scholarly journals Dust size and spatial distributions in debris discs: predictions for exozodiacal dust dragged in from an exo-Kuiper belt

2020 ◽  
Vol 497 (1) ◽  
pp. 1143-1165 ◽  
Author(s):  
Jessica K Rigley ◽  
Mark C Wyatt

ABSTRACT The spectral energy distributions of some nearby stars show mid-infrared (IR) excesses from warm habitable zone dust, known as exozodiacal dust. This dust may originate in collisions in a planetesimal belt before being dragged inwards. This paper presents an analytical model for the size distribution of particles at different radial locations in such a scenario, considering evolution due to destructive collisions and Poynting–Robertson (P–R) drag. Results from more accurate but computationally expensive numerical simulations of this process are used to validate the model and fit its free parameters. The model predicts 11 μm excesses (R11) for discs with a range of dust masses and planetesimal belt radii using realistic grain properties. We show that P–R drag should produce exozodiacal dust levels detectable with the Large Binocular Telescope Interferometer (LBTI) ($R_{11} \gt 0.1{{\ \rm per\ cent}}$) in systems with known outer belts; non-detection may indicate dust depletion, e.g. by an intervening planet. We also find that LBTI could detect exozodiacal dust dragged in from a belt too faint to detect at far-IR wavelengths, with fractional luminosity f ∼ 10−7 and radius ∼10–80 au. Application to systems observed with LBTI shows that P–R drag can likely explain most (5/9) of the exozodiacal dust detections in systems with known outer belts; two systems (β Uma and η Corvi) with bright exozodi may be due to exocomets. We suggest that the three systems with exozodiacal dust detections but no known belt may have cold planetesimal belts too faint to be detectable in the far-IR. Even systems without outer belt detections could have exozodiacal dust levels $R_{11} \gt 0.04{{\ \rm per\ cent}}$ which are problematic for exo-Earth imaging.

2021 ◽  
Vol 21 (10) ◽  
pp. 260
Author(s):  
Cheng Cheng ◽  
Jia-Sheng Huang ◽  
Hai Xu ◽  
Gao-Xiang Jin ◽  
Chuan He ◽  
...  

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.


2008 ◽  
Vol 684 (1) ◽  
pp. 136-152 ◽  
Author(s):  
C. Gruppioni ◽  
F. Pozzi ◽  
M. Polletta ◽  
G. Zamorani ◽  
F. La Franca ◽  
...  

2013 ◽  
Vol 9 (S304) ◽  
pp. 311-314
Author(s):  
Sarah C. Gallagher ◽  
Mathew M. Abado ◽  
John E. Everett

AbstractMass ejection in the form of winds or jets appears to be as fundamental to quasar activity as accretion. A convincing argument for radiation pressure driving this ionized outflow can be made within the dust sublimation radius. Beyond, radiation pressure is even more ubiquitous, as high energy photons from the central engine can now push on dust grains. This physics underlies the dusty-wind model for the putative obscuring torus. Specifically, the dusty wind in our model is first launched from the outer accretion disk as a magneto-centrifugal wind and then accelerated and shaped by radiation pressure from the central continuum. Such a wind can plausibly account for both the necessary obscuring medium to explain the observed ratio of broad-to-narrow-line quasars and the mid-infrared emission commonly seen in quasar spectral energy distributions.


2014 ◽  
Vol 212 (2) ◽  
pp. 18 ◽  
Author(s):  
Michael J. I. Brown ◽  
John Moustakas ◽  
J.-D. T. Smith ◽  
Elisabete da Cunha ◽  
T. H. Jarrett ◽  
...  

2011 ◽  
Vol 7 (S279) ◽  
pp. 401-402
Author(s):  
Tamás Szalai ◽  
József Vinkó

AbstractWe present detailed analysis of mid-infrared (MIR) data for 9 type II-P supernovae from the public Spitzer database. Spectral energy distributions (SEDs) from observed fluxes are fitted with simple models to get basic information about the dust as the presumed source of MIR radiation. We found two SNe, 2005ad and 2005af, which likely have newly-formed dust in their environment, while in the other seven cases the observed MIR flux may originate from pre-existing circumstellar or interstellar dust.


