scholarly journals Physical parameters of helium-rich subdwarf B stars from spectral energy distributions

2003 ◽  
Vol 413 (1) ◽  
pp. 323-327 ◽  
Author(s):  
A. Ahmad ◽  
C. S. Jeffery
Keyword(s):  
Spectral Energy ◽  
Physical Parameters ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
B Stars ◽  
Subdwarf B Stars

scholarly journals The spectral energy distributions of the entire Herschel Reference Survey

2011 ◽  
Vol 7 (S284) ◽  
pp. 283-285
Author(s):  
Laure Ciesla ◽  
Keyword(s):  
Far Infrared ◽  
Infrared Emission ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Distant Galaxies ◽  
First Results ◽  
Nearby Galaxies ◽  
Stellar Masses

AbstractWe present the spectral energy distributions (SED) of the 323 galaxies of the Herschel Reference Survey. In order to provide templates for nearby galaxies calibrated on physical parameters, we computed mean SEDs per bin of morphological types and stellar masses. They will be very useful to study more distant galaxies and their evolution with redshift. This preliminary work aims to study how the most commonly used libraries (Chary & Elbaz 2001, Dale & Helou 2002 and Draine & Li 2007) reproduce the far-infrared emission of galaxies. First results show that they reproduce well the far-infrared part of mean SEDs. For single galaxies the Draine & Li (2007) models seem to reproduce very well the far-infrared emission, as does the Dale & Helou (2002).

Solar analogs: Spectral energy distributions and physical parameters of their atmospheres

2000 ◽  
Vol 44 (4) ◽  
pp. 246-254 ◽  
Author(s):  
I. N. Glushneva ◽  
V. I. Shenavrin ◽  
I. A. Roshchina
Keyword(s):  
Spectral Energy ◽  
Physical Parameters ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Solar Analogs

scholarly journals Variations of the physical parameters of the blazar Mrk 421 based on analysis of the spectral energy distributions

2020 ◽  
Vol 72 (3) ◽  
Author(s):  
Yurika Yamada ◽  
Makoto Uemura ◽  
Ryosuke Itoh ◽  
Yasushi Fukazawa ◽  
Masanori Ohno ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Optimal Solution ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Zone Model ◽  
Spectral Energy Distributions ◽  
Large Area ◽  
Energy Distributions ◽  
X Ray ◽  
The One

Abstract We report on the variations of the physical parameters of the jet observed in the blazar Mrk 421, and discuss the origin of X-ray flares in the jet, based on analysis of several spectral energy distributions (SEDs). The SEDs are modeled using the one-zone synchrotron self-Compton model, its parameters determined using a Markov chain Monte Carlo method. The lack of data at TeV energies means many of the parameters cannot be uniquely determined and are correlated. These are studied in detail. We find that the optimal solution can be uniquely determined only when we apply a constraint to one of four parameters: the magnetic field (B), the Doppler factor, the size of the emitting region, and the normalization factor of the electron energy distribution. We used 31 sets of SEDs from 2009 to 2014 with optical–UV data observed with UVOT/Swift and the Kanata telescope, X-ray data with XRT/Swift, and γ-ray data with the Fermi Large Area Telescope. The result of our SED analysis suggests that, in the X-ray faint state, the emission occurs in a relatively small area (∼1016 cm) with a relatively strong magnetic field (B ∼ 10−1 G). The X-ray bright state shows a tendency opposite to that of the faint state, that is, a large emitting area (∼1018 cm), probably downstream of the jet, and a weak magnetic field (B ∼ 10−3 G). The high X-ray flux was due to an increase in the maximum energy of electrons. On the other hand, the presence of two kinds of emitting areas implies that the one-zone model is unsuitable for reproducing at least part of the observed SEDs.

scholarly journals HELP: modelling the spectral energy distributions of Herschel detected galaxies in the ELAIS N1 field

2018 ◽  
Vol 620 ◽  
pp. A50 ◽  
Author(s):  
K. Małek ◽  
V. Buat ◽  
Y. Roehlly ◽  
D. Burgarella ◽  
P. D. Hurley ◽  
...  
Keyword(s):  
Near Infrared ◽  
Stellar Mass ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Mass Star ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
The Impact ◽  
Attenuation Laws ◽  
Peculiar Galaxies

