Star formation sustained by gas accretion

Alméida, J. Sánchez; Elmegreen, Bruce G.; Muñoz–Tuñón, C.; Elmegreen, D. M.

doi:10.1007/s00159-014-0071-1

Cited by 183 publications

(145 citation statements)

References 359 publications

(414 reference statements)

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“…It implies that the metal-poor gas in XMPs was recently accreted from a nearly pristine cloud, very much in line with the expected cosmic cold-flow accretion predicted to build disk galaxies (Birnboim & Dekel 2003;Kereš et al 2005;Dekel et al 2009), but which has been so difficult to test observationally (e.g., Sancisi et al 2008;Putman et al 2012;Sánchez Almeida et al 2014a). The gas expected in cosmological gas accretion events is described in detail by Sánchez Almeida et al (2014a). Thus, XMPs seem to be local galaxies that are growing through the physical process that created and shaped disk galaxies in the early universe.…”

mentioning

confidence: 58%

“…However, mixing with external gas cannot modify the pre-existing ratio between metals, leaving the N/O ratio unchanged. This argument has been put forward before to support the gas accretion scenario (Amorín et al 2010(Amorín et al , 2012Sánchez Almeida et al 2014a). The value for log(N/O) that we infer, around −1.5, is also consistent with the N/O ratio found in metal-poor α−enhanced stars in the solar neighborhood (e.g., Israelian et al 2004;Spite et al 2005).…”

Section: Chemical Propertiesmentioning

confidence: 81%

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Kinematics of Extremely Metal-Poor Galaxies: Evidence for Stellar Feedback

Olmo-García

Alméida

Muñoz–Tuñón

et al. 2017

ApJ

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The extremely metal-poor (XMP) galaxies analyzed in a previous paper have large star-forming regions with a metallicity lower than the rest of the galaxy. Such a chemical inhomogeneity reveals the external origin of the metal-poor gas fueling star formation, possibly indicating accretion from the cosmic web. This paper studies the kinematic properties of the ionized gas in these galaxies. Most XMPs have rotation velocity around a few tens of km s −1 . The star-forming regions appear to move coherently. The velocity is constant within each region, and the velocity dispersion sometimes increases within the star-forming clump towards the galaxy midpoint, suggesting inspiral motion toward the galaxy center. Other regions present a local maximum in velocity dispersion at their center, suggesting a moderate global expansion. The Hα line wings show a number of faint emission features with amplitudes around a few percent of the main Hα component, and wavelength shifts between 100 and 400 km s −1 . The components are often paired, so that red and blue emission features with similar amplitudes and shifts appear simultaneously. Assuming the faint emission to be produced by expanding shell-like structures, the inferred mass loading factor (mass loss rate divided by star formation rate) exceeds 10. Since the expansion velocity exceeds by far the rotational and turbulent velocities, the gas may eventually escape from the galaxy disk. The observed motions involve energies consistent with the kinetic energy released by individual core-collapse supernovae. Alternative explanations for the faint emission have been considered and discarded.

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confidence: 58%

Section: Chemical Propertiesmentioning

confidence: 81%

Kinematics of Extremely Metal-Poor Galaxies: Evidence for Stellar Feedback

Olmo-García

Alméida

Muñoz–Tuñón

et al. 2017

ApJ

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“…The mechanisms regulating galaxy growth, such as gas accretion and SF feedback are still not completely understood, and the scarcity of direct observations of outflows and gas accretion (as well as a quantification of their rate) represent a limit to a deeper insight (Sánchez Almeida et al 2014a). However, since the stellar-mass build-up in galaxies is accompanied by the chemical enrichment of their interstellar medium (ISM), studying the gas-phase metallicity and its relation with stellar mass and SFR can help us to investigate which of these processes are playing major roles.…”

Section: Introductionmentioning

confidence: 99%

Characterization of star-forming dwarf galaxies at 0.1 ≲z ≲ 0.9 in VUDS: probing the low-mass end of the mass-metallicity relation

