scholarly journals Extragalactic Background Light, MACHOs, and the Cosmic Stellar Baryon Budget

2001 ◽  
Vol 204 ◽  
pp. 359-372 ◽  
Author(s):  
Piero Madau ◽  
Francesco Haardt ◽  
Lucia Pozzetti
Keyword(s):  
Mass Density ◽  
Mass Function ◽  
Initial Mass Function ◽  
Cumulative Emission ◽  
Extragalactic Background Light ◽  
Background Light ◽  
New Synthesis ◽  
Total Luminosity ◽  
Night Sky ◽  
X Ray Background

The optical/far–IR extragalactic background light (EBL) from both resolved and unresolved extragalactic sources is an indicator of the total luminosity of cosmic structures, as the cumulative emission from young and evolved galactic systems, as well as from active galactic nuclei (AGNs), is recorded in this radiation. This is a brief review of some of the implications of the observed brightness of the night sky for the stellar mass density and average metallicity of the universe today, and of the possible contribution of MACHO progenitors and QSOs to the EBL. Assuming a Salpeter initial mass function with a cutoff below 0.6 M⊙, a lower limit of Ωg+Sh2 > 0.0015 I60 can be derived to the visible (recycled gas + stars) mass density required to generate an EBL at a level of IEBL = 60 I60 nW m−2 sr−1. Our latest, ‘best–guess’ estimate is Ωg+sh2 ≈ 0.0023 I60, which implies a mean metallicity at the present–epoch of yZΩg+s/Ωb ≈ 0.2 Z⊙. If massive dark halos around spiral galaxies are partially composed of faint, old white dwarfs, i.e., if a non–negligible fraction (~ a few percent) of the nucleosynthetic baryons is locked in the remnants (MACHOs) of intermediate–mass stars forming at very high redshifts, then the bright early phases of such halos should contribute significantly to the observed EBL. Assuming a standard black hole accretion model for quasar activity and using recent observations of the quasar population and new synthesis models for the cosmic X-ray background, we estimate a present mass density of QSO remnants of ρBH ≈ 3 x 105 M⊙ Mpc−3 for a 10% efficiency of accreted mass–to–radiation conversion. The quasar contribution to the brightness of the night sky is IQSO ≈ 2 nW m−2 sr−1.

scholarly journals The evolution of the UV-to-mm extragalactic background light: evidence for a top-heavy initial mass function?

2019 ◽  
Vol 487 (3) ◽  
pp. 3082-3101 ◽  
Author(s):  
William I Cowley ◽  
Cedric G Lacey ◽  
Carlton M Baugh ◽  
Shaun Cole ◽  
Carlos S Frenk ◽  
...  
Keyword(s):  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Extragalactic Background Light ◽  
Background Light

scholarly journals The Fundamental Plane of cluster spheroidal galaxies at z ∼ 1.3: evidence for mass-dependent evolution

2019 ◽  
Vol 491 (2) ◽  
pp. 1777-1794 ◽  
Author(s):  
P Saracco ◽  
A Gargiulo ◽  
F La Barbera ◽  
M Annunziatella ◽  
D Marchesini
Keyword(s):  
Mass Density ◽  
High Redshift ◽  
Structural Evolution ◽  
Stellar Populations ◽  
Mass Function ◽  
Initial Mass Function ◽  
Fundamental Plane ◽  
Stellar Velocity ◽  
A Minor ◽  
Mass Dependent

ABSTRACT We present spectroscopic observations obtained at the Large Binocular Telescope in the field of the cluster XLSSJ0223−0436 at z = 1.22. We confirm 12 spheroids cluster members and determine stellar velocity dispersion for 7 of them. We combine these data with those in the literature for clusters RXJ0848+4453 at z = 1.27 (8 galaxies) and XMMJ2235−2557 at z = 1.39 (7 galaxies) to determine the Fundamental Plane (FP) of cluster spheroids. We find that the FP at z ∼ 1.3 is offset and rotated (∼3σ) with respect to the local FP. The offset corresponds to a mean evolution Δlog(Mdyn/LB) = (−0.5 ± 0.1)z. High-redshift galaxies follow a steeper mass-dependent Mdyn/LB–Mdyn relation than local ones. Assuming Δ log(Mdyn/LB) = Δ log(M*/LB), higher mass galaxies [log(Mdyn/M⊙) ≥ 11.5] have a higher formation redshift (zf ≥ 6.5) than lower mass ones [zf ≤2 for log(Mdyn/M⊙ ≤ 10)], with a median zf ≃ 2.5 for the whole sample. Also, galaxies with higher stellar mass density host stellar populations formed earlier than those in lower density galaxies. At fixed initial mass function, Mdyn/M* varies systematically with mass and mass density. It follows that the evolution of the stellar populations (M*/LB) accounts for the observed evolution of Mdyn/LB for Mdyn > 1011 M⊙ galaxies, while accounts for ∼85 per cent of the evolution at Mdyn < 1011 M⊙. We find no evidence in favour of structural evolution of individual galaxies, while we find evidences that spheroids later added to the population may account for the observed discrepancy between Δlog(Mdyn/LB) and Δ log(M*/LB) at masses <1011 M⊙. Thus, the evolution of the FP of cluster spheroids is consistent with the mass-dependent and mass density-dependent evolution of their stellar populations superimposed to a minor contribution of spheroids joining the population at later times.

