We revisit the H i size–mass (
$D_{\rm H\,{\small I}}$
–M
H i
) relation of galaxies with a sample of more than 500 nearby galaxies covering over five orders of magnitude in H i mass and more than 10 ...B-band magnitudes. The relation is remarkably tight with a scatter σ ∼ 0.06 dex, or 14 per cent. The scatter does not change as a function of galaxy luminosity, H i richness or morphological type. The relation is linked to the fact that dwarf and spiral galaxies have a homogeneous radial profile of H i surface density in the outer regions when the radius is normalized by D
H i
. The early-type disc galaxies typically have shallower H i radial profiles, indicating a different gas accretion history. We argue that the process of atomic-to-molecular gas conversion or star formation cannot explain the tightness of the D
H i
–M
H i
relation. This simple relation puts strong constraints on simulation models for galaxy formation.
Line intensity mapping (LIM) is a promising approach to study star formation and the interstellar medium (ISM) in galaxies by measuring the aggregate line emission from the entire galaxy population. ...In this work, we develop a simple yet physically motivated framework for modeling the line emission as would be observed in LIM experiments. It is done by building on analytic models of the cosmic infrared background that connect total infrared luminosity of galaxies to their host dark matter halos. We present models of the 21 cm, CO (1−0), 158 m, and 122 and 205 m lines consistent with current observational constraints. With four case studies of various combinations of these lines that probe different ISM phases, we demonstrate the potential for reliably extracting physical properties of the ISM, and the evolution of these properties with cosmic time, from auto- and cross-correlation analysis of these lines as measured by future LIM experiments.
ABSTRACT
The Fornax cluster is the nearest large cluster in the southern sky, and is currently experiencing active assembly of mass. It is thus the target of a number of ongoing observing campaigns ...at optical, near-infrared, and radio wavelengths, using state-of-the-art facilities in the Southern hemisphere. Spectroscopic redshifts are essential not only for determining cluster membership, but also kinematics within the cluster and identifying substructures. We present a compilation of all available major spectroscopic campaigns undertaken within the Fornax region, including new and previously unpublished spectroscopy. This provides not only a comprehensive census of Fornax cluster membership as a resource for the many ongoing studies of this dynamic system, but also probes the large-scale structure in the background volume.
Bioenergy buffers are linear landscape elements cultivated with perennial herbaceous or woody biomass crops placed along arable field margins and watercourses. This systematic review evaluates the ...potential impact of bioenergy buffers on multiple ecosystem services (ES) provision while describing key factors along the biomass supply chain. An Impact Assessment (IA) methodology was adopted to capture the direction and the level of confidence of impact on multiple ES including regulating (climate, water and biodiversity), supporting (soil health) and provisioning services (biomass and energy yield). The IA revealed that the implementation of bioenergy buffers on previous croplands rather than on grasslands sustains long-term provision of multiple ES such as climate, water quality and biodiversity regulation and soil health. Herbaceous buffers were found to be more effective than woody buffers in the provision of multiple ES. Knowledge gaps relative to climate and water quality regulation services were identified for the establishment phase of bioenergy buffers (0-3y). Regarding biomass logistics, the limited operating space for farm machinery was the main shortcoming when comparing bioenergy buffers to large-scale bioenergy plantations. The intra- and inter-farm spatial fragmentation of biomass supply areas may increase environmental costs related to biomass collection and transport operations, but this has not yet been fully tested. Establishing a network of bioenergy buffers increases landscape connectivity and the overall area of ES provision in the agricultural landscape. Payments for ES obtained from bioenergy buffers can ultimately improve the economics of sustainable bioenergy and help achieving environmental goals of EU policies on water, soil and biodiversity protection.
Display omitted
Within the GASP survey, aimed at studying the effect of ram pressure stripping on star formation quenching in cluster galaxies, we analyze here ALMA observations of the jellyfish galaxy JW100. We ...find an unexpected large amount of molecular gas (∼2.5 × 1010 ), 30% of which is located in the stripped gas tail out to ∼35 kpc from the galaxy center. The overall kinematics of the molecular gas is similar to the one shown by the ionized gas, but for clear signatures of double components along the stripping direction detected only out to 2 kpc from the disk. The line ratio r21 has a clumpy distribution and in the tail can reach large values (≥1), while its average value is low (0.58 with a 0.15 dispersion). All these evidence strongly suggest that the molecular gas in the tail is newly born from stripped H i gas or newly condensed from stripped diffuse molecular gas. The analysis of interferometric data at different scales reveals that a significant fraction (∼40%) of the molecular gas is extended over large scales (≥8 kpc) in the disk, and this fraction becomes predominant in the tail (∼70%). By comparing the molecular gas surface density with the star formation rate surface density derived from the H emission from MUSE data, we find that the depletion time on 1 kpc scale is particularly large (5-10 Gyr) both within the ram-pressure-disturbed region in the stellar disk and in the complexes along the tail.
Galactic archaeology based on star counts is instrumental to reconstruct the past mass assembly of Local Group galaxies. The development of new observing techniques and data reduction, coupled with ...the use of sensitive large field of view cameras, now allows us to pursue this technique in more distant galaxies exploiting their diffuse low surface brightness (LSB) light. As part of the ATLAS3D project, we have obtained with the MegaCam camera at the Canada–France–Hawaii Telescope extremely deep, multiband images of nearby early-type galaxies (ETGs). We present here a catalogue of 92 galaxies from the ATLAS3D sample, which are located in low- to medium-density environments. The observing strategy and data reduction pipeline, which achieve a gain of several magnitudes in the limiting surface brightness with respect to classical imaging surveys, are presented. The size and depth of the survey are compared to other recent deep imaging projects. The paper highlights the capability of LSB-optimized surveys at detecting new prominent structures that change the apparent morphology of galaxies. The intrinsic limitations of deep imaging observations are also discussed, among those, the contamination of the stellar haloes of galaxies by extended ghost reflections, and the cirrus emission from Galactic dust. The detection and systematic census of fine structures that trace the present and past mass assembly of ETGs are one of the prime goals of the project. We provide specific examples of each type of observed structures – tidal tails, stellar streams and shells – and explain how they were identified and classified. We give an overview of the initial results. The detailed statistical analysis will be presented in future papers.
