Shape Of Spectral Energy Distribution Research Articles

Distance Estimate Method for Asymptotic Giant Branch Stars Using Infrared Spectral Energy Distributions

We present a method to estimate distances to asymptotic giant branch (AGB) stars in the Galaxy, using spectral energy distributions (SEDs) in the near- and mid-infrared. By assuming that a given set of source properties (initial mass, stellar temperature, composition, and evolutionary stage) will provide a typical SED shape and brightness, sources are color matched to a distance-calibrated template and thereafter scaled to extract the distance. The method is tested by comparing the distances obtained to those estimated from very long baseline interferometry or Gaia parallax measurements, yielding a strong correlation in both cases. Additional templates are formed by constructing a source sample likely to be close to the Galactic center, and thus with a common, typical distance for calibration of the templates. These first results provide statistical distance estimates to a set of almost 15,000 Milky Way AGB stars belonging to the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey, with typical distance errors of ±35%. With these statistical distances, a map of the intermediate-age population of stars traced by AGBs is formed, and a clear bar structure can be discerned, consistent with the previously reported inclination angle of 30° to the GC–Sun direction vector. These results motivate deeper studies of the AGB population to tease out the intermediate-age stellar distribution throughout the Galaxy, as well as determining statistical properties of the AGB population luminosity and mass-loss-rate distributions.

A Systematic Analysis of the X-Ray Emission in Optically Selected Tidal Disruption Events: Observational Evidence for the Unification of the Optically and X-Ray-selected Populations

We present a systematic analysis of the X-ray emission of a sample of 17 optically selected, X-ray-detected tidal disruption events (TDEs) discovered between 2014 and 2021. The X-ray light curves show a diverse range of temporal behaviors, with most sources not following the expected power-law decline. The X-ray spectra are mostly extremely soft and consistent with thermal emission from the innermost region of an accretion disk, which cools as the accretion rate decreases. Three sources show formation of a hard X-ray corona at late times. The spectral energy distribution shape, probed by the ratio (L BB/L X) between the UV/optical and X-ray, shows a wide range of L BB/L X ∈ (0.5, 3000) at early times and converges to disklike values of L BB/L X ∈ (0.5, 10) at late times. We estimate the fraction of optically discovered TDEs with L X ≥ 1042 erg s−1 to be at least 40% and show that X-ray loudness is independent of black hole mass. We argue that distinct disk formation timescales are unlikely to be able to explain the diverse range of X-ray evolution. We combine our sample with X-ray-discovered ones to construct an X-ray luminosity function, best fit by a broken power law, with a break at L X ≈ 1044 erg s−1. We show that there is no dichotomy between optically and X-ray-selected TDEs; instead, there is a continuum of early-time L BB/L X, at least as wide as L BB/L X ∈ (0.1, 3000), with optical/X-ray surveys selecting preferentially, but not exclusively, from the higher/lower end of the distribution. Our findings are consistent with unification models for the overall TDE population.

Cluster Analysis of the Roma-BZCAT Blazars

Based on the collected multiwavelength data, namely in the radio (NVSS, FIRST, RATAN-600), IR (WISE), optical (Pan-STARRS), UV (GALEX), and X-ray (ROSAT, Swift-XRT) ranges, we have performed a cluster analysis for the blazars of the Roma-BZCAT catalog. Using two machine learning methods, namely a combination of PCA with k-means clustering and Kohonen’s self-organizing maps (SOMs), we have constructed an independent classification of the blazars (five classes) and compared the classes with the known Roma-BZCAT classification (FSRQs, BL Lacs, galaxy-dominated BL Lacs, and blazars of an uncertain type) as well as with the high synchrotron peaked (HSP) blazars from the 3HSP catalog and blazars from the TeVCat catalog. The obtained groups demonstrate concordance with the BL Lac/FSRQ classification along with a continuous character of the change in the properties. The group of HSP blazars stands out against the overall distribution. We examine the characteristics of the five groups and demonstrate distinctions in their spectral energy distribution shapes. The effectiveness of the clustering technique for objective analysis of multiparametric arrays of experimental data is demonstrated.

