The Hunt for Massive Stars Hiding in the Milky Way Matthew S. Povich NSF Astronomy & Astrophysics Postdoctoral Fellow The Pennsylvania State University Brief Background Or, How I Became a Massive Stars Guy Without Really Trying 3 Bow shocks: Stellar winds meet moving gas Povich et al. (2008) Bow shocks: Spitzer “Color Code 1” Stellar winds meet moving gas IRAC 3.6 µm • stars, PAHs IRAC 4.5 µm • stars, shocked/ionized gas IRAC 8.0 µm • PAHs [+hot dust] Povich et al. (2007, 2008) No. 2, 2008 IR DUST BUBBLES 1345 Chandra diffuse soft X-rays Contours: VLA 20 cm (0.5–2 keV) continuum IRAC 5.8 µm Diamonds: OB stars MSX 21.3 µm Spitzer “color code 2” IRAC 4.5 µm • stars Fig. 8.—N49 slice at latitude b 0:23, with 20 cm (solid line, magnified [+shocked/ionized gas] 106 times), 24 m(dotted line), and¼À 8 m(dashed line, magnified 5 times). Note that there is no central peak at 24 m, as there is in N10 and N21. IRAC 8.0 µm • PAHs [+hot dust] 24 m/20 cm dip appears to be the central wind-evacuated cavity MIPS 24 µm • warm dust expected around early-O stars. 4. ANALYSIS Bubble N49 We proposeText the following picture for the IR bubbles: ionized gas with a hot dust component is surrounded by a PDR contain- ing swept-up interstellar gas, PAHs, and dust. The ionized gas is traced by 20 cm free-free emission, and the hot dust within the H ii region is bright at 24 m via thermal continuum emission. The IR bubbles are enclosed by a shell of 8memissiondominated by PAH emission features in IRAC bands 3.6, 5.8, and 8.0 m. The inner face of the 8 m shell defines the PAH destruction radius from the central ionizing star(s). In the following sections, we determine the PAH destruction radii and PDR shell thick- Triggered massivenesses based on 5.8 m/4.5 m and 8.0 m/4.5 m fluxTownsley density et al. star formation?ratios. (2003) C. Watson, Povich et al. 4.1. PAH Destruction Povich et al. (2007) Povich et al. (2007) argued that ratios of IRAC bands that con- tain strong PAH emission features (8.0 and 5.8 m bands) to the 4.5 m band (which contains no PAH feature) can be used to de- Everett & Churchwell (2010): Dust terminemust the be PAH continuously destruction radius and definereplenished the extent of within N49. PDRs around hot stars. This technique was applied by Povich Fig. 7.—N49Draine 24 m(red (2011):), 8 m(green), 4.520m( cmblue), andshell 20 cm ( con-in N49 shaped by radiation pressure and winds. tours, bottom panel). The white dashed line in the top panel indicates the loca- et al. (2007) to derive both the PAH destruction region in M17 tion of the cross-cut in Fig. 8. and the extent of its PDR because the 8.0, 5.8, and 3.6 m IRAC bands all contain PAH bands, whereas band ratios involving the 4.5 m PAH-free band should be especially sensitive to regions of 5:7 0:6 kpc (Churchwell et al. 2006). At 1.4 GHz it has an containing PAHs. They supported their interpretation of these ra- integratedÆ flux density of 2.8 Jy and an angular radius out to the tios by showing that the 5.8 m/3.6 m ratio does not delineate background of 1.50 ( 2.5 pc; Helfand et al. 2006). To maintain the PDR boundaries. They also presented IRS spectra that proved 48 1 its ionization, 7:8 ; 10 ionizing photons sÀ are necessary, equiv- the disappearance of PAH features within the M17 H ii region. alent to a single O6 V star (MSH05). The radius to the inner face Povich et al. (2007) were unable to use the 8.0 m images of of the 8 m shell is 1.20 (2.0 pc), and out to the background level M17 because the detector was saturated over large regions. We it is 1.70 (2.3 pc). have applied this technique to N10, N21, and N49. The quanti- N49 has a double-shell structure, the outer traced by 8m emis- tative ratios are different from those toward M17 because M17 sion and the inner traced by 24 m and 20 cm emission (see is a much more luminous region, but the principle is the same. Fig. 7). As in N10 and N21, 8memissionenclosesboththe24m Since N10, N21, and N49 do not saturate the 8.0 m detector, we and 20 cm emission. The transition between the 8 m emission are able to use this band in our analysis as well. ring and the 24 m and 20 cm emission ring can be clearly seen Figs. 9–11 show false-color images of the 5.8 m/4.5 m and in the slice at constant latitude in Figure 8. The 20 