Enhancing Phronesis

Olofsson, Anders; Lindberg, J. Oola

doi:10.4018/978-1-59140-971-7.ch002

Cited by 6 publications

(6 citation statements)

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“…Thus, in most of these dwarf irregular galaxies both oxygen and nitrogen appear to be well mixed. Similar results have been found in other extensive studies of dwarf irregular galaxy abundances (e.g., Kobulnicky & Skillman 1996, 1997Vílchez & Iglesias-Páramo 1998;Lee & Skillman 2004). Given their small dimensions and spatially homogeneous star formation histories (e.g., van Zee 2001), such uniform abundances are perhaps expected in dwarf irregular galaxies.…”

Section: Global Abundancessupporting

confidence: 87%

“…However, the behavior of the strong optical oxygen line intensities ([O II] λ3727 and [O III] λλ4959, 5007) as a function of oxygen abundance has been examined extensively via semi-empirical methods (e.g. Searle 1971;Pagel et al 1979;Alloin et al 1979;Edmunds & Pagel 1984;Dopita & Evans 1986;Skillman 1989) and derived from H II region ionization models (e.g., McGaugh 1991;Olofsson 1997;Kewley & Dopita 2002). At low metallicities, the dominant coolant is the collisionally excited Lyman series, and thus the total oxygen line intensity (R 23 ) increases as the abundance increases.…”

Section: Photoionization Model Gridsmentioning

confidence: 99%

“…McGaugh 1991; Kewley & Dopita 2002). Thus, systematic abundance errors may be introduced when H II regions age, as both the ionization parameter and shape of the ionizing spectrum will evolve (e.g., Stasińska & Leitherer 1996;Olofsson 1997). As discussed in van Zee et al (2005), such effects may be significant for H II regions with log ([O III]/[O II]) < -0.4.…”

Section: Photoionization Model Gridsmentioning

confidence: 99%

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Oxygen and Nitrogen in Isolated Dwarf Irregular Galaxies

Zee

Haynes

2006

ApJ

208

163

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We present long slit optical spectroscopy of 67 HII regions in 21 dwarf irregular galaxies to investigate the enrichment of oxygen, nitrogen, neon, sulfur, and argon in low mass galaxies. Oxygen abundances are obtained via direct detection of the temperature sensitive emission lines for 25 HII regions; for the remainder of the sample, oxygen abundances are estimated from strong line calibrations. The direct abundance determinations are compared to the strong-line abundance calibrations of both McGaugh (1991) and Pilyugin (2000). Global oxygen and nitrogen abundances for this sample of dwarf irregular galaxies are examined in the context of open and closed box chemical evolution models. While several galaxies are consistent with closed box chemical evolution, the majority of this sample have an effective yield ~1/4 of the expected yield for a constant star formation rate and Salpeter IMF, indicating that either outflow of enriched gas or inflow of pristine gas has occurred. The effective yield strongly correlates with M_H/L_B in the sense that gas-rich galaxies are more likely to be closed systems. However, the effective yield does not appear to correlate with other global parameters such as dynamical mass, absolute magnitude, star formation rate or surface brightness. A correlation is found between the observed nitrogen-to-oxygen ratio and the color of the underlying stellar population; redder dwarf irregular galaxies have higher N/O ratios than blue dwarf irregular galaxies. The relative abundance ratios are interpreted in the context of delayed release of nitrogen and varied star formation histories.Comment: 47 pages, 11 figures. Accepted to Ap

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Section: Global Abundancessupporting

confidence: 87%

Section: Photoionization Model Gridsmentioning

confidence: 99%

Section: Photoionization Model Gridsmentioning

confidence: 99%

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Oxygen and Nitrogen in Isolated Dwarf Irregular Galaxies

Zee

Haynes

2006

ApJ

208

163

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“…Pagel et al 1979;Alloin et al 1979;Edmunds & Pagel 1984;Skillman 1989;Zaritsky et al 1994;Pilyugin 2000) and also using theoretical photoionization models (e.g. Dopita & Evans 1986;McGaugh 1991;Olofsson 1997;Dopita et al 2000;Charlot & Longhetti 2001).…”

Section: Physical Conditions and Abundance Analysismentioning

confidence: 99%

“…McGaugh's (1991) models assume unevolving ionizing stellar clusters, whereas it is known that both, the ionization parameter as well as the shape of the ionizing spectrum may evolve (e.g. Stasinska & Leitherer 1996;Olofsson 1997). The effect of cluster evolution on the oxygen line fluxes is expected to be important especially at high metallicity, where diagnostic diagrams could change as a function of time (e.g.…”

