PoS(Bash11)006 Spitzer http://pos.sissa.it/ regions. As strong sources of regions are dominant sources of II II region in the . I summarize II region evolution across the full range of luminosities II regions by enlisting >35,000 "citizen scientists" to search II regions, emphasizing complications to the theoretical picture revealed II † ∗ regions serve as readily-observable beacons of massive formation in the survey images for bubble-shaped structures. The MWP and similar large cata- II regions may prove more important than supernovae as triggers of through lo- [email protected] II Region Feedback Speaker. NSF and Astrophysics Postdoctoral Fellow. recombination- and forbidden-line emission, infraredcontinuum, continuum, H and thermal (free-free) feedback in star-forming , injectingH radiative and mechanical luminositycalized into compression the of ISM. cold cloud cores.and time-evolution In of this H review, I give a broad overview of the structure Space and external galaxies. Along with supernovae, H by multiwavelength observations. I discuss aback recent mechanism controversy in surrounding 30 the Doradus, dominant the feed- most luminous H logs enable empirical studies of Galactic H Massive produce copious quantitiestoionizing of the radiation interstellar beyond medium the (ISM) Lyman limit, and pho- producing H the first results from the Milky Waythousand Project candidate (MWP), Galactic which H has produced a new catalog of several and statistical studies of triggered star formation. II ∗ † Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c

Frank N. Bash Symposium 2011: NewOctober Horizons 9-11, in 2011 Astronomy Austin, Texas, USA Penn State E-mail: Matthew S. Povich Beyond Strömgren Spheres and Wind-Blown Bubbles: An Observational Perspective on H PoS(Bash11)006 re- (1.1) II regions 4 II 5 4 1 , compiled − 01 . . . . 1 ]. Generally 0 0 0 0 10 4 ] realized that ∼ ∼ ∼ ∼ ∼ 3 912 Å) is negli- Matthew S. Povich regions, localized < II λ to produce observable 0 300 Q ∼ ) (pc) factor

M , — 3000 9 3 0.05 70 — / 1 Total Mass Scaleheight Filling  B a 0 2 H 6 ]. The coexistence of at such dramatically Q 4 n 2 2 3 10 T π 5000 1.0 900 10 4 ∼ 10–50 1.3 75 ∼ is the Case B recombination coefficient [  B = a regions ought not to be regarded as a proper ISM phase 6 ) (K) (10 0 4 3 S II − 004 R . –10 Phases of ISM Gas in the Milky Way 2 0 (cm ∼ ] and Draine [ 1 Table 1: Region Feedback II regions. Regions 1–10 II II is the ionizing rate (which depends on the star or stars responsible for the H is the gas density, and 0 H PhaseHot ionized medium Warm neutral mediumWarm ionized medium 0.5–0.6Cold neutral 0.1–0.3 medium 8000 Density Molecular Clouds 30–50 2.8 80–100 10 2.2 100 H Q n regions rapidly become overpressured compared to the ambient ISM and expand. If the dom- In one of the immortalized insights of early modern astrophysics, Strömgren [ Most students of astronomy will encounter a course on the physics of the Because the ionizing stars provide an internal source of radiative and mechanical luminosity, II the mean free path in neutral hydrogengibly of small UV compared beyond to the the Lyman size limit of ( therefore the have ionized sharp hydrogen region boundaries, produced or by I-fronts, arate. hot where star. For the H a recombination rate singleStrömgren balances star radius, the in an ambient medium of constant density, this boundary is defined as the where from the textbooks by Tielens [ gion), speaking, main-sequence or giant stars earlier than B3 emit sufficient different densities, temperatures, and ionizationdifferent filling fractions factors in of each the phase. same Whilemeasured the and precise is values controversial, for explained the the by filling basicsmaller factors the clouds picture remain within poorly- that the more the diffuse, warm/hot colder, phases, denser is well phases established. of H the ISM exists as (ISM; the gas and dust occupyingor the space