2018A&A...612A..15T


Query : 2018A&A...612A..15T

2018A&A...612A..15T - Astronomy and Astrophysics, volume 612A, 15-15 (2018/4-1)

The spatial extent of polycyclic aromatic hydrocarbons emission in the Herbig star HD 179218.

TAHA A.S., LABADIE L., PANTIN E., MATTER A., ALVAREZ C., ESQUEJ P., GRELLMANN R., REBOLO R., TELESCO C. and WOLF S.

Abstract (from CDS):

Aim. We investigate, in the mid-infrared, the spatial properties of the polycyclic aromatic hydrocarbons (PAHs) emission in the disk of HD 179218, an intermediate-mass Herbig star at ∼300pc.
Methods. We obtained mid-infrared images in the PAH-1, PAH-2 and Si-6 filters centered at 8.6, 11.3, and 12.5µm, and N-band low-resolution spectra using CanariCam on the 10-m Gran Telescopio Canarias (GTC). We compared the point spread function (PSF) profiles measured in the PAH filters to the profile derived in the Si-6 filter, where the thermal continuum emission dominates. We performed radiative transfer modeling of the spectral energy distribution (SED) and produced synthetic images in the three filters to investigate different spatial scenarios.
Results. Our data show that the disk emission is spatially resolved in the PAH-1 and PAH-2 filters, while unresolved in the Si-6 filter. Thanks to very good observing conditions, an average full width at half maximum (FWHM) of 0.232'', 0.280'' and 0.293'' is measured in the three filters, respectively. Gaussian disk fitting and quadratic subtraction of the science and calibrator PSFs suggests a lower-limit characteristic angular diameter of the emission of ∼100mas, or ∼30au. The photometric and spectroscopic results are compatible with previous findings. Our radiative transfer (RT) modeling of the continuum suggests that the resolved emission should result from PAH molecules on the disk atmosphere being UV-excited by the central star. Simple geometrical models of the PAH component compared to the underlying continuum point to a PAH emission uniformly extended out to the physical limits of the disk model. Furthermore, our RT best model of the continuum requires a negative exponent of the surface density power-law, in contrast with earlier modeling pointing to a positive exponent.
Conclusions. We have spatially resolved - for the first time to our knowledge - the PAHs emission in the disk of HD 179218 and set constraints on its spatial extent. Based on spatial and spectroscopic considerations as well as on qualitative comparison with IRS 48 and HD 97048, we favor a scenario in which PAHs extend out to large radii across the flared disk surface and are at the same time predominantly in an ionized charge state due to the strong UV radiation field of the 180L central star.

Abstract Copyright: © ESO 2018

Journal keyword(s): protoplanetary disks - radiation mechanisms: non-thermal - stars: variables: T Tauri, Herbig Ae/Be

Simbad objects: 13

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Number of rows : 13
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 V* AB Aur Ae* 04 55 45.8458932216 +30 33 04.292077032 7.20 7.16 7.05 6.96 6.70 A0Ve 1067 2
2 V* HR Leo EB* 11 04 42.2950937784 -02 58 19.978097484   9.35 8.943     F2V 20 0
3 HD 97048 Ae* 11 08 03.3109731720 -77 39 17.490777444 9.03 8.76 9.00   8.64 A0Vep 543 0
4 HD 100546 Be* 11 33 25.4408872296 -70 11 41.241297948   6.71 6.30   6.64 A0VaekB8_lB 806 1
5 HD 135344 * 15 15 48.9462675744 -37 08 55.731368400   7.84 7.76     A0V 143 1
6 HD 139614 Ae? 15 40 46.3820275416 -42 29 53.538761832   8.47 8.24     A9VekA5mA5(_lB) 209 0
7 IRAS 16245-2423 TT* 16 27 37.1906433768 -24 30 35.025246828       16.66 14.67 B5-F2 307 0
8 * 109 Her ** 18 23 41.8897062084 +21 46 11.109609046 6.18 5.02 3.84 2.99 2.39 K2IIIab 178 0
9 HD 169142 Ae* 18 24 29.7799891464 -29 46 49.327400568   8.42 8.16     F1VekA3mA3_lB? 448 0
10 EM* MWC 297 Ae* 18 27 39.5265500160 -03 49 52.133050776 15.57 14.34 12.31 11.34   B1.5Ve 297 0
11 HD 178219 * 19 08 03.4968731544 -08 44 54.012901632   9.80 9.66     B9III 4 0
12 HD 179218 Ae* 19 11 11.2538919456 +15 47 15.636008472 7.55 7.476 7.39 7.25 7.21 A0Ve 255 0
13 * alf Aql dS* 19 50 46.99855 +08 52 05.9563 1.07 0.98 0.76 0.62 0.49 A7Vn 875 1

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