scholarly journals Spectral Energy Density in an Axisymmetric Galaxy as Predicted by an Analytical Model for the Maxwell Field

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Mayeul Arminjon
Keyword(s):  
Spatial Variation ◽  
Analytical Model ◽  
Present Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Energy Distributions ◽  
The Galaxy ◽  
Theory Of Gravitation ◽  
Future Work ◽  
Radiation Transfer Model

An analytical model for the Maxwell radiation field in an axisymmetric galaxy, proposed previously, is first checked for its predictions of the spatial variation of the spectral energy distributions (SEDs) in our Galaxy. First, the model is summarized. It is now shown how to compute the SED with this model. Then the model is adjusted by asking that the SED predicted at our local position in the Galaxy coincides with the available observations. Finally, the first predictions of the model for the spatial variation of the SED in the Galaxy are compared with those of a radiation transfer model. We find that the two predictions do not differ too much. This indicates that, in a future work, it should be possible with the present model to check if the “interaction energy” predicted by an alternative, scalar theory of gravitation, contributes to the dark matter.

scholarly journals Probing the opacity of local Universe GAMA galaxies using attenuation-inclination relations

2011 ◽  
Vol 7 (S284) ◽  
pp. 312-314
Author(s):  
Ellen Andrae ◽  
Richard J. Tuffs ◽  
Cristina C. Popescu ◽  
Mark Seibert ◽  
Keyword(s):  
Spiral Galaxies ◽  
Spectral Energy ◽  
Transfer Model ◽  
Energy Distributions ◽  
Local Universe ◽  
Infrared Measurements ◽  
The Galaxy ◽  
The Mean ◽  
Mass Assembly ◽  
Radiation Transfer Model

AbstractEven though attenuation by dust strongly attenuates and reddens the UV/optical spectral energy distributions of spiral galaxies, quantifying these effects is challenging, particularly when, as is most often the case, infrared measurements of the absorbed energy are not available. We have initiated a study to model the dependence on inclination of the attenuation of light from galaxies measured in the Galaxy and Mass Assembly (GAMA) survey. We present preliminary results using SDSS galaxies in the phase-I GAMA catalogue, comparing observed attenuation-inclination relations with the predictions of the radiation transfer model of Popescu et al. (2011) to derive a statistical measurement of the mean face-on B-band optical depth of disks τfB in a sample of spiral galaxies complete to the SDSS spectroscopic r-band limit of 17.8 mag.

scholarly journals Molecular Envelopes of Planetary Nebulae and Proto-Planetary Nebulae

1994 ◽  
Vol 140 ◽  
pp. 152-153
Author(s):  
Sun Kwok
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
High Rate ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Energy Distributions ◽  
Cool Component ◽  
Dust Envelope ◽  
Peak Energy

As stars evolve up the asymptotic giant branch (AGB), they begin to lose mass at a high rate, and in the process they create extended circumstellar molecular envelopes. Since the transition from AGB to planetary nebula stages is of the order of 1000 yr, the remnant of such molecular envelopes should still be observable in pro to-planetary nebulae (PPN) and planetary nebulae (PN). Recent ground-based survey of cool IRAS sources have discovered ~30 candidates of PPN (Kwok 1992). These sources show the characteristic “double-peak” energy distribution. The cool component is due to the remnant of the AGB dust envelope, and the hot component represents the reddened photosphere. The fact that the two components are clearly separated suggests that the dust envelope is well detached from the photosphere. Radiative transfer model fits to the spectral energy distributions of PPN suggest a typical separation of ~1 arc sec between the dust envelope and the photosphere, and such “hole-in-the-middle” structure can be mapped by millimeter interferometry in CO.

scholarly journals Spectral energy distribution similarity of the local galaxies and the 3.6 μm selected galaxies from the Spitzer Extended Deep Survey

