Dark-matter halo mergers as a fertile environment for low-mass Population III star formation

ABSTRACT How do galaxy properties (such as stellar mass, luminosity, star formation rate, and morphology) and their evolution depend on the mass of their host dark matter halo? Using the Galaxy and Mass Assembly group catalogue, we address this question by exploring the dependence on host halo mass of the luminosity function (LF) and stellar mass function (SMF) for grouped galaxies subdivided by colour, morphology, and central/satellite. We find that spheroidal galaxies in particular dominate the bright and massive ends of the LF and SMF, respectively. More massive haloes host more massive and more luminous central galaxies. The satellites LF and SMF, respectively, show a systematic brightening of characteristic magnitude, and increase in characteristic mass, with increasing halo mass. In contrast to some previous results, the faint-end and low-mass slopes show little systematic dependence on halo mass. Semi-analytic models and simulations show similar or enhanced dependence of central mass and luminosity on halo mass. Faint and low-mass simulated satellite galaxies are remarkably independent of halo mass, but the most massive satellites are more common in more massive groups. In the first investigation of low-redshift LF and SMF evolution in group environments, we find that the red/blue ratio of galaxies in groups has increased since redshift z ≈ 0.3 relative to the field population. This observation strongly suggests that quenching of star formation in galaxies as they are accreted into galaxy groups is a significant and ongoing process.

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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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Magnetic field evolution in dwarf and Magellanic-type galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201730566 ◽

2018 ◽

Vol 611 ◽

pp. A7 ◽

Cited By ~ 1

Author(s):

H. Siejkowski ◽

M. Soida ◽

K. T. Chyży

Keyword(s):

Magnetic Field ◽

Star Formation ◽

Large Scale ◽

Magnetic Energy ◽

Galactic Disk ◽

Cosmic Ray ◽

Dark Matter Halo ◽

Field Evolution ◽

Low Mass ◽

The Magnetic Field

Aims. Low-mass galaxies radio observations show in many cases surprisingly high levels of magnetic field. The mass and kinematics of such objects do not favour the development of effective large-scale dynamo action. We attempted to check if the cosmic-ray-driven dynamo can be responsible for measured magnetization in this class of poorly investigated objects. We investigated how starburst events on the whole, as well as when part of the galactic disk, influence the magnetic field evolution. Methods. We created a model of a dwarf/Magellanic-type galaxy described by gravitational potential constituted from two components: the stars and the dark-matter halo. The model is evolved by solving a three-dimensional (3D) magnetohydrodynamic equation with an additional cosmic-ray component, which is approximated as a fluid. The turbulence is generated in the system via supernova explosions manifested by the injection of cosmic-rays. Results. The cosmic-ray-driven dynamo works efficiently enough to amplify the magnetic field even in low-mass dwarf/Magellanic-type galaxies. The e-folding times of magnetic energy growth are 0.50 and 0.25 Gyr for the slow (50 km s−1) and fast (100 km s−1) rotators, respectively. The amplification is being suppressed as the system reaches the equipartition level between kinetic, magnetic, and cosmic-ray energies. An episode of star formation burst amplifies the magnetic field but only for a short time while increased star formation activity holds. We find that a substantial amount of gas is expelled from the galactic disk, and that the starburst events increase the efficiency of this process.

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A flexible analytic model of cosmic variance in the first billion years

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2828 ◽

2020 ◽

Vol 499 (2) ◽

pp. 2401-2415

Author(s):

A C Trapp ◽

Steven R Furlanetto

Keyword(s):

Dark Matter ◽

Star Formation ◽

Luminosity Function ◽

Large Scale ◽

High Redshift ◽

Mass Function ◽

Dark Matter Halo ◽

Analytic Model ◽

Stellar Feedback ◽

High Redshift Universe

ABSTRACT Cosmic variance is the intrinsic scatter in the number density of galaxies due to fluctuations in the large-scale dark matter density field. In this work, we present a simple analytic model of cosmic variance in the high-redshift Universe (z ∼ 5–15). We assume that galaxies grow according to the evolution of the halo mass function, which we allow to vary with large-scale environment. Our model produces a reasonable match to the observed ultraviolet (UV) luminosity functions in this era by regulating star formation through stellar feedback and assuming that the UV luminosity function is dominated by recent star formation. We find that cosmic variance in the UV luminosity function is dominated by the variance in the underlying dark matter halo population, and not by differences in halo accretion or the specifics of our stellar feedback model. We also find that cosmic variance dominates over Poisson noise for future high-z surveys except for the brightest sources or at very high redshifts (z ≳ 12). We provide a linear approximation of cosmic variance for a variety of redshifts, magnitudes, and survey areas through the public python package galcv. Finally, we introduce a new method for incorporating priors on cosmic variance into estimates of the galaxy luminosity function and demonstrate that it significantly improves constraints on that important observable.