Section: The Log([oiii]/[oii]) Versus Log R 23 Diagnostic Diagram Is mentioning

confidence: 99%

Spectroscopy of Dwarf Galaxies in the Virgo Cluster. I. Data, Chemical Abundances, and Ionization Structure

Vı́lchez¹,

Iglésias-Páramo²

2003

ASTROPHYS J SUPPL S

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Long-slit spectroscopy has been obtained for a sample of 22 blue dwarf galaxies selected in the direction of the Virgo Cluster as part of a larger sample of Virgo blue dwarf galaxies for which deep Hα imaging has been collected. Most of the galaxies in the present sample appear classified as BCDs or dwarf Irregulars in the Virgo Cluster Catalog. Line fluxes, Hβ equivalent width and extinction coefficients, spatial emission profiles, ionization structure and physical conditions are presented for the galaxies of the sample. Chemical abundances have been derived either using a direct determination of the electron temperature or after detailed examination of the predictions of different empirical calibrations. The oxygen abundance derived for the sample of Virgo dwarf galaxies span in the range 7.6 ≤ 12 + log O/H ≤ 8.9 , and the corresponding nitrogen to oxygen abundance ratio cover from values typical of low metallicity field BCD galaxies up to near solar.

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A Study of Nine High-Redshift Clusters of Galaxies. IV. Photometry and Spectra of Clusters 1324+3011 and 1604+4321

Postman

Lubin

Oke

2001

The Astronomical Journal

114

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New photometric and spectroscopic observations of galaxies in the directions of three distant clusters are presented as part of our on-going high-redshift cluster survey. The clusters are CL1324+3011 at z = 0.76, CL1604+4304 at z = 0.90, and CL1604+4321 at z = 0.92. We have spectroscopically confirmed cluster membership for 20 to 40 galaxies in each system and have also obtained spectra for over 280 field galaxies spanning the range 0 < z < 2.5. Kinematic estimates of the mass within the central 770h −1 65 kpc of each cluster are in excess of 8 × 10 14 h −1 65 M ⊙ . The observed x-ray luminosities in these clusters are at least a factor of 3 smaller than those observed in clusters with similar velocity dispersions at z ≤ 0.4.These clusters contain a significant population of elliptical-like galaxies, although these galaxies are not nearly as dominant as in massive clusters at z ≤ 0.5. We also find a large population of blue cluster members. Defining an active galaxy as one in which the rest equivalent width of [OII] is greater than 15Å, the fraction of active cluster galaxies, within the central 1.0 h −1 65 Mpc, is 45%. In the field population, we find that 65% of the galaxies with redshifts between z = 0.40 and z = 0.85 are active, while the fraction is 79% for field galaxies at z > 0.85. The star formation rate normalized by the rest AB B−band magnitude, SFRN, increases as the redshift increases at a given evolving luminosity. At a given redshift, however, SFRN decreases linearly with increasing luminosity indicating a remarkable insensitivity of the star formation rate to the intrinsic luminosity of the galaxy over the range −18 ≥ ABB ≥ −22. Cluster galaxies in the central 1h −1 65 Mpc regions exhibit depressed star formation rates and contain a larger fraction of galaxies with "k" type spectra. The star formation rates in galaxies lying between 1 − 2.5h −1 65 Subject headings: galaxies: clusters: general -cosmology: observations -9from those in Table 3 because we used different object detection software. The absolute AB magnitudes in our 4 passbands, ABB, ABV, ABR, and ABI, are given in columns 2 through 5. Geocentric redshifts and our measure of the redshift quality (see Paper I) are given in columns 6 and 7. The slope b (defined above in units of AB mag per unit interval of log ν) is listed in column 8. The contents of the remaining columns are described in subsequent sections. Cluster Mass and M/L EstimatesAs in Paper II, we derive cluster masses based on three popular virial theorem mass estimators: the traditional pairwise mass estimator, M P W , the projected mass estimator, M P M (Bahcall & Tremaine 1981;Heisler, Tremaine, & Bahcall 1985), and the ring-wise mass estimator, M RW (Carlberg et al. 1996). The mathematical definitions of these estimators are given in equations 2 -6 in Paper II. Each estimator has its strengths and weaknesses. The M P W estimate does not require one to specify a cluster center. However M P M and M RW , which do require a center to be defined, tend to be much more robust agai...

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Enhancing Phronesis

Cited by 6 publications

References 0 publications

Oxygen and Nitrogen in Isolated Dwarf Irregular Galaxies

Oxygen and Nitrogen in Isolated Dwarf Irregular Galaxies

Spectroscopy of Dwarf Galaxies in the Virgo Cluster. I. Data, Chemical Abundances, and Ionization Structure

A Study of Nine High-Redshift Clusters of Galaxies. IV. Photometry and Spectra of Clusters 1324+3011 and 1604+4321

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