Feedback in Galaxy Formation

There is now good observational evidence that some type of feedback process must operate within galaxies. Such a process has long been thought to exist on the basis of theoretical studies of galaxy formation. This feedback is responsible for regulating the rate of star formation and thereby preventing the formation of an overabundance of low–mass galaxies. There is gathering evidence that this feedback process must somehow involve the supermassive black holes thought to dwell in the centres of galaxies.

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Testing galaxy formation simulations with damped Lyman-α abundance and metallicity evolution

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa056 ◽

2020 ◽

Vol 492 (2) ◽

pp. 2835-2846 ◽

Cited By ~ 4

Author(s):

Sultan Hassan ◽

Kristian Finlator ◽

Romeel Davé ◽

Christopher W Churchill ◽

J Xavier Prochaska

Keyword(s):

Star Formation ◽

Galaxy Formation ◽

Star Formation Rate ◽

Initial Conditions ◽

Mass Density ◽

Formation Rate ◽

Thomson Scattering ◽

Stellar Mass ◽

Rate Functions ◽

Metallicity Distribution

ABSTRACT We examine the properties of damped Lyman-α absorbers (DLAs) emerging from a single set of cosmological initial conditions in two state-of-the-art cosmological hydrodynamic simulations: simba and technicolor dawn. The former includes star formation and black hole feedback treatments that yield a good match with low-redshift galaxy properties, while the latter uses multifrequency radiative transfer to model an inhomogeneous ultraviolet background (UVB) self-consistently and is calibrated to match the Thomson scattering optical depth, UVB amplitude, and Ly α forest mean transmission at z > 5. Both simulations are in reasonable agreement with the measured stellar mass and star formation rate functions at z ≥ 3, and both reproduce the observed neutral hydrogen cosmological mass density, $\Omega _{\rm H\, \small{I}}(z)$. However, the DLA abundance and metallicity distribution are sensitive to the galactic outflows’ feedback and the UVB amplitude. Adopting a strong UVB and/or slow outflows underproduces the observed DLA abundance, but yields broad agreement with the observed DLA metallicity distribution. By contrast, faster outflows eject metals to larger distances, yielding more metal-rich DLAs whose observational selection may be more sensitive to dust bias. The DLA metallicity distribution in models adopting an H2-regulated star formation recipe includes a tail extending to [M/H] ≪ −3, lower than any DLA observed to date, owing to curtailed star formation in low-metallicity galaxies. Our results show that DLA observations play an important role in constraining key physical ingredients in galaxy formation models, complementing traditional ensemble statistics such as the stellar mass and star formation rate functions.

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The role of the dark matter haloes on the cosmic star formation rate

New Astronomy ◽

10.1016/j.newast.2015.06.001 ◽

2015 ◽

Vol 41 ◽

pp. 48-52

Author(s):

Eduardo S. Pereira ◽

Oswaldo D. Miranda

Keyword(s):

Dark Matter ◽

Star Formation ◽

Star Formation Rate ◽

Formation Rate

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Properties of simulated galaxies and supermassive black holes in cosmic voids

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa219 ◽

2020 ◽

Vol 493 (1) ◽

pp. 899-921

Author(s):

Mélanie Habouzit ◽

Alice Pisani ◽

Andy Goulding ◽

Yohan Dubois ◽

Rachel S Somerville ◽

...

Keyword(s):

Black Holes ◽

Star Formation ◽

Star Formation Rate ◽

Large Fraction ◽

Formation Rate ◽

Dark Matter Halo ◽

Wide Field ◽

Void Galaxies ◽

Low Mass ◽

Cosmic Voids

ABSTRACT Cosmic voids, the underdense regions of the cosmic web, are widely used to constrain cosmology. Voids contain few, isolated galaxies, presumably expected to be less evolved and preserving memory of the pristine Universe. We use the cosmological hydrodynamical simulation Horizon-AGN coupled to the void finder vide to investigate properties of galaxies in voids at z = 0. We find that, closer to void centres, low-mass galaxies are more common than their massive counterparts. At a fixed dark matter halo mass, they have smaller stellar masses than in denser regions. The star formation rate of void galaxies diminishes when approaching void centres, but their specific star formation rate slightly increases, suggesting that void galaxies form stars more efficiently with respect to their stellar mass. We find that this cannot only be attributed to the prevalence of low-mass galaxies. The inner region of voids also predominantly hosts low-mass black holes (BHs). However, the BH mass-to-galaxy mass ratios resemble those of the whole simulation at z = 0. Our results suggest that even if the growth channels in cosmic voids are different from those in denser environments, voids grow their galaxies and BHs in a similar way. While a large fraction of the BHs have low Eddington ratios, we find that $\text{$\sim$} 20{{\ \rm per\ cent}}$ could be observed as active galactic nuclei with $\log _{10} L_{\rm 2\!-\!10 \, keV}=41.5\!-\!42.5 \, \rm erg\, s^{-1}$. These results pave the way to future work with larger next-generation hydro-simulations, aiming to confirm our findings and prepare the application on data from upcoming large surveys such as Prime Focus Spectrograph, Euclid, and Wide Field Infrared Survey Telescope.

