Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userJINGLE V: Dust properties of nearby galaxies derived from hierarchical Bayesian SED fitting
71
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We study the dust properties of 192 nearby galaxies from the JINGLE survey using photometric data in the 22-850micron range. We derive the total dust mass, temperature T and emissivity index beta of the galaxies through the fitting of their spectral energy distribution (SED) using a single modified black-body model (SMBB). We apply a hierarchical Bayesian approach that reduces the known degeneracy between T and beta. Applying the hierarchical approach, the strength of the T-beta anti-correlation is reduced from a Pearson correlation coefficient R=-0.79 to R=-0.52. For the JINGLE galaxies we measure dust temperatures in the range 17-30 K and dust emissivity indices beta in the range 0.6-2.2. We compare the SMBB model with the broken emissivity modified black-body (BMBB) and the two modified black-bodies (TMBB) models. The results derived with the SMBB and TMBB are in good agreement, thus applying the SMBB, which comes with fewer free parameters, does not penalize the measurement of the cold dust properties in the JINGLE sample. We investigate the relation between T and beta and other global galaxy properties in the JINGLE and Herschel Reference Survey (HRS) sample. We find that beta correlates with the stellar mass surface density (R=0.62) and anti-correlates with the HI mass fraction (M(HI)/M*, R=-0.65), whereas the dust temperature correlates strongly with the SFR normalized by the dust mass (R=0.73). These relations can be used to estimate T and beta in galaxies with insufficient photometric data available to measure them directly through SED fitting.
rate research
Read More
We build a rigorous statistical framework to provide constraints on the chemical and dust evolution parameters for nearby late-type galaxies with a wide range of gas fractions ($3%<f_g<94%$). A Bayesian Monte Carlo Markov Chain framework provides statistical constraints on the parameters used in chemical evolution models. Nearly a million one-zone chemical and dust evolution models were compared to 340 galaxies. Relative probabilities were calculated from the $chi^2$ between data and models, marginalised over the different time steps, galaxy masses and star formation histories. We applied this method to find `best fitting model parameters related to metallicity, and subsequently fix these metal parameters to study the dust parameters. For the metal parameters, a degeneracy was found between the choice of initial mass function, supernova metal yield tables and outflow prescription. For the dust parameters, the uncertainties on the best fit values are often large except for the fraction of metals available for grain growth, which is well constrained. We find a number of degeneracies between the dust parameters, limiting our ability to discriminate between chemical models using observations only. For example, we show that the low dust content of low-metallicity galaxies can be resolved by either reducing the supernova dust yields and/or including photo-fragmentation. We also show that supernova dust dominates the dust mass for low metallicity galaxies and grain growth dominates for high metallicity galaxies. The transition occurs around $12+log({rm O/H})=7.75$, which is lower than found in most studies in the literature.
Using a local reference sample of 21 galaxies, we compare observations of the $lambda$2.16 $mu$m Brackett-$gamma$ (Br$gamma$) hydrogen recombination line with predictions from the Prospector Bayesian inference framework, which was used to fit the broadband photometry of these systems. This is a clean test of the spectral-energy-distribution-derived star formation rates (SFRs), as dust is expected to be optically thin at this wavelength in nearly all galaxies; thus, the internal conversion of SFR to predicted line luminosity does not depend strongly on the adopted dust model and posterior dust parameters, as is the case for shorter-wavelength lines such as H$alpha$. We find that Prospector predicts Br$gamma$ luminosities and equivalent widths with small offsets ($sim$0.05 dex), and scatter ($sim$0.2 dex), consistent with measurement uncertainties, though we caution that the derived offset is dependent on the choice of stellar isochrones. We demonstrate that even when the Prospector-derived dust attenuation does not well describe, e.g., H$alpha$ line properties or observed reddening between H$alpha$ and Br$gamma$, the underlying SFRs are accurate, as verified by the dust-free Br$gamma$ comparison. Finally, we discuss in what ways Br$gamma$ might be able to help constrain model parameters when treated as an input to the model, and comment on its potential as an accurate monochromatic SFR indicator in the era of JWST multiobject near-IR spectroscopy.