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Star formation history from the cosmic infrared background anisotropies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732499 ◽

2018 ◽

Vol 614 ◽

pp. A39 ◽

Cited By ~ 12

Author(s):

A. S. Maniyar ◽

M. Béthermin ◽

G. Lagache

Keyword(s):

Dark Matter ◽

Star Formation ◽

Star Formation Rate ◽

Formation Rate ◽

Star Formation History ◽

Dark Matter Halo ◽

Model Parameters ◽

Formation History ◽

Infrared Background ◽

Cosmic Infrared Background

We present a linear clustering model of cosmic infrared background (CIB) anisotropies at large scales that is used to measure the cosmic star formation rate density up to redshift 6, the effective bias of the CIB, and the mass of dark matter halos hosting dusty star-forming galaxies. This is achieved using the Planck CIB auto- and cross-power spectra (between different frequencies) and CIB × CMB (cosmic microwave background) lensing cross-spectra measurements, as well as external constraints (e.g. on the CIB mean brightness). We recovered an obscured star formation history which agrees well with the values derived from infrared deep surveys and we confirm that the obscured star formation dominates the unobscured formation up to at least z = 4. The obscured and unobscured star formation rate densities are compatible at 1σ at z = 5. We also determined the evolution of the effective bias of the galaxies emitting the CIB and found a rapid increase from ~0.8 at z = 0 to ~8 at z = 4. At 2 < z < 4, this effective bias is similar to that of galaxies at the knee of the mass functions and submillimetre galaxies. This effective bias is the weighted average of the true bias with the corresponding emissivity of the galaxies. The halo mass corresponding to this bias is thus not exactly the mass contributing the most to the star formation density. Correcting for this, we obtained a value of log(Mh/M⊙) = 12.77−0.125+0.128 for the mass of the typical dark matter halo contributing to the CIB at z = 2. Finally, using a Fisher matrix analysis we also computed how the uncertainties on the cosmological parameters affect the recovered CIB model parameters, and find that the effect is negligible.

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EDGE: the mass–metallicity relation as a critical test of galaxy formation physics

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3053 ◽

2019 ◽

Vol 491 (2) ◽

pp. 1656-1672 ◽

Cited By ~ 14

Author(s):

Oscar Agertz ◽

Andrew Pontzen ◽

Justin I Read ◽

Martin P Rey ◽

Matthew Orkney ◽

...

Keyword(s):

Star Formation ◽

Galaxy Formation ◽

Dwarf Galaxy ◽

Self Regulation ◽

Stellar Mass ◽

Dark Matter Halo ◽

V Band ◽

The Galaxy ◽

Unique Constraint ◽

Low Mass

ABSTRACT We introduce the ‘Engineering Dwarfs at Galaxy Formation’s Edge’ (EDGE) project to study the cosmological formation and evolution of the smallest galaxies in the Universe. In this first paper, we explore the effects of resolution and sub-grid physics on a single low-mass halo ($M_{\rm halo}=10^{9}{\, \rm M}_\odot$), simulated to redshift z = 0 at a mass and spatial resolution of $\sim 20{\, \rm M}_\odot$ and ∼3 pc. We consider different star formation prescriptions, supernova feedback strengths, and on-the-fly radiative transfer (RT). We show that RT changes the mode of galactic self-regulation at this halo mass, suppressing star formation by causing the interstellar and circumgalactic gas to remain predominantly warm (∼104 K) even before cosmic reionization. By contrast, without RT, star formation regulation occurs only through starbursts and their associated vigorous galactic outflows. In spite of this difference, the entire simulation suite (with the exception of models without any feedback) matches observed dwarf galaxy sizes, velocity dispersions, V-band magnitudes, and dynamical mass-to-light-ratios. This is because such structural scaling relations are predominantly set by the host dark matter halo, with the remaining model-to-model variation being smaller than the observational scatter. We find that only the stellar mass–metallicity relation differentiates the galaxy formation models. Explosive feedback ejects more metals from the dwarf, leading to a lower metallicity at a fixed stellar mass. We conclude that the stellar mass–metallicity relation of the very smallest galaxies provides a unique constraint on galaxy formation physics.