Calabró

Amorín

Fontana

et al. 2017

A&A

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Context. The study of statistically significant samples of star-forming dwarf galaxies (SFDGs) at different cosmic epochs is essential for the detailed understanding of galaxy assembly and chemical evolution. However, the main properties of this large population of galaxies at intermediate redshift are still poorly known. Aims. We present the discovery and spectrophotometric characterization of a large sample of 164 faint (i AB ∼ 23-25 mag) SFDGs at redshift 0.13 ≤ z ≤ 0.88 selected by the presence of bright optical emission lines in the VIMOS Ultra Deep Survey (VUDS). We investigate their integrated physical properties and ionization conditions, which are used to discuss the low-mass end of the mass-metallicity relation (MZR) and other key scaling relations. Methods. We use optical VUDS spectra in the COSMOS, VVDS-02h, and ECDF-S fields, as well as deep multi-wavelength photometry that includes HST-ACS F814W imaging, to derive stellar masses, extinction-corrected star-formation rates (SFR), and gas-phase metallicities of SFDGs. For the latter, we use the direct method and a T e -consistent approach based on the comparison of a set of observed emission lines ratios with the predictions of detailed photoionization models. Results. The VUDS SFDGs are compact (median r e ∼ 1.2 kpc), low-mass (M * ∼ 10 7 -10 9 M ) galaxies with a wide range of starformation rates (SFR(Hα) ∼ 10 −3 -10 1 M /yr) and morphologies. Overall, they show a broad range of subsolar metallicities (12 + log(O/H) = 7.26-8.7; 0.04 < ∼ Z/Z < ∼ 1). Nearly half of the sample are extreme emission-line galaxies (EELGs) characterized by high equivalent widths and emission line ratios indicative of higher excitation and ionization conditions. The MZR of SFDGs shows a flatter slope compared to previous studies of galaxies in the same mass range and redshift. We find the scatter of the MZR is partly explained in the low mass range by varying specific SFRs and gas fractions amongst the galaxies in our sample. In agreement with recent studies, we find the subclass of EELGs to be systematically offset to lower metallicity compared to SFDGs at a given stellar mass and SFR, suggesting a younger starburst phase. Compared with simple chemical evolution models we find that most SFDGs do not follow the predictions of a "closed-box" model, but those from a gas-regulating model in which gas flows are considered. While strong stellar feedback may produce large-scale outflows favoring the cessation of vigorous star formation and promoting the removal of metals, younger and more metal-poor dwarfs may have recently accreted large amounts of fresh, very metal-poor gas, that is used to fuel current star formation.

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“…Milky Way-like galaxies and those of lower mass seem to have assembled their mass through streams of cold gas from the cosmic web (Sánchez Almeida et al 2014). In this context the galaxy's gas accretion and star formation rates (SFR) are expected to be associated with the cosmological dark matter specific accretion rate (Neistein et al 2006;Birnboim et al 2007;Neistein & Dekel 2008;Dutton et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Spatially-resolved star formation histories of CALIFA galaxies

Delgado

Pérez

Fernandes

et al. 2017

A&A

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This paper presents the spatially resolved star formation history (SFH) of nearby galaxies with the aim of furthering our understanding of the different processes involved in the formation and evolution of galaxies. To this end, we apply the fossil record method of stellar population synthesis to a rich and diverse data set of 436 galaxies observed with integral field spectroscopy in the CALIFA survey. The sample covers a wide range of Hubble types, with stellar masses ranging from M ∼ 10 9 to 7 × 10 11 M . Spectral synthesis techniques are applied to the datacubes to retrieve the spatially resolved time evolution of the star formation rate (SFR), its intensity (Σ SFR ), and other descriptors of the 2D-SFH in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd), and five bins of stellar mass. Our main results are: (a) Galaxies form very fast independently of their current stellar mass, with the peak of star formation at high redshift (z > 2). Subsequent star formation is driven by M and morphology, with less massive and later type spirals showing more prolonged periods of star formation. (b) At any epoch in the past the SFR is proportional to M , with most massive galaxies having the highest absolute (but lowest specific) SFRs. (c) While nowadays Σ SFR is similar for all spirals, and significantly lower in early type galaxies (ETG), in the past Σ SFR scales well with morphology. The central regions of today's ETGs are where Σ SFR reached the highest values (> 10 3 M Gyr −1 pc −2 ), similar to those measured in high redshift star forming galaxies. (d) The evolution of Σ SFR in Sbc systems matches that of models for Milky-Way-like galaxies, suggesting that the formation of a thick disk may be a common phase in spirals at early epochs. (e) The SFR and Σ SFR in outer regions of E's and S0's show that they have undergone an extended phase of growth in mass between z = 2 and 0.4. The mass assembled in this phase is in agreement with the two-phase scenario proposed for the formation of ETG. (f) Evidence of an early and fast quenching is found only in the most massive (M > 2 × 10 11 M ) E galaxies of the sample, but not in spirals of similar mass, suggesting that halo-quenching is not the main mechanism for the shut down of star formation in galaxies. Less massive E and disk galaxies show more extended SFHs and a slow quenching. (g) Evidence of fast quenching is also found in the nuclei of ETG and early spirals, with SFR and Σ SFR indicating that they can be the relic of the "red nuggets" detected at high redshift.

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Star formation sustained by gas accretion

Cited by 183 publications

References 359 publications

Kinematics of Extremely Metal-Poor Galaxies: Evidence for Stellar Feedback

Kinematics of Extremely Metal-Poor Galaxies: Evidence for Stellar Feedback

Characterization of star-forming dwarf galaxies at 0.1 ≲z ≲ 0.9 in VUDS: probing the low-mass end of the mass-metallicity relation

Spatially-resolved star formation histories of CALIFA galaxies

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