We present physical properties of radio galaxies (RGs) with $f_{rm 1.4 GHz} >$ 1 mJy discovered by Subaru Hyper Supreme-Cam (HSC) and VLA Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. For 1056 FIRST RGs at $0 < z leq 1.7$ with HSC counterparts in about 100 deg$^2$, we compiled multi-wavelength data of optical, near-infrared (IR), mid-IR, far-IR, and radio (150 MHz). We derived their color excess ($E (B-V)_{*}$), stellar mass, star formation rate (SFR), IR luminosity, the ratio of IR and radio luminosity ($q_{rm IR}$), and radio spectral index ($alpha_{rm radio}$) that are derived from the SED fitting with CIGALE. We also estimated Eddington ratio based on stellar mass and integration of the best-fit SEDs of AGN component. We found that $E (B-V)_{*}$, SFR, and IR luminosity clearly depend on redshift while stellar mass, $q_{rm IR}$, and $alpha_{rm radio}$ do not significantly depend on redshift. Since optically-faint ($i_{rm AB} geq 21.3$) RGs that are newly discovered by our RG survey tend to be high redshift, they tend to not only have a large dust extinction and low stellar mass but also have high SFR and AGN luminosity, high IR luminosity, and high Eddington ratio compared to optically-bright ones. The physical properties of a fraction of RGs in our sample seem to differ from a classical view of RGs with massive stellar mass, low SFR, and low Eddington ratio, demonstrating that our RG survey with HSC and FIRST provides us curious RGs among entire RG population.
Over the past few years ALMA has detected dust-rich galaxies whose cold dust emission is spatially disconnected from the UV rest-frame emission. This represents a challenge for modeling their spectral energy distributions with codes based on an energy budget between the stellar and dust components. We want to verify the validity of energy balance modeling on a sample of galaxies observed from the UV to the sub-millimeter rest frame with ALMA and decipher what information can be reliably retrieved from the analysis of the full SED and from subsets of wavelengths. We select 17 sources at z~2 in the Hubble Ultra-Deep Field and in the GOODS- South field detected with ALMA and Herschel and for which UV to NIR. rest-frame ancillary data are available. We fit the data with CIGALE exploring different configurations for dust attenuation and star formation histories, considering either the full dataset or one that is reduced to the stellar and dust emission. We compare estimates of the dust luminosities, star formation rates, and stellar masses. The fit of the stellar continuum alone with the starburst attenuation law can only reproduce up to 50% of the total dust luminosity observed by Herschel and ALMA. This deficit is found to be consistent with similar quantities estimated in the COSMOS field and is found to increase with the specific star formation rate. The combined stellar and dust SEDs are well fitted when different attenuation laws are introduced. Shallow attenuation curves are needed for the galaxies whose cold dust distribution is very compact compared to starlight. The stellar mass estimates are affected by the choice of the attenuation law. The star formation rates are robustly estimated as long as dust luminosities are available. The large majority of the galaxies are above the average main sequence of star forming galaxies and one source is a strong starburst.
The first Herschel Hi-Gal images of the galactic plane unveil the far-infrared diffuse emission of the interstellar medium with an unprecedented angular resolution and sensitivity. In this paper, we present the first analysis of these data in combination with that of Spitzer Glimpse & Mipsgal. We selected a relatively diffuse and low excitation region of the l~59,^{circ} Hi-Gal Science Demonstration Phase field to perform a pixel by pixel fitting of the 8 to 500 microns SED using the DustEM dust emission model. We derived maps of the Very Small Grains (VSG) and PAH abundances from the model. Our analysis allows us to illustrate that the Aromatic Infrared Bands (AIB) intensity does not trace necessarily the PAH abundance but rather the product of abundance x column density x intensity of the exciting radiation field. We show that the spatial structure of PACS70microns map resembles the shorter wavelengths (e.g. IRAC8microns) maps, because they trace both the intensity of exciting radiation field and column density. We also show that the modeled VSG contribution to PACS70microns (PACS160microns) band intensity can be up to 50% (7%). The interpretation of diffuse emission spectra at these wavelengths must take stochastically heated particles into account. Finally, this preliminary study emphasizes the potential of analyzing the full dust SED sampled by Herschel and Spitzer data, with a physical dust model (DustEM) to reach the properties of the dust at simultaneously large and small scales.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
