On the self-regulation of intense star-formation in galaxies at<i>z</i>= 1−3

Lehnert, M. D.; Tiran, L. Le; Nesvadba, N. P. H.; Driel, W. van; Boulanger, F.; Matteo, P. Di

doi:10.1051/0004-6361/201220555

Cited by 78 publications

(117 citation statements)

References 119 publications

(242 reference statements)

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“…The star formation rate per unit area is probably also low in the outer disks (as is observed both in local and distant galaxies, e.g. Kennicutt & Evans 2012;Lehnert et al 2013). Thus both the enrichment and the mixing timescales will be much longer since the star formation occurs at a much lower intensity.…”

Section: Scenario Within the Context Of Distant Galaxiesmentioning

confidence: 95%

“…Such a value for the star formation intensity, which is likely a lower limit, would imply that Milky Way would have a star formation intensity similar to that of nearby starbursts and distant intensely star-forming galaxies at z ∼ 2−3 (e.g. Lehnert & Heckman 1996;Dib et al 2006;Lehnert et al 2009Lehnert et al , 2013 Above these values, there is a sharp increase in the velocity dispersion of the ISM with Σ SFR . We thus suggest that the relations found between stellar vertical velocity (or z max ) and age reflects similar relations in the ISM: stars formed in a thick ISM, whose high dispersions were sustained for several Gyr by intense star formation (but notice not necessarily high star formation rates overall).…”

Section: Inside-out Formation Of the Diskmentioning

confidence: 99%

“…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 turnover time of large scale turbulence is H/σ gas which in the case of a 1 kpc thick disk and a dispersion of 100 km s −1 (which are rough characteristics of high redshift star forming galaxies; Lehnert et al 2009Lehnert et al , 2013, leads to a timescale of 10 Myrs which is a about a tenth of a rotation time, for a rotation speed of 150 km s −1 and at r e = 2.5 kpc (about the rotation speed and half light radius of the thick disk; Förster Schreiber et al 2006Schreiber et al , 2009 and similar to the evolutionary timescale of massive stars that enrich the ISM with metals through stellar winds and supernovae. Thus the metals lost to the ISM by massive stars will mix very quickly with some being lost to outflows because of the intense star formation (e.g.…”

Section: Scenario Within the Context Of Distant Galaxiesmentioning

confidence: 99%

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The age structure of stellar populations in the solar vicinity

Haywood

Matteo

Lehnert

et al. 2013

A&A

517

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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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Section: Scenario Within the Context Of Distant Galaxiesmentioning

confidence: 95%

Section: Inside-out Formation Of the Diskmentioning

confidence: 99%

Section: Scenario Within the Context Of Distant Galaxiesmentioning

confidence: 99%

Section: Scenario Within the Context Of Distant Galaxiesmentioning

confidence: 99%

See 2 more Smart Citations

The age structure of stellar populations in the solar vicinity

Haywood

Matteo

Lehnert

et al. 2013

A&A

517

174

864

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“…The effects of feedback from massive stars and active galactic nuclei allow this direct coupling of star formation with the gas supply to be broken (e.g. Peirani et al 2012;Lehnert et al 2013). This decoupling is important as not only do we need the relative growth of galaxies not to track the gas supply too closely, as observed in the evolution of the sSFR, but also because baryonic mass fraction in galaxies is small and does not follow the halo mass function (Baldry et al 2008;Papastergis et al 2012) suggesting that either a fraction of the baryons are not accreted or they are efficiently removed from the galaxy.…”