A Close Look at Lyα Emitters with JWST/NIRCam at z ≈ 3.1

We study 10 spectroscopically confirmed Lyα emitters (LAEs) at z ≈ 3.1 in the Ultra Deep Survey field, covered by the James Webb Space Telescope/NIRCam in the Public Release Imaging for Extragalactic Research program. All LAEs are detected in all NIRCam bands from F090W to F444W, corresponding to rest frame wavelengths of 2200 Å to 1.2 μm. Based on morphological analysis of the F200W images, three out of the 10 targets are resolved into pair-like systems with separations of <0.″9, and another three show asymmetric structures. We then construct the spectral energy distributions (SEDs) of these LAEs, which show little to no extinction. All sources, including the pairs, show similar SED shapes, with a prominent flux excess in the F200W band, corresponding to extremely strong [O iii]+Hβ emission lines (EWrest = 740–6500 Å). The median effective radii, stellar mass, and UV slope of our sample are 0.36 kpc, 3.8 × 107 M ⊙, and −2.48, respectively. The average burst age, estimated by stellar mass over star formation rate, is <40 Myr. These measurements reveal an intriguing starbursting dwarf galaxy population lying off the extrapolations of the z ∼ 3 scaling relations to the low-mass end: ∼0.7 dex above the star-forming main sequence, ∼0.35 dex below the mass–size relation, and bluer in the UV slope than typical high-z galaxies at similar UV luminosities. We speculate that these numbers may require a larger main-sequence scatter or tail in the dwarf galaxy regime toward the starburst outliers.

ALMA Millimeter/Submillimeter Sources among Spitzer SMUVS Galaxies at z > 2 in the COSMOS Field

Submillimeter observations reveal the star formation activity obscured by dust in the young Universe. It still remains unclear how galaxies detected at submillimeter wavelengths are related to ultraviolet/optical-selected galaxies in terms of their observed quantities, physical properties, and evolutionary stages. Deep near- and mid-infrared observational data are crucial to characterize the stellar properties of galaxies detected with submillimeter emission. In this study, we make use of a galaxy catalog from the Spitzer Matching survey of the UltraVISTA ultra-deep Stripes. By crossmatching with a submillimeter source catalog constructed with archival data of the Atacama Large Millimeter/submillimeter Array (ALMA), we search for galaxies at z > 2 with a submillimeter detection in our galaxy catalog. We find that the ALMA-detected galaxies at z > 2 are systematically massive and have redder K s –[4.5] colors than the nondetected galaxies. The redder colors are consistent with the larger dust reddening values of the ALMA-detected galaxies obtained from spectral energy distribution (SED) fitting. We also find that the ALMA-detected galaxies tend to have brighter 4.5 μm magnitudes. This may suggest that they tend to have smaller mass-to-light ratios and thus to be younger than star-forming galaxies fainter at submillimeter wavelengths with similar stellar masses. We identify starburst galaxies with high specific star formation rates among both ALMA-detected and nondetected SMUVS sources. Irrespective of their brightness at submillimeter wavelengths, these populations have similar dust reddening values, which may suggest a variety of dust SED shapes among the starburst galaxies at z > 2.

The Accretion History of AGN: The Spectral Energy Distributions of X-Ray-luminous Active Galactic Nuclei

