Emissivity determination from spectral energy brightness distribution from a hot body

1981 ◽  
Vol 34 (3) ◽  
pp. 330-333
Author(s):  
V. N. Snopko
Keyword(s):  
Brightness Distribution ◽  
Spectral Energy ◽  
Energy Brightness

scholarly journals Embedded AGN and star formation in the central 80 pc of IC 3639

2018 ◽  
Vol 611 ◽  
pp. A46 ◽  
Author(s):  
J. A. Fernández-Ontiveros ◽  
K. R. W. Tristram ◽  
S. Hönig ◽  
P. Gandhi ◽  
G. Weigelt
Keyword(s):  
Fine Structure ◽  
Star Formation ◽  
Spatial Scales ◽  
Large Fraction ◽  
Spectral Energy Distribution ◽  
Brightness Distribution ◽  
Continuum Emission ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Ir Emission

Aims. Our goal is to probe the inner structure and the nature of the mid-IR emission in the active galaxy IC 3639, which hosts a Seyfert 2 nucleus and shows signatures of strong star-forming activity. Methods. We used interferometric observations in the N-band with VLTI/MIDI to resolve the mid-IR emission of this nucleus. The origin of the nuclear infrared emission is determined from: (1) the comparison of the correlated fluxes from VLTI/MIDI with the fluxes measured at subarcsecond resolution (VLT/VISIR, VLT/ISAAC); (2) diagnostics based on IR fine-structure line ratios, the IR continuum emission, IR bands produced by polycyclic aromatic hydrocarbons (PAH) and silicates; and (3) the high-angular resolution spectral energy distribution. Results. A large fraction of the total mid-IR emission of IC 3639 is produced in the innermost ≲80 pc with only ~1% of the total luminosity released in the UV/optical range. The unresolved flux of IC 3639 is 90 ± 20 mJy at 10.5 μm, measured with three different baselines in VLTI (UT1–UT2, UT3–UT4, and UT2–UT3; 46–58 m), making this the faintest measurement so far achieved with mid-IR interferometry. The correlated flux is a factor of 3–4 times fainter than the VLT/VISIR total flux measurement. The observations suggest that most of the mid-IR emission has its origin on spatial scales between 10 and 80 pc (40–340 mas). The emission confined within the inner 80 pc is either dominated by a starburst component or by the AGN core. The brightness distribution could be reproduced by a single component associated with the AGN, although this scenario would imply a very extended dust distribution when compared to other nearby Seyfert galaxies detected with MIDI. The extended component could also be associated with polar dust emission, that is, with a dusty wind blown by the AGN. However, a mixed contribution dominated by the star formation component over the AGN is favoured by the diagnostics based on ratios of IR fine-structure emission lines, the shape of the IR continuum, and the PAH and silicate bands. Conclusions. A composite AGN-starburst scenario is able to explain both the mid-IR brightness distribution and the IR spectral properties observed in the nucleus of IC 3639. The nuclear starburst would dominate the mid-IR emission and the ionisation of low-excitation lines (e.g. [Ne II]12.8 μm) with a net contribution of ~70%. The AGN accounts for the remaining ~30% of the mid-IR flux, ascribed to the unresolved component in the MIDI observations, and the ionisation of high-excitation lines (e.g. [Ne V]14.3 μm and [O Iv]25.9 μm).

ANALYSIS OF THE SPECTRAL CHARACTERISTICS OF DESERT LANDSCAPES OF THE NORTH-WESTERN CASPIAN

2020 ◽  
Author(s):  
Valeriy YUFEREV ◽  
Natalya TKACHENKO
Keyword(s):  
Energy Distribution ◽  
Spectral Characteristics ◽  
Thermodynamic Characteristics ◽  
Test Site ◽  
Brightness Distribution ◽  
Distribution Data ◽  
Descurainia Sophia ◽  
The North ◽  
Energy Brightness ◽  
North Western

Studies of the thermodynamic characteristics of semi-desert landscapes were carried out with the PSR-1100 Spectroradiometer in the range from 320 to 1100 nm. Energy distribution data for the parts of the spectrum for plant phytocenosis Poa bulbosa, Descurainia Sophia were obtained from the energy brightness distribution spectrogram at the Tavn-Gashun test site.

