Molecular gas in low-metallicity starburst galaxies:

Amorín, R.; Muñoz–Tuñón, C.; Aguerri, J. A. L.; Planesas, P.

doi:10.1051/0004-6361/201526397

Cited by 83 publications

(136 citation statements)

References 145 publications

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“…Note that we estimated the H 2 masses from the CO fluxes assuming that the conversion factor ("X-factor") does not depend on metallicity. However, a number of studies show that CO is a poor indicator of molecular gas in LM galaxies [28][29][30]. If the X-factor is linearly correlated with the metallicity (approximately in agreement with the observed dependences), we have underestimated M H 2 in the LM SFRs by about an order of magnitude (which corresponds to the difference inmetallicity between the LM and HM samples).…”

Section: Discussionsupporting

confidence: 79%

Relation between the parameters of dust and of molecular and atomic gas in extragalactic star-forming regions

et al. 2017

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The relationships between atomic and molecular hydrogen and dust of various sizes in extragalactic star-forming regions are considered, based on observational data from the Spitzer and Herschel infrared space telescopes, the Very Large Array (atomic hydrogen emission) and IRAM (CO emission). The source sample consists of approximately 300 star-forming regions in 11 nearby galaxies. Aperture photometry has been applied to measure the fluxes in eight infrared bands (3.6, 4.5, 5.8, 8, 24, 70, 100, and 160µm), the atomic hydrogen (21 cm) line and CO (2-1) lines.The parameters of the dust in the starforming regions were determined via syntheticspectra fitting, such as the total dust mass, the fraction of polycyclic aromatic hydrocarbons (PAHs), etc. Comparison of the observed fluxes with the measured parameters shows that the relationships between atomic hydrogen, molecular hydrogen, and dust are different in low-and high-metallicity regions. Low-metallicity regions contain more atomic gas, but less molecular gas and dust, including PAHs. The mass of dust constitutes about 1% of the mass of molecular gas in all regions considered. Fluxes produced by atomic and molecular gas do not correlate with the parameters of the stellar radiation, whereas the dust fluxes grow with increasing mean intensity of stellar radiation and the fraction of enhanced stellar radiation.The ratio of the fluxes at 8 and 24 µm, which characterizes the PAH content, decreases with increasing intensity of the stellar radiation, possibly indicating evolutionary variations of the PAH content. The results confirm that the contribution of the 24 µm emission to the total IR luminosity of extragalactic star-forming regions does not depend on the metallicity. *

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Section: Discussionsupporting

confidence: 79%

Relation between the parameters of dust and of molecular and atomic gas in extragalactic star-forming regions

et al. 2017

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“…These results for the whole sample could be an indication that the star-formation efficiency has been very low or that our galaxies are very young and still assembling most of their stellar mass. In the local Universe, such values of gas fractions can be found in low-mass, low-metallicity and highly star-forming galaxies (e.g., Lara-López et al 2013;Filho et al 2016;Amorín et al 2016). …”

Section: Resultsmentioning

confidence: 99%

Characterization of star-forming dwarf galaxies at 0.1 ≲z ≲ 0.9 in VUDS: probing the low-mass end of the mass-metallicity relation

Calabró

Amorín

Fontana

et al. 2017

A&A

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Context. The study of statistically significant samples of star-forming dwarf galaxies (SFDGs) at different cosmic epochs is essential for the detailed understanding of galaxy assembly and chemical evolution. However, the main properties of this large population of galaxies at intermediate redshift are still poorly known. Aims. We present the discovery and spectrophotometric characterization of a large sample of 164 faint (i AB ∼ 23-25 mag) SFDGs at redshift 0.13 ≤ z ≤ 0.88 selected by the presence of bright optical emission lines in the VIMOS Ultra Deep Survey (VUDS). We investigate their integrated physical properties and ionization conditions, which are used to discuss the low-mass end of the mass-metallicity relation (MZR) and other key scaling relations. Methods. We use optical VUDS spectra in the COSMOS, VVDS-02h, and ECDF-S fields, as well as deep multi-wavelength photometry that includes HST-ACS F814W imaging, to derive stellar masses, extinction-corrected star-formation rates (SFR), and gas-phase metallicities of SFDGs. For the latter, we use the direct method and a T e -consistent approach based on the comparison of a set of observed emission lines ratios with the predictions of detailed photoionization models. Results. The VUDS SFDGs are compact (median r e ∼ 1.2 kpc), low-mass (M * ∼ 10 7 -10 9 M ) galaxies with a wide range of starformation rates (SFR(Hα) ∼ 10 −3 -10 1 M /yr) and morphologies. Overall, they show a broad range of subsolar metallicities (12 + log(O/H) = 7.26-8.7; 0.04 < ∼ Z/Z < ∼ 1). Nearly half of the sample are extreme emission-line galaxies (EELGs) characterized by high equivalent widths and emission line ratios indicative of higher excitation and ionization conditions. The MZR of SFDGs shows a flatter slope compared to previous studies of galaxies in the same mass range and redshift. We find the scatter of the MZR is partly explained in the low mass range by varying specific SFRs and gas fractions amongst the galaxies in our sample. In agreement with recent studies, we find the subclass of EELGs to be systematically offset to lower metallicity compared to SFDGs at a given stellar mass and SFR, suggesting a younger starburst phase. Compared with simple chemical evolution models we find that most SFDGs do not follow the predictions of a "closed-box" model, but those from a gas-regulating model in which gas flows are considered. While strong stellar feedback may produce large-scale outflows favoring the cessation of vigorous star formation and promoting the removal of metals, younger and more metal-poor dwarfs may have recently accreted large amounts of fresh, very metal-poor gas, that is used to fuel current star formation.

