Gas-to-dust mass ratios in local galaxies over a 2 dex metallicity range

Rémy-Ruyer, A.; Madden, S.; Galliano, F.; Galametz, M.; Takeuchi, Tsutomu T.; Asano, Ryosuke; Zhukovska, Svitlana; Lebouteiller, V.; Cormier, D.; Jones, A. P.; Bocchio, Marco; Baes, M.; Bendo, G. J.; Boquien, M.; Boselli, A.; DeLooze, I.; Doublier-Pritchard, V.; Hughes, T. M.; Karczewski, O. Ł.; Spinoglio, L.

doi:10.1051/0004-6361/201322803

Cited by 605 publications

(759 citation statements)

References 162 publications

(267 reference statements)

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“…The GTD estimated from our dust mass of 1.5 x 10 4 M ¤ and our gas mass derived from virial and stellar masses is ~47 (embedded cluster) or 120 (cluster outside cloud). Either is significantly lower than the value of 650 predicted 64 from scaling the Galactic value of 160 65 to the metallicity of NGC 5253. We argue that the high dust mass is from in situ enrichment by the cluster.…”

Section: Methodsmentioning

confidence: 73%

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

Turner

Beck

Benford

et al. 2015

Nature

103

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Gas clouds in present-day galaxies are inefficient at forming stars. Low star formation efficiency is a critical parameter in galaxy evolution: it is why stars are still forming nearly fourteen billion years after the Big Bang 1 and why star clusters generally do not survive their births, instead dispersing to form galactic disks, halos, or bulges 2 . Yet the existence of ancient massive star clusters in the Milky Way, globular clusters, suggests that efficiencies were higher when they formed ten billion years ago. A local dwarf galaxy, NGC 5253, has a young star cluster that may provide an example of highly efficient star formation 3 . Here we report the detection of the J= 3-2 rotational transition of CO at the location of the massive cluster. The gas cloud is hot, dense, quiescent, and extremely dusty. Its gas-to-dust ratio is lower than the Galactic value, which we attribute to dust enrichment by the embedded star cluster. Its star formation efficiency exceeds 50%, ten times higher than clouds in the Milky Way: this cloud is a factory of stars and soot. We suggest that high efficiency results from the force-feeding of star formation by a streamer of gas falling into the galaxy.The Submillimeter Array image of NGC 5253, shown in Figure 1, reveals a bright CO(3-2) source coincident with the giant cluster and its "supernebula" 4 . "Cloud D" 3 is one of only two molecular clouds detected within the galaxy; the second cloud is smaller and located ~5" (90 pc) to the southwest. A "streamer" of gas extending along the minor axis is also detected in CO(3-2). This streamer, previously detected in lower J CO lines, appears to be falling into the galaxy near the supernebula 3,5 . Both the streamer and Cloud D emit 870µm continuum emission, as shown in Figure 2. Also shown is an image of 350µm continuum, in which both Cloud D and the streamer are detected. Figure 1. CO J=3-2 emission in NGC 5253. The SMA CO(3-2) integrated line intensity, in red, is shown atop a λ814nm Hubble Space Telescope image. The SMA beam is 4" x 2" (74 pc x 37 pc). The field covers 40" x 40" (740 pc x740 pc), north up, east left. Image registration is to < 1". The CO streamer coincides with the optical dust lane to the east. The massive star cluster is located at the bright CO peak, Cloud D; it is embedded 8.9 , and not visible here. Cloud F is to the southwest of Cloud D.The molecular gas in Cloud D is hot. This is clear from the increase in brightness from CO(2-1) 3 to CO(3-2). The intensity ratio of the two lines is I 32 /I 21 = 2.6±0.5 (I line = ∫T line dv). This ratio is nonthermal, although the thermal limit of 2.25 (~ν 2 ) is within the uncertainties, and is what we adopt. Non-LTE modeling of this ratio using RADEX 6 indicates a minimum kinetic temperature of T K > 200 K for the 1σ lower limit, and T K > 350 K for the adopted value of I 32 /I 21 = 2.25 (see Methods). The high gas temperature is consistent with a thermal origin for H 2 2.2µm emission in the region 7 . Cloud D appears to be a Photon-Dominated Region (PDR), heated by ultraviol...