Spectral energy distributions (SEDs) from X-ray to far-infrared (FIR) wavelengths are presented for a sample of 1246 X-ray-luminous active galactic nuclei (AGNs; L 0.5–10 keV > 1043 erg s−1), with z spec < 1.2, selected from Stripe 82X, COSMOS, and GOODS-N/S. The rest-frame SEDs show a wide spread (∼2.5 dex) in the relative strengths of broad continuum features at X-ray, ultraviolet (UV), mid-infrared (MIR), and FIR wavelengths. A linear correlation (log–log slope of 0.7 ± 0.04) is found between L MIR and L X. There is significant scatter in the relation between the L UV and L X owing to heavy obscuration; however, the most luminous and unobscured AGNs show a linear correlation (log–log slope of 0.8 ± 0.06) in the relation above this scatter. The relation between L FIR and L X is predominantly flat, but with decreasing dispersion at L X > 1044 erg s−1. The ratio between the “galaxy-subtracted” bolometric luminosity and the intrinsic L X increases from a factor of ∼10 to 70 from log L bol/(erg s−1) = 44.5 to 46.5. Characteristic SED shapes have been determined by grouping AGNs based on relative strengths of the UV and MIR emission. The average L 1μm is constant for the majority of these SED shapes, while AGNs with the strongest UV and MIR emission have elevated L 1μm, consistent with the AGN emission dominating their SEDs at optical and near-infrared wavelengths. A strong correlation is found between the SED shape and both the L X and L bol, such that L bol/L X = 20.4 ± 1.8, independent of the SED shape. This is consistent with an evolutionary scenario of increasing L bol with decreasing obscuration as the AGN blows away circumnuclear gas.

High Eddington quasars as discovery tools: current state and challenges

A landmark of accretion processes in active galactic nuclei (AGN) is the continuum originating from a complex structure, i.e., an accretion disk and a corona around a supermassive black hole. Modelling the broad-band spectral energy distribution (SED) effectively ionizing the gas-rich broad emission line region (BLR) is key to understanding the various radiative processes at play and their importance that eventually leads to the emission from diverse physical conditions. Photoionization codes are a useful tool to investigate two aspects, the importance of the shape of the spectral energy distribution, and the physical conditions in the broad emission line region. In this work, we critically review long-standing issues pertaining to the spectral energy distribution shape and the anisotropic continuum radiation from the central regions around the accreting supermassive black holes (few 10–100 gravitational radii), with a focus on black holes accreting at high rates, possibly much above the Eddington limit. The anisotropic emission is a direct consequence of the development of a geometrically and optically thick structure at regions very close to the black hole due to a marked increase in the accretion rates. The analysis presented in this paper took advantage of the look at the diversity of the type-1 active galactic nuclei provided by the main sequence of quasars. The main sequence permitted us to assess the importance of the Eddington ratio and hence to locate the super Eddington sources in observational parameter space, as well as to constrain the distinctive physical conditions of their line-emitting BLR. This feat is posing the basis for the exploitation of quasars as cosmological distance indicators, hopefully allowing us to use the fascinating super Eddington quasars up to unprecedented distances.

Radio Spectral Energy Distributions for Single Massive Star Winds with Free–Free and Synchrotron Emission

The mass-loss rates from single massive stars are high enough to form radio photospheres at large distances from the stellar surface, where the wind is optically thick to (thermal) free–free opacity. Here we calculate the far-infrared, millimeter, and radio band spectral energy distributions (SEDs) that can result from the combination of free–free processes and synchrotron emission, to explore the conditions for nonthermal SEDs. Simplifying assumptions are adopted in terms of scaling relations for the magnetic field strength and the spatial distribution of relativistic electrons. The wind is assumed to be spherically symmetric, and we consider the effect of Razin suppression on the synchrotron emission. Under these conditions, long-wavelength SEDs with synchrotron emission can be either more steep or more shallow than the canonical asymptotic power-law SED from a nonmagnetic wind. When nonthermal emission is present, the resultant SED shape is generally not a power law; however, the variation in the slope can change slowly with wavelength. Consequently, over a limited range of wavelengths, the SED can masquerade as approximately a power law. While most observed nonthermal long-wavelength spectra are associated with binarity, synchrotron emission can have only a mild influence on single-star SEDs, requiring finer levels of wavelength sampling for the detection of the effect.