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Fundamental metallicity relation in CALIFA, SDSS-IV MaNGA, and high-z galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834637 ◽

2019 ◽

Vol 627 ◽

pp. A42 ◽

Cited By ~ 11

Author(s):

G. Cresci ◽

F. Mannucci ◽

M. Curti

Keyword(s):

Star Formation ◽

Dynamic Range ◽

Star Formation Rate ◽

Formation Rate ◽

Active Galaxies ◽

Small Samples ◽

Local Relation ◽

Different Shapes ◽

Intrinsic Scatter

The metallicity of local galaxies is tightly related not only to stellar mass, i.e. the mass-metallicity relation, but also to the star formation rate (SFR) through the so-called fundamental metallicity relation (FMR); more active galaxies show lower metallicities at fixed mass. Interestingly, high-z galaxies up to z ∼ 2.5 follow the same relation defined by SDSS locally. However, different shapes have been proposed for local galaxies, and the existence of a FMR and the role of the SFR has been recently questioned by some authors. In this paper we first discuss the various parametrizations of this mass-metallicity-SFR relation that has appeared in the literature to understand the origin of their different shapes. We then reanalysed data from CALIFA and SDSS-IV MaNGA surveys, which were used to suggest no dependency of metallicity on the SFR in local galaxies. Contrary to those claims, we find that those datasets are instead fully consistent with the predictions, showing the expected dependency on the SFR at fixed mass. Finally, we analysed those high-z data whose consistency with the local relation was questioned. While an internal dependency on the SFR among the subsamples is difficult to detect at high-z because of the limited dynamic range sampled in the three parameters and the intrinsic scatter and uncertainties of such small samples, all these datasets are compatible with the relation defined locally by SDSS galaxies. This confirms the lack of evolution of the FMR in these data up to z ∼ 2.3.

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The VANDELS survey: the role of ISM and galaxy physical properties in the escape of Lyα emission in z ∼ 3.5 star-forming galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935495 ◽

2019 ◽

Vol 631 ◽

pp. A19 ◽

Cited By ~ 11

Author(s):

F. Marchi ◽

L. Pentericci ◽

L. Guaita ◽

M. Talia ◽

M. Castellano ◽

...

Keyword(s):

Star Formation ◽

Physical Properties ◽

Emission Line ◽

Column Density ◽

Star Formation Rate ◽

Spectral Energy Distribution ◽

Formation Rate ◽

Stellar Mass ◽

Dust Extinction

Aims. We wish to investigate the physical properties of a sample of Lyα emitting galaxies in the VANDELS survey, with particular focus on the role of kinematics and neutral hydrogen column density in the escape and spatial distribution of Lyα photons. Methods. From all the Lyα emitting galaxies in the VANDELS Data Release 2 at 3.5 ≲ z ≲ 4.5, we selected a sample of 52 galaxies that also have a precise systemic redshift determination from at least one nebular emission line (HeII or CIII]). For these galaxies, we derived different physical properties (stellar mass, age, dust extinction, and star formation rate) from spectral energy distribution (SED) fitting of the exquisite multiwavelength photometry available in the VANDELS fields, using the dedicated spectral modeling tool BEAGLE and the UV β slope from the observed photometry. We characterized the Lyα emission in terms of kinematics, equivalent width (EW), full width at half-maximum, and spatial extension and then estimated the velocity of the neutral outflowing gas. The ultra-deep VANDELS spectra (up to 80 h on-source integration) enable this for individual galaxies without the need to rely on stacks. We then investigated the correlations between the Lyα properties and the other measured properties to study how they affect the shape and intensity of Lyα emission. Results. We reproduce some of the well-known correlations between Lyα EW and stellar mass, dust extinction, and UV β slope, in the sense that the emission line appears brighter in galaxies with lower mass that are less dusty and bluer. We do not find any correlation with the SED-derived star formation rate, while we find that galaxies with brighter Lyα tend to be more compact in both UV and in Lyα. Our data reveal an interesting correlation between the Lyα velocity offset and the shift of the interstellar absorption lines with respect to the systemic redshift, observed for the first time at high redshifts: galaxies with higher interstellar medium (ISM) outflow velocities show smaller Lyα velocity shifts. We interpret this relation in the context of the shell-model scenario, where the velocity of the ISM and the HI column density contribute together in determining the Lyα kinematics. In support to our interpretation, we observe that galaxies with high HI column densities have much more extended Lyα spatial profiles; this is a sign of increased scattering. However, we do not find any evidence that the HI column density is related to any other physical properties of the galaxies, although this might be due in part to the limited range of parameters that our sample spans.

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