Studying the spatially resolved Schmidt-Kennicutt law in interacting galaxies: the case of Arp 158

Boquien, M.; Lisenfeld, U.; Duc, Pierre–Alain; Braine, J.; Bournaud, F.; Brinks, E.; Charmandaris, V.

doi:10.1051/0004-6361/201117004

Cited by 35 publications

(46 citation statements)

References 78 publications

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“…High-spatial resolution observations can help to disentangle the role of largescale dynamics in the small-scale spatially resolved SF laws both in normal galaxies and in extreme starbursts (e.g. Boquien et al 2011).…”

Section: Discussionmentioning

confidence: 99%

Star-formation laws in luminous infrared galaxies

García‐Burillo

Usero

Alonso‐Herrero

et al. 2012

A&A

174

261

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Context. The observational study of star-formation relations in galaxies is central for unraveling the related physical processes that are at work on local and global scales. It is still debated whether star formation can be described by a universal law that remains valid in different populations of galaxies. Aims. We aim to expand the sample of extreme starbursts, represented by local luminous and ultra-luminous infrared galaxies (LIRGs and ULIRGs), with high-quality observations in the 1-0 line of HCN, which is taken as a proxy for the dense molecular gas content. The new data presented in this work allow us to enlarge in particular the number of LIRGs studied in HCN by a factor 3 compared to previous works. The chosen LIRG sample has a range of HCN luminosities that partly overlaps with that of the normal galaxy population. We study if a universal law can account for the star-formation relations observed for the dense molecular gas in normal star-forming galaxies and extreme starbursts and explore the validity of different theoretical prescriptions of the star-formation law. Methods. We have used the IRAM 30 m telescope to observe a sample of 19 LIRGs in the 1-0 lines of CO, HCN and HCO + . The galaxies were extracted from a sample of local LIRGs with available high-quality and high-resolution images obtained at optical, near and mid IR wavelengths, which probe the star-formation activity. We therefore derived the star-formation rates using different tracers and determined the sizes of the star-forming regions of all targets. Results. The analysis of the new data proves that the efficiency of star formation in the dense molecular gas (SFE dense ) of extreme starbursts is a factor 3-4 higher compared to normal galaxies. Kennicutt-Schmidt (KS) power laws were also derived. We find a duality in KS laws that is further reinforced if we account for the likely different conversion factor for HCN (α HCN ) in extreme starbursts and for the unobscured star-formation rate in normal galaxies. This result extends the more extreme bimodal behavior of star-formation laws that was derived from CO molecular lines by two recent surveys to the higher molecular densities probed by HCN lines. Conclusions. We compared our observations with the predictions of theoretical models in which the efficiency of star formation is determined by the ratio of a constant star-formation rate per free-fall time (SFR ff ) to the local free-fall time (t ff ). We find that it is possible to fit the observed differences in the SFE dense between normal galaxies and LIRGs/ULIRGs using a common constant SFR ff and a set of physically acceptable HCN densities, but only if SFR ff ∼ 0.005-0.01 and/or if α HCN is a factor of ∼a few lower than our favored values. Star-formation recipes that explicitly depend on the galaxy global dynamical time scales do not significantly improve the fit to the new HCN data presented in this work.

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Section: Discussionmentioning

confidence: 99%

Star-formation laws in luminous infrared galaxies

García‐Burillo

Usero

Alonso‐Herrero

et al. 2012

A&A

174

261

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“…For example, in the overlap region of the Antennae galaxies, Wei et al (2012) observe a bimodal distribution of molecular clouds, finding both a population of GMCs typical of nearby galaxies and a population of unusually large, massive, and efficiently star-forming clouds. Boquien et al (2011) also previously reported significantly different star formation efficiencies in different regions of the interacting galaxy Arp 158, and Papadopoulos et al (2012) argue in general that accurate modeling of the interstellar medium (ISM) of luminous infrared galaxies (LIRGs) requires consideration of both a central dense, efficiently star-forming phase and a more diffuse disk-like component where star formation proceeds at a more modest pace.…”

Section: Introductionmentioning

confidence: 95%

The Impact of Interactions, Bars, Bulges, and Active Galactic Nuclei on Star Formation Efficiency in Local Massive Galaxies

