Galaxy evolution and star formation efficiency at 0.2  &lt; <i>z</i> &lt;  0.6

Combes, F.; García‐Burillo, S.; Braine, J.; Schinnerer, E.; Walter, Fabian; Colina, L.

doi:10.1051/0004-6361/201015739

Cited by 97 publications

(150 citation statements)

References 64 publications

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“…We can estimate the density of the dense molecular gas using observations of distant galaxies with star formation rates and general properties similar to ours. H 2 gas mass surface density measurements are available for galaxies similar to those studied here (z ∼ 1 and 2; Daddi et al 2010;Aravena et al 2010;Dannerbauer et al 2009;Tacconi et al 2010;Combes et al 2011) which suggest that at z ∼ 2 the mean value is about 500 M pc −2 and that total gas fractions ∼30−50% Tacconi et al 2010). The volume weighted H 2 gas density, n H 2 = Σ gas /H m H 2 = 10.2Σ gas,500 /H 1 kpc , where Σ gas,500 is the gas mass surface density in units of 500 M pc −2 and H 1kpc is the thickness of the gas layer in units of 1 kpc.…”

Section: A72 Page 12 Of 18mentioning

confidence: 88%

On the self-regulation of intense star-formation in galaxies atz= 1−3

Lehnert

Tiran

Nesvadba

et al. 2013

A&A

104

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We have analyzed the properties of the Hα and [Nii]λ6583 rest-frame optical emission lines of a sample of 53 intensely star forming galaxies at z = 1.3 to 2.7 observed with SINFONI on the ESO-VLT. Similar to previous authors, we find large velocity dispersions in the lines, σ = few 10−250 km s −1 . Our data agree well with simulations where we applied beam-smearing and assumed a scaling relation of the form: velocity dispersion is proportional to the square root of the star-formation intensity (star-formation rate per unit surface area). We conclude that the dispersions are primarily driven by star formation. To explain the high surface brightness and optical line ratios, high thermal pressures in the warm ionized medium, WIM, are required (P/k ∼ > 10 6 −10 7 K cm −3 ). Such thermal pressures in the WIM are similar to those observed in nearby starburst galaxies, but occur over much larger physical scales. Moreover, the relatively low ionization parameters necessary to fit the high surface brightnesses and optical line ratios suggest that the gas is not only directly associated with regions of star formation, but is wide spread throughout the general interstellar medium (ISM). Thus the optical emission line gas is a tracer of the large scale dynamics of the bulk of the ISM. We present a simple model for the energy input from young stars in an accreting galaxy, to argue that the intense star-formation is supporting high turbulent pressure, which roughly balances the gravitational pressure and thus enables distant gas accreting disks to maintain a Toomre disk instability parameter Q ∼ 1. For a star formation efficiency of 3%, only 5−15% of the mechanical energy from young stars that is deposited in the ISM is needed to support the level of turbulence required for maintaining this balance. Since this balance is maintained by energy injected into the ISM by the young stars themselves, this suggests that star formation in high redshift galaxies is self-regulating.

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Section: A72 Page 12 Of 18mentioning

confidence: 88%

On the self-regulation of intense star-formation in galaxies atz= 1−3

Lehnert

Tiran

Nesvadba

et al. 2013

A&A

104

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“…Actively star forming galaxies at high redshift are known to be both gas rich, have high gas mass surface densities Aravena et al 2010;Dannerbauer et al 2009;Tacconi et al 2010;Combes et al 2011), have high velocity dispersions in their gas and intense star formation (Lehnert et al 2009(Lehnert et al , 2013Swinbank et al 2011). Within the context of gas rich distant intensely star forming galaxies, global disk instabilities may have played an important role in regulating star formation in the early universe.…”

