The Survey for Ionization in Neutral Gas Galaxies. I. Description and Initial Results

Meurer, G. R.; Hanish, D. J.; Ferguson, Henry C.; Knezek, Patricia; Kilborn, V. A.; Putman, Mary E.; Smith, Randall; Koribalski, B. S.; Meyer, M.; Oey, M. S.; Ryan-Weber, E. V.; Zwaan, M. A.; Heckman, T. M.; Kennicutt, Robert C.; Lee, Janice; Webster, R. L.; Bland-Hawthorn, Joss; Dopita, Michael A.; Freeman, K. C.; Doyle, M. T.; Drinkwater, Michael J.; Staveley‐Smith, L.; Werk, Jessica K.

doi:10.1086/504685

Cited by 181 publications

(157 citation statements)

References 121 publications

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“…Recently, Meurer et al (2009) have examined correlations in the Hα-to-FUV flux ratio with the Hα and R-band surface brightnesses, using the H i-selected samples of the Survey of Ionization in Neutral Gas Galaxies (SINGG; Meurer et al 2006) and the Survey of UV emission in Neutral Gas Galaxies (SUNGG). Meurer et al find that the Hα-to-FUV flux ratio decreases with decreasing surface brightness.…”

Section: Imfmentioning

confidence: 99%

COMPARISON OF Hα AND UV STAR FORMATION RATES IN THE LOCAL VOLUME: SYSTEMATIC DISCREPANCIES FOR DWARF GALAXIES

Lee

Paz

Tremonti

et al. 2009

ApJ

503

724

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Using a complete sample of ∼300 star-forming galaxies within 11 Mpc of the Milky Way, we evaluate the consistency between star formation rates (SFRs) inferred from the far ultraviolet (FUV) non-ionizing continuum and Hα nebular emission, assuming standard conversion recipes in which the SFR scales linearly with luminosity at a given wavelength. Our analysis probes SFRs over 5 orders of magnitude, down to ultra-low activities on the order of ∼10 −4 M yr −1 . The data are drawn from the 11 Mpc Hα and Ultraviolet Galaxy Survey (11HUGS), which has obtained Hα fluxes from ground-based narrowband imaging, and UV fluxes from imaging with GALEX. For normal spiral galaxies (SFR ∼ 1 M yr −1 ), our results are consistent with previous work which has shown that FUV SFRs tend to be lower than Hα SFRs before accounting for internal dust attenuation, but that there is relative consistency between the two tracers after proper corrections are applied. However, a puzzle is encountered at the faint end of the luminosity function. As lower luminosity dwarf galaxies, roughly less active than the Small Magellanic Cloud, are examined, Hα tends to increasingly underpredict the total SFR relative to the FUV. The trend is evident prior to corrections for dust attenuation, which affects the FUV more than the nebular Hα emission, so this general conclusion is robust to the effects of dust. Although past studies have suggested similar trends, this is the first time this effect is probed with a statistical sample for galaxies with SFR 0.1 M yr −1 . By SFR ∼ 0.003 M yr −1 , the average Hα-to-FUV flux ratio is lower than expected by a factor of two, and at the lowest SFRs probed, the ratio exhibits an order of magnitude discrepancy for the handful of galaxies that remain in the sample. A range of standard explanations does not appear to be able to fully account for the magnitude of the systematic. Some recent work has argued for a stellar initial mass function which is deficient in high-mass stars in dwarf and low surface brightness galaxies, and we also consider this scenario. Under the assumption that the FUV traces the SFR in dwarf galaxies more robustly, the prescription relating Hα luminosity to SFR is re-calibrated for use in the low SFR regime when FUV data are not available.

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Section: Imfmentioning

confidence: 99%

COMPARISON OF Hα AND UV STAR FORMATION RATES IN THE LOCAL VOLUME: SYSTEMATIC DISCREPANCIES FOR DWARF GALAXIES

Lee

Paz

Tremonti

et al. 2009

ApJ

503

724

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“…To facilitate a direct comparison, we utilize R-band imaging from either SDSS or LVL, and follow the surface brightness measurement procedure described in Meurer et al (2006). Below, we briefly summarize the methodology.…”

Section: Measuring R-band Surface Brightnessmentioning

confidence: 99%

MODELING THE EFFECTS OF STAR FORMATION HISTORIES ON Hα AND ULTRAVIOLET FLUXES IN NEARBY DWARF GALAXIES

Weisz

Johnson

et al. 2011

ApJ

178

156

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We consider the effects of non-constant star formation histories (SFHs) on Hα and GALEX far-ultraviolet (FUV) star formation rate (SFR) indicators. Under the assumption of a fully populated Chabrier initial mass function (IMF), we compare the distribution of Hα-to-FUV flux ratios from ∼1500 simple, periodic model SFHs with observations of 185 galaxies from the Spitzer Local Volume Legacy survey. We find a set of SFH models that are well matched to the data, such that more massive galaxies are best characterized by nearly constant SFHs, while low-mass systems experience burst amplitudes of ∼30 (i.e., an increase in the SFR by a factor of 30 over the SFR during the inter-burst period), burst durations of tens of Myr, and periods of ∼250 Myr; these SFHs are broadly consistent with the increased stochastic star formation expected in systems with lower SFRs. We analyze the predicted temporal evolution of galaxy stellar mass, R-band surface brightness, Hα-derived SFR, and blue luminosity, and find that they provide a reasonable match to observed flux distributions. We find that our model SFHs are generally able to reproduce both the observed systematic decline and increased scatter in Hα-to-FUV ratios toward low-mass systems, without invoking other physical mechanisms. We also compare our predictions with those from the Integrated Galactic IMF theory with a constant SFR. We find that while both predict a systematic decline in the observed ratios, only the time variable SFH models are capable of producing the observed population of low-mass galaxies (M * 10 7 M ) with normal Hα-to-FUV ratios. These results demonstrate that a variable IMF alone has difficulty explaining the observed scatter in the Hα-to-FUV ratios. We conclude by considering the limitations of the model SFHs and discuss the use of additional empirical constraints to improve future SFH modeling efforts.

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“…There are several active star forming regions. The H-band image is from the VISTA Phase III survey 4 and the Hα + R-band is from the SINGG survey (Meurer et al 2006). Table 2 summarizes information available on J1609-04.…”

Section: Notesmentioning

confidence: 99%

Nebular Metallicities in Two Isolated Local Void Dwarf Galaxies

Nicholls

Jerjen

Dopita

et al. 2013

ApJ

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Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H ii regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609-04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity H ii region, while the second is in a more vigorous star forming phase with several bright H ii regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral hydrogen.

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The Survey for Ionization in Neutral Gas Galaxies. I. Description and Initial Results

Cited by 181 publications

References 121 publications

COMPARISON OF Hα AND UV STAR FORMATION RATES IN THE LOCAL VOLUME: SYSTEMATIC DISCREPANCIES FOR DWARF GALAXIES

COMPARISON OF Hα AND UV STAR FORMATION RATES IN THE LOCAL VOLUME: SYSTEMATIC DISCREPANCIES FOR DWARF GALAXIES

MODELING THE EFFECTS OF STAR FORMATION HISTORIES ON Hα AND ULTRAVIOLET FLUXES IN NEARBY DWARF GALAXIES

Nebular Metallicities in Two Isolated Local Void Dwarf Galaxies

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