Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.atnf.csiro.au/research/workshops/2012/ALMA/Hill_ALMAWorkshop2012.pdf Äàòà èçìåíåíèÿ: Tue Mar 20 07:03:41 2012 Äàòà èíäåêñèðîâàíèÿ: Tue Feb 5 12:30:36 2013 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: annular solar eclipse

Herschel (HOBYS) as a Pathfinder for alma!
PACS!

and A. Abergel, L. D. Anderson, Z. Balog, J.-P. Baluteau, J.-Ph. Bernard, P. Cox, L. Deharveng, P. Didelon, A.-M. di Giorgio, P. Hargrave, M. Huang, J. Kirk, S. Leeks, J. Z. Li, P. Martin, S. Molinari, G. Olofsson, N. Peretto, P. Persi, S. Pezzuto, H. Roussel, D. Russeil, S. Sadavoy, M. Sauvage, B. Sibthorpe, L. Spinoglio, L. Testi, D. Teyssier, R. Vavrek, C. D. Wilson, A. Woodcraft + other new comers

PI: F. Motte, A. Zavagno, S. Bontemps, N. Schneider, M. Hennemann, J. Di Francesco, Ph. AndrÈ, P. Saraceno, M. Griffin, A. Marston, D. Ward-Thompson, G. White, V. Minier, A. Men'shchikov, Q. Nguyen-Luong

Tracey Hill - AIM Paris-Saclay!


Background: massive star formation!
Open Questions:!
How do High Mass (OB > 8M! ) stars form?!
­ Quasi-static vs dynamic scenario ! ­ powerful gas (competitive) accretion vs coalescence! ­ Scaled up low mass star formation?!

What are the initial conditions (density, temperature, kinematics) for high-mass star formation?!

Obser vational evolutionary sequence:!

­ Massive prestellar cores (?) in IRDCs (e.g. Peretto & Fuller 2009)!

· (e.g. Molinari et al. 1998, Bontemps et al. 2010)! · Associated with hot cores, masers, powerful outflows, no radio cm! · Identified within: IR-quiet protostellar dense cores (e.g. Motte et al. 2007), IR-bright protostellar dense cores or HMPOs or Hot Molecular Cores (e.g Beuther et al. 2002, Cesaroni et al. 2005)!

Evolution

­ HII regions -> UC HII -> HII! ­ High mass protostars: evolving from envelope-dominated to stardominated.!


The Herschel Imaging Survey of OB Young Stellar Objects (HOBYS)
­ High-mass analogues of prestellar cores ­ do they exist?! ­ Massive IR-quiet protostellar dense cores! ­ Massive IR-bright protostellar dense cores!

"

· Identify & characterise the precursors of OB stars!

· Measure core/envelope mass & ! ! ! ! ! !bolometric luminosity!

­ Build an evolutionary diagram! ­ Estimate lifetime of each evolutionary stage!

· Make the link between cloud structure and ! ! ! ! ! !star formation!
­ Differentiate low & high-mass star-forming filaments.! ­ By comparing well-behaved HII regions to ! ! !more common HMSF regions!

DR21

· Assess the importance of triggering!
MAMBO 1.25 mm Spitzer 24 µm


Sample & Observations!
· Image all OB star-forming complexes < 3 kpc!
­ Expect ~250 high-mass protostars! ­ Statistical importance! ­ Study precursors of stars up to 20M!!

Near-IR extinction map of the Galaxy

· Wide-field PACS/SPIRE images (70, 160,250, 350, 500µm)! · Complementarity!
­ HPBW = 6''-36.9'' @ 0.7-3 kpc => down to 0.05-0.3 pc cloud structures!

­ Progenitors of low mass stars ­ Gould Belt Sur vey (AndrÈ et al)! ­ Precursors of OB stellar clusters ­ HI-GAL Sur vey (Molinari et al)

!


