ABSTRACT
We exploit EAGLE, a cosmological hydrodynamical simulation, to reproduce the selection of the observed submillimetre (submm) galaxy population by selecting the model galaxies at z ≥ 1 with ...mock submm fluxes $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy. We find a reasonable agreement between the model galaxies within this sample and the properties of the observed submm population, such as their star formation rates (SFRs) at z < 3, redshift distribution, and many integrated galaxy properties. We find that the median redshift of the $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy model population is z ≈ 2.5, and that they are massive galaxies (M* ∼ 1011 M⊙) with high dust masses (Mdust ∼ 108 M⊙), gas fractions (fgas ≈ 50 per cent), and SFRs ($\dot{M}_* \approx 100$ M⊙ yr−1). In addition, we find that they have major and minor merger fractions similar to the general population, suggesting that mergers are not the sole driver of the high SFRs in the model submm galaxies. Instead, the $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy model galaxies yield high SFRs primarily because they maintain a significant gas reservoir as a result of hosting an undermassive black hole relative to comparably massive galaxies. Not all ‘highly star-forming’ ($\dot{M}_* \ge 80$ M⊙ yr−1) eagle galaxies have submm fluxes $S_{850\, \mu \mathrm{m}}$ ≥ 1 mJy. We investigate the nature of these highly star-forming ‘Submm-Faint’ galaxies (i.e. $\dot{M}_* \ge 80$ M⊙ yr−1 but $S_{850\, \mu \mathrm{m}}$ < 1 mJy) and find that they are similar to the model submm galaxies, being gas rich and hosting undermassive black holes. However, they are also typically at higher redshifts (z > 4) and are lower mass (M* ∼ 1010 M⊙). These typically higher redshift galaxies show stronger evidence for having been triggered by major mergers, and critically, they are likely missed by most current submm surveys due to their higher dust temperatures and lower dust masses.
We present dust-attenuated and dust emission fluxes for sufficiently resolved galaxies in the EAGLE suite of cosmological hydrodynamical simulations, calculated with the SKIRT radiative transfer ...code. The post-processing procedure includes specific components for star formation regions, stellar sources, and diffuse dust and takes into account stochastic heating of dust grains to obtain realistic broadband fluxes in the wavelength range from ultraviolet to submillimeter. The mock survey includes nearly half a million simulated galaxies with stellar masses above across six EAGLE models. About two-thirds of these galaxies, residing in 23 redshift bins up to z = 6, have a sufficiently resolved metallic gas distribution to derive meaningful dust attenuation and emission, with the important caveat that the same dust properties were used at all redshifts. These newly released data complement the already publicly available information about the EAGLE galaxies, which includes intrinsic properties derived by aggregating the properties of the smoothed particles representing matter in the simulation. We further provide an open-source framework of Python procedures for post-processing simulated galaxies with the radiative transfer code SKIRT. The framework allows any third party to calculate synthetic images, spectral energy distributions, and broadband fluxes for EAGLE galaxies, taking into account the effects of dust attenuation and emission.
