The triggering of starbursts in low-mass galaxies

Lelli, Federico; Verheijen, Marc; Fraternali, Filippo

doi:10.1093/mnras/stu1804

Cited by 99 publications

(107 citation statements)

References 119 publications

(164 reference statements)

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“…For the galaxies with resolved observations, for comparison with CO, we have attempted to compute the H I mass, M HI , by integrating the mean H I surface density within only the optical radius. Because virtually all metal-poor dwarf galaxies show H I emission well outside their optical radius (e.g., Hunter et al 1994a;van Zee et al 1998;van Zee 2000;Ekta et al 2009;Lelli et al 2012Lelli et al , 2014, these values of M HI are typically a factor of 2-10 lower than the total H I mass, integrated over the entire H I extent. Table 1 reports both values of M HI when resolved H I maps are available.…”

Section: H I Measurementsmentioning

confidence: 99%

Molecular depletion times and the CO-to-H₂conversion factor in metal-poor galaxies

Hunt

García‐Burillo

Casasola

et al. 2015

A&A

113

149

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Tracing molecular hydrogen content with carbon monoxide in low-metallicity galaxies has been exceedingly difficult. Here we present a new effort, with IRAM 30-m observations of 12 CO(1-0) of a sample of 8 dwarf galaxies having oxygen abundances ranging from 12 + log(O/H) ∼ 7.7 to 8.4. CO emission is detected in all galaxies, including the most metal-poor galaxy of our sample (0.1 Z ); to our knowledge this is the largest number of 12 CO(1-0) detections ever reported for galaxies with 12 + log(O/H) < ∼ 8 (0.2 Z ) outside the Local Group. We calculate stellar masses, M star , and star-formation rates (SFRs), and analyze our results in conjunction with galaxy samples from the literature. Extending previous results for a correlation of the molecular gas depletion time, τ dep , with M star and specific SFR (sSFR), we find a variation in τ dep of a factor of 200 or more (from < ∼ 50 Myr to ∼10 Gyr) over a spread of ∼10 3 in sSFR and M star . We exploit the variation of τ dep to constrain the CO-to-H 2 mass conversion factor α CO at low metallicity, and assuming a power-law variation find α CO ∝ Z/Z −2 , similar to results based on dust continuum measurements compared with gas mass. By including H I measurements, we show that the fraction of total gas mass relative to the baryonic mass is higher in galaxies that are metal poor, of low mass, and with high sSFR. Finally, comparisons of the data with star-formation models of the molecular gas phases show that the models are generally quite successful, but at metallicities Z/Z < ∼ 0.2, there are some discrepancies.

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Section: H I Measurementsmentioning

confidence: 99%

Molecular depletion times and the CO-to-H₂conversion factor in metal-poor galaxies

Hunt

García‐Burillo

Casasola

et al. 2015

A&A

113

149

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“…In the case of dwarf galaxies it has been suggested that interactions are responsible for the class of blue compact dwarfs (BCDs; Paudel et al 2015): dwarf galaxies with a significant, centrally concentrated young stellar population (e.g., Gil de Paz et al 2003). In general many dwarf systems with increased star formation rates (SFR) have been found to be irregular or to show signs of disturbances (Taylor et al 1995;Ekta & Chengalur 2010;López-Sánchez 2010;Holwerda et al 2013;Lelli et al 2014b;Knapen & Cisternas 2015), but in a number of cases no visible companion has been found (Brosch et al 2004;Ekta & Chengalur 2010;López-Sánchez 2010;Lelli et al 2014b). Other possible origins of the increase in star formation and the irregular morphology are cosmological gas inflows (see for example Verbeke et al 2014) or re-accretion of material blown out by previous starbursts, and varying internal instabilities (e.g., Meurer et al 1998;van Zee et al 2001;Lelli et al 2014a;Elmegreen et al 2012;Bekki & Freeman 2002).…”

