A sub-millimeter Mapping Survey of Herbig AeBe Stars

TL;DR

This study presents sub-millimeter observations of Herbig Ae/Be stars, revealing disk properties, dust grain sizes, and evolutionary differences across spectral types, with implications for planet formation.

Contribution

First comprehensive sub-millimeter survey of Herbig Ae/Be stars, linking disk characteristics to stellar types and dust grain evolution.

Findings

Disks are less common around B-type stars, indicating shorter dissipation times.

Low beta values correlate with large grain sizes and low disk masses.

Some disks show very flat SEDs, possibly indicating planet formation stages.

Abstract

We have acquired sub-millimeter observations of 33 fields containing 37 Herbig Ae/Be (HAEBE) stars or potential HAEBE stars, including SCUBA maps of all but two of these stars. Nine target stars show extended dust emission. The other 18 are unresolved, suggesting that the dust envelopes or disks around these stars are less than a few arcseconds in angular size. In several cases we find that the strongest sub-millimeter emission originates from younger, heavily embedded sources rather than from the HAEBE star, which means that previous models must be viewed with caution. These new data, in combination with far-infrared flux measurements available in the literature, yield SEDs from far-infrared to millimeter wavelengths for all the observed objects. Isothermal fits to these SEDs demonstrate excellent fits, in most cases, to the flux densities longward of 100 {\mu}m. We find that a smaller proportion of B-type stars than A and F-type stars are surrounded by circumstellar disks, suggesting that disks around B stars dissipate on shorter time scales than those around later spectral types. Our models also reveal that the mass of the circumstellar material and the value of beta are correlated, with low masses corresponding to low values of beta. Since low values of beta imply large grain sizes, our results suggest that a large fraction of the mass in low-beta sources is locked up in very large grains. Several of the isolated HAEBE stars have disks with very flat sub-millimeter SEDs. These disks may be on the verge of forming planetary systems.