2021 ◽  
Vol 21 (10) ◽  
pp. 260
Author(s):  
Cheng Cheng ◽  
Jia-Sheng Huang ◽  
Hai Xu ◽  
Gao-Xiang Jin ◽  
Chuan He ◽  
...  
Keyword(s):  
High Redshift ◽  
Spectral Energy Distribution ◽  
Mass Function ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Mid Infrared ◽  
Redshift Galaxy ◽  
The Galaxy ◽  
Deep Survey ◽  
Multi Wavelength

Abstract The Spitzer Extended Deep Survey (SEDS) as a deep and wide mid-infrared (MIR) survey project provides a sample of 500 000+ sources spreading 1.46 square degree and a depth of 26 AB mag (3σ). Combining with the previous available data, we build a PSF-matched multi-wavelength photometry catalog from u band to 8 μm. We fit the SEDS galaxies spectral energy distributions by the local galaxy templates. The results show that the SEDS galaxy can be fitted well, indicating the high redshift galaxy (z ∼ 1) shares the same templates with the local galaxies. This study would facilitate the further study of the galaxy luminosity and high redshift mass function.

scholarly journals SuperMassive Blackholes grow from stellar BHs of star formation history?

2015 ◽  
Vol 11 (S319) ◽  
pp. 64-65
Author(s):  
Brigitte Rocca-Volmerange
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Star Formation History ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Formation History ◽  
The Galaxy ◽  
Black Hole Masses ◽  
Early Type Galaxy ◽  
Size Scales

AbstractThe origin of the supermassive black hole masses MSMBH discovered at the highest redshifts is still actively debated. Moreover the statistically significant relation of MSMBH with bulge luminosities LV, extended on several magnitude orders, confirms a common physical process linking small (≤ 1pc) to large (kpcs) size scales. The Spectral Energy Distributions (SEDs) of two z=3.8 radio galaxies 4C41.17 and TN J2007-1316, best-fitted by evolved early type galaxy and starburst scenarios also imply masses of stellar remnants. Computed with the evolutionary code Pegase.3, the cumulated stellar black hole mass MsBH reach up to several 109M⊙, similar to MSMBH at same z. We propose the SMBH growth is due to the migration of the stellar dense residues (sBH) towards the galaxy core by dynamical friction. Discussed in terms of time-scales, this process which is linking AGN and star formation, also fully justifies the famous relation MSMBH-LV.

scholarly journals Radiative transfer model of the dust structures of CRL 2688

2011 ◽  
Vol 7 (S283) ◽  
pp. 520-521
Author(s):  
Dejan Vinković ◽  
Bruce Balick
Keyword(s):  
Energy Distribution ◽  
Radiation Transfer ◽  
Spectral Energy Distribution ◽  
Polar Axis ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Giant Star ◽  
Basic Features ◽  
Radiation Transfer Model

AbstractNew Hubble images of the reflection nebula CRL 2688 from 0.6 to 1.6μm reveal significant variations of color and opacity in the distribution of scattered starlight. We have constructed a detailed radiation-transfer model consisting principally of an optically thick equatorial disk-like structure; bipolar lobes with density enhancements along the polar axis and at the base of lobes; an optically thin extended envelope containing spherical density-enhanced shells to mimic the outer rings of CRL 2688; and a pair of near-stellar caps that collimate and redden the dispersing starlight near its source. Our model nicely reproduces all of the basic features detected in the HST images, including the famous searchlights and arcs, as well as the measured spectral energy distribution (“SED”) of CRL 2688. Assuming a distance of 420 pc we estimate the light originates in a giant star with a temperature T ~ 7000 K and a luminosity L = 5500 ± 1100 L⊙.

scholarly journals Longslit Optical Spectroscopy of Powerful Far-Infrared Galaxies

1989 ◽  
Vol 134 ◽  
pp. 414-415
Author(s):  
Lee Armus ◽  
Timothy M. Heckman ◽  
George K. Miley
Keyword(s):  
Direct Evidence ◽  
Thermal Emission ◽  
Large Range ◽  
Far Infrared ◽  
Spectral Energy ◽  
Infrared Galaxies ◽  
Energy Distributions ◽  
Hii Region ◽  
The Galaxy ◽  
Infrared Spectral

