Star Formation Histories of the LEGUS Dwarf Galaxies. III. The Nonbursty Nature of 23 Star-forming Dwarf Galaxies*

Cignoni, M.; Sacchi, Elena; Tosi, M.; Aloisi, Alessandra; Cook, D.; Calzetti, Daniela; Lee, Janice; Sabbi, E.; Thilker, David A.; Adamo, Angela; Dale, Daniel A.; Elmegreen, Bruce G.; Gallagher, John S.; Grebel, Eva K.; Johnson, K. E.; Messa, Matteo; Smith, Linda J.; Úbeda, Leonardo

doi:10.3847/1538-4357/ab53d5

Cited by 42 publications

(32 citation statements)

References 147 publications

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“…Older stars in Ho II are more centrally concentrated than younger stars (Bernard et al 2012), and this is consistent with the tendency for dwarf irregular galaxies to have recent star forming activity that is more diffusely distributed than at earlier epochs (e.g. Cignoni et al 2019).…”

Section: Introductionsupporting

confidence: 60%

“…These galaxies have similar morphologies, integrated brightnesses, and distances. Cignoni et al (2019) find that dwarf irregular galaxies such as these tend to have had more or less constant SFRs during the past 100 Myr, with departures that are no more than 3× that from historic means, and so it is then expected that galaxies of this type will harbor intrinsically luminous LPVs and massive stars. Basic observational properties of these galaxies are summarized in Table 1.…”

Section: Introductionmentioning

confidence: 99%

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Red Variable Stars in Three M81 Group Dwarf Galaxies

Davidge

2022

Preprint

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Archival [3.6] and [4.5] images are used to identify and characterize variable stars in the Magellanic-type galaxies Holmberg II, NGC 2366, and IC 2574. Using parametric and non-parametric detection methods, 74 confirmed or suspected long period variables (LPVs) are found. The period distributions of the LPVs in NGC 2366 and IC 2574 are similar. While the period distribution of LPVs in Ho II is uncertain due to small number statistics there appears to be a deficiency of LPVs with periods between 550 and 650 days when compared with NGC 2366 and IC 2574. The LPVs are diffusely distributed on the sky, and do not follow the underlying light from unresolved stars, as expected if episodes of star formation within the past few hundred Myr have occured throughout the galaxies, including their outer regions. Distances computed for Ho II and NGC 2366 from the period-luminosity relations (PLRs) agree to within ∼ 0.1 magnitudes with those based on the tip of the red giant branch (RGB). Efforts to estimate an LPV-based distance modulus for IC 2574 are complicated by the presence of first overtone pulsators among LPVs with periods ∼ 600 days, although the PLR at the long period end is consistent with the distance estimated from the RGB-tip. In addition to the LPVs, 10 candidate sgB[e] or luminous blue variables and 2 candidate red supergiant variables are also identified. Nine candidate sgB[e] stars that do not show evidence of variability are also identified based on their locations in the color-magnitude diagram.

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Section: Introductionsupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Red Variable Stars in Three M81 Group Dwarf Galaxies

Davidge

2022

Preprint

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“…This result is supported by SFH studies based on colormagnitude diagrams. NGC 4449 and NGC 3738 are found to have approximately constant SFHs in the last 200 Myr (Cignoni et al 2018(Cignoni et al , 2019Sacchi et al 2018). Sacchi et al (2019) also reported that the SFH of NGC 7793, which contributes 40% of our final sample (see Table 1), is not bursty and suggests inside-out star formation in this galaxy.…”

Section: Pahmentioning

confidence: 63%

The Age Dependence of Mid-infrared Emission around Young Star Clusters

Lin

Calzetti

Kong

et al. 2020

ApJ

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Using the star cluster catalogs from the Hubble Space Telescope program Legacy Extragalactic UV survey (LEGUS) and 8 μm images from the IRAC camera on the Spitzer Space Telescope for five galaxies within 5 Mpc, we investigate how the 8 μm dust luminosity correlates with the stellar age on the 30-50 pc scale of star-forming regions. We construct a sample of 97 regions centered at local peaks of 8 μm emission, each containing one or more young star cluster candidates from the LEGUS catalogs. We find a tight anticorrelation with a Pearson correlation coefficient of r=−0.84±0.05 between the mass-normalized dust-only 8 μm luminosity and the age of stellar clusters younger than 1 Gyr; the 8 μm luminosity decreases with increasing age of the stellar population. Simple assumptions on a combination of stellar and dust emission models reproduce the observed trend. We also explore how the scatter of the observed trend depends on assumptions of stellar metallicity, polycyclic aromatic hydrocarbon (PAH) abundance, fraction of stellar light absorbed by dust, and instantaneous versus continuous star formation models. We find that variations in stellar metallicity have little effect on the scatter, while PAH abundance and the fraction of dust-absorbed light bracket the full range of the data. We also find that the trend is better explained by continuous star formation, rather than instantaneous burst models. We ascribe this result to the presence of multiple star clusters with different ages in many of the regions. Upper limits of the dust-only 8 μm emission as a function of age are provided.

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“…It has a rich population of young, intermediate, and old star clusters, making it the best sampled dwarf galaxy in our study, potentially due to a rich star formation history sculpted by earlier interactions and mergers (see for e.g. Cignoni et al 2019). Whitmore et al (2020) include this galaxy in the recent H α-LEGUS survey that add narrowband H α imaging to a subsample of LEGUS galaxies, allowing the production of new cluster catalogs with improved ages.…”

Section: Ngc 4449mentioning

confidence: 99%

The dependence of the hierarchical distribution of star clusters on galactic environment

Menon

Grasha

Elmegreen³

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We use the angular Two Point Correlation Function (TPCF) to investigate the hierarchical distribution of young star clusters in 12 local (3–18 Mpc) star-forming galaxies using star cluster catalogues obtained with the Hubble Space Telescope (HST) as part of the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). The sample spans a range of different morphological types, allowing us to infer how the physical properties of the galaxy affect the spatial distribution of the clusters. We also prepare a range of physically motivated toy models to compare with and interpret the observed features in the TPCFs. We find that, conforming to earlier studies, young clusters (T ≲ 10 Myr) have power-law TPCFs that are characteristic of fractal distributions with a fractal dimension D2, and this scale-free nature extends out to a maximum scale lcorr beyond which the distribution becomes Poissonian. However, lcorr, and D2 vary significantly across the sample, and are correlated with a number of host galaxy physical properties, suggesting that there are physical differences in the underlying star cluster distributions. We also find that hierarchical structuring weakens with age, evidenced by flatter TPCFs for older clusters (T ≳ 10 Myr), that eventually converges to the residual correlation expected from a completely random large-scale radial distribution of clusters in the galaxy in ∼100 Myr. Our study demonstrates that the hierarchical distribution of star clusters evolves with age, and is strongly dependent on the properties of the host galaxy environment.

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Star Formation Histories of the LEGUS Dwarf Galaxies. III. The Nonbursty Nature of 23 Star-forming Dwarf Galaxies*

Cited by 42 publications

References 147 publications

Red Variable Stars in Three M81 Group Dwarf Galaxies

Red Variable Stars in Three M81 Group Dwarf Galaxies

The Age Dependence of Mid-infrared Emission around Young Star Clusters

The dependence of the hierarchical distribution of star clusters on galactic environment

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