post-graduate between the studies. stars) at Hencerough some point pressure the in equilibrium concept their with undergraduate that eachcharacterizing the other, the ISM may major phases be exists of familiar in ISM to gas several in most distinct the readers. Milky “phases,” Way Physical are in summarized quantities in Table Bash Symposium ’11—H 1. Introduction: The Interstellar Medium Out of Balance regions of photo-ionized gas produced byof hot, massive, the OB-type ISM stars, occupy volume, a hence negligible fraction perhaps H Galactic H H at all. However, massive starsfar-ultraviolet form (UV) in radiation the first densest photo-dissociates regionsmulti-phase of physics and of cold, then the molecular ISM photo-ionizes clouds, can , and be the as studied within their a single, small volume. PoS(Bash11)006 (1.2) ]: regions 4 II ]. The basic, region is never 11 ] 6 – II Matthew S. Povich 7 from the star before ) region collapses into ) ) C IF W II W R R R R . The highly supersonic 1 shell

region. II X-rays ; ; ] provided analytical models for shock ( shock 6 K 7 , 7 / 4 Wind  t 0 2 S s R c Hot! >10 Hot! Photoionized Not to scale! to Not 7 4 Outer, I-front shock ( Outer,shock I-front 3 Contact discontinuity ( discontinuity Contact + 1 IF  ] and Weaver et al. [ R 5 ) = ], and magnetic fields threading through the clouds con- ]. Turbulence provides additional pressure and facilitates C t ( region destroy the molecules, creating a photodissociation R S 12 13 R II W R region. II ]. Region Feedback still represents the outer boundary of the H is the sound speed in the ionized gas. The expansion velocity obtained Anatomy of a wind-blown bubble, adapted from Weaver et al. [ II 15 1 IF , − region. The ambient ISM is generally in motion with respect to the ionizing R regions. Castor et al. [ ) flows freely outward for a short distance 14 1 II II − Figure 1: 10 km s O stars and OB giants drive powerful winds that fundamentally alter the structure of ∼ 2 s c . The I-front at Many complications separate the ideal models of Strömgren spheres and wind-blown bubbles Early C R mixing at the interfaces between gasradiation layers. pressure Early [ models neglected completely the contribution of by differentiating this relationmedium, can hence expanding exceed I-fronts often the become shock (significantlyUV waves. lower) If photons the sound emerging ambient medium speed from is molecular, in the H the ambient from reality. The ISM is clumpy, hence the ambient medium surrounding an H where region (PDR) around the H more luminous H a photoionized shell of gas, (imperfectly) separatedat from the hot gas zone by a contact discontinuity tribute anisotropic pressure support [ wind-blown bubbles produced by isolated,fined hot these stars, models and using numerous a authors variety“onion-layer” of have semi-analytical structure subsequently and re- of numerical a techniques wind-blown [ (1000–2000 bubble km is s illustrated init Figure is shocked, producing a bubble of very hot, ionized gas. The “classical” H uniform. Massive stars tend to formtion in of clusters, a hence single multiple stars H often contribute to the ioniza- enables dramatic, radiative cooling [ star(s), and stellar winds need not be spherically symmetric. Dust mixed with gas in H Bash Symposium ’11—H inant source of pressure isthe collisional expansion heating follows the of simple gas analytic by relation free from , Lyman Spitzer’s then classic the ISM text time-evolution [ of PoS(Bash11)006 ], = soft 18 0 Q region is II Chandra m, green/blue = region M17 [ µ is likely located is defined by the Matthew S. Povich II 1 evidence for stellar IF R m, blue = µ regions, the basic struc- /MIPS 24 direct II in Figure C m emission. Everett & Church- R Spitzer µ ] and the giant H 2. 