Simulated synchrotron emission for the Tycho’s supernova remnants: an asymmetric initial mass model

2020 ◽  
Vol 494 (2) ◽  
pp. 1531-1538
Author(s):  
A Moranchel-Basurto ◽  
P F Velázquez ◽  
G Ares de Parga ◽  
E M Reynoso ◽  
E M Schneiter ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Brightness Distribution ◽  
Radio Continuum ◽  
Initial Mass ◽  
Continuum Emission ◽  
Synchrotron Emission ◽  
Mass Model ◽  
Mhd Simulations ◽  
Tycho’S Snr ◽  
Good Agreement

ABSTRACT We have performed 3D magnetohydrodynamics (MHD) numerical simulations with the aim of exploring the scenario in which the initial mass distribution of a supernova (SN) explosion is anisotropic. The purpose is to analyse if this scenario can also explain the radio-continuum emission and the expansion observed in young supernova remnants (SNRs). To study the expansion, synthetic polarized synchrotron emission maps were computed from the MHD simulations. We found a good agreement (under a number of assumptions) between this expansion study and previous observational results applied to Tycho’s SNR, which represents a good example of asymmetric young SNRs. Additionally, both the observed morphology and the brightness distribution are qualitatively reproduced.

scholarly journals Characterization of M dwarfs using optical mid-resolution spectra for exploration of small exoplanets

2020 ◽  
Author(s):  
Yohei Koizumi ◽  
Masayuki Kuzuhara ◽  
Masashi Omiya ◽  
Teruyuki Hirano ◽  
John Wisniewski ◽  
...  
Keyword(s):  
Sample Selection ◽  
Optical Spectra ◽  
Average Error ◽  
Spectral Energy ◽  
M Dwarfs ◽  
Energy Distributions ◽  
Fitting Procedures ◽  
Optical Region ◽  
Selection For

Abstract We present the optical spectra of 338 nearby M dwarfs, and compute their spectral types, effective temperatures (Teff), and radii. Our spectra were obtained using several optical spectrometers with spectral resolutions that range from 1200 to 10000. As many as 97% of the observed M-type dwarfs have a spectral type of M3–M6, with a typical error of 0.4 subtype, among which the spectral types M4–M5 are the most common. We infer the Teff of our sample by fitting our spectra with theoretical spectra from the PHOENIX model. Our inferred Teff is calibrated with the optical spectra of M dwarfs whose Teff have been well determined with the calibrations that are supported by previous interferometric observations. Our fitting procedures utilize the VO absorption band (7320–7570 Å) and the optical region (5000–8000 Å), yielding typical errors of 128 K (VO band) and 85 K (optical region). We also determine the radii of our sample from their spectral energy distributions. We find most of our sample stars have radii of <0.6 R⊙, with the average error being 3%. Our catalog enables efficient sample selection for exoplanet surveys around nearby M-type dwarfs.

scholarly journals Liquid-Mirror Telescope Surveys

1998 ◽  
Vol 11 (1) ◽  
pp. 464-467
Author(s):  
P. Hickson
Keyword(s):  
Integration Time ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Ccd Cameras ◽  
Photometric Redshifts ◽  
Rotating Liquid ◽  
Liquid Mirrors ◽  
Under Construction ◽  
Optical Telescopes ◽  
Mirror Telescope