scholarly journals Observations of the Extragalactic Background Light

1990 ◽  
Vol 139 ◽  
pp. 257-268 ◽  
Author(s):  
K. Mattila
Keyword(s):  
Galaxy Formation ◽  
Basic Problem ◽  
Dark Cloud ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Galaxy Formation And Evolution ◽  
Intergalactic Space ◽  
Formation And Evolution ◽  
Night Sky ◽  
Observational Techniques

We present a review of the presently available observations of the extragalactic background light (EBL) obtained by means of night sky photometry. The EBL is a quantity of great cosmological importance; areas which are directly affected include galaxy formation and evolution, the appropriateness of different cosmological models, and the local luminosity density due to galaxies and other matter in intergalactic space. The basic problem in measuring the EBL is its separation from other, much stronger components of the light of the night sky. None of the different observational techniques have succeeded in providing a generally accepted measurement of the EBL. After a review of available methods, we present new results from an experiment by Mattila and Schnur (1989) utilizing the dark cloud technique in the area of L1642, a high-latitude dark nebula in the galactic anticentre direction.

scholarly journals The Central Dark Matter Fraction of Massive Early-Type Galaxies

2022 ◽  
Vol 8 ◽  
Author(s):  
C. Tortora ◽  
N. R. Napolitano
Keyword(s):  
Dark Matter ◽  
Total Mass ◽  
Mass Density ◽  
Mass Function ◽  
Initial Mass Function ◽  
Early Type ◽  
Galaxy Model ◽  
Stellar Initial Mass Function ◽  
Evolution With Time

Dark matter (DM) is predicted to be the dominant mass component in galaxies. In the central region of early-type galaxies it is expected to account for a large amount of the total mass, although the stellar mass should still represent the majority of the mass budget, depending on the stellar initial mass function (IMF). We discuss latest results on the DM fraction and mean DM density for local galaxies and explore their evolution with redshifts in the last 8 Gyr of the cosmic history. We compare these results with expectations from the ΛCDM model and discuss the role of the IMF and galaxy model through the central total mass density slope. We finally present future perspectives offered by next-generation instruments/surveys (Rubin/LSST, Euclid, CSST, WEAVE, 4MOST, and DESI), which will provide the unique chance to measure the DM evolution with time for an unprecedented number of galaxies and constrain their evolutionary scenario.

scholarly journals The total stellar halo mass of the Milky Way

2019 ◽  
Vol 490 (3) ◽  
pp. 3426-3439 ◽  
Author(s):  
Alis J Deason ◽  
Vasily Belokurov ◽  
Jason L Sanders
Keyword(s):  
Density Profile ◽  
Galactic Halo ◽  
Mass Function ◽  
Initial Mass Function ◽  
Total Luminosity ◽  
Stellar Halo ◽  
Merger Event ◽  
Red Giant ◽  
Number Counts ◽  
Good Agreement

ABSTRACT We measure the total stellar halo luminosity using red giant branch (RGB) stars selected from Gaia data release 2. Using slices in magnitude, colour, and location on the sky, we decompose RGB stars belonging to the disc and halo by fitting two-dimensional Gaussians to the Galactic proper motion distributions. The number counts of RGB stars are converted to total stellar halo luminosity using a suite of isochrones weighted by age and metallicity, and by applying a volume correction based on the stellar halo density profile. Our method is tested and calibrated using Galaxia and N-body models. We find a total luminosity (out to 100 kpc) of $L_{\rm halo} = 7.9 \pm 2.0 \times 10^8\, \mathrm{L}_\odot$ excluding Sgr, and $L_{\rm halo} = 9.4 \pm 2.4 \times 10^8\, \mathrm{L}_\odot$ including Sgr. These values are appropriate for our adopted stellar halo density profile and metallicity distribution, but additional systematics related to these assumptions are quantified and discussed. Assuming a stellar mass-to-light ratio appropriate for a Kroupa initial mass function (M⋆/L = 1.5), we estimate a stellar halo mass of $M^\star _{\rm halo} = 1.4 \pm 0.4\times 10^9 \, \mathrm{M}_\odot$. This mass is larger than previous estimates in the literature, but is in good agreement with the emerging picture that the (inner) stellar halo is dominated by one massive dwarf progenitor. Finally, we argue that the combination of a ${\sim}10^9\, \mathrm{M}_\odot$ mass and an average metallicity of 〈[Fe/H]〉 ∼ −1.5 for the Galactic halo points to an ancient (∼10 Gyr) merger event.

scholarly journals Statistical mass function of prestellar cores from the density distribution of their natal clouds