17 / ] demonstrated that 1 15 < region M17, ionized by a dozen O stars, IF m, green = IRAC 5.8 II R ]. In N49, the I-front at µ regions, but noted that the central hole in N49 / C 18 II R 4 )[ Regions 21.3 1 − II Text s MSX 50 M17 M17 10 ]. This X-ray emission provides ). A spectacular plume of hot, X-ray-emitting plasma (blue) × m emission. Draine [ 19 2 3 µ = 0 Q m torus in N49, hence Region Feedback µ ] is compared to the giant H m (green) polycyclic aromatic hydrocarbon (PAH) emission from the PDR, II µ m. M17 image: red = 17 , a prototypical wind-blown bubble ionized by a single O6.5 V star ( µ 2 , 16 Bubble N49 )[ 1 − s Multiwavelength images of the wind-blown bubble N49 [ 48 ] found that the lifetime of dust grains within the harsh environment of this H /IRAC 8.0/4.5 10 12 Unlike N49, M17 is far from round, yet similar morphological features can be discerned, In spite of the messy complexity governing the structure of real H × 5 . with one important addition (Figure is too large tocontributes. be explained An by interface radiation analogous pressure to alone the and contact suggested discontinuity that the stellar wind also including several O4 V stars ( well [ extremely short, and suggested that dustclumps must to be produce continuously the replenished observed from 24 evaporatingcan dense produce evacuated cavities in the centers of H within the radio shell/24 occupies the central cavity of M17 [ 2. Multiwavelength Observations of H neatly encapsulating the photoionized gasand shell heated (contours). by Dust radiation mixed from with the the central photoionized star gas forms a torus of 24 Figure 2: displayed at approximately the same physical scale. N49 image:(0.5–2 keV), red diffuse = X-rays. In both20 images, cm diamonds thermal denote known radio O continuum. and early B stars and contours show tures predicted by theimages. wind-blown bubble In Figure models8 are identifiable in modern, multiwavelength sharp inner rim of 8.0 Bash Symposium ’11—H Spitzer PoS(Bash11)006 1 51 m, µ 10 × 2 . 4 = , this plasma 0 1 Q − Matthew S. Povich m, green = 8.0 µ erg s regions where stellar II 34 ]. 10 13 (Not to scale) × ]. This discrepancy may be 7 20 [ = Galactic Starburst Region W43 X it is fainter than the predictions of L regions reveal layered bubble morpholo- region in the Local Group ( II II regions, but regions. Left: Image of 30 Dor in the Large Magellanic 5 II m. Right: Image of W43, red = 24 II µ region complexes, with the ionizing clusters partially (in 30 II , in which the PDRs appear yellow-green and dust mixed within 2 m, blue = 3.6 µ , a Galactic starburst region, W43, is compared to 30 Doradus in the 3 Region Feedback II falls at the inner edge of the photoionized shell and heated dust emission, region volume) in comparison to that of N49. The photoionized shell in M17 is C are part of larger H R II m, green = 4.5 mid-IR images of two starburst H 3 µ 2 in M17. The inner cavity in M17 is clearly larger (both in absolute volume and as a / m. 1 µ Spitzer ≈ ]). Mid- (IR) images of the starburst H R136 and Central 30 Dor Bubble 21 IF Although N49 and M17 are representative of a range of Galactic H R ;[ / 1 C − Figure 3: Cloud, red = 8.0 wind-blown-bubble theory by more than an order of magnitude fraction of the H winds play an important role,starburst on regions. the In Galactic Figure scale feedback is dominated by the most luminous, gies that are remarkably similarpanel between of Figure the two regions.Dor) The or completely large (W43) bubble obscured lobes bythe shown dense, 30 in foreground Dor filaments each image, of the bright, PDRs mid-IRmatches appear emission. the pink color-code In and of the Figure photo-ionizedphotoionized shells shell green, appears while the red. W43 Here image it is most appropriate to describe the photoionized gas struc- blue = 4.5 supported by a combination of radiation pressure and hot gas pressure [ does not effectively separateAgain the assuming photoionzed gas/dusty shellR from the hot gas bubble in M17. (LMC), the most luminous H Bash Symposium ’11—H wind shocks. Atis an unusually