Dust spectral energy distributions in Milky Way-like galaxies in the IllustrisTNG simulations based on the evolution of grain size distribution

ABSTRACT To understand how the evolution of grain size distribution in galaxies affects observed dust properties, we apply a post-processing dust evolution model to galaxy merger trees from the IllustrisTNG cosmological hydrodynamical simulation. Our dust model includes stellar dust production, sputtering in hot gas, dust growth by accretion and coagulation in the dense interstellar medium (ISM), and shattering in the diffuse ISM. We decompose the grain size distribution into different dust species depending on the elemental abundances and the dense ISM fraction given by the simulation. In our previous work, we focused on Milky Way (MW) analogues and reproduced the observed MW extinction curve. In this study, we compute dust spectral energy distributions (SEDs) for the MW analogues. Our simulated SEDs broadly reproduce the observed MW SED within their dispersion and so does the observational data of nearby galaxies, although they tend to underpredict the MW SED at short wavelengths where emission is dominated by polycyclic aromatic hydrocarbons. We find that metallicity and dense gas fraction are the most critical factors for the SED shape, through their influence on coagulation and shattering. The overall success of our models in reproducing the MW SED further justifies the dust evolution processes included in the model and predicts the dispersion in the SEDs caused by the variety in the assembly history. We also show that the most significant increase in the dust SED occurs between redshifts z ∼ 3 and 2 in the progenitors of the simulated MW-like galaxies.

Infrared Spectral Energy Distributions and Dust Masses of Sub-solar Metallicity Galaxies at z ∼ 2.3

Abstract We present results from Atacama Large Millimeter/submillimeter Array (ALMA) 1.2 mm continuum observations of a sample of 27 star-forming galaxies at z = 2.1–2.5 from the MOSFIRE Deep Evolution Field survey with metallicity and star formation rate measurements from optical emission lines. Using stacks of Spitzer, Herschel, and ALMA photometry (rest frame ∼8–400 μm), we examine the infrared (IR) spectral energy distributions (SED) of z ∼ 2.3 subsolar-metallicity (∼0.5 Z ⊙) luminous infrared galaxies (LIRGs). We find that the data agree well with an average template of higher-luminosity local low-metallicity dwarf galaxies (reduced χ 2 = 1.8). When compared with the commonly used templates for solar-metallicity local galaxies or high-redshift LIRGs and ultraluminous IR galaxies, even in the most favorable case (with reduced χ 2 = 2.8), the templates are rejected at &gt;98% confidence. The broader and hotter IR SED of both the local dwarfs and high-redshift subsolar-metallicity galaxies may result from different grain properties or a harder/more intense ionizing radiation field that increases the dust temperature. The obscured star formation rate (SFR) indicated by the far-IR emission of the subsolar-metallicity galaxies is only ∼60% of the total SFR, considerably lower than that of the local LIRGs with ∼96%–97% obscured fractions. Due to the evolving IR SED shape, the local LIRG templates fit to mid-IR data overestimate the Rayleigh–Jeans tail measurements by a factor of 2–20. These templates underestimate IR luminosities if fit to the observed ALMA fluxes by &gt;0.4 dex. At a given stellar mass or metallicity, dust masses at z ∼ 2.3 are an order of magnitude higher than z ∼ 0. Given the predicted molecular gas fractions, the observed z ∼ 2.3 dust-to-stellar mass ratios suggest lower dust-to-molecular gas masses than in local galaxies with similar metallicities.