Aims. The Herschel Extragalactic Legacy Project (HELP) focuses on the data from ESA’s Herschel mission, which covered over 1300 deg2 and is preparing to publish a multi-wavelength catalogue of millions of objects. Our main goal is to find the best approach to simultaneously fitting spectral energy distributions (SEDs) of millions of galaxies across a wide redshift range to obtain homogeneous estimates of the main physical parameters of detected infrared (IR) galaxies. Methods. We perform SED fitting on the ultraviolet(UV)/near-infrared(NIR) to far-infrared(FIR) emission of 42 047 galaxies from the pilot HELP field: ELAIS N1. To do this we use the latest release of CIGALE, a galaxy SED fitting code relying on energy balance, to deliver the main physical parameters such as stellar mass, star formation rate, and dust luminosity. We implement additional quality criteria to the fits by calculating χ2 values for the stellar and dust part of the spectra independently. These criteria allow us to identify the best fits and to identify peculiar galaxies. We perform the SED fitting of ELAIS N1 galaxies by assuming three different dust attenuation laws separately allowing us to test the impact of the assumed law on estimated physical parameters. Results. We implemented two additional quality value checks for the SED fitting method based on stellar mass estimation and energy budget. This method allows us to identify possible objects with incorrect matching in the catalogue and peculiar galaxies; we found 351 possible candidates of lensed galaxies using two complementary χ2s criteria (stellar and infrared χ2s) and photometric redshifts calculated for the IR part of the spectrum only. We find that the attenuation law has an important impact on the stellar mass estimate (on average leading to disparities of a factor of two). We derive the relation between stellar mass estimates obtained by three different attenuation laws and we find the best recipe for our sample. We also make independent estimates of the total dust luminosity parameter from stellar emission by fitting the galaxies with and without IR data separately.

scholarly journals Physical Parameters of the Visually Close Binary Systems Hip70973 and Hip72479

2012 ◽  
Vol 29 (4) ◽  
pp. 523-528 ◽  
Author(s):  
M. Al-Wardat
Keyword(s):  
Binary Systems ◽  
Spectral Energy Distribution ◽  
Close Binary ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Spectral Energy Distributions ◽  
Combined System ◽  
Energy Distributions ◽  
Close Binary Systems ◽  
The Individual

AbstractAtmospheric modelling of the components of the visually close binary systems Hip70973 and Hip72479 was used to estimate the individual physical parameters of their components. The model atmospheres were constructed using a grid of Kurucz solar metalicity blanketed models and used to compute a synthetic spectral energy distribution for each component separately, and hence for the combined system. The total observational spectral energy distributions of the systems were used as a reference for comparison with the synthetic ones. We used the feedback modified parameters and iteration method to obtain the best fit between synthetic and observational spectral energy distributions. The physical parameters of the components of the system Hip70973 were derived as = 5700 ± 75 K, = 5400 ± 75 K, log ga = 4.50 ± 0.05, log gb = 4.50 ± 0.05, Ra = 0.98 ± 0.07 R⊙, Rb = 0.89 ± 0.07 R⊙, and π = 26.25 ± 1.95 mas, with G4 and G9 spectral types, and those of the system Hip72479 as = 5400 ± 50 K, = 5180 ± 50 K, log ga = 4.50 ± 0.05, log gb = 4.60 ± 0.05, Ra = 0.89 ± 0.07 R⊙, Rb = 0.80 ± 0.07 R⊙, and π = 23.59 ± 1.00 mas, with G9 and K1 spectral types.

scholarly journals Physical properties of the CDFS X-ray sources through fitting spectral energy distributions

2019 ◽  
Vol 492 (2) ◽  
pp. 1887-1901 ◽  
Author(s):  
Xiaotong Guo ◽  
Qiusheng Gu ◽  
Nan Ding ◽  
E Contini ◽  
Yongyun Chen
Keyword(s):  
Star Formation ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Type I ◽  
Type Ii ◽  
Host Galaxies ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
X Ray ◽  
Normal Galaxies