absorption-corrected bright X-ray in luminosity comparison to other H explained by collisional interactions withplasma, dust and/or grains depressurization providing a ofconfined mechanism the by for wind-blown cooling the bubble the . where hot the Either plasma interpretation is implies not that completely the contact discontinuity in Figure s PoS(Bash11)006 dir P (3.2) (3.3) (3.1) region. II region, while II Matthew S. Povich ]. Recently, Lopez . Indeed, the bubbles 21 is the distance traveled IF r R ≈ ], and similar plasma would C is not calculated for the cavity R 22 observations were obtained. U at each position, U , 0 bol L regions ionized by late O or early B stars, . c L 2 i H II 0). It will be useful to bear this trend in mind r 50 kpc, 30 Dor is the best nearby laboratory bol ν π L cn 0 h = = 4 2 region in the Local Group and its location in the h Q r C , hereafter P11] carried out independent, parallel d H 6 II π R ∑ 4 21 Un = = region structure at the high-luminosity extreme. = dir II U P stars Chandra X-ray Observatory P , a trend becomes apparent: as the luminosity of the ionizing cluster 3 is the bolometric luminosity of each star and and hence the ionization parameter bol and ) for the nebular geometry and used photoionization models to calculate , the size of the central cavity relative to the overall size of the H 0. P11 then approximated the pressure exerted on the observed ionized Region Feedback L 3 H 2 IF II n → R / H C n R 2 r , hereafter L11] and Pellegrini et al. [ 0). 23 = Thanks to its status as the most luminous H L11 used the simplest definition of direct radiation pressure, By contrast, P11 constructed a non-symmetric, cavity model (based on the central region of Comparing Figures r Doradus? gas by starlight in terms of the ionization parameter as The divergent behavior of this expressionthe ionized is gas avoided is by confined to implementing shellinteriors, the structures cavity where near model, the I-fronts, in and which the density of H atoms low- environment of the LMC,long 30 received Dor intense (popularly observational known scrutiny. asfor At the studying Tarantula the Nebula) physical has conditionsregions that that prevailed dominated in the the unresolvable, major high-redshift cosmological star-forming epoch of galaxy-building [ increases, so does We may extend this trend downfor to which the low-luminosity central H cavity disappears entirelywhen ( considering the controversial issue ofor precisely which direct feedback radiation mechanism, pressure, hot dominates gas H pressure et al. [ (their equation 1), where 3. A Rumble in the Tarantula: What is the Dominant Feedback Mechanism in 30 30 Dor shown in Figure Bash Symposium ’11—H tures as shells, occupying thin layers just interior to the PDRs,likely with be found in W43 if comparable studies of the feedback processesinterpreting shaping multiwavelength datasets, 30 Dor. theseL11 authors Using reported reached fundamentally that diametrically different direct opposed approaches stellarP11 conclusions; to radiation argued pressure that the dominates pressure the of interiordynamics. the of hot, X-ray-emitting the This plasma H disagreement shapes the isdifferent large-scale assumed rooted structure nebular and in geometries used the in different the definitions two studies. of radiation pressure and the by the starlight to reach a givendeclines point sharply in with the distance nebula, from deprojected the assuming central afor star spherical cluster, geometry. R136 (note that this expression diverges in 30 Dor are known to be filled with hot, X-ray-emitting plasma [ PoS(Bash11)006 (3.4) as the , doing dir P 3.1 as definited stars P . In contrast, the stars (assumed to Matthew S. Povich ]. It is difficult to 1 − all 24 erg s ], and pressure from either vanishes. 36 22 H 10 n × . P11 treated 30 Dor as a “bunch 5 X . n 4 ], as any given sightline will contain = 20 X L , X observation of 30 Dor [ kT X n 9 7 . 