Section: Introductionmentioning

confidence: 99%

Dark influences

Starkenburg

Helmi

Sales

2016

A&A

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Context. It has been proposed that mergers induce starbursts and lead to important morphological changes in galaxies. Most studies so far have focused on large galaxies, but dwarfs might also experience such events, since the halo mass function is scale-free in the concordance cosmological model. Notably, because of their low mass, most of their interactions will be with dark satellites. Aims. In this paper we follow the evolution of gas-rich disky dwarf galaxies as they experience a minor merger with a dark satellite. We aim to characterize the effects of such an interaction on the dwarf's star formation, morphology, and kinematical properties. Methods. We performed a suite of carefully set-up hydrodynamical simulations of dwarf galaxies that include dark matter, gas, and stars merging with a satellite consisting solely of dark matter. For the host system we vary the gas fraction, disk size and thickness, halo mass, and concentration, while we explore different masses, concentrations, and orbits for the satellite. Results. We find that the interactions cause strong starbursts of both short and long duration in the dwarfs. Their star formation rates increase by factors of a few to 10 or more. They are strongest for systems with extended gas disks and high gas fractions merging with a high-concentration satellite on a planar, radial orbit. In contrast to analogous simulations of Milky Way-mass galaxies, many of the systems experience strong morphological changes and become spheroidal even in the presence of significant amounts of gas. Conclusions. The simulated systems compare remarkably well with the observational properties of a large selection of irregular dwarf galaxies and blue compact dwarfs. This implies that mergers with dark satellites might well be happening but not be fully evident, and may thus play a role in the diversity of the dwarf galaxy population.

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“…These lower-mass galaxies are important, as are minor mergers (e.g., Kaviraj 2014), because they contribute significantly to the evolution of the overall galaxy population (e.g., Lelli, Verheijen & Fraternali 2014;Stierwalt et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Interacting galaxies in the nearby Universe: only moderate increase of star formation

Knapen

Cisternas

Querejeta

2015

Mon. Not. R. Astron. Soc.

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We investigate the influence of interactions on the star formation by studying a sample of almost 1500 of the nearest galaxies, all within a distance of ∼ 45 Mpc. We define the massive star formation rate (SFR), as measured from far-IR emission, and the specific star formation rate (SSFR), which is the former quantity normalised by the stellar mass of the galaxy, and explore their distribution with morphological type and with stellar mass. We then calculate the relative enhancement of these quantities for each galaxy by normalising them by the median SFR and SSFR values of individual control populations of similar non-interacting galaxies. We find that both SFR and SSFR are enhanced in interacting galaxies, and more so as the degree of interaction is higher. The increase is, however, moderate, reaching a maximum of a factor of 1.9 for the highest degree of interaction (mergers). The SFR and SSFR are enhanced statistically in the population, but in many individual interacting galaxies they are not enhanced at all. We discuss how those galaxies with the largest SFR and/or SSFR enhancement can be defined as starbursts. This study is based on a representative sample of nearby galaxies, including many low-mass and dwarf/irregular galaxies, and we argue that it should be used to place constraints on studies based on samples of galaxies at larger distances, beyond the local Universe.

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The triggering of starbursts in low-mass galaxies

Cited by 99 publications

References 119 publications

Molecular depletion times and the CO-to-H₂conversion factor in metal-poor galaxies

Molecular depletion times and the CO-to-H₂conversion factor in metal-poor galaxies

Dark influences

Interacting galaxies in the nearby Universe: only moderate increase of star formation

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The triggering of starbursts in low-mass galaxies

Cited by 99 publications

References 119 publications

Molecular depletion times and the CO-to-H2conversion factor in metal-poor galaxies

Molecular depletion times and the CO-to-H2conversion factor in metal-poor galaxies

Dark influences

Interacting galaxies in the nearby Universe: only moderate increase of star formation

Contact Info

Product

Resources

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Molecular depletion times and the CO-to-H₂conversion factor in metal-poor galaxies

Molecular depletion times and the CO-to-H₂conversion factor in metal-poor galaxies