It has been known since the IRAS mission that there exist galaxies with far-infrared luminosities of 1011–1012Lo, and LFTR/LB = 10–100. Through extensive modelling and observations of HII-region/molecular cloud complexes in the Galaxy, this infrared radiation is believed to be thermal emission from heated dust grains (c.f. review by Stein and Soifer 1983). While starburst models are consistent with the data over a large range in wavelength, direct evidence for sizeable populations of young stars is scarce, and in many cases the presence of an active nucleus either cannot be ruled out, or is required on the basis of energy considerations. In order to better understand the energy source responsible for heating the dust, we have undertaken a spectroscopic survey of galaxies chosen to have far-infrared spectral energy distributions similar to the prototypical class members Arp 220, NGC 6240, NGC 3690, and Mrk 231. It was required that between 25μ and 60μ, α ≤ −1.5, and that between 60μ and 100μ, α ≥ −0.5, where Sv α vα.

scholarly journals The evolutionary nature of RV Tauri stars in the SMC and LMC

2018 ◽  
Vol 618 ◽  
pp. A21 ◽  
Author(s):  
Rajeev Manick ◽  
Hans Van Winckel ◽  
Devika Kamath ◽  
Sanjay Sekaran ◽  
Katrien Kolenberg
Keyword(s):  
Time Series ◽  
Systematic Study ◽  
Orbital Motion ◽  
Circumstellar Dust ◽  
Spectral Energy ◽  
Agb Stars ◽  
Energy Distributions ◽  
The Galaxy ◽  
Red Giant ◽  
Lower Luminosity

Context. Based on their stellar parameters and the presence of a mid-IR excess due to circumstellar dust, RV Tauri stars have been classified as post-AGB stars. Our recent studies, however, reveal diverse spectral energy distributions (SEDs) among RV Tauri stars, suggesting they may occupy other evolutionary channels as well. Aims. The aim of this paper is to present the diverse SED characteristics of RV Tauri stars and investigate their evolutionary nature as a function of their SEDs. Methods. We carried out a systematic study of RV Tauri stars in the SMC and LMC because of their known distances and hence luminosities. Their SEDs were classified into three groups: dusty (disc-type), non-dusty (non-IR), and uncertain. A period-luminosity-colour (PLC) relation was calibrated. The luminosities from the PLC were complemented with those found using their SEDs and the stars were placed on a Hertzsprung-Russell diagram (HRD). I-band time series were used to search for period changes via (O−C) analyses to identify period changes. Results. The four main results from this study are: (1) RV Tauri stars with a clear IR excess have disc-type SEDs, which indicates that the dust is trapped in a stable disc. Given the strong link between disc-type SEDs and binarity in the Galaxy, we postulate that these are binaries as well. These cover a range of luminosities and we argue that the more luminous binaries are post-AGB stars while the lower luminosity binaries are likely post-red giant branch (post-RGB) stars. (2) Two of these objects have variable mean brightness with periods of 916 and 850 days, respectively, caused by variable extinction during orbital motion. (3) Non-dusty RV Tauri stars and objects with an uncertain SED evolve such that the circumstellar dust has dispersed. If they are single stars, they are post-AGB objects of low initial mass (<1.25 M⊙), while if they are binaries, the low-luminosity portion of the sample are likely post-RGB stars. (4) We find that RV Tauri stars with dust are on average more luminous than the rest of the sample.

scholarly journals Infrared properties of ultracompact H II regions in the Galaxy and the LMC

2006 ◽  
Vol 2 (S237) ◽  
pp. 472-472
Author(s):  
Marta Sewiło ◽  
Ed Churchwell ◽  
Barbara Whitney ◽  
Keyword(s):  
Massive Star ◽  
Large Magellanic Cloud ◽  
Spectral Energy ◽  
Stellar Winds ◽  
H Ii Regions ◽  
Energy Distributions ◽  
Protostellar Jets ◽  
The Galaxy ◽  
Bow Shocks ◽  
Star Formation Regions

