MASSIV: Mass Assembly Survey with SINFONI in VVDS

Divoy, C.; Contini, T.; Pérez-Montero, E.; Queyrel, J.; Épinat, B.; López-Sanjuan, C.; Vergani, D.; Moultaka, J.; Amram, P.; Garilli, B.; Kissler-Patig, M.; Fèvre, O. Le; Paioro, L.; Tasca, L.; Tresse, L.; Perret, V.

doi:10.1051/0004-6361/201117711

Cited by 169 publications

(267 citation statements)

References 58 publications

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“…We note from Stott et al (2013a) that galaxies on the main sequence at any redshift have a low major merger fraction (∼10 per cent) whereas those in the starburst region may have a merger fraction of ∼50 per cent. Environmental classifications for isolated and potentially interacting galaxies exist for the Queyrel et al (2012) sample (see Epinat et al 2012). From this, we find that the interacting galaxies do have a higher biweight average metallicity gradient of 0.028 ± 0.010 dex kpc −1 than the isolated galaxies, which have an average gradient of 0.003 ± 0.008 dex kpc −1 , but this is only an ∼2σ difference.…”

Section: Metallicity Gradientsmentioning

confidence: 78%

A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS

Stott¹,

Sobral²,

Swinbank³

et al. 2014

Monthly Notices of the Royal Astronomical Society

109

142

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We have observed a sample of typical z ∼ 1 star forming galaxies, selected from the HiZELS survey, with the new KMOS near-infrared, multi-IFU instrument on the VLT, in order to obtain their dynamics and metallicity gradients. The majority of our galaxies have a metallicity gradient consistent with being flat or negative (i.e. higher metallicity cores than outskirts). Intriguingly, we find a trend between metallicity gradient and specific star formation rate (sSFR), such that galaxies with a high sSFR tend to have relatively metal-poor centres, a result which is strengthened when combined with datasets from the literature. This result appears to explain the discrepancies reported between different high redshift studies and varying claims for evolution. From a galaxy evolution perspective, the trend we see would mean that a galaxy's sSFR is governed by the amount of metal poor gas that can be funnelled into its core, triggered either by merging or through efficient accretion. In fact merging may play a significant role as it is the starburst galaxies at all epochs, which have the more positive metallicity gradients. Our results may help to explain the origin of the fundamental metallicity relation, in which galaxies at a fixed mass are observed to have lower metallicities at higher star formation rates, especially if the metallicity is measured in an aperture encompassing only the central regions of the galaxy. Finally, we note that this study demonstrates the power of KMOS as an efficient instrument for large scale resolved galaxy surveys.

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Section: Metallicity Gradientsmentioning

confidence: 78%

A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS

Stott¹,

Sobral²,

Swinbank³

et al. 2014

Monthly Notices of the Royal Astronomical Society

109

142

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“…With the higher dispersions necessary to keep the disk near the line of stability suggests that the disks are generally thicker than disks in the local universe as perhaps observed (e.g. Elmegreen et al 2009;Epinat et al 2012). …”

Section: Scenario Within the Context Of Distant Galaxiesmentioning

confidence: 93%

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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“…The i-band images were also used to correct for SINFONI astrometry, using the relative position of the PSF star. The morphology and kinematics maps of the 50 first-epoch galaxies are presented in Epinat et al (2012) together with a more extensive discussion on the model fitting procedure. The 34 second-epoch galaxies, already included in the present work, will be presented in a future paper.…”

Section: The Massiv Data Setmentioning

confidence: 99%

“…3.3, for details), while setting r min p = 0. We therefore searched for close companions in the kinematical maps of the MASSIV sources, analysing and classifying the sample using the velocity field and the velocity dispersion map (see Epinat et al 2012, for details about the classification). Note that spectroscopic redshifts from the VVDS sources outside MASSIV are not used in this close pair search and only those sources detected in the SINFONI data cubes are taken into account.…”

Section: Measuring the Merger Fraction From Ifs Datamentioning

confidence: 99%

“…As described in Epinat et al (2012), we had performed a classification of the MASSIV sources based on the shape of the velocity field (regular or irregular) and the close environment (isolated or not-isolated). From this classification, we had pre-selected as close pair candidates the non-isolated sources and those identified as mergers from the velocity field (see Epinat et al 2012, for more details). We identified 20 close pair candidates ( Goranova et al 2009).…”

Section: Mergers Classification and The Gas-rich Major Merger Fractiomentioning

confidence: 99%

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MASSIV: Mass Assembly Survey with SINFONI in VVDS

López-Sanjuán

Fèvre

Tasca

et al. 2013

A&A

Self Cite

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Context. The contribution of the merging process to the early phase of galaxy assembly at z > 1 and, in particular, to the build-up of the red sequence, still needs to be accurately assessed. Aims. We aim to measure the major merger rate of star-forming galaxies at 0.9 < z < 1.8, using close pairs identified from integral field spectroscopy (IFS). Methods. We use the velocity field maps obtained with SINFONI/VLT on the MASSIV sample, selected from the star-forming population in the VVDS. We identify physical pairs of galaxies from the measurement of the relative velocity and the projected separation (r p ) of the galaxies in the pair. Using the well constrained selection function of the MASSIV sample, we derive at a mean redshift up to z = 1.54 the gas-rich major merger fraction (luminosity ratio μ = L 2 /L 1 ≥ 1/4), and the gas-rich major merger rate using merger time scales from cosmological simulations. Results. We find a high gas-rich major merger fraction of 20.8 +15.2 −6.8 %, 20.1 +8.0 −5.1 %, and 22.0 +13.7 −7.3 % for close pairs with r p ≤ 20 h −1 kpc in redshift ranges z = [0.94, 1.06], [1.2, 1.5), and [1.5, 1.8), respectively. This translates into a gas-rich major merger rate of 0.116 +0.084 −0.038 Gyr −1 , 0.147 +0.058 −0.037 Gyr −1 , and 0.127 +0.079 −0.042 Gyr −1 at z = 1.03, 1.32, and 1.54, respectively. Combining our results with previous studies at z < 1, the gas-rich major merger rate evolves as (1 + z) n , with n = 3.95 ± 0.12, up to z = 1.5. From these results we infer that ∼35% of the star-forming galaxies with stellar masses M = 10 10 −10 10.5 M have undergone a major merger since z ∼ 1.5. We develop a simple model that shows that, assuming that all gas-rich major mergers lead to early-type galaxies, the combined effect of gas-rich and dry mergers is able to explain most of the evolution in the number density of massive early-type galaxies since z ∼ 1.5, with our measured gas-rich merger rate accounting for about two-thirds of this evolution. Conclusions. Merging of star-forming galaxies is frequent at around the peak in star formation activity. Our results show that gasrich mergers make an important contribution to the growth of massive galaxies since z ∼ 1.5, particularly on the build-up of the red sequence.

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MASSIV: Mass Assembly Survey with SINFONI in VVDS

Cited by 169 publications

References 58 publications

A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS

A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS

The age structure of stellar populations in the solar vicinity

MASSIV: Mass Assembly Survey with SINFONI in VVDS

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