Section: Introductionmentioning

confidence: 99%

On the cosmic evolution of the specific star formation rate

Lehnert

Driel

Tiran

et al. 2015

A&A

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The apparent correlation between the specific star formation rate (sSFR) and total stellar mass (M ) of galaxies is a fundamental relationship indicating how they formed their stellar populations. To attempt to understand this relation, we hypothesize that the relation and its evolution is regulated by the increase in the stellar and gas mass surface density in galaxies with redshift, which is itself governed by the angular momentum of the accreted gas, the amount of available gas, and by self-regulation of star formation. With our model, we can reproduce the specific SFR− M relations at z ∼ 1-2 by assuming gas fractions and gas mass surface densities similar to those observed for z = 1-2 galaxies. We further argue that it is the increasing angular momentum with cosmic time that causes a decrease in the surface density of accreted gas. The gas mass surface densities in galaxies are controlled by the centrifugal support (i.e., angular momentum), and the sSFR is predicted to increase as, sSFR(z) = (1 + z) 3 /t H0 , as observed (where t H0 is the Hubble time and no free parameters are necessary). In addition, the simple evolution for the star-formation intensity we propose is in agreement with observations of Milky Way-like galaxies selected through abundance matching. At z > ∼ 2, we argue that star formation is self-regulated by high pressures generated by the intense star formation itself. The star formation intensity must be high enough to either balance the hydrostatic pressure (a rather extreme assumption) or to generate high turbulent pressure in the molecular medium which maintains galaxies near the line of instability (i.e. Toomre Q ∼ 1). We provide simple prescriptions for understanding these self-regulation mechanisms based on solid relationships verified through extensive study. In all cases, the most important factor is the increase in stellar and gas mass surface density with redshift, which allows distant galaxies to maintain high levels of sSFR. Without a strong feedback from massive stars, such galaxies would likely reach very high sSFR levels, have high star formation efficiencies, and because strong feedback drives outflows, ultimately have an excess of stellar baryons.

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Planck’s dusty GEMS: The brightest gravitationally lensed galaxies discovered with thePlanckall-sky survey

Cañameras

Nesvadba

Guery

et al. 2015

A&A

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We present an analysis of CO spectroscopy and infrared-to-millimetre dust photometry of 11 exceptionally bright far-infrared (FIR) and sub-mm sources discovered through a combination of the Planck all-sky survey and follow-up Herschel-SPIRE imaging -"Planck's Dusty Gravitationally Enhanced subMillimetre Sources". Each source has a secure spectroscopic redshift z = 2.2-3.6 from multiple lines obtained through a blind redshift search with EMIR at the IRAM 30-m telescope. Interferometry was obtained at IRAM and the SMA, and along with optical/near-infrared imaging obtained at the CFHT and the VLT reveal morphologies consistent with strongly gravitationally lensed sources, including several giant arcs. Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 µm and 2 mm, respectively. The SEDs of our sources peak near either the 350 µm or 500 µm bands of SPIRE with peak flux densities between 0.35 and 1.14 Jy. All objects are extremely bright isolated point sources in the 18 beam of SPIRE at 250 µm, with apparent FIR luminosities of up to 3 × 10 14 L (not correcting for the lensing effect). Their morphologies, sizes, CO line widths, CO luminosities, dust temperatures, and FIR luminosities provide additional empirical evidence that these are amongst the brightest strongly gravitationally lensed high-redshift galaxies on the sub-mm sky. Our programme extends the successful wide-area searches for strongly gravitationally lensed high-redshift galaxies (carried out with the South Pole Telescope and Herschel) towards even brighter sources, which are so rare that their systematic identification requires a genuine all-sky survey like Planck. Six sources are above the 600 mJy 90% completeness limit of the Planck catalogue of compact sources (PCCS) at 545 and 857 GHz, which implies that these must literally be amongst the brightest high-redshift FIR and sub-mm sources on the extragalactic sky. We discuss their dust masses and temperatures, and use additional WISE 22-µm photometry and template fitting to rule out a significant contribution of AGN heating to the total infrared luminosity. Six sources are detected in FIRST at 1.4 GHz, and the others have sensitive upper limits. Four have flux densities brighter than expected from the local FIR-radio correlation, but in the range previously found for high-z sub-mm galaxies, one has a deficit of FIR emission, and 6 are consistent with the local correlation, although this includes 3 galaxies with upper limits. We attribute this to the turbulent interstellar medium of these galaxies, rather than the presence of radio AGN. The global dust-to-gas ratios and star-formation efficiencies of our sources are predominantly in the range expected from massive, metal-rich, intense, high-redshift starbursts. An extensive multi-wavelength follow-up programme is being carried out to further characterize these sources and the intense star formation within them.Key words. galaxies: high-redshift -galaxies: star formation -galaxies: starburst -submillimeter: galaxies -gravi...

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

Cited by 78 publications

References 119 publications

The age structure of stellar populations in the solar vicinity

The age structure of stellar populations in the solar vicinity

On the cosmic evolution of the specific star formation rate

Planck’s dusty GEMS: The brightest gravitationally lensed galaxies discovered with thePlanckall-sky survey

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