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Spikes in the SED and ripples in the outskirts of galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312009015 ◽

2011 ◽

Vol 7 (S284) ◽

pp. 173-179

Author(s):

Sukanya Chakrabarti

Keyword(s):

Dark Matter ◽

Star Formation ◽

Galaxy Evolution ◽

Dwarf Galaxies ◽

Time Sequence ◽

Indirect Detection ◽

Dynamical Simulations ◽

Galactic Satellites ◽

Low Mass ◽

Interaction History

AbstractWe describe a new method that allows us to quantitatively characterize galactic satellites from analysis of disturbances in outer gas disks, without requiring knowledge of their optical light. We have demonstrated the validity of this method, which we call Tidal Analysis, by applying it to local spirals with known optical companions, including M51 and NGC 1512. These galaxies span the range from having a low mass companion (~ one-hundredth the mass of the primary galaxy) to a fairly massive companion (~ one-third the mass of the primary galaxy). This approach has broad implications for many areas of astrophysics – for the indirect detection of dark matter (or dark matter-dominated dwarf galaxies), and for galaxy evolution in its use as a decipher of the dynamical impact of satellites on galactic disks. Here, we present some preliminary results on the emergent SEDs and images, calculated along the time sequence of these dynamical simulations using the 3-D self-consistent Monte Carlo radiative transfer code RADISHE. We explore star formation prescriptions and how they affect the emergent SEDs and images. Our goal is to identify SED colors that are primarily affected by the galaxy's interaction history, and are not significantly affected by the choice of star formation prescription. If successful, we may be able to utilize the emergent UV-IR SED of the primary galaxy to understand its recent interaction history.

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Is Dark Matter Light?

10.20944/preprints202012.0680.v1 ◽

2020 ◽

Author(s):

Lorne Hofstetter

Keyword(s):

Dark Matter ◽

Star Formation ◽

Thought Experiment ◽

Time History ◽

Gravitational Effect ◽

Dark Matter Halo ◽

Accelerating Universe ◽

Mass Model ◽

Stellar Objects ◽

Death Rates

Elucidating the nature of dark matter in galactic systems remains one of the important unsolved mysteries of modern cosmology. As a thought experiment, we consider a galaxy model where the light radiating outward from stellar objects produces a gravitational effect larger than Einstein's theory of gravity predicts. Using computer simulations, we observe that this assumption allows the basic rotation curve profiles observed in both dwarf and late-type spiral galaxies to be recreated. It is important to highlight that a separate mass model describing the dark matter halo is not needed or used. This toy model may also lead to insights about the nature of dark energy. If the gravitational effects in the universe are currently dominated by radiated light as this toy model may suggest, the cosmic scale factor would be closely linked to the time-history and spatial distribution of star formation and death rates. An accelerating universe may simply be a manifestation of star death rates exceeding star formation rates in the current epoch.

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GRB host galaxies: theoretical investigation

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312013312 ◽

2011 ◽

Vol 7 (S279) ◽

pp. 353-354

Author(s):

Jirong Mao

Keyword(s):

Dark Matter ◽

Star Formation ◽

Galaxy Evolution ◽

Gamma Ray ◽

Dark Matter Halo ◽

Host Galaxy ◽

Host Galaxies ◽

X Ray ◽

Star Forming ◽

Stellar Masses

AbstractLong gamma-ray bursts (GRBs) can be linked to the massive stars and their host galaxies are assumed to be the star-forming galaxies within small dark matter halos. We apply a galaxy evolution model, in which the star formation process inside the virialized dark matter halo at a given redshift is achieved. The star formation rates (SFRs) in the GRB host galaxies at different redshifts can be derived from our model. The related stellar masses, luminosities, and metalicities of these GRB host galaxies are estimated. We also calculate the X-ray and optical absorption of GRB afterglow emission. At higher redshift, the SFR of host galaxy is stronger, and the absorption in the X-ray and optical bands of GRB afterglow is stronger, when the dust and metal components are locally released, surrounding the GRB environment. These model predictions are compared with some observational data as well.

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