The dusty environment of HD 97300 as seen by Herschel and Spitzer^⋆

¹ Research and Scientific Support Department, European Space Agency (ESA-ESTEC, SRE-SA), PO Box 299, 2200 AG Noordwijk, The Netherlands
e-mail: akospal@rssd.esa.int
² Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
³ Laboratoire AIM Paris – Saclay, CEA/DSM – CNRS – Université Paris Diderot, IRFU, Service d’Astrophysique, Centre d’Études de Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France
⁴ Herschel Science Centre, ESA-ESAC, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain

Received: 15 January 2012
Accepted: 2 March 2012

Abstract

Aims. We analyze the surroundings of HD 97300, one of two intermediate-mass stars in the Chamaeleon I star-forming region. The star is known to be surrounded by a conspicuous ring of polycyclic aromatic hydrocarbons (PAHs).

Methods. We present infrared images taken with Herschel and Spitzer using 11 different broad-band filters between 3.6   μm and 500   μm. We compare the morphology of the emission using cuts along different position angles. We construct spectral energy distributions, which we compare to different dust models, and calculate dust temperatures. We also derive opacity maps and analyze the density structure of the environment of HD 97300.

Results. We find that HD 97300 has no infrared excess at or below 24   μm, confirming its zero-age main-sequence nature. The morphology of the ring is very similar between 3.6   μm and 24   μm. The emission at these wavelengths is dominated by either PAH features or PAH continuum. At longer wavelengths, only the northwestern part of the ring is visible. A fit to the 100–500   μm observations suggests that the emission is due to relatively warm ( ≈ 26 K) dust. The temperature gradually decreases with increasing distance from the ring. We find a general decrease in the density from north to south, and an approximate 10% density increase in the northeastern part of the ring.

Conclusions. Our results are consistent with the theory that the ring around HD 97300 is essentially a bubble blown into the surrounding interstellar matter and heated by the star.