Fitting AGN/Galaxy X-Ray-to-radio SEDs with CIGALE and Improvement of the Code

Abstract Modern and future surveys effectively provide a panchromatic view for large numbers of extragalactic objects. Consistently modeling these multiwavelength survey data is a critical but challenging task for extragalactic studies. The Code Investigating GALaxy Emission (cigale) is an efficient python code for spectral energy distribution (SED) fitting of galaxies and active galactic nuclei (AGNs). Recently, a major extension of cigale (named x-cigale) has been developed to account for AGN/galaxy X-ray emission and improve AGN modeling at UV-to-IR wavelengths. Here, we apply x-cigale to different samples, including Cosmological Evolution Survey (COSMOS) spectroscopic type 2 AGNs, Chandra Deep Field-South X-ray detected normal galaxies, Sloan Digital Sky Survey quasars, and COSMOS radio objects. From these tests, we identify several weaknesses of x-cigale and improve the code accordingly. These improvements are mainly related to AGN intrinsic X-ray anisotropy, X-ray binary emission, AGN accretion-disk SED shape, and AGN radio emission. These updates improve the fit quality and allow for new interpretation of the results, based on which we discuss physical implications. For example, we find that AGN intrinsic X-ray anisotropy is moderate, and can be modeled as L X ( θ ) ∝ 1 + cos θ , where θ is the viewing angle measured from the AGN axis. We merge the new code into the major branch of cigale, and publicly release this new version as cigale v2022.0 on https://cigale.lam.fr.

Astrophysical Neutrinos and Blazars

We review and discuss recent results on the search for correlations between astrophysical neutrinos and γ-ray-detected sources, with many extragalactic studies reporting potential associations with different types of blazars. We investigate possible dependencies on blazar sub-classes by using the largest catalogues and all the multi-frequency data available. Through the study of similarities and differences in these sources we conclude that blazars come in two distinct flavours: LBLs and IHBLs (low-energy-peaked and intermediate-high-energy-peaked objects). These are distinguished by widely different properties such as the overall spectral energy distribution shape, jet speed, cosmological evolution, broad-band spectral variability, and optical polarisation properties. Although blazars of all types have been proposed as neutrino sources, evidence is accumulating in favour of IHBLs being the counterparts of astrophysical neutrinos. If this is indeed the case, we argue that the peculiar observational properties of IHBLs may be indirectly related to proton acceleration to very high energies.

Probing the spectral shape of dust emission with the DustPedia galaxy sample

ABSTRACT The objective of this paper is to understand the variance of the far-infrared (FIR) spectral energy distribution (SED) of the DustPedia galaxies, and its link with the stellar and dust properties. An interesting aspect of the dust emission is the inferred FIR colours which could inform us about the dust content of galaxies, and how it varies with the physical conditions within galaxies. However, the inherent complexity of dust grains as well as the variety of physical properties depending on dust, hinder our ability to utilize their maximum potential. We use principal component analysis (PCA) to explore new hidden correlations with many relevant physical properties such as the dust luminosity, dust temperature, dust mass, bolometric luminosity, star formation rate (SFR), stellar mass, specific SFR, dust-to-stellar mass ratio, the fraction of absorbed stellar luminosity by dust (fabs), and metallicity. We find that 95 per cent of the variance in our sample can be described by two principal components (PCs). The first component controls the wavelength of the peak of the SED, while the second characterizes the width. The physical quantities that correlate better with the coefficients of the first two PCs, and thus control the shape of the FIR SED are the dust temperature, the dust luminosity, the SFR, and fabs. Finally, we find a weak tendency for low-metallicity galaxies to have warmer and broader SEDs, while on the other hand high-metallicity galaxies have FIR SEDs that are colder and narrower.

Homogeneous study of Herbig Ae/Be stars from spectral energy distributions and Gaia EDR3