2020 ◽  
Vol 635 ◽  
pp. A88
Author(s):  
S. Donkov ◽  
T. V. Veltchev ◽  
Ph. Girichidis ◽  
R. S. Klessen
Keyword(s):  
Power Law ◽  
Molecular Clouds ◽  
Mass Density ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Core Mass ◽  
Density Relationship ◽  
Prestellar Cores ◽  
Spherical Cloud

The mass function of clumps observed in molecular clouds raises interesting theoretical issues, especially in its relation to the stellar initial mass function (IMF). We propose a statistical model of the mass function of prestellar cores (CMF), formed in self-gravitating isothermal clouds at a given stage of their evolution. The latter is characterized by the mass-density probability distribution function (ρ-PDF), which is a power-law with slope q. The different molecular clouds are divided into ensembles according to the PDF slope and each ensemble is represented by a single spherical cloud. The cores are considered as elements of self-similar structure typical for fractal clouds and are modeled by spherical objects populating each cloud shell. Our model assumes relations between size, mass, and density of the statistical cores. Out of these, a core mass-density relationship ρ ∝ mx is derived where x = 1∕(1 + q). We find that q determines the existence or nonexistence of a threshold density for core collapse. The derived general CMF is a power law of slope − 1 while the CMF of gravitationally unstable cores has a slope (−1 + x∕2), comparable with the slopes of the high-mass part of the stellar IMF and of observational CMFs.

Brown and Black Dwarfs: their Structure, Evolution and Contribution to the Missing Mass

1978 ◽  
Vol 3 (3) ◽  
pp. 227-229 ◽  
Author(s):  
D. J. Stevenson
Keyword(s):  
Galactic Plane ◽  
Mass Density ◽  
Mass Function ◽  
Initial Mass Function ◽  
Structure Evolution ◽  
Low Mass Stars ◽  
Hydrogen Burning ◽  
Missing Mass ◽  
Dwarf Stars ◽  
Low Mass

According to Oort (1965), the mass density in the solar neighbourhood (inferred from the gravity component normal to the galactic plane) is between 50% and 150% greater than the mass density inferred from non-dwarf stars. One possible explanation for the “missing mass” is an overabundance of faint M-dwarfs (Weistrop 1972), but present indications are that this overabundance is either small (Weistrop 1976; Sanduleak 1976) or non-existent (Faber et al. 1976; Eggen 1976). Nevertheless, Salpeter’s initial mass function (Salpeter 1955) suggests that the total mass may be dominated by low mass stars, including masses M≤0.08M⊙ which never undergo significant hydrogen burning.

scholarly journals 21. Light of the Night Sky

1982 ◽  
Vol 18 (1) ◽  
pp. 211-218
Author(s):  
H. Tanabe ◽  
R.H. Giese ◽  
R. Dumont ◽  
M. Harwit ◽  
C. Leinert ◽  
...  
Keyword(s):  
Light Source ◽  
Large Distance ◽  
Zodiacal Light ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Night Sky ◽  
Light Components ◽  
Celestial Sphere

The light of the night sky includes several components which spread all over the celestial sphere. These light components are terrestrial (airglow), interplanetary (zodiacal light), galactic (integrated starlight, diffuse galactic light) and extragalactic (extragalactic background light). Thus the study of nature of each light source, covering large distance, is pursued in different fields of astronomy. However, the techniques of measurement for respective components are similar and the knowledge of other lights is indispensable even in the study of a particular component.

scholarly journals Recalibrating the cosmic star formation history

2019 ◽  
Vol 490 (4) ◽  
pp. 5359-5365 ◽  
Author(s):  
Stephen M Wilkins ◽  
Christopher C Lovell ◽  
Elizabeth R Stanway
Keyword(s):  
Star Formation ◽  
Spectral Synthesis ◽  
Mass Density ◽  
Formation Rate ◽  
Thermal Infrared ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Formation History ◽  
Binary Evolution

ABSTRACT The calibrations linking observed luminosities to the star formation rate (SFR) depend on the assumed stellar population synthesis model, initial mass function, star formation and metal enrichment history, and whether reprocessing by dust and gas is included. Consequently the shape and normalization of the inferred cosmic star formation history is sensitive to these assumptions. Using v2.2.1 of the Binary Population and Spectral Synthesis (bpass) model we determine a new set of calibration coefficients for the ultraviolet, thermal infrared, and hydrogen recombination lines. These ultraviolet and thermal infrared coefficients are 0.15–0.2 dex higher than those widely utilized in the literature while the H α coefficient is ∼0.35 dex larger. These differences arise in part due to the inclusion binary evolution pathways but predominantly reflect an extension in the IMF to 300 M⊙ and a change in the choice of reference metallicity. We use these new coefficients to recalibrate the cosmic star formation history, and find improved agreement between the integrated cosmic star formation history and the in situ measured stellar mass density as a function of redshift. However, these coefficients produce new tension between SFR densities inferred from the ultraviolet and thermal infrared and those from H α.

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