Saintonge¹,

Tacconi²,

Fabello³

et al. 2012

ApJ

251

323

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Using atomic and molecular gas observations from the GASS and COLD GASS surveys and complementary optical/UV data from the Sloan Digital Sky Survey and the Galaxy Evolution Explorer, we investigate the nature of the variations in the molecular gas depletion time observed across the local massive galaxy population. The large and unbiased COLD GASS sample allows us for the first time to statistically assess the relative importance of galaxy interactions, bar instabilities, morphologies, and the presence of active galactic nuclei (AGNs) in regulating star formation efficiency. We find that both the H 2 mass fraction and depletion time vary as a function of the distance of a galaxy from the main sequence traced by star-forming galaxies in the SFR-M * plane. The longest gas depletion times are found in below-main-sequence bulge-dominated galaxies (μ * > 5 × 10 8 M kpc −2 , C > 2.6) that are either gas-poor (M H 2 /M * < 1.5%) or else on average less efficient by a factor of ∼2 than disk-dominated galaxies at converting into stars any cold gas they may have. We find no link between the presence of AGNs and these long depletion times. In the regime where galaxies are disk-dominated and gas-rich, the galaxies undergoing mergers or showing signs of morphological disruptions have the shortest molecular gas depletion times, while those hosting strong stellar bars have only marginally higher global star formation efficiencies as compared to matched control samples. Our interpretation is that the molecular gas depletion time variations are caused by changes in the ratio between the gas mass traced by the CO(1-0) observations and the gas mass in high-density star-forming cores (as traced by observations of, e.g. , HCN(1-0)). While interactions, mergers, and bar instabilities can locally increase pressure and raise the ratio of efficiently star-forming gas to CO-detected gas (therefore lowering the CO-based depletion time), massive bulges may prevent the formation of dense clumps by stabilizing gas disks against fragmentation, therefore producing the long depletion times. Building a sample representative of the local galaxy population with M * > 10 10 M , we derive a global Kennicutt-Schmidt star formation relation of slope 1.18 ± 0.24 and observe structure within the scatter around this relation, with galaxies having low (high) stellar mass surface densities lying systematically above (below) the mean relation, suggesting that Σ H 2 is not the only parameter driving the global star formation ability of a galaxy.

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“…However, regions with recent star formation are also regions where the atomic and molecular gas have the highest surface density, which makes their relative importance uncertain. Studies have shown that the emission of the warm gas is more closely associated to star formation than the emission of the cold gas (Bendo et al 2010(Bendo et al , 2012aBoquien et al 2011). In nearby galaxies, the warm-to-cold dust mass ratio has been shown to vary from ∼100 to a few 1000 s (e.g.…”

Section: Ionised Gasmentioning

confidence: 99%

Towards understanding the relation between the gas and the attenuation in galaxies at kpc scales

Boquien

Boselli

Buat

et al. 2013

A&A

Self Cite

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Context. Understanding the relation between the attenuation and the gas is fundamental for interpreting the appearance of galaxies. This can now be done down to a local scale in the local Universe, thanks to the high spatial resolution achievable from the farultraviolet (FUV) to the far-infrared (FIR). More importantly, this relation is also crucial for predicting the emission of galaxies. This is essential in semi-analytic models that link dark matter from large cosmological simulations, to the baryonic matter which we can observe directly. Aims. The aim of the present paper is to provide new and more detailed relations at the kpc scale between the gas surface density and the face-on optical depth directly calibrated on galaxies, in order to compute the attenuation not only for semi-analytic models, but also for observational models as new and upcoming radio observatories are able to trace gas ever farther away in the Universe. Methods. We have selected a sample of 4 nearby resolved galaxies and a sample of 27 unresolved galaxies from the Herschel Reference Survey and the Very Nearby Galaxies Survey, for which we have a large set of multi-wavelength data from the FUV to the FIR including metallicity gradients for resolved galaxies, along with radio HI and CO observations. For each pixel in resolved galaxies and for each galaxy in the unresolved sample, we compute the face-on optical depth from the attenuation determined with the CIGALE spectral energy distribution fitting code and an assumed geometry. We determine the gas surface density from HI and CO observations with a metallicity-dependent X CO factor. Results. We provide new, simple-to-use relations to determine the face-on optical depth from the gas surface density, taking the metallicity into account, which proves to be crucial for a proper estimate. The method used to determine the gas surface density or the face-on optical depth has little impact on the relations except for galaxies that have an inclination over 50• . Finally, we provide detailed instructions on how to efficiently compute the attenuation from the gas surface density taking into account possible information on the metallicity. Conclusions. Examination of the influence of these new relations on simulated FUV and IR luminosity functions shows a clear impact compared to older, more-frequently used relations, which in turn could affect the conclusions drawn from studies based on large-scale cosmological simulations.

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Studying the spatially resolved Schmidt-Kennicutt law in interacting galaxies: the case of Arp 158

Cited by 35 publications

References 78 publications

Star-formation laws in luminous infrared galaxies

Star-formation laws in luminous infrared galaxies

The Impact of Interactions, Bars, Bulges, and Active Galactic Nuclei on Star Formation Efficiency in Local Massive Galaxies

Towards understanding the relation between the gas and the attenuation in galaxies at kpc scales

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