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Section: Methodsmentioning

confidence: 73%

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

Turner

Beck

Benford

et al. 2015

Nature

103

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“…The information about the gas and dust content in these galaxies can be found in Rémy-Ruyer et al (2014, 2015. The DGS sample mostly consists of dwarf galaxies in the local Universe, also including irregulars and blue compact dwarfs.…”

Section: Data Samplementioning

confidence: 99%

The cosmic dust rate across the Universe

Gioannini¹,

Matteuccí

Calura

2017

Monthly Notices of the Royal Astronomical Society

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We investigate the evolution of interstellar dust in the Universe by means of chemical evolution models of galaxies of different morphological types, reproducing the main observed features of present day galaxies. We adopt the most updated prescriptions for dust production from supernovae and asymptotic giant branch (AGB) stars as well as for dust accretion and destruction processes. Then, we study the cosmic dust rate in the framework of three different cosmological scenarios for galaxy formation: i) a pure luminosity scenario (PLE), ii) a number density evolution scenario (DE), as suggested by the classical hierarchical clustering scenario and iii) an alternative scenario, in which both spirals and ellipticals are allowed to evolve in number on an observationally motivated basis. Our results give predictions about the evolution of the dust content in different galaxies as well as the cosmic dust rate as a function of redshift. Concerning the cosmic dust rate, the best scenario is the alternative one, which predicts a peak at 2 < z < 3 and reproduces the cosmic star formation rate. We compute the evolution of the comoving dust density parameter Ω dust and find agreement with data for z < 0.5 in the framework of DE and alternative scenarios. Finally, the evolution of the average cosmic metallicity is presented and it shows a quite fast increase in each scenario, reaching the solar value at the present time, although most of the heavy elements are incorporated into solid grains, and therefore not observable in the gas phase.

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“…Since H 2 can self-shield from UV photons in regions where CO is photodissociated (Wolfire et al 2010), at low metallicity, not only is the CO abundance reduced, but as dust opacity is reduced and ionized regions become hotter and more porous, a CO,Gal can severely underestimate the molecular gas mass. Considerable effort has been invested in detecting and interpreting CO emission at metallicity 50 times lower than the solar metallicity, [ ] + 12 log O H ∼7.0, to assess the molecular gas content (Leroy et al 2011;Schruba et al 2012;Cormier et al 2014;Rémy-Ruyer et al 2014). Dust emission can be used to estimate the molecular gas mass in the ISM, assuming a constant DGR; however, it is essential to know the change in DGR with metallicity.…”

Section: Effect Of Dust Temperature On the Warm H 2 Fractionmentioning

confidence: 99%

“…Another method to assess H 2 content is to use dust as a tracer, with a presumed or recovered dust-to-gas (DGR) ratio (e.g., Sandstrom et al 2013;Rémy-Ruyer et al 2014). Among other biases, both the CO and dust-based methods lose reliability at low metallicity.…”

Section: Introductionmentioning

confidence: 99%

LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER

Togi

Smith

2016

ApJ

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Robust knowledge of molecular gas mass is critical for understanding star formation in galaxies. The H 2 molecule does not emit efficiently in the cold interstellar medium, hence the molecular gas content of galaxies is typically inferred using indirect tracers. At low metallicity and in other extreme environments, these tracers can be subject to substantial biases. We present a new method of estimating total molecular gas mass in galaxies directly from pure mid-infrared rotational H 2 emission. By assuming a power-law distribution of H 2 rotational temperatures, we can accurately model H 2 excitation and reliably obtain warm (T100 K) H 2 gas masses by varying only the power law's slope. With sensitivities typical of Spitzer/IRS, we are able to directly probe the H 2 content via rotational emission down to ∼80 K, accounting for ∼15% of the total molecular gas mass in a galaxy. By extrapolating the fitted power-law temperature distributions to a calibrated single lower cutoff temperature, the model also recovers the total molecular content within a factor of ∼2.2 in a diverse sample of galaxies, and a subset of broken powerlaw models performs similarly well. In ULIRGs, the fraction of warm H 2 gas rises with dust temperature, with some dependency on α CO . In a sample of five low-metallicity galaxies ranging down to [ ] + = 12 log O H 7.8, the model yields molecular masses up to ∼100×larger than implied by CO, in good agreement with other methods based on dust mass and star formation depletion timescale. This technique offers real promise for assessing molecular content in the early universe where CO and dust-based methods may fail.

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Gas-to-dust mass ratios in local galaxies over a 2 dex metallicity range

Cited by 605 publications

References 162 publications

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

The cosmic dust rate across the Universe

LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER

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Gas-to-dust mass ratios in local galaxies over a 2 dex metallicity range

Cited by 605 publications

References 162 publications

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion

The cosmic dust rate across the Universe

LIGHTING THE DARK MOLECULAR GAS: H2 AS A DIRECT TRACER

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Product

Resources

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LIGHTING THE DARK MOLECULAR GAS: H₂ AS A DIRECT TRACER