Physical Processes in Gaseous Nebulae. II. Theory of the Balmer Decrement

Menzel, Donald H.; Baker, James G.

doi:10.1086/143844

Cited by 32 publications

(8 citation statements)

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“…We quantify the amount of dust extinction using the Balmer decrement, the ratio of Hα flux to Hβ . It is possible to determine the expected ratio between these lines based on the properties of the absorbing medium (Menzel & Baker 1937;Baker & Menzel 1938). The flux ratio depends weakly on gas temperature and density (Osterbrock & Ferland 2006) but is strongly affected by dust.…”

Section: Dust Contentmentioning

confidence: 99%

Red Misfits in the Sloan Digital Sky Survey: properties of star-forming red galaxies

Evans

Parker

Roberts

2018

Monthly Notices of the Royal Astronomical Society

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We study Red Misfits, a population of red, star-forming galaxies in the local Universe. We classify galaxies based on inclination-corrected optical colours and specific star formation rates derived from the Sloan Digital Sky Survey Data Release 7. Although the majority of blue galaxies are star-forming and most red galaxies exhibit little to no ongoing star formation, a small but significant population of galaxies (∼11 per cent at all stellar masses) are classified as red in colour yet actively star-forming. We explore a number of properties of these galaxies and demonstrate that Red Misfits are not simply dusty or highly-inclined blue cloud galaxies or quiescent red galaxies with poorly-constrained star formation. The proportion of Red Misfits is nearly independent of environment and this population exhibits both intermediate morphologies and an enhanced likelihood of hosting an AGN. We conclude that Red Misfits are a transition population, gradually quenching on their way to the red sequence and this quenching is dominated by internal processes rather than environmentally-driven processes. We discuss the connection between Red Misfits and other transition galaxy populations, namely S0's, red spirals and green valley galaxies.

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Section: Dust Contentmentioning

confidence: 99%

Red Misfits in the Sloan Digital Sky Survey: properties of star-forming red galaxies

Evans

Parker

Roberts

2018

Monthly Notices of the Royal Astronomical Society

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“…As the atomic structure of hydrogen is so simple, it is possible to determine the exact electronic transition rates, and therefore the ratios of resulting emission lines from these transitions, as a function of physical conditions in the interstellar medium (see Menzel & Baker (1937); Baker & Menzel (1938) for the original theory, with updated work by Seaton (1959) and Storey & Hummer (1995), and treatments of this theory found in textbooks such as Osterbrock & Ferland (2006) or Dopita & Sutherland (2003)). In particular, two cases exist for which the Balmer decrement has been determined over a range of temperatures and densities: Case A and Case B.…”

Section: Balmer Emission Linesmentioning

confidence: 99%

The Balmer decrement of Sloan Digital Sky Survey galaxies

Groves

Brinchmann

Walcher

2011

Monthly Notices of the Royal Astronomical Society

108

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High‐resolution spectra are necessary to distinguish and correctly measure the Balmer emission lines due to the presence of strong metal and Balmer absorption features in the stellar continuum. This accurate measurement is necessary for use in emission‐line diagnostics, such as the Balmer decrement (i.e. Hα/Hβ), used to determine the attenuation of galaxies. Yet at high redshifts, obtaining such spectra becomes costly. Balmer emission‐line equivalent widths are much easier to measure, requiring only low‐resolution spectra or even simple narrow‐band filters and therefore shorter observation times. However, a correction for the stellar continuum is still needed for this equivalent width Balmer decrement. We present here a statistical analysis of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) emission‐line galaxy sample, using the spectrally determined Balmer emission‐line fluxes and equivalent widths. Using the large numbers of galaxies available in the SDSS catalogue, we determined an equivalent width Balmer decrement including a statistically based correction for the stellar continuum. Based on this formula, the attenuation of galaxies can now be obtained from low spectral resolution observations. In addition, this investigation also revealed an error in the Hβ line fluxes, within the SDSS DR7 MPA/JHU† catalogue, with the equivalent widths underestimated by average ∼0.35 Å in the emission‐line galaxy sample. This error means that Balmer decrement determined attenuations are overestimated by a systematic 0.1 mag in AV, and future analyses of this sample need to include this correction.

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“…The Balmer lines arise from the recombination and subsequent cascade transitions to the second (n = 2) level of hydrogen. The expected relative fluxes of the Balmer lines can be computed theoretically (Menzel & Baker 1937;Baker & Menzel 1938;Seaton 1959;Hummer & Storey 1998;Osterbrock & Ferland 2006;Dopita & Sutherland 2003). These predicted line ratios are a function of the temperature and electron density in the nebular regions, however the functional dependence is weak 10 Carnegie Fellow.…”

Section: Introductionmentioning

confidence: 99%

NEBULAR ATTENUATION IN Hα-SELECTED STAR-FORMING GALAXIES ATz= 0.8 FROM THE NewHα SURVEY

Momcheva

Lee

et al. 2013

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We present measurements of the dust attenuation of Hα-selected emission-line galaxies at z = 0.8 from the NewHα narrowband survey. The analysis is based on deep follow-up spectroscopy with Magellan/IMACS, which captures the strong rest-frame optical emission lines fromThe spectroscopic sample used in this analysis consists of 341 confirmed Hα emitters. We place constraints on the active galactic nucleus (AGN) fraction using diagnostics that can be applied at intermediate redshift. We find that at least 5% of the objects in our spectroscopic sample can be classified as AGNs and 2% are composite, i.e., powered by a combination of star formation and AGN activity. We measure the dust attenuation for individual objects from the ratios of the higher order Balmer lines. The Hβ and Hγ pair of lines is detected with S/N > 5 in 55 individual objects and the Hβ and Hδ pair is detected in 50 individual objects. We also create stacked spectra to probe the attenuation in objects without individual detections. The median attenuation at Hα based on the objects with individually detected lines is A(Hα) = 0.9 ± 1.0 mag, in good agreement with the attenuation found in local samples of star-forming galaxies. We find that the z = 0.8 galaxies occupy a similar locus of attenuation as a function of magnitude, mass, and star formation rate (SFR) as a comparison sample drawn from the SDSS DR4. Both the results from the individual z = 0.8 galaxies and from the stacked spectra show consistency with the mass-attenuation and SFR-attenuation relations found in the local universe, indicating that these relations are also applicable at intermediate redshift.

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Physical Processes in Gaseous Nebulae. II. Theory of the Balmer Decrement

Cited by 32 publications

References 0 publications

Red Misfits in the Sloan Digital Sky Survey: properties of star-forming red galaxies

Red Misfits in the Sloan Digital Sky Survey: properties of star-forming red galaxies

The Balmer decrement of Sloan Digital Sky Survey galaxies

NEBULAR ATTENUATION IN Hα-SELECTED STAR-FORMING GALAXIES ATz= 0.8 FROM THE NewHα SURVEY

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