Context. Herbig Ae/Be stars (HAeBes) have so far been studied based on relatively small samples that are scattered throughout the sky. Their fundamental stellar and circumstellar parameters and statistical properties were derived with heterogeneous approaches before Gaia. Aims. Our main goal is to contribute to the study of HAeBes from the largest sample of such sources to date, for which stellar and circumstellar properties have been determined homogeneously from the analysis of the spectral energy distributions (SEDs) and Gaia EDR3 parallaxes and photometry. Methods. Multiwavelength photometry was compiled for 209 bona fide HAeBes for which Gaia EDR3 distances were estimated. Using the Virtual Observatory SED Analyser (VOSA), photospheric models were fit to the optical SEDs to derive stellar parameters, and the excesses at infrared (IR) and longer wavelengths were characterized to derive several circumstellar properties. A statistical analysis was carried out to show the potential use of such a large dataset. Results. The stellar temperature, luminosity, radius, mass, and age were derived for each star based on optical photometry. In addition, their IR SEDs were classified according to two different schemes, and their mass accretion rates, disk masses, and the sizes of the inner dust holes were also estimated uniformly. The initial mass function fits the stellar mass distribution of the sample within 2 &lt; M*∕M⊙ &lt; 12. In this aspect, the sample is therefore representative of the HAeBe regime and can be used for statistical purposes when it is taken into account that the boundaries are not well probed. Our statistical study does not reveal any connection between the SED shape from the Meeus et al. (2001, A&amp;A, 365, 476) classification and the presence of transitional disks, which are identified here based on the SEDs that show an IR excess starting at the K band or longer wavelengths. In contrast, only ~28% of the HAeBes have transitional disks, and the related dust disk holes are more frequent in HBes than in HAes (~34% vs. 15%). The relatively small inner disk holes and old stellar ages estimated for most transitional HAes indicate that photoevaporation cannot be the main mechanism driving disk dissipation in these sources. In contrast, the inner disk holes and ages of most transitional HBes are consistent with the photoevaporation scenario, although these results alone do not unambiguously discard other disk dissipation mechanisms. Conclusions. The complete dataset is available online through a Virtual Observatory-compliant archive, representing the most recent reference for statistical studies on the HAeBe regime. VOSA is a complementary tool for the future characterization of newly identified HAeBes.

Improved Fe ii Emission-line Models for AGNs Using New Atomic Data Sets

Abstract Understanding the Fe II emission from active galactic nuclei (AGNs) has been a grand challenge for many decades. The rewards from understanding the AGN spectra would be immense, involving both quasar classification schemes such as “Eigenvector 1” and tracing the chemical evolution of the cosmos. Recently, three large Fe II atomic data sets with radiative and electron collisional rates have become available. We have incorporated these into the spectral synthesis code Cloudy and examined predictions using a new generation of AGN spectral energy distribution (SED), which indicates that the ultraviolet (UV) emission can be quite different depending on the data set utilized. The Smyth et al. data set better reproduces the observed Fe II template of the I ZW 1 Seyfert galaxy in the UV and optical regions, and we adopt these data. We consider both thermal and microturbulent clouds and show that a microturbulence of ≈100 km s−1 reproduces the observed shape and strength of the so-called Fe II “UV bump.” Comparing our predictions to the observed Fe II template, we derive a typical cloud density of 1011 cm−3 and photon flux of 1020 cm−2 s−1, and show that these largely reproduce the observed Fe II emission in the UV and optical. We calculate the I(Fe II)/I(Mg II) emission-line intensity ratio using our best-fitting model and obtain log(I(Fe II)/I(Mg II)) ∼ 0.7, suggesting many AGNs have a roughly solar Fe/Mg abundance ratio. Finally, we vary the Eddington ratio and SED shape as a step in understanding the Eigenvector 1 correlation.

The VLA-COSMOS 3 GHz Large Project: Average radio spectral energy distribution of active galactic nuclei