2020 ◽  
Vol 635 ◽  
pp. A33 ◽  
Author(s):  
M. A. T. Groenewegen

Spectral energy distributions (SEDs) were constructed for a sample of 477 classical Cepheids (CCs); including stars that have been classified in the literature as such but are probably not. The SEDs were fitted with a dust radiative transfer code. Four stars showed a large mid- or far-infrared excess and the fitting then included a dust component. These comprise the well-known case of RS Pup, and three stars that are (likely) Type-II Cepheids (T2Cs), AU Peg, QQ Per, and FQ Lac. The infrared excess in FQ Lac is reported for the first time in this work. The remainder of the sample was fitted with a stellar photosphere to derive the best-fitting luminosity and effective temperature. Distance and reddening were taken from the literature. The stars were plotted in a Hertzsprung-Russell diagram (HRD) and compared to evolutionary tracks for Cepheids and theoretical instability strips. For the large majority of stars, the position in the HRD is consistent with the instability strip for a CC or T2C. About 5% of the stars are outliers in the sense that they are much hotter or cooler than expected. A comparison to effective temperatures derived from spectroscopy suggests in some cases that the photometrically derived temperature is not correct and that this is likely linked to an incorrectly adopted reddening. Two three-dimensional reddening models have been used to derive alternative estimates of the reddening for the sample. There are significant systematic differences between the two estimates with a non-negligible scatter. In this work the presence of a small near-infrared (NIR) excess, as has been proposed in the literature for a few well-known Cepheids, is investigated. Firstly, this was done by using a sample of about a dozen stars for which a mid-infrared spectrum is available. This data is particularly constraining as the shape of the observed spectrum should match that of the photosphere and any dust spectrum, both dust continuum and any spectral features of, for example, silicates or aluminium oxide. This comparison provides constraints on the dust composition, in agreement with a previous work in the literature. Secondly, the SEDs of all stars were fitted with a dust model to see if a statistically significant better fit could be obtained. The results were compared to recent work. Eight new candidates for exhibiting a NIR excess are proposed, solely based on the photometric SEDs. Obtaining mid-infrared spectra would be needed to confirm this excess. Finally, period-bolometric luminosity and period-radius relations are presented for samples of over 370 fundamental-mode CCs.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
K. Wagner ◽  
A. Boehle ◽  
P. Pathak ◽  
M. Kasper ◽  
R. Arsenault ◽  
...  

AbstractGiant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, α Centauri. Based on 75–80% of the best quality images from 100 h of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of α Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around α Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes.


2009 ◽  
Vol 5 (S267) ◽  
pp. 132-132
Author(s):  
C. Ramos Almeida ◽  
N. A. Levenson ◽  
J. M. Rodríguez Espinosa ◽  
A. Alonso Herrero ◽  
A. Asensio Ramos ◽  
...  

We present subarcsecond resolution mid-infrared (mid-IR) photometry in the range from 8 to 20 μm of 18 nearby Seyfert galaxies, reporting high spatial resolution nuclear fluxes for the entire sample (see Table 3 of Ramos Almeida et al. 2009). We construct spectral energy distributions (SEDs) that the AGN dominates, relatively uncontaminated by starlight, adding near-IR measurements from the literature at similar angular resolution. We find that the IR SEDs of intermediate-type Seyferts are flatter and present higher 10 to 18 μm ratios than those of Seyfert 2 (Sy2) galaxies.


2021 ◽  
Vol 912 (2) ◽  
pp. 161
Author(s):  
J.-S. Huang ◽  
Y.-S. Dai ◽  
S. P. Willner ◽  
S. M. Faber ◽  
C. Cheng ◽  
...  

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