Integral field spectroscopy in the near infrared of NGC 3125-A and SBS 0335-052

Vanzi, L.; Cresci, G.; Sauvage, M.; Thompson, Rodger I.

doi:10.1051/0004-6361/201117399

Cited by 10 publications

(8 citation statements)

References 41 publications

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“…While such clumps could be directly detected with high spatial resolution CO observations, it is also possible to observe relatively strong signatures from [C i] and from the warm molecular layer in the mid-IR H 2 lines − in particular S(0) ( Table 8) − as long as the molecular clouds remain excited by the X-ray source and by the stellar clusters (hence providing a significant gas temperature). The near-IR H 2 line 1-0 S(1) at 2.12 µm is a few orders of magnitude below the current observed upper limit (Izotov & Thuan 2016), suggesting that 8 m class telescopes could possibly reach such levels predicted by our models (e.g., Vanzi et al 2011). Clumps may also exist at significant distances from the clusters, where they can be near isothermal equilibrium with the CMB and CR, in which case only cold molecular gas can be detected.…”

Section: Dense Molecular Clumps (Variant M4c)mentioning

confidence: 50%

Neutral gas heating by X-rays in primitive galaxies: Infrared observations of the blue compact dwarf I Zw 18 with Herschel

Lebouteiller

Pequignot

Cormier

et al. 2017

A&A

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Context. The neutral interstellar medium of galaxies acts as a reservoir to fuel star formation. The dominant heating and cooling mechanisms in this phase are uncertain in extremely metal-poor star-forming galaxies. The low dust-to-gas mass ratio and low polycyclic aromatic hydrocarbon abundance in such objects suggest that the traditional photoelectric effect heating may not be effective. Aims. Our objective is to identify the dominant thermal mechanisms in one such galaxy, I Zw 18 (1/30 Z ), assess the diagnostic value of fine-structure cooling lines, and estimate the molecular gas content. Even though molecular gas is an important catalyst and tracer of star formation, constraints on the molecular gas mass remain elusive in the most metal-poor galaxies.Methods. Building on a previous photoionization model describing the giant H ii region of I Zw 18-NW within a multi-sector topology, we provide additional constraints using, in particular, the [ Results. The heating of the H i region appears to be mainly due to photoionization by radiation from a bright X-ray binary source, while the photoelectric effect is negligible. Significant cosmic ray heating is not excluded. Inasmuch as X-ray heating dominates in the H i gas, the infrared fine-structure lines provide an average X-ray luminosity of order 4 × 10 metal-rich sources (∼1%), it cannot be safely used as a photoelectric heating efficiency proxy. This ratio seems to be kept stable owing to a correlation between the X-ray luminosity and the star formation rate. Conclusions. X-ray heating could be an important process in extremely metal-poor sources. The lack of photoelectric heating due to the low dust-to-gas ratio tends to be compensated for by the larger occurrence and power of X-ray binaries in low-metallicity galaxies. We speculate that X-ray heating may quench star formation.

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Section: Dense Molecular Clumps (Variant M4c)mentioning

confidence: 50%

Neutral gas heating by X-rays in primitive galaxies: Infrared observations of the blue compact dwarf I Zw 18 with Herschel

Lebouteiller

Pequignot

Cormier

et al. 2017

A&A

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“…Despite its extremely low abundance, SBS 0335−052E is known to have extremely high extinction (A V > ∼ 15 mag, Plante & Sauvage 2002;Houck et al 2004), and > ∼ 10 4 M of dust surrounding only the two youngest SSCs (Hunt et al , 2014. Warm H 2 is clearly present in this galaxy, with strong emission from ro-vibrational transitions at 2 µm (Vanzi et al 2000(Vanzi et al , 2011. The cm-regime radio spectrum is highly self-absorbed, implying ionized-gas densities of > ∼ 3000 cm −3 Johnson et al 2009).…”

Section: Sbs 0335−052ementioning

confidence: 89%

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

Hunt

García‐Burillo

Casasola

et al. 2015

A&A

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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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“…For these reasons our group has undertaken a long term program to investigate the internal physical properties of these star forming galaxies through spatially resolved spectroscopy in the optical and in the near-IR, in order to assess their kinematics, physical conditions and their relation to their local star formation properties (see e.g. Vanzi et al 2008Vanzi et al , 2011Cresci et al 2010a;Lagos et al 2012;Telles et al 2014). tent with an early-type system (Nguyen et al 2014).…”

Section: Introductionmentioning

confidence: 99%

The MUSE view of He 2-10: No AGN ionization but a sparkling starburst

Cresci

Vanzi

Telles

et al. 2017

A&A

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We study the physical and dynamical properties of the ionized gas in the prototypical HII galaxy Henize 2-10 using MUSE integral field spectroscopy. The large scale dynamics is dominated by extended outflowing bubbles, probably the results of massive gas ejection from the central star forming regions. We derive a mass outflow rateṀ out ∼ 0.30 M yr −1 , corresponding to mass loading factor η ∼ 0.4, in range with similar measurements in local LIRGs. Such a massive outflow has a total kinetic energy that is sustainable by the stellar winds and Supernova Remnants expected in the galaxy. We use classical emission line diagnostic to study the dust extinction, electron density and ionization conditions all across the galaxy, confirming the extreme nature of the highly star forming knots in the core of the galaxy, which show high density and high ionization parameter. We measure the gas phase metallicity in the galaxy taking into account the strong variation of the ionization parameter, finding that the external parts of the galaxy have abundances as low as 12 + log(O/H) ∼ 8.3, while the central star forming knots are highly enriched with super solar metallicity. We find no sign of AGN ionization in the galaxy, despite the recent claim of the presence of a super massive active Black Hole in the core of He 2-10. We therefore reanalyze the X-ray data that were used to propose the presence of the AGN, but we conclude that the observed X-ray emission can be better explained with sources of a different nature, such as a Supernova Remnant.

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Integral field spectroscopy in the near infrared of NGC 3125-A and SBS 0335-052

Cited by 10 publications

References 41 publications

Neutral gas heating by X-rays in primitive galaxies: Infrared observations of the blue compact dwarf I Zw 18 with Herschel

Neutral gas heating by X-rays in primitive galaxies: Infrared observations of the blue compact dwarf I Zw 18 with Herschel

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

The MUSE view of He 2-10: No AGN ionization but a sparkling starburst

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Integral field spectroscopy in the near infrared of NGC 3125-A and SBS 0335-052

Cited by 10 publications

References 41 publications

Neutral gas heating by X-rays in primitive galaxies: Infrared observations of the blue compact dwarf I Zw 18 with Herschel

Neutral gas heating by X-rays in primitive galaxies: Infrared observations of the blue compact dwarf I Zw 18 with Herschel

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

The MUSE view of He 2-10: No AGN ionization but a sparkling starburst

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