1 ] while L11 performed their own spectral fitting to . Spectral modeling of diffuse emission structures in = Chandra X 22 X n P can be combined and trivially reduced to Equation region. The justification brings to mind the old philosophical . It is particularly difficult to discern whether regions of 30 1 II 20 eV is average energy per ionizing photon (their equation 8). 3.2 − i ∼ and erg s ν h keV and absorption-corrected h 3.3 Region Feedback 37 II 02 03 . . 10 0 0 − + × ], which yields higher are the density and temperature of the X-ray-emitting plasma. P11 used the 9 are the total bolometric and ionizing photon luminosity for 64 . . 22 0 X 0 L T 2–1 = . 1 X and and accurately from the emission measure returned by spectral fitting because it depends = kT X X bol X n n L L Although Equations Both L11 and P11 reported values for the hot gas pressure in 30 Dor. The pressure of the where results of spectral fits by Townsley et al. [ regions like 30 Dor isplasma a from tremendously multiple complicated origins, tasktemperatures, including [ densities, both and stellar compositions. wind To illustrateI shocks the note and pitfalls that , of over-interpreting at different theseof a approaches data, 30 variety to of Dor the yield spectralreported significantly fitting of different the results. themost recent global, L11 spectral fits fit diffuse by X-ray a L.(plus K. emission single-temperature numerous Townsley (private gaussian plasma communication) profiles employ model 3 to plasmayield and fit components unidentified emission lines) ranging from 0.3–0.8 keV and the same archival data plus a newer, 90-ks Dor that appear X-ray darkthe represent plasma the extends boundaries behind of foreground confined, material hot that plasma absorbs bubbles, the or soft whether X-rays. The existing 114 ks strongly on the assumedwith geometry a of global, spherical the geometry, X-ray which effectively bubbles. minimizes L11 treated 30 Dor as a “beach ball” be centered at R136) and derive of grapes,” assuming aTownsley spherical et al. geometry [ for each smaller, diffuse X-ray region identified by X-ray-emitting plasma can be calculated as Bash Symposium ’11—H where so hides the ambiguous role of radiation pressure in regions where the hot, X-ray plasma or the warm,walls photoionized (L11, gas P11). can exceed Radiation the pressure radiation could pressurethe have on past, dominated the the when cavity expansion they of were thesethe smaller large hot (P11). cavities gas in pressure It in is 30 difficult Dor to remains answer uncertain. this question definitively because by P11 represents thealternative momentum definition imparted of radiation to pressure, the butenergy claim observed density that nebular of “it gas. is the necessary radiation tobudget L11 field, characterize available since acknowledge to that this drive definition motion.” reflectsstars the could This impart total definition momentum energy implies with and 100% that momentum efficiencythat the everywhere could in luminosity the never emitted nebula occur at in by once, athought the an experiment real ideal OB about case H whether a treeto falling in hear a it. forest makes a Ifexperience sound one an if dropped there enormous is a radiation no cloud pressure.the one radiation-pressure-dominated around of region But dense, identified there by neutral L11. are gasconsists Instead, no of close the dense evacuated interior to cavities clouds structure filled the of of with 30 R136 neutral hot, Dor star highly gas ionized cluster, within plasma it [ would PoS(Bash11)006 ] 25 ]). To 17 ]. In spite of 34 – Matthew S. Povich regions require the 32 II regions. regions at cosmological II ] cataloged nearly 600 IR bubbles, unresolved regions and PDRs in unprecedented 26 II , regions. The wealth of new IR imaging 16 II regions can exert external pressure on cold, II provides an example, with two luminous young regions. 