Section: Scenario Within the Context Of Distant Galaxiesmentioning

confidence: 99%

The age structure of stellar populations in the solar vicinity

Haywood

Matteo

Lehnert

et al. 2013

A&A

532

175

868

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We analyze a sample of solar neighborhood stars that have high-quality abundance determinations and show that there are two distinct regimes of [α/Fe] versus age, which we identify as the epochs of the thick and thin disk formation. A tight correlation between metallicity and [α/Fe] versus age is clearly identifiable for thick disk stars, implying that this population formed from a well mixed interstellar medium, probably initially in starburst and then more quiescently, over a time scale of 4−5 Gyr. Thick disk stars have vertical velocity dispersions which correlate with age, with the youngest objects of this population having small scale heights similar to those of thin disk stars. A natural consequence of these two results is that a vertical metallicity gradient is expected in this population. We suggest that the youngest thick disk set the initial conditions from which the inner thin disk started to form about 8 Gyr ago, at [Fe/H] in the range of (−0.1, +0.1) dex and [α/Fe] ∼ 0.1 dex. This also provides an explanation for the apparent coincidence between the existence of a step in metallicity at 7−10 kpc in the thin disk and the confinement of the thick disk within R < 10 kpc. We suggest that the outer thin disk developed outside the influence of the thick disk, giving rise to a separate structure, but also that the high alphaenrichment of those regions may originate from a primordial pollution of the outer regions by the gas expelled from the forming thick disk. Metal-poor thin disk stars ([Fe/H] < −0.4 dex) in the solar vicinity, whose properties are best explained by them originating in the outer disk, are shown to be as old as the youngest thick disk (9−10 Gyr). This implies that the outer thin disk started to form while the thick disk was still forming stars in the inner parts of the Galaxy. Hence, while the overall inner (thick+thin) disk is comprised of two structures with different scale lengths and whose combination may give the impression of an inside-out formation process, the thin disk itself probably formed its first stars in its outskirts. Moreover, we point out that, given the tight age−metallicity and age-[α/Fe] relations that exist in the thick disk, an inside-out process would give rise to a radial gradient in metallicity and α-elements in this population, which is not observed. Finally, we argue that our results leave little room for radial migration (in the sense of churning) either to have contaminated the solar vicinity, or, on a larger scale, to have redistributed stars in significant proportion across the solar annulus.

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“…Combes et al (2011Combes et al ( , 2012Combes et al ( , 2013, Danielson et al (2011), Fu et al (2012, Sharon et al (2013), Rawle et al (2014), and Magdis et al (2014).…”

Section: Comparison Samplementioning

confidence: 99%

Molecular gas content in strongly lensedz~ 1.5−3 star-forming galaxies with low infrared luminosities

Dessauges‐Zavadsky

Zamojski

Schaerer

et al. 2015

A&A

Self Cite

111

126

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To extend the molecular gas measurements to more typical star-forming galaxies (SFGs) with star formation rates SFR < 40 M yr −1 and stellar masses M * < 2.5 × 10 10 M at z ∼ 1.5−3, we have observed CO emission with the IRAM Plateau de Bure Interferometer and the IRAM 30 m telescope for five strongly lensed galaxies, selected from the Herschel Lensing Survey. These observations are combined with a compilation of CO measurements from the literature. From this, we infer the CO luminosity correction factors r 2,1 = 0.81 ± 0.20 and r 3,1 = 0.57 ± 0.15 for the J = 2 and J = 3 CO transitions, respectively, valid for SFGs at z > 1. The combined sample of CO-detected SFGs at z > 1 shows a large spread in star formation efficiency (SFE) with a dispersion of 0.33 dex, such that the SFE extends well beyond the low values of local spirals and overlaps the distribution of z > 1 submm galaxies. We find that the spread in SFE (or equivalently in molecular gas depletion timescale) is due to the variations of several physical parameters, primarily the specific star formation rate, and also stellar mass and redshift. The dependence of SFE on the offset from the main sequence and the compactness of the starburst is less clear. The possible increase of the molecular gas depletion timescale with stellar mass, now revealed by low M * SFGs at z > 1 and also observed at z = 0, contrasts with the generally acknowledged constant molecular gas depletion timescale and refutes the linearity of the Kennicutt-Schmidt relation. A net rise of the molecular gas fraction ( f gas ) is observed from z ∼ 0.2 to z ∼ 1.2, followed by a very mild increase toward higher redshifts, as found in earlier studies. At each redshift the molecular gas fraction shows a large dispersion, mainly due to the dependence of f gas on stellar mass, producing a gradient of increasing f gas with decreasing M * . We provide the first measurement of the molecular gas fraction of z > 1 SFGs at the low-M * end between 10 9.4 < M * /M < 10 9.9 , reaching a mean f gas = 0.69 ± 0.18, which shows a clear f gas upturn at these lower stellar masses. Finally, we find evidence for a nonuniversal dust-to-gas ratio among high-redshift SFGs, high-redshift submm galaxies, local spirals, and local ultraluminous IR galaxies with near-solar metallicities, as inferred from a homogeneous analysis of their rest-frame 850 μm luminosity per unit gas mass. The SFGs with z > 1 show a trend for a lower L ν (850 μm)/M gas mean by 0.33 dex compared to the other galaxy populations.

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Galaxy evolution and star formation efficiency at 0.2 < z < 0.6

Cited by 97 publications

References 64 publications

On the self-regulation of intense star-formation in galaxies atz= 1−3

On the self-regulation of intense star-formation in galaxies atz= 1−3

The age structure of stellar populations in the solar vicinity

Molecular gas content in strongly lensedz~ 1.5−3 star-forming galaxies with low infrared luminosities

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