cm and 24 m 8.0 m/4.5 m band ratios, with accompanying longitude or emission are coincident, and both have a central cavity. The latitude cuts (averaged over 20 pixels) for all three bubbles. We The Chandra Carina Complex Project (CCCP) Candidate X-ray Emitting OB Stars (Povich et al. 2011a) 7 CCCP Collaboration 16 papers published in a May 2011 Special Issue of ApJS! Available at http://cochise.astro.psu.edu/Carina_public/special_issue.html Penn State Core Group MSP’s Coauthors Leisa Townsley – Mighty Leader at Other Institutions Patrick Broos – Data Sage Nathan Smith Steve Majewski Konstantin Getman Marc Gagné Eric Feigelson Brian Babler Yasuo Fukui Rémy Indebetouw Marilyn Meade Thomas Robitaille Keivan Stassun Richard Townsend Barbara Whitney PLUS: About 50 other people! Yoshinori Yonekura Hubble Space Telescope image of Herbig-Haro jets and pillars in the Carina Nebula 9 Hubble Space Telescope ~6´×12´ mosaic of the Great Nebula in Carina 10 Tr Tr14 14 Narrow-band visual images by John Gleason, D ~ 2.3 kpc, The Great Nebula http://jpgleason.zenfolio.com/ 10′ ~ 6.7 pc. ~2°x2° in Carina Bipolar, proto- • Carina is a “starburst superbubble! region,” an example of the large-scale star formation seen in starburst galaxies. • Carina contains at least 200 O and early-B stars, including the prototype O2 I star, +WRs +Eta Car. Tr 14 Tr Tr14 14 Narrow-band visual images by John Gleason, D ~ 2.3 kpc, The Great Nebula http://jpgleason.zenfolio.com/ 10′ ~ 6.7 pc. ~2°x2° in Carina Bipolar, proto- superbubble! • Carina’s stellar population is a cluster of clusters. The 3 most massive clusters, Tr 14, 15, and 16, dominate the bright central region of the nebula. Tr 15 Tr 14 Tr 16 2MASS JHK, ~28´×28´ Tr 14 Spitzer 8.0 µm 4.5 µm 3.6 µm The Vela–Carina Survey PI S. R. Majewski Chandra 0.50 – 0.70 keV 0.70 – 0.86 keV 0.86 – 0.96 keV Townsley et al. (2011) Massive Stars: Optical–IR SED fitting O6 V O6 V • Spectral energy distribution (SED) fitting uses all available photometric data. • Fit reddened spectra to data, using an extinction law characterized by RV = AV/E(B–V). Note standard diffuse ISM law has RV = 3.1. (See Cardelli et al. 1989, Indebetouw et al. 2005, Robitaille et al. 2007.) 17 SED fitting results on the HR diagram Note degeneracy of AV and Teff. Secure OB candidate Marginal OB candidate: Lbol(MS) = 104 Lsun Pre-main-sequence degenerate case 18 The Carina Nebula: Central 1° Visible Light Digitized Sky Survey Near-Infrared Two-Micron All-Sky Survey Mid-Infrared Spitzer Space Telescope The best-studied regions of the Carina Nebula are not obscured, but much of the nebula has been hidden by dust. This wide-field image could fit 4 full Moons and contains over 50,000 stars. There are many places for massive stars to hide! 19 Known massive, O and B–type stars The Carina Nebula: Central 1° Visible Light Digitized Sky Survey Near-Infrared Two-Micron All-Sky Survey Mid-Infrared Spitzer Space Telescope 140 known ◊high-mass stars, located in the less- obscured regions and in the well- studied, famous clusters. 20 Known massive, O and B–type stars The Carina Nebula: Candidate massive, O and Central 1° early B–type stars Visible Light Digitized Sky Survey Near-Infrared Two-Micron All-Sky Survey Mid-Infrared Spitzer Space Telescope 140 known ◊high-mass stars, located in the less- obscured regions and in the well- studied, famous clusters. 94 new candidate high-mass stars, located in the more-obscured regions and outside the famous clusters. 21 0 3.6 µm -59:00:00. 182 Cataloged OB stars Dec (J2000) 10:00.0 (Gagné et al. 2011) Trumpler 15 94 Candidate OB stars 20:00.0 (Povich et al. 2011a) YSOs Trumpler 14 Trumpler 16 (Povich et al. 2011b) 30:00.0 Contours: CCCP 40:00.0 stellar density Treasure Chest (Feigelson et al. 2011) 50:00.0 Correcting for selection biases, -60:00:00.0 Bochum 11 candidate OB stars could double the 10:00.0 massive stellar population. 20:00.0 R.A. (J2000) 30:00.0 50:00.0 48:00.0 46:00.0 44:00.0 42:00.0 10:40:00.0 OB search ACIS 3.6 µm in M17 Pointing 3: 40 ks Heather Busk (PSU grad student) OB candidate from X-ray/ SED method Candidate is known OB star Pointing 1: 320 ks Pointing 2: 96 ks 23 Bolometric luminosities and reddening of known Carina OB stars: SED fitting method compared to B – V photometric method.