Aims. We analyze the applicability of far-infrared fine-structure lines Cii 158 μm, Oi 63 μm, and Oiii 88 μm to reliably trace the star formation rate (SFR) in a sample of low-metallicity dwarf ...galaxies from the Herschel Dwarf Galaxy Survey and, furthermore, extend the analysis to a broad sample of galaxies of various types and metallicities in the literature. Methods. We study the trends and scatter in the relation between the SFR (as traced by GALEX FUV and MIPS 24 μm) and far-infrared line emission, on spatially resolved and global galaxy scales, in dwarf galaxies. We assemble far-infrared line measurements from the literature and infer whether the far-infrared lines can probe the SFR (as traced by the total infrared luminosity) in a variety of galaxy populations. Results. In metal-poor dwarfs, the Oi63 and Oiii88 lines show the strongest correlation with the SFR with an uncertainty on the SFR estimates better than a factor of 2, while the link between Cii emission and the SFR is more dispersed (uncertainty factor of 2.6). The increased scatter in the SFR–LCII relation toward low metal abundances, warm dust temperatures, and large filling factors of diffuse, highly ionized gas suggests that other cooling lines start to dominate depending on the density and ionization state of the gas. For the literature sample, we evaluate the correlations for a number of different galaxy populations. The Cii and Oi63 lines are considered to be reliable SFR tracers in starburst galaxies, recovering the star formation activity within an uncertainty of factor 2. For sources with composite and active galactic nucleus (AGN) classifications, all three FIR lines can recover the SFR with an uncertainty factor of 2.3. The SFR calibrations for ultra-luminous infrared galaxies (ULIRGs) are similar to starbursts/AGNs in terms of scatter but offset from the starburst/AGN SFR relations because of line deficits relative to their total infrared luminosity. While the number of detections of the FIR fine-structure lines is still very limited at high redshift for Oi63 and Oiii88, we provide an SFR calibration for Cii.
ABSTRACT
We present infrared luminosity functions and dust mass functions for the EAGLE cosmological simulation, based on synthetic multiwavelength observations generated with the SKIRT radiative ...transfer code. In the local Universe, we reproduce the observed infrared luminosity and dust mass functions very well. Some minor discrepancies are encountered, mainly in the high luminosity regime, where the EAGLE-SKIRT luminosity functions mildly but systematically underestimate the observed ones. The agreement between the EAGLE-SKIRT infrared luminosity functions and the observed ones gradually worsens with increasing lookback time. Fitting modified Schechter functions to the EAGLE-SKIRT luminosity and dust mass functions at different redshifts up to z = 1, we find that the evolution is compatible with pure luminosity/mass evolution. The evolution is relatively mild: within this redshift range, we find an evolution of L⋆,250 ∝ (1 + z)1.68, L⋆,TIR ∝ (1 + z)2.51 and M⋆,dust ∝ (1 + z)0.83 for the characteristic luminosity/mass. For the luminosity/mass density we find ε250 ∝ (1 + z)1.62, εTIR ∝ (1 + z)2.35, and ρdust ∝ (1 + z)0.80, respectively. The mild evolution of the dust mass density is in relatively good agreement with observations, but the slow evolution of the infrared luminosity underestimates the observed luminosity evolution significantly. We argue that these differences can be attributed to increasing limitations in the radiative transfer treatment due to increasingly poorer resolution, combined with a slower than observed evolution of the SFR density in the EAGLE simulation and the lack of AGN emission in our EAGLE-SKIRT post-processing recipe.
ABSTRACT We present a new step in our systematic effort to develop self-consistent dynamical models with a finite radial extent. The focus is on models with simple analytical density profiles ...allowing for analytical calculations of many dynamical properties. In this paper, we introduce a family of models, termed Wendland models, based on compactly supported radial basis functions. The family of models is characterized by a parameter k that controls the smoothness of the transition at the truncation radius. In the limit $k\rightarrow \infty$, the Wendland model reduces to a non-truncated model with a Gaussian density profile. For each Wendland model, the density, mass and gravitational potential are simple truncated polynomial functions of radius. Via the sphecow tool we demonstrate that all Wendland models can be supported by isotropic distribution functions. Surprisingly, the isotropic distribution function exhibits varied behaviour across different Wendland models. Additionally, each model can be supported by a continuum of Osipkov–Merritt orbital structures, ranging from radially anisotropic to completely tangential at the truncation radius. To the best of our knowledge, the Wendland models presented here are the first family of models accommodating both radial and tangential Osipkov–Merritt distribution functions. Using linear superposition, these models can easily be combined to generate Wendland models with even more diverse orbital structures. While the Wendland models are not fully representative of real dynamical systems due to their Gaussian-like density profile, this study lays important groundwork for constructing more realistic models with truncated density profiles that can be supported by a range of orbital structures.
Context.