8 2 m PAH emission. The majority of these structures II µ ]. starburst region, investigators wishing to extend these re- 27 region visible on the lower rim of the bubble [ II Region Catalog II resolved regions, representing an order of magnitude improvement in com- 000 internet users from around the world have been searching for II , Galactic Legacy Infrared Mid-Plane Extraordinaire (GLIMPSE) [ ] but recently has seen a resurgence of observational and theoretical ) with elliptical annuli (or mark the locations of bubbles that are barely regions, from energetic, wind-blown bubbles to low-luminosity nebulae 35 2 31 Region Feedback > II – II Spitzer 28 integration represents a very shallow observation at the distance of 30 Dor survey images of the Galactic plane as part of the Milky Way Project (MWP; Spitzer Chandra Over the past year, The MWP bubbles catalog will facilitate the study of triggered star formation on the Galactic Strong empirical constraints on the time-evolution of feedback-driven H The story of 30 Dor has a moral; given the complexity and ambiguity involved in interpreting interest, motivated in large part by thestellar identification objects, of numerous masers, instances and of other smallthe bubbles, observational young signposts rims of of recent GLIMPSE or bubbles ongoing (N49 star in formation Figure near stellar objects and an ultracompactdate, most H studies of triggered starround formation have bubbles focused with on prominent individual, “best-case” sub-clustersthe regions, or very long-standing, smaller widely bubbles popular on idea theirtriggering that sites rims supernovae have trigger [ been star identified formation, near far supernova remnants fewer than candidate near H resolved with boxes). By carefullythe combining sky, the the results MWP from simultaneouslyeye-brain many leverages system individuals the and for superior takes each advantage pattern-recognition partpresents of skills a of the catalog of “wisdom of the 5,106 of human H crowds.” The MWP First Data Release are PDRs surrounding H pleteness compared to previous catalogs [ cores, resultingaround in for self-propagating, decades sequential [ massive star formation has been surrounding B-type stars. scale. The idea that feedback from expanding H comparative study of large observational samples of H and subsequent high-resolution surveys of theof Milky dust Way in allow us the to Galacticdetail. penetrate plane, the Using revealing obscuring the the veil GLIMPSE structurering images, of and Churchwell H arc-shaped et structures al. apparent [ in 8 bubbles in http://www.milkywayproject.org), a recent installment in theline Zooniverse, the “citizen premier science” series projects of (http://www.zooniverze.org). on- and Upon logging creating into a milkywayproject.org, MWP Zooniverseinstructed account volunteers to are identify and presented fit with structuresbling a the within regions random that in image image Figure that and resemble bubble rims (PDRs resem- 4. The Milky Way Project H Bash Symposium ’11—H combined distances do so at their own risk. data provided by the when compared to observations of Galactic H the multiwavelength data on this sults to draw conclusions about feedback mechanisms shaping PoS(Bash11)006 ] 27 region II Matthew S. Povich regions. Both the regions. Thompson II ] catalog. Corrobora- II 16 mode of star formation as region theory but reveal impor- II region evolution and star formation regions, but the X-ray luminosity is important II II region volume appears to increase with II region models. Single-band IR diagnostics of . Because the effective dust temperature sets the II ). This trend puts dust at larger distances from 9 3 and ]) have become increasingly popular in the era of large, Herschel 2 36 and region structure. X-rays from hot, wind-shocked plasma are II regions in the form of IR bubbles. The large MWP database [ ]. Triggered star formation need not produce observable