AbstractWe report the preliminary results of the study on the infrared properties of ultracompact (UC) H II regions in our Galaxy and in the Large Magellanic Cloud (LMC) based on the GLIMPSE (the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) and SAGE (Surveying the Agents of a Galaxy's Evolution) data, respectively. We found that ~60% of the Galactic UC H II regions do not have IR counterparts. Large extinction and very strong stellar winds evacuating H II regions from dust may explain this result. The same effect is observed in the LMC. One of the goals of this research is to develop a means of identifying UC H IIs based on their mid-IR properties, e.g. positions on color-color and color-magnitude plots and/or shape of spectral energy distributions. GLIMPSE showed that bow shocks, protostellar jets/outflows, and bubbles are common phenomena in massive star formation regions (MSFRs).

BAaDE: The Bulge Asymmetries and Dynamical Evolution survey

2019 ◽  
Vol 14 (S353) ◽  
pp. 45-46
Author(s):  
Loránt O. Sjouwerman ◽  
Ylva M. Pihlström ◽  
Michael C. Stroh ◽  
Megan O. Lewis ◽  
Mark J Claussen ◽  
...  
Keyword(s):  
Dynamical Evolution ◽  
High Rate ◽  
Spectral Energy ◽  
Dynamical Structure ◽  
Energy Distributions ◽  
Evolved Stars ◽  
The Galaxy ◽  
Maser Line ◽  
Infrared Spectral ◽  
Infrared Sources

AbstractThe Bulge Asymmetries and Dynamical Evolution (BAaDE) survey aims to use circumstellar SiO maser line-of-sight velocities as probes for the Galactic gravitational potential and dynamical structure. The SiO masers are detected at a high rate in specific color-selected MSX infrared sources. Furthermore, the SiO maser properties and line ratios, in combination with infrared spectral energy distributions and location in the Galaxy, will statistically yield detailed information on population and evolution of low- to intermediate-mass evolved stars in the Galaxy.

scholarly journals The XXL Survey

2020 ◽  
Vol 638 ◽  
pp. A45
Author(s):  
V. A. Masoura ◽  
I. Georgantopoulos ◽  
G. Mountrichas ◽  
C. Vignali ◽  
E. Koulouridis ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Selection Criteria ◽  
Galactic Nuclei ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Energy Distributions ◽  
X Ray ◽  
Spectral Fitting ◽  
The Galaxy ◽  
X Ray Absorption

The combination of optical and mid-infrared (MIR) photometry has been extensively used to select red active galactic nuclei (AGNs). Our aim is to explore the obscuration properties of these red AGNs with both X-ray spectroscopy and spectral energy distributions (SEDs). In this study, we re-visit the relation between optical/MIR extinction and X-ray absorption. We use IR selection criteria, specifically the W1 and W2 WISE bands, to identify 4798 AGNs in the XMM-XXL area (∼25 deg2). Application of optical/MIR colours (r−W2 >  6) reveals 561 red AGNs (14%). Of these, 47 have available X-ray spectra with at least 50 net (background-subtracted) counts per detector. For these sources, we construct SEDs from the optical to the MIR using the CIGALE code. The SED fitting shows that 44 of these latter 47 sources present clear signs of obscuration based on the AGN emission and the estimated inclination angle. Fitting the SED also reveals ten systems (∼20%) which are dominated by the galaxy. In these cases, the red colours are attributed to the host galaxy rather than AGN absorption. Excluding these ten systems from our sample and applying X-ray spectral fitting analysis shows that up to 76% (28/37) of the IR red AGNs present signs of X-ray absorption. Thus, there are nine sources (∼20% of the sample) that although optically red, are not substantially X-ray absorbed. Approximately 50% of these sources present broad emission lines in their optical spectra. We suggest that the reason for this apparent discrepancy is that the r−W2 criterion is sensitive to smaller amounts of obscuration relative to the X-ray spectroscopy. In conclusion, it appears that the majority of red AGNs present considerable obscuration levels as shown by their SEDs. Their X-ray absorption is moderate with a mean of NH ∼ 1022 cm−2.

Sign in / Sign up

Export Citation Format

Share Document