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“…Since the abundances in our sample are not particularly extreme (see Sect. 3.3), we adopted the metallicity-dependent CO-to-H 2 conversion factor by Amorín et al (2016), which is derived combining lowmetallicity starburst galaxies with more metal-rich galaxy objects, including the Milky Way and Local Volume galaxies from Leroy et al (2011): X CO ∝ (Z/Z ) −1.5 (see the fit in Fig. 11 of Amorín et al 2016, where the conversion factor is given in terms of the equivalent α CO [M pc −2 (K km s −1 ) −1 ] = 1.6 × 10 −20 X CO [cm −2 (K km s −1 ) −1 ]).…”

Section: Derivation Of the 12 Co Flux Within The Optical Diskmentioning

confidence: 99%

The ISM scaling relations in DustPedia late-type galaxies: A benchmark study for the Local Universe

Casasola

Bianchi

Vis

et al. 2020

A&A

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Aims. The purpose of this work is the characterization of the main scaling relations between all of the interstellar medium (ISM) components, namely dust, atomic, molecular, and total gas, and gas-phase metallicity, as well as other galaxy properties, such as stellar mass (M star ) and galaxy morphology, for late-type galaxies in the Local Universe. Methods. This study was performed by extracting late-type galaxies from the entire DustPedia sample and by exploiting the large and homogeneous dataset available thanks to the DustPedia project. The sample consists of 436 galaxies with morphological stage spanning from T = 1 to 10, M star from 6 × 10 7 to 3 × 10 11 M , star formation rate from 6 × 10 −4 to 60 M yr −1 , and oxygen abundance from 12 + log(O/H) = 8 to 9.5. Molecular and atomic gas data were collected from the literature and properly homogenized. All the masses involved in our analysis refer to the values within the optical disks of galaxies. The scaling relations involving the molecular gas are studied by assuming both a constant and a metallicity-dependent CO-to-H 2 conversion factor (X CO ). The analysis was performed by means of the survival analysis technique, in order to properly take into account the presence of both detection and nondetection in the data. Results. We confirm that the dust mass correlates very well with the total gas mass, and find -for the first time-that the dust mass correlates better with the atomic gas mass than with the molecular one. We characterize important mass ratios such as the gas fraction, the molecular-to-atomic gas mass ratio, the dust-to-total gas mass ratio (DGR), and the dust-to-stellar mass ratio, and study how they relate to each other, to galaxy morphology, and to gas-phase metallicity. Only the assumption of a metallicity-dependent X CO reproduces the expected decrease of the DGR with increasing morphological stage and decreasing gas-phase metallicity, with a slope of about 1. The DGR, the gas-phase metallicity, and the dust-to-stellar mass ratio are, for our galaxy sample, directly linked to galaxy morphology. The molecular-to-atomic gas mass ratio and the DGR show a positive correlation for low molecular gas fractions, but for galaxies rich in molecular gas this trend breaks down. To our knowledge, this trend has never been found before, and provides new constraints for theoretical models of galaxy evolution and a reference for high-redshift studies. We discuss several scenarios related to this finding. Conclusions. The DustPedia database of late-type galaxies is an extraordinary tool for the study of the ISM scaling relations, thanks to its homogeneous collection of data for the different ISM components. The database is made publicly available to the whole community.

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Molecular gas in low-metallicity starburst galaxies:

Cited by 83 publications

References 145 publications

Relation between the parameters of dust and of molecular and atomic gas in extragalactic star-forming regions

Relation between the parameters of dust and of molecular and atomic gas in extragalactic star-forming regions

Characterization of star-forming dwarf galaxies at 0.1 ≲z ≲ 0.9 in VUDS: probing the low-mass end of the mass-metallicity relation

The ISM scaling relations in DustPedia late-type galaxies: A benchmark study for the Local Universe

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