The Einasto model has become one of the most popular models for describing the density profile of dark matter haloes. There have been relatively few comprehensive studies on the dynamical ...structure of the Einasto model, mainly because only a limited number of properties can be calculated analytically.
Aims.
We want to systematically investigate the photometric and dynamical structure of the family of Einasto models over the entire model parameter space.
Methods.
We used the
SpheCow
code to explore the properties of the Einasto model. We systematically investigated how the most important properties change as a function of the Einasto index
n
. We considered both isotropic models and radially anisotropic models with an Osipkov-Merritt orbital structure.
Results.
We find that all Einasto models with
n
< 1/2 have a formal isotropic or Osipkov-Merritt distribution function that is negative in parts of phase space, and hence cannot be supported by such orbital structures. On the other hand, all models with larger values of
n
can be supported by an isotropic orbital structure, or by an Osipkov-Merritt anisotropy, as long as the anisotropy radius is larger than a critical value. This critical anisotropy radius is a decreasing function of
n
, indicating that less centrally concentrated models allow for a larger degree of radial anisotropy.
Conclusions.
Studies of the structure and dynamics of models for galaxies and dark matter haloes should not be restricted to completely analytical models. Numerical codes such as
SpheCow
can help open up the range of models that are systematically investigated. This applies to the Einasto model discussed here, but also to other proposed models for dark matter haloes, including different extensions to the Einasto model.
The C ii 157.74 μm line is an important coolant for the neutral interstellar gas. Since C ii is the brightest spectral line for most galaxies, it is a potentially powerful tracer of star formation ...activity. In this paper, we present a calibration of the star formation rate (SFR) as a function of the C ii luminosity for a sample of 24 star-forming galaxies in the nearby Universe. This sample includes objects classified as H ii regions or low-ionization nuclear emission-line regions, but omits all Seyfert galaxies with a significant contribution from the active galactic nucleus to the mid-infrared photometry. In order to calibrate the SFR against the line luminosity, we rely on both Galaxy Evolution Explorer far-ultraviolet data, which is an ideal tracer of the unobscured star formation, and MIPS 24 μm, to probe the dust-enshrouded fraction of star formation. In the case of normal star-forming galaxies, the C ii luminosity correlates well with the SFR. However, the extension of this relation to more quiescent (Hα EW ≤ 10 Å) or ultraluminous galaxies should be handled with caution, since these objects show a non-linearity in the
-to-L
FIR ratio as a function of L
FIR (and thus, their star formation activity).
We provide two possible explanations for the origin of the tight correlation between the C ii emission and the star formation activity on a global galaxy-scale. A first interpretation could be that the C ii emission from photodissociation regions (PDRs) arises from the immediate surroundings of star-forming regions. Since PDRs are neutral regions of warm dense gas at the boundaries between H ii regions and molecular clouds and they provide the bulk of C ii emission in most galaxies, we believe that a more or less constant contribution from these outer layers of photon-dominated molecular clumps to the C ii emission provides a straightforward explanation for this close link between the C ii luminosity and SFR. Alternatively, we consider the possibility that the C ii emission is associated with the cold interstellar medium, which advocates an indirect link with the star formation activity in a galaxy through the Schmidt law.
ABSTRACT Supermassive black holes launching plasma jets at close to the speed of light, producing gamma-rays, have ubiquitously been found to be hosted by massive elliptical galaxies. Since ...elliptical galaxies are generally believed to be built through galaxy mergers, active galactic nuclei (AGN) launching relativistic jets are associated with the latest stages of galaxy evolution. We have discovered a pseudobulge morphology in the host galaxy of the gamma-ray AGN PKS 2004-447. This is the first gamma-ray emitter radio-loud AGN found to have been launched from a system where both the black hole and host galaxy have been actively growing via secular processes. This is evidence of an alternative black hole-galaxy co-evolutionary path to develop powerful relativistic jets, which is not merger driven.
PDF
![The reliability of [C ii] a...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0035-8711_1365-8711_1365-2966/small "The reliability of [C ii] as an indicator of the star formation rate")