Abstract Recent advances in the technology of rotating liquid-mirrors now make feasible the construction of large optical telescopes for dedicated survey programs. Two three-metre-class astronomical telescopes have been built and asix-metre telescope is under construction. These instruments observe in zenith-pointing mode, using drift-scanning CCD cameras to record continuous imaging of a strip of sky typically 20 arcmin wide. This enables them to observe of order 100 square degrees of sky with an integration time of a few minutes per night. Data can be co-added from night to night in order to increase the depth of the survey. Liquid-mirror telescopes are particularly wellsuited to surveys using broad or intermediate bandwidth filters to obtain photometric redshifts and spectral energy distributions for faint galaxies and quasars.

scholarly journals Erratum: ProSpect: generating spectral energy distributions with complex star formation and metallicity histories

2020 ◽  
Vol 500 (3) ◽  
pp. 2859-2860
Author(s):  
A S G Robotham ◽  
S Bellstedt ◽  
C del P Lagos ◽  
J E Thorne ◽  
L J Davies ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions

scholarly journals The Crab nebula variability at short time-scales with the Cherenkov telescope array

2020 ◽  
Vol 501 (1) ◽  
pp. 337-346
Author(s):  
E Mestre ◽  
E de Oña Wilhelmi ◽  
D Khangulyan ◽  
R Zanin ◽  
F Acero ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Telescope Array ◽  
Cherenkov Telescopes ◽  
Cherenkov Telescope ◽  
Emission Models ◽  
Short Time ◽  
The Crab Nebula

ABSTRACT Since 2009, several rapid and bright flares have been observed at high energies (>100 MeV) from the direction of the Crab nebula. Several hypotheses have been put forward to explain this phenomenon, but the origin is still unclear. The detection of counterparts at higher energies with the next generation of Cherenkov telescopes will be determinant to constrain the underlying emission mechanisms. We aim at studying the capability of the Cherenkov Telescope Array (CTA) to explore the physics behind the flares, by performing simulations of the Crab nebula spectral energy distribution, both in flaring and steady state, for different parameters related to the physical conditions in the nebula. In particular, we explore the data recorded by Fermi during two particular flares that occurred in 2011 and 2013. The expected GeV and TeV gamma-ray emission is derived using different radiation models. The resulting emission is convoluted with the CTA response and tested for detection, obtaining an exclusion region for the space of parameters that rule the different flare emission models. Our simulations show different scenarios that may be favourable for achieving the detection of the flares in Crab with CTA, in different regimes of energy. In particular, we find that observations with low sub-100 GeV energy threshold telescopes could provide the most model-constraining results.

scholarly journals The effects of star formation history in the SFR–M* relation of H ii galaxies

2020 ◽  
Vol 500 (3) ◽  
pp. 3240-3253
Author(s):  
Amanda R Lopes ◽  
Eduardo Telles ◽  
Jorge Melnick
Keyword(s):  
Star Formation ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Star Formation History ◽  
Spectral Energy ◽  
Distribution Fitting ◽  
Good Tool ◽  
Star Forming ◽  
Additional Information ◽  
Star Formation Histories

ABSTRACT We discuss the implications of assuming different star formation histories (SFH) in the relation between star formation rate (SFR) and mass derived by the spectral energy distribution fitting (SED). Our analysis focuses on a sample of H ii galaxies, dwarf starburst galaxies spectroscopically selected through their strong narrow emission lines in SDSS DR13 at z < 0.4, cross-matched with photometric catalogues from GALEX, SDSS, UKIDSS, and WISE. We modelled and fitted the SEDs with the code CIGALE adopting different descriptions of SFH. By adding information from different independent studies, we find that H ii galaxies are best described by episodic SFHs including an old (10 Gyr), an intermediate age (100−1000 Myr) and a recent population with ages < 10 Myr. H ii galaxies agree with the SFR−M* relation from local star-forming galaxies, and only lie above such relation when the current SFR is adopted as opposed to the average over the entire SFH. The SFR−M* demonstrated not to be a good tool to provide additional information about the SFH of H ii galaxies, as different SFH present a similar behaviour with a spread of <0.1 dex.

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