Context.As the Square Kilometer Array (SKA) is expected to be operational in the next decade, investigations of the radio sky in the range of 100 MHz–10 GHz have become important for simulating SKA observations. In determining physical properties of galaxies from radio data, the radio spectral energy distribution (SED) is often assumed to be described by a simple power law, usually with a spectral index of 0.7 for all sources. Even though radio SEDs have been shown to exhibit deviations from this assumption, both in differing spectral indices and complex spectral shapes, it is often presumed that their individual differences can be canceled out in large samples.Aims.Since the average spectral index around 1 GHz (observed-frame) is important for determining physical properties of large samples of galaxies, we aim to test whether individual differences in the spectra of radio-identified active galactic nuclei align with the simple assumption ofα = 0.7 and test the evolution of the parameters of the synchrotron aging model with redshift and radio luminosity.Methods.We use a sample of 744 radio-excess active galactic nuclei (RxAGN), defined as those that exhibit more than a 3σradio luminosity excess with respect to the value expected only from the contribution from star formation, out toz ∼ 4. We constructed their average radio SED by combining Very Large Array (VLA) observations of the COSMOS field at 1.4 GHz and 3 GHz with Giant Meterwave Radio Telescope (GMRT) observations at 325 MHz and 610 MHz. To account for nondetections in the GMRT maps, we employed the survival analysis technique. We binned the RxAGN sample into luminosity- and redshift-complete subsamples. In each bin, we constrained the shape of the average radio SED by fitting a broken power-law model.Results.We find that the RxAGN sample can be described by a spectral index ofα1 = 0.28 ± 0.03 below the break frequencyνb = (4.1 ± 0.2) GHz andα2 = 1.16 ± 0.04 above it, while a simple power-law model, capturing fewer spectral features, yields a single spectral index of 0.64 ± 0.07. By binning in 1.4 GHz of radio luminosity and redshift, we find that the power-law spectral index is positively correlated with redshift and that the broken power-law spectral index above 4 GHz is positively correlated with both the redshift and source size. By selecting sources with sizes less than 1 kpc, we find a subsample of flat-spectrum sources, which can be described by a spectral index ofα = 0.41 ± 0.07 and a broken power-law spectral index ofα1 = 0.1 ± 0.1 (α2 = 0.55 ± 0.09) below (above) a break frequency ofνb = (2.7 ± 0.5) GHz.Conclusions.We have constrained the radio SED for a sample of RxAGN in the COSMOS field using available VLA and GMRT data, corresponding to the rest-frame frequency range from ∼0.3 GHz to ∼10 GHz. We describe our derived average radio SED of RxAGN using power-law and broken power-law models, yielding a radio SED that steepens above ∼4 GHz.

Spectral energy distributions of dust and PAHs based on the evolution of grain size distribution in galaxies

ABSTRACT Based on a one-zone evolution model of grain size distribution in a galaxy, we calculate the evolution of infrared spectral energy distribution (SED), considering silicate, carbonaceous dust, and polycyclic aromatic hydrocarbons (PAHs). The dense gas fraction (ηdense) of the interstellar medium (ISM), the star formation time-scale (τSF), and the interstellar radiation field intensity normalized to the Milky Way value (U) are the main parameters. We find that the SED shape generally has weak mid-infrared (MIR) emission in the early phase of galaxy evolution because the dust abundance is dominated by large grains. At an intermediate stage (t ∼ 1 Gyr for τSF = 5 Gyr), the MIR emission grows rapidly because the abundance of small grains increases drastically by the accretion of gas-phase metals. We also compare our results with observational data of nearby and high-redshift (z ∼ 2) galaxies taken by Spitzer. We broadly reproduce the flux ratios in various bands as a function of metallicity. We find that small ηdense (i.e. the ISM dominated by the diffuse phase) is favoured to reproduce the 8 $\rm{\mu m}$ intensity dominated by PAHs for both the nearby and the z ∼ 2 samples. A long τSF raises the 8 $\rm{\mu m}$ emission to a level consistent with the nearby low-metallicity galaxies. The broad match between the theoretical calculations and the observations supports our understanding of the grain size distribution, but the importance of the diffuse ISM for the PAH emission implies the necessity of spatially resolved treatment for the ISM.