daughter II Spitzer 27 Region Feedback II regions are among the most beautiful objects appearing in astronomical images. The ] recently found a strong correlation between young stellar objects identified as luminous II 35 regions and its effects on H Feedback in large, starburst regions like 30 Dor presents a particularly complicated problem. It H In this review, I have given a brief update on recent, multiwavelength observations, particu- To establish that triggering merits investigation as an The size of the central cavities as a fraction of H II would be premature to assume that asuch single regions source of until feedback, we radiation achieve pressure a (L11),and dominates better supernovae. understanding of the contributions from massive star winds strong aesthetic appeal of thesewhom images were helped not to motivate professional MWPmeasuring scientists, volunteers, several thousand to the H vast spend majority tens of of thousands of person-hours finding and shape of the IRaccount spectral when energy calibrating the distribution IR in diagnostics. unresolved regions, feedback must be taken into high-resolution surveys from provides an unmatched resource fortriggered statistical by studies massive of star H feedback.tions I in expect the that coming the years, MWP involving both will professional spawn researchers many and follow-up citizen investiga- scientists. the ionizing stars inpared starburst to regions, static which or reduces thermalextragalactic the pressure-dominated star effective H formation temperature rates of (e.g. the [ dust com- opposed to an astrophysical curiosity,tistically, the and prevalence in of an triggeringGLIMPSE unbiased sites and fashion, MWP must bubbles among be catalogs established representative includebubbles sta- that flags samples could for of be hierarchical the H structure, “daughters” identifyingare of smaller members larger, of “parent” bubbles. hierarchies Among [ the MWP bubbles, 29% et al. [ structures. Observations corroborate the basic predictions of H bubbles if the second generation of stars is toomid-IR young point to sources have and produced the H rims of bubbles from the Churchwell et al. [ larly in the mid-IR and X-rays, that have revealed wind-blown and radiation-dominated H 5. Summary Bash Symposium ’11—H tion of this correlation usingstrengthen the the more case complete that sample triggering is of a bubbles prevalent from mode the of Galactic MWP star would formation. greatly tant differences, too. TheoryH still struggles to explain bothfrequently the observed existence to of fill dust large,more within central than energetic cavities an in order giant of H magnitude lower than predicted by wind-blown bubble theory. increasing ionizing luminosity (Figures PoS(Bash11)006 , , , , 658, ApJ , 2007, Matthew S. Povich , 218, 377 , 732, 100 , Cambridge University ApJ ApJ , 89, 526 , 713, 592 , 660, 346 , 200, L107 ApJ , Princeton University Press, 2011 ApJ ApJ , 1977, , 2011, , 113, 677 ApJ , 649, 759 , 594, 888 PASP , 1939, , 2010, , 2007, ApJ , Wiley-Interscience, New York, 1978 ApJ , 1975, , 2001, , 2006, , 2003, , 681, 1341 10 Star ApJ Photoionized stellar wind bubbles in a cloudy medium

Massive Stars and the Energy Balance of the Interstellar , 388, 93 , 2008, Interstellar bubbles The Dynamics of Radiation-pressure-dominated H II Regions Relative Effects of Ionizing Radiation and Winds from O-Type ApJ Dusty Wind-blown Bubbles One-Dimensional Dynamical Models of the Nebula Bubble Dynamics of wind bubbles and . I - Slow winds and fast , 1992, A Magnetically Supported in M17 10 MK Gas in M17 and the : X-Ray Flows in Galactic H II The Bubbling Galactic Disk Region Feedback The Physics and Chemistry of the Interstellar Medium A Multiwavelength Study of M17: The Spectral Energy Distribution and PAH II , 593, 874 Infrared Dust Bubbles: Probing the Detailed Structure and Young Massive Stellar Interstellar bubbles. II - Structure