B. Daly

University of Maryland, College Park, College Park, MD, United States

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Publications (3)5.99 Total impact

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    ABSTRACT: PDS 144 is a pair of Herbig Ae stars that are separated by 535 on the sky. It has previously been shown to have an A2Ve Herbig Ae star viewed at 83° inclination as its northern member and an A5Ve Herbig Ae star as its southern member. Direct imagery revealed a disk occulting PDS 144 N—the first edge-on disk observed around a Herbig Ae star. The lack of an obvious disk in direct imagery suggested PDS 144 S might be viewed face-on or not physically associated with PDS 144 N. Multi-epoch Hubble Space Telescope imagery of PDS 144 with a 5 year baseline demonstrates PDS 144 N & S are comoving and have a common proper motion with TYC 6782-878-1. TYC 6782-878-1 has previously been identified as a member of Upper Sco sub-association A at d = 145 ± 2 pc with an age of 5-10 Myr. Ground-based imagery reveals jets and a string of Herbig-Haro knots extending 13' (possibly further) which are aligned to within 7° ± 6° on the sky. By combining proper motion data and the absence of a dark mid-plane with radial velocity data, we measure the inclination of PDS 144 S to be i = 73° ± 7°. The radial velocity of the jets from PDS 144 N & S indicates they, and therefore their disks, are misaligned by 25° ± 9°. This degree of misalignment is similar to that seen in T Tauri wide binaries.
    Full-text · Article · Dec 2011 · The Astrophysical Journal
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    ABSTRACT: We present the results of an on-going pan-chromatic investigation of PDS 144, which has an A0V Herbig Ae star viewed at 83° inclination as its northern member (Perrin et al. 2006), and an A5V southern member. While the northern star clearly showed a disk in HST and Keck direct imagery, no such disk was apparent for PDS 144S, despite the presence of an IR excess. Recent USNO proper motion data suggested that the stars were not co-moving. We test this hypothesis with second-epoch HST/ACS optical imagery, and detect the disk of PDS 144S in the optical and UV after PSF subtraction. We also place limits on the X-ray properties of both PDS 144 stars with Chandra ACIS/S imagery.
    No preview · Conference Paper · Aug 2010
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    ABSTRACT: Photoelectric neutral Hydrogen absorption, N(H), is a probe of the gas and dust column towards the star. Kastner et al. (2005) found a correlation between N(H) and proplyd aspect ratio in the Orion nebula cluster. We extend this study to Taurus-Auriga by combining publicly available N(H) data from the XMM-Newton Extended Survey of the Taurus molecular cloud (XEST), with published disk inclination data obtained from HST coronagraphic imagery and mm interferometry. Additional inclinations were derived from jet proper motion and radial velocity data obtained from archival HST imagery and the Apache Point Observatory 3.5m telescope's Goddard Fabry-Perot and DIS long-slit spectrograph. Both N(H) and extinction have linear relations with system inclination, where the extinction has a smaller slope than the N(H) trend. Correlations with system inclination demonstrate that the bulk of both N(H) and extinction arise in the disk rather than in remnant envelopes, nearby molecular cloud material, or foreground material. The deficit in extinction compared with predictions for ISM-like gas to dust ratios is consistent with grain growth and settling toward the disk midplane and stratification in disks occurring by 2 Myr. However, the disks remain gas-rich, indicating that giant planet formation is still feasible.
    No preview · Conference Paper · Jan 2010