ALMA characterizes the dust temperature of z ∼ 5.5 star-forming galaxies

ABSTRACT The infrared (IR) spectral energy distributions (SEDs) of main-sequence galaxies in the early Universe (z &amp;gt; 4) is currently unconstrained as IR continuum observations are time-consuming and not feasible for large samples. We present Atacama Large Millimetre Array Band 8 observations of four main-sequence galaxies at z ∼ 5.5 to study their IR SED shape in detail. Our continuum data (rest-frame 110 $\rm \mu m$, close to the peak of IR emission) allows us to constrain luminosity-weighted dust temperatures and total IR luminosities. With data at longer wavelengths, we measure for the first time the emissivity index at these redshifts to provide more robust estimates of molecular gas masses based on dust continuum. The Band 8 observations of three out of four galaxies can only be reconciled with optically thin emission redward of rest-frame $100\, {\rm \mu m}$. The derived dust peak temperatures at z ∼ 5.5 ($30\!-\!43\, {\rm K}$) are elevated compared to average local galaxies, however, $\sim 10\, {\rm K}$ below what would be predicted from an extrapolation of the trend at z &amp;lt; 4. This behaviour can be explained by decreasing dust abundance (or density) towards high redshifts, which would cause the IR SED at the peak to be more optically thin, making hot dust more visible to the external observer. From the $850{\hbox{-}}{\rm \mu m}$ dust continuum, we derive molecular gas masses between 1010 and $10^{11}\, {\rm M_{\odot }}$ and gas fractions (gas over total mass) of $30\!-\!80{{\ \rm per\ cent}}$ (gas depletion times of $100\!-\!220\, {\rm Myr}$). All in all, our results provide a first measured benchmark SED to interpret future millimetre observations of normal, main-sequence galaxies in the early Universe.

Particle acceleration in low-power hotspots: modelling the broad-band spectral energy distribution

ABSTRACT The acceleration and radiative processes active in low-power radio hotspots are investigated by means of new deep near-infrared (NIR) and optical Very Large Telescope (VLT) observations, complemented with archival, high-sensitivity VLT, radio Very Large Array (VLA), and X-ray Chandra data. For the three studied radio galaxies (3C 105, 3C 195, and 3C 227), we confirm the detection of NIR/optical counterparts of the observed radio hotspots. We resolve multiple components in 3C 227 West and in 3C 105 South and characterize the diffuse NIR/optical emission of the latter. We show that the linear size of this component (≳4 kpc) makes 3C 105 South a compelling case for particles’ re-acceleration in the post-shock region. Modelling of the radio-to-X-ray spectral energy distribution (SED) of 3C 195 South and 3C 227 W1 gives clues on the origin of the detected X-ray emission. In the context of inverse Compton models, the peculiarly steep synchrotron curve of 3C 195 South sets constraints on the shape of the radiating particles’ spectrum that are testable with better knowledge of the SED shape at low (≲GHz) radio frequencies and in X-rays. The X-ray emission of 3C 227 W1 can be explained with an additional synchrotron component originating in compact (&amp;lt;100 pc) regions, such those revealed by radio observations at 22 GHz, provided that efficient particle acceleration (γ ≳ 107) is ongoing. The emerging picture is that of systems in which different acceleration and radiative processes co-exist.

The KMOS3D Survey: Data Release and Final Survey Paper*

Abstract We present the completed KMOS3D survey, an integral field spectroscopic survey of 739 galaxies at 0.6 &lt; z &lt; 2.7 using the K-band Multi Object Spectrograph (KMOS) at the Very Large Telescope. The KMOS3D survey provides a population-wide census of kinematics, star formation, outflows, and nebular gas conditions both on and off the star-forming galaxy main sequence through the spatially resolved and integrated properties of Hα, [N ii], and [S ii] emission lines. We detect Hα emission for 91% of galaxies on the main sequence of star formation and 79% overall. The depth of the survey has allowed us to detect galaxies with star formation rates below 1 M ⊙ yr−1, as well as to resolve 81% of detected galaxies with ≥3 resolution elements along the kinematic major axis. The detection fraction of Hα is a strong function of both color and offset from the main sequence, with the detected and nondetected samples exhibiting different spectral energy distribution shapes. Comparison of Hα and UV+IR star formation rates reveal that dust attenuation corrections may be underestimated by 0.5 dex at the highest masses ( ). We confirm our first year results of a high rotation-dominated fraction (monotonic velocity gradient and v rot/ ) of 77% for the full KMOS3D sample. The rotation-dominated fraction is a function of both stellar mass and redshift, with the strongest evolution measured over the redshift range of the survey for galaxies with . With this paper, we include a final data release of all 739 observed objects (http://www.mpe.mpg.de/ir/KMOS3D).