and evolution ApJ The Physical State of Interstellar Hydrogen. Physics of the Interstellar and Intergalactic Medium On Radiation Pressure in Static, Dusty H II Regions Physical processes in the interstellar medium , 278, L115 , 693, 1696 , 703, 1352 , 2003, ApJ ApJ ApJ Press, 2005 1984, winds. II - Analytic theory Stars on the Structure and Dynamics of H II Regions Medium. I. The Impact of an Isolated 60 M Emission Morphology of a Massive Star Formation Region 2009, 1119 2009, Populations of Galactic H II Regions Regions I thank the organizers of the Frank N. Bash Symposium 2011 for their invitation to speak and [1] Tielens, A. G. G. M., [2] Draine, B. T., [3] Strömgren, B., [4] Spitzer, L., [8] Koo, B.-C. & C. F. McKee, [5] Castor, J., R. McCray, & R.[6] Weaver, Weaver, R., et al., [7] McKee, C. F., D. van Buren, & B. Lazareff, [9] Capriotti, E. R. & J. F. Kozminski, to contribute to these proceedings. L.tions K. and Townsley and insights E. that W. Pellegrini greatly provideda improved helpful National this conversa- Science contribution. Foundation I AstronomyAST-0901646. gratefully & acknowledge Astrophysics support Postdoctoral from Fellowship under award References Bash Symposium ’11—H Acknowledgments [10] Freyer, T., G. Hensler, & H. W. Yorke, [18] Povich, M. S., et al., [12] Everett, J. E. & E. Churchwell, [14] Krumholz, M. R. & C. D. Matzner, [15] Draine, B. T., [11] Harper-Clark, E. & N. Murray, [13] Pellegrini, E. W., et al., [16] Churchwell, E., et al., [17] Watson, C., et al., [19] Townsley, L. K., et al., PoS(Bash11)006 , , , , ApJ , 666, ApJ PASP , 2012, ApJ , 1156, 225 , 1989, , 1977, , 2009, Matthew S. Povich , 2007, AIPC , 670, 428 ApJ , 433, 565 , 2009, , 446, 171 A&A A&A , 2007, ◦ 20 , 2005, , 2006, Radiation-driven implosions in molecular clouds Structure and Feedback in 30 Doradus. II. Structure , 194, 16 11 , 518, L81 ApJS Triggered massive-star formation on the borders of Galactic A&A , in press [arXiv:1111.0972] , 738, 34 , 2011, ApJ , 2010, Sequential formation of subgroups in OB associations MNRAS , 2011, , 731, 91 The statistics of triggered star formation: an overdensity of massive YSOs The Preferential Formation of High-Mass Stars in Shocked Interstellar Gas A Chandra ACIS Study of 30 Doradus. I. Superbubbles and Supernova The Integrated Diffuse X-ray Emission of the Compared to , 2011, The Spitzer/GLIMPSE Surveys: A New View of the Milky Way The Bubbling Galactic Disk. II. The Inner , 268, 291 Region Feedback ApJ The Milky Way Project First Data Release: A Bubblier Galactic Disk II What Drives the Expansion of Giant H II Regions?: A Study of Stellar Feedback , 131, 2140 Triggered massive-star formation on the borders of Galactic H II regions. II. Star formation triggered by the Galactic H II region RCW 120. First results from The Calibration of Mid-Infrared Star Formation Rate Indicators AJ Diffuse X-ray Structures in Massive Star-forming Regions , 2011, MNRAS The photoevaporation of interstellar clouds. I - Radiation-driven implosion , 260, 183 , 2006, , in press [arXiv:1201.6357] , 1994, ApJ MNRAS in 30 Doradus Remnants Layers and Chemical Abundances 121, 213 214, 725 1982, 346, 735 Other Massive Star-forming Regions H II regions. I. A search for “collect and collapse” candidates around Spitzer bubbles Evidence for the collect and collapse process around RCW 79 the Herschel Space Observatory 870 [24] Townsley, L. K., [25] Churchwell, E., et al., [28] Elmegreen, B. G. & C. J. Lada, [23] Lopez, L. A., et al., [22] Townsley, L. K., et al., [26] Churchwell, E., et al., [29] Sandford, M. T., II, R. W. Whitaker, & R. I. Klein, [30] Bertoldi, F., [31] Whitworth, A. P., et al., [32] Deharveng, L., A. Zavagno, & J. Caplan, Bash Symposium ’11—H [20] Townsley, L. K., et al., [27] Simpson, R. J., et al., [35] Thompson, M. A., et al., [21] Pellegrini, E. W., J. A. Baldwin, & G. J. Ferland, [36] Calzetti, D., et al., [33] Zavagno, A., et al., [34] Zavagno, A., et al.,