1 / 13

Spitzer IRS spectra of PAH emission from Herbig Ae/Be stars

Spitzer IRS spectra of PAH emission from Herbig Ae/Be stars. Eric Leibensperger (Ithaca College, Ithaca, NY) And Luke Keller (Advisor) In collaboration with the Spitzer IRS Disks Team:.

archie
Download Presentation

Spitzer IRS spectra of PAH emission from Herbig Ae/Be stars

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Spitzer IRS spectra of PAH emission from Herbig Ae/Be stars Eric Leibensperger (Ithaca College, Ithaca, NY) And Luke Keller (Advisor) In collaboration with the Spitzer IRS Disks Team: G.C. Sloan (Cornell University), W.J. Forrest (University of Rochester), A. Li (University of Missouri-Columbia), J. Najita (NOAO), D.M. Watson (University of Rochester), C.H. Chen (NOAO), J.D. Green (University of Rochester), F. Kemper (University of Virginia), L. Hartmann (CfA), T.L. Herter (Cornell University), P. D'Alessio (UNAM), B. Sargent (University of Rochester), P. W. Morris (IPAC/CalTech), D.J. Barry (Cornell University), P. Hall (Cornell University), B.R. Brandl (Sterrewacht Leiden), P.C. Myers (CfA), and J.R. Houck (Cornell University)

  2. H H H H H H H H H H H H Our love-hate relationship with Polycyclic Aromatic Hydrocarbons… • What can the PAHs tell us about AeBe stars • and their disks? • Physical structure of the disks: e.g. PAH primarily from far out (~100 AU) in a flared disk • Physical properties of the emission regions • ionization fraction (radiation field and e- density), gas temperature, not to mention chemical properties • Dust grain processing and evolution

  3. Herbig Ae/Be stars • Intermediate mass (2-8 M) • Main sequence stars of spectral type B, A, F • Broad line emission in optical-IR • IR excess due to thermal emission from dust • No requirement for association with nebulosity Current sample: 4 of 16 Ae/Be stars in IRS Disks program These four stars have “clean” PAH spectra: no other solid state features in their 5-14 mm spectra

  4. The Spitzer Space Telescope • Background-limited sensitivity 3 – 180 m • 85 cm f/12 beryllium R-C telescope, T < 5.5K • Three scientific instruments provide: • Imaging/photometry, 3-180 m • Spectroscopy, 5-40 m (R = 90 & 600) • Spectrophotometry, 50-100 m • 5.5 yr lifetime • Launched on 25 August 2003 • Birth stone: forsterite

  5. IRS SL IRS SL IRS SL IRS SL Physical structure of the disks: SEDs (UV-mm) LL LL LL LL (Malfait et al. 1998)

  6. H H H H H H H H H H H H 6.2 mm C-C stretch “skeletal modes” 11.3, 12.0, & 12.7 mm C-H out-of-plane bend Polycyclic Aromatic Hydrocarbons 7.7-7.9 mm C-C stretch 8.6 mm C-H in-plane bend (coronene) Sloan et al. 2005 (submitted to ApJ)

  7. Measuring PAH feature strengths and their ratios • Simple line segment achors • Model independent • Error bars: s of mean of two • telescope nods HD 141569

  8. PAH ionization: • Ionization correlates with • F7.9/F11.3

  9. C-C stretch C-H bend Lab data showing spectral signature of PAH ionization: (From Peeters et al. 2002 & Allamandola et al. 1999)

  10. ISM (more processed)AeBe, PnePost AGB (less processed) IRAS 03260+3111 (YSO in MC, PAH Class A) HD 44179 (Post AGB star “Red Rectangle” PAH Class B) AFGL 2688 (Post AGB star “Cygnus Egg” PAH Class C) HD 100546 (Isolated Ae/Be star, PAH Class B) Figure from Sloan et al. 2005 (adapted from Peeters et al. 2002)

  11. HD 135344 (F4),169142 (A5),34282 (A0),141569 (A0) Foutlier/F11.3 F6.2/F7.9 F12.7/F11.3 F7.9/F11.3 • Conclusions: • Ae/Be stars seem to have distinctive PAH spectra among strong PAH emitters • As ionization increases, PAH size decreases (this is consistent with their star spectral types) • All based on a VERY small sample…

  12. The next steps: • Larger sample (WANTED: more blue outliers) • Isolate PAH from solid state • features • Model PAH & dust emission • Li & Lunine (2004): • porous cometary-type dust, • PAHs ionized

  13. Thanks! If you would like more information on this or any other IRS Disks Projects, e-mail Dr. Keller (lkeller@ithaca.edu) or myself (eleiben1@ithaca.edu)

More Related