We study the volume-limited and nearly mass-selected (stellar mass M
stars 6 × 109 M) ATLAS3D sample of 260 early-type galaxies (ETGs, ellipticals Es and lenticulars S0s). We construct detailed ...axisymmetric dynamical models (Jeans Anisotropic MGE), which allow for orbital anisotropy, include a dark matter halo and reproduce in detail both the galaxy images and the high-quality integral-field stellar kinematics out to about 1R
e, the projected half-light radius. We derive accurate total mass-to-light ratios (M/L)
e
and dark matter fractions f
DM, within a sphere of radius
centred on the galaxies. We also measure the stellar (M/L)stars and derive a median dark matter fraction f
DM = 13 per cent in our sample. We infer masses M
JAM ≡ L × (M/L)
e
2 × M
1/2, where M
1/2 is the total mass within a sphere enclosing half of the galaxy light. We find that the thin two-dimensional subset spanned by galaxies in the
coordinates system, which we call the Mass Plane (MP) has an observed rms scatter of 19 per cent, which implies an intrinsic one of 11 per cent. Here,
is the major axis of an isophote enclosing half of the observed galaxy light, while σ
e
is measured within that isophote. The MP satisfies the scalar virial relation
within our tight errors. This show that the larger scatter in the Fundamental Plane (FP) (L, σ
e
, R
e) is due to stellar population effects including trends in the stellar initial mass function (IMF). It confirms that the FP deviation from the virial exponents is due to a genuine (M/L)
e
variation. However, the details of how both R
e and σ
e
are determined are critical in defining the precise deviation from the virial exponents. The main uncertainty in masses or M/L estimates using the scalar virial relation is in the measurement of R
e. This problem is already relevant for nearby galaxies and may cause significant biases in virial mass and size determinations at high redshift. Dynamical models can eliminate these problems. We revisit the (M/L)
e
-σ
e
relation, which describes most of the deviations between the MP and the FP. The best-fitting relation is
(r band). It provides an upper limit to any systematic increase of the IMF mass normalization with σ
e
. The correlation is more shallow and has smaller scatter for slow rotating systems or for galaxies in Virgo. For the latter, when using the best distance estimates, we observe a scatter in (M/L)
e
of 11 per cent, and infer an intrinsic one of 8 per cent. We perform an accurate empirical study of the link between σ
e
and the galaxies circular velocity V
circ within 1R
e (where stars dominate) and find the relation max (V
circ) 1.76 × σ
e
, which has an observed scatter of 7 per cent. The accurate parameters described in this paper are used in the companion Paper XX (Cappellari et al.) of this series to explore the variation of global galaxy properties, including the IMF, on the projections of the MP.
Much of our knowledge of galaxies comes from analysing the radiation emitted by their stars, which depends on the present number of each type of star in the galaxy. The present number depends on the ...stellar initial mass function (IMF), which describes the distribution of stellar masses when the population formed, and knowledge of it is critical to almost every aspect of galaxy evolution. More than 50 years after the first IMF determination, no consensus has emerged on whether it is universal among different types of galaxies. Previous studies indicated that the IMF and the dark matter fraction in galaxy centres cannot both be universal, but they could not convincingly discriminate between the two possibilities. Only recently were indications found that massive elliptical galaxies may not have the same IMF as the Milky Way. Here we report a study of the two-dimensional stellar kinematics for the large representative ATLAS(3D) sample of nearby early-type galaxies spanning two orders of magnitude in stellar mass, using detailed dynamical models. We find a strong systematic variation in IMF in early-type galaxies as a function of their stellar mass-to-light ratios, producing differences of a factor of up to three in galactic stellar mass. This implies that a galaxy's IMF depends intimately on the galaxy's formation history.
Abstract The presence of dense, neutral hydrogen clouds in the hot, diffuse intragroup and intracluster (IC) medium is an important clue to the physical processes controlling the survival of cold gas ...and sheds light on cosmological baryon flows in massive halos. Advances in numerical modeling and observational surveys mean that theory and observational comparisons are now possible. In this paper, we use the high-resolution TNG50 cosmological simulation to study the H i distribution in seven halos with masses similar to the Fornax galaxy cluster. Adopting observational sensitivities similar to the MeerKAT Fornax Survey (MFS), an ongoing H i survey that will probe to column densities of 10 18 cm −2 , we find that Fornax-like TNG50 halos have an extended distribution of neutral hydrogen clouds. Within 1 R vir , we predict the MFS will observe a total H i covering fraction of ∼12% (mean value) for 10 kpc pixels and 6% for 2 kpc pixels. If we restrict this to gas more than 10 half-mass radii from galaxies, the mean values only decrease mildly, to 10% (4%) for 10 (2) kpc pixels (albeit with significant halo-to-halo spread). Although there are large amounts of H i outside of galaxies, the gas seems to be associated with satellites, judging both by the visual inspection of projections and by comparison of the line of sight velocities of galaxies and IC H i .
PDF