ABSTRACT The physical parameters of galaxies and/or active galactic nucleus (AGNs) can be derived by fitting their multiband spectral energy distributions (SEDs). By using cigale code, we perform multiband SED fitting (from ultraviolet to infrared) for 791 X-ray sources (518 AGNs and 273 normal galaxies) in the 7 Ms Chandra Deep Field-south survey (CDFS). We consider the contributions from AGNs and adopt more accurate redshifts than published before. Therefore, more accurate star formation rates (SFRs) and stellar masses (M*) are derived. We classify the 518 AGNs into type-I and type-II based on their optical spectra and their SEDs. Moreover, six AGN candidates are selected from the 273 normal galaxies based on their SEDs. Our main results are as follows: (1) the host galaxies of AGNs have larger M* than normal galaxies, implying that AGNs prefer to host in massive galaxies; (2) the specific star formation rates (sSFRs) of AGN host galaxies are different from those of normal galaxies, suggesting that AGN feedback may play an important role in the star formation activity; (3) we find that the fraction of optically obscured AGNs in CDFS decreases with the increase of intrinsic X-ray luminosity, which is consistent with previous studies; and (4) the host galaxies of type-I AGNs tend to have lower M* than type-II AGNs, which may suggest that dust in the host galaxy may also contribute to the optical obscuration of AGNs.

scholarly journals The Quasar Continuum

2009 ◽  
Vol 5 (S267) ◽  
pp. 55-64
Author(s):  
Martin Elvis
Keyword(s):  
Continuum Emission ◽  
Spectral Energy ◽  
Scaling Relations ◽  
Physical Parameters ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
X Ray ◽  
Wide Range

AbstractThe powerful compact continuum emission from quasars is understood only in outline. New surveys allow investigation of the quasar continuum over a wide range of parameters (z, L, L/LEdd) and wavelengths (radio to X-ray). I review the spectral energy distributions of quasars and how new scaling relations with physical parameters promise to take us to a deeper understanding of the quasar continuum.

On the Construction of a New 3D Atlas of Stellar Spectral Energy Distributions

2014 ◽  
Vol 23 (3-4) ◽  
Author(s):  
A. V. Mironov ◽  
A. I. Zakharov ◽  
V. G. Moshkalev ◽  
O. Yu. Malkov ◽  
E. Yu. Kilpio
Keyword(s):  
Three Dimensional ◽  
Systematic Errors ◽  
Spectral Energy ◽  
Ultraviolet Region ◽  
Physical Parameters ◽  
Large Set ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Stellar Spectra ◽  
Semi Empirical

AbstractModern spectrophotometric atlases are burdened with significant systematic errors. In particular, the problems of spectrum calibration in the ultraviolet region are not solved; different parts of the spectrum are not thoroughly fit to each other; spectra of (even bright) stars, obtained by different authors, display large discrepancies. Here we discuss a possibility to construct a new atlas of spectral energy distributions (SEDs) for a large set of stars by comparison of empirical stellar spectra in dozens of modern spectrophotometric atlases, as well as the comparison of synthetic and observed color indices in different multicolor photometric systems. In this way we suppose to exclude most of systematic errors and construct a new three-dimensional (spectral class, luminosity class, metallicity) atlas of empirical stellar spectra for several thousand stars. After exclusion of interstellar reddenings, a semi-empirical atlas of average SEDs can be constructed for about 150–200 spectral subtypes. This would allow us to make calibrations of spectrophotometric and photometric parameters in terms of spectral types and physical parameters (

scholarly journals A simple model to interpret the ultraviolet, optical and infrared SEDs of galaxies

2009 ◽  
Vol 5 (S262) ◽  
pp. 81-84
Author(s):  
Elisabete da Cunha ◽  
Stéphane Charlot ◽  
David Elbaz
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Nearby Galaxy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Large Samples ◽  
Wide Range ◽  
Galaxy Sample

AbstractWe present a simple, largely empirical but physically motivated model, which is designed to interpret consistently multi-wavelength observations from large samples of galaxies in terms of physical parameters, such as star formation rate, stellar mass and dust content. Our model is both simple and versatile enough to allow the derivation of statistical constraints on the star formation histories and dust contents of large samples of galaxies using a wide range of ultraviolet, optical and infrared observations. We illustrate this by deriving median-likelihood estimates of a set of physical parameters describing the stellar and dust contents of local star-forming galaxies from the Spitzer Infrared Nearby Galaxy Sample (SINGS) and from a newly-matched sample of SDSS galaxies observed with GALEX, 2MASS, and IRAS. The model reproduces well the observed spectral energy distributions of these galaxies across the entire wavelength range from the far-ultraviolet to the far-infrared. We find important correlations between the physical parameters of galaxies which are useful to investigate the star formation activity and dust properties of galaxies. Our model can be straightforwardly applied to interpret observed ultraviolet-to-infrared spectral energy distributions (SEDs) from any galaxy sample.

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