiral galaxies. All galaxies were observed out to 2.4 effective radii using integral field spectroscopy (IFS) over the wavelength range ∼3700 to ∼6900 Å. The near uniform sample has been assembled from the PPAK IFS Nearby Galaxy (PINGS) survey and a sample described in Paper I. We develop a new automatic procedure to detect H ii regions, based on the contrast of the Hα intensity maps extracted from the datacubes. Once detected, the algorithm provides us with the integrated spectra of each individual segmented region. In total, we derive good quality spectroscopic information for ∼2600 independent H ii regions/complexes. This is by far the largest H ii region survey of its kind. Our selection criteria and the use of 3D spectroscopy guarantee that we cover the regions in an unbiased way. A welltested automatic decoupling procedure has been applied to remove the underlying stellar population, deriving the main properties (intensity, dispersion and velocity) of the strongest emission lines in the considered wavelength range (covering from [O ii] λ3727 to [S ii] λ6731). A final catalogue of the spectroscopic properties of H ii regions has been created for each galaxy, which includes information on morphology, spiral structure, gas kinematics, and surface brightness of the underlying stellar population. In the current study, we focus on the understanding of the average properties of the H ii regions and their radial distributions. We find a significant change in the ionisation characteristics of H ii regions within r < 0.25 r e due to contamination from sources with different ionising characteristics, as we discuss. We find that the gas-phase oxygen abundance and the Hα equivalent width present a negative and positive gradient, respectively. The distribution of slopes is statistically compatible with a random Gaussian distribution around the mean value, if the radial distances are measured in units of the respective effective radius. No difference in the slope is found for galaxies of different morphologies, e.g. barred/non-barred, grand-design/flocculent. Therefore, the effective radius is a universal scale length for gradients in the evolution of galaxies. Some properties have a large variance across each object and between galaxies (e.g. electron density) without a clear characteristic value. But other properties are well described by an average value either galaxy by galaxy or among the different galaxies (e.g. dust attenuation).

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Section: Sample Of Galaxiesmentioning

confidence: 96%

Section: Extraction Of the H II Regionsmentioning

confidence: 99%

Integral field spectroscopy of a sample of nearby galaxies

Sánchez

Rosales-Ortega

Marino

et al. 2012

A&A

186

189

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“…On the other hand, HIIexplorer also considers extragalactic H ii regions to have a typical physical size of about a few hundred parsecs (González Delgado & Pérez 1997;Oey et al 2003;Lopez et al 2011). Taking into account these assumptions, we can summarise the main steps of the process as follows:…”

Section: Detection Of Ionised Regionsmentioning

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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“…The procedure is based on some basic assumptions: (a) H ii regions are peaky and isolated structures with a strong ionized gas emission, which is significantly above the stellar continuum emission and the average ionized gas emission across the galaxy. This is particularly true for Hα because (b) H ii regions have a typical physical size of about a hundred 4 http://www.caha.es/sanchez/HII_explorer/ or a few hundred parsecs (e.g., González Delgado & Perez 1997;Lopez et al 2011;Oey et al 2003), which corresponds to a typical projected size of a few arcsec at the distance of the galaxies.…”

Section: Detection Of Ionized Regionsmentioning

confidence: 99%

A characteristic oxygen abundance gradient in galaxy disks unveiled with CALIFA

Sánchez

Rosales-Ortega

Iglésias-Páramo

et al. 2014

A&A

414

289

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We present the largest and most homogeneous catalog of H ii regions and associations compiled so far. The catalog comprises more than 7000 ionized regions, extracted from 306 galaxies observed by the CALIFA survey. We describe the procedures used to detect, select, and analyze the spectroscopic properties of these ionized regions. In the current study we focus on characterizing of the radial gradient of the oxygen abundance in the ionized gas, based on the study of the deprojected distribution of H ii regions. We found that all galaxies without clear evidence of an interaction present a common gradient in the oxygen abundance, with a characteristic slope of α O/H = −0.1 dex/r e between 0.3 and 2 disk effective radii (r e ), and a scatter compatible with random fluctuations around this value, when the gradient is normalized to the disk effective radius. The slope is independent of morphology, the incidence of bars, absolute magnitude, or mass. Only those galaxies with evidence of interactions and/or clear merging systems present a significantly shallower gradient, consistent with previous results. The majority of the 94 galaxies with H ii regions detected beyond two disk effective radii present a flattening in the oxygen abundance. The flattening is statistically significant. We cannot provide a conclusive answer regarding the origin of this flattening. However, our results indicate that its origin is most probably related to the secular evolution of galaxies. Finally, we find a drop/truncation of the oxygen abundance in the inner regions for 26 of the galaxies. All of them are non-interacting, mostly unbarred Sb/Sbc galaxies. This feature is associated with a central star-forming ring, which suggests that both features are produced by radial gas flows induced by resonance processes. Our result suggests that galaxy disks grow inside-out, with metal enrichment driven by the local star formation history and with a small variation galaxy-by-galaxy. At a certain galactocentric distance, the oxygen abundance seems to be correlated well with the stellar mass density and total stellar mass of the galaxies, independently of other properties of the galaxies. Other processes, such as radial mixing and inflows/outflows seem to have a limited effect on shaping of the radial distribution of oxygen abundances, although they are not ruled out.

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HiiRegions in Spiral Galaxies: Size Distribution, Luminosity Function, and New Isochrone Diagnostics of Density-Wave Kinematics

Cited by 62 publications

References 40 publications

Integral field spectroscopy of a sample of nearby galaxies

Integral field spectroscopy of a sample of nearby galaxies

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

A characteristic oxygen abundance gradient in galaxy disks unveiled with CALIFA

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