HOBYS targets !
Molecular cloud complexes ! Vela! Mon R1-R2 Rosette! Cygnus X! M16/M17/Sh40! NGC 6334! NGC 6357! W3/KR140! NGC 7538! W48! ! Area (deg 2) 3.1 ! 2.0 ! 1.5 ! 6 ! 2.5 ! 1.7 ! 1.7 ! 1.5 ! 0.6 ! 3.9 ! Dist (kpc) 0.7 ! 0.8 ! 1.5 ! 1.7 ! 1.7 ! 1.7 ! 2.2 ! 2.8 ! 3.0 ! rms250µm (mJy/beam) 20 ! 20 ! 20 ! 20 ! 20 ! 20 ! 20 ! 20 ! SPIRE+PACS Time (hr) 13 ! 15 ! 25.5 ! 10.5 ! 7 ! 7 ! 6.5 ! 2.5 ! 16.5 ! Responsible Team(s) Rome/Saclay! Cardiff/Saclay! Saclay/Canada! Saclay/HSC! HSC/RAL! Marseille/Rome! RAL/Marseille! Canada/Rome! Canada/Cardiff! Saclay/Rome!


The First herschel Images reveal: !
· Extensive networks of filaments, among which "ridges" (dominating super critical filaments) are forming high mass stars.!

· Feedback of OB star clusters on molecular cloud structure, such as heating, pillars and triggered star formation.!

­ The Vela C Ridge ­ Hill et al., 2011, A&A 533, 94! · Giannini et al., accepted. Minier et al., in prep.! ­ The IRDC G35.39-00.33 in W48 ­ Nguyen Luong et al., 2011!

· Clusters of protostars!

­ Reid et al., NGC 7538, Hill et al., M16; Schneider et al., Rosette, Hennemann et al., DR21! ­ Among which a few good candidates are high-mass class 0 protostars and starless cores.!


Characterisation of a Ridge in VELA C!
3 deg2 Herschel mapping (Hill et al. 2011; Giannini et al. accepted) ALMA targets! X X RCW34 N RCW36 XXXXX 70um, 160µm, 250µm

X

· The Vela C molecular Cloud (700pc, 5 x105 M!), 2 HII regions.! · Sources extracted with getsources, a multi-wavelength, multi-resolution sources extraction algorithm (Men'shchikov et al. 2011) . ! · 13 high-mass sources 14-70 M!! · ! 0.04 pc cloud structures -> protostellar or prestellar cores, i.e., the direct progenitors of individual high-mass stars.!



Identifying Filaments & RIDGES!
· Dust temperature and column density from greybody fits (37'')! · Census of filaments: DisPerSE (Sousbie 2011)! · Above Av > 50 mag all filaments identified have supercritical masses per unit length and are thus likely forming stars!
Av ~ 25 mag Av ~ 50 mag Av ~ 100 mag

Ridge


Cloud structure in Sub-regions !
· Disorganised network of filaments vs single dominating ridge.! · High-mass stars form preferentially in ridges, high-column density (Av > 100 mag), wide (>0.3 pc) filaments present in specific regions.! (Hill, Motte, Didelon et al. 2011)
South-Nest Centre-Ridge

Ridge
!"#$%&&'('&)*+',-.*-/0-1''


Mechanisms at play !
· PDFs! · At Av~ 7 mag, Vela C segregates into 5 sub -regions of similar mass! · South-Nest and Centre-Ridge two most contrasting! · CR has a high col den. tail and flatter PDF slope than SN.! " May suggest that gravity rather than turbulence is shaping the cloud.! - Flatter PDF obser ved for coherent structures created via constructive large-scale flows in some numerical simulations (Federrath et al., 2010)!


M16 under the influence of NGC66111 !
Picture Credit: J. Hester & P. Scowen

Pillars of Creation
H-alpha, Oxygen [OIII], Sulfur [SII] Picture credit: T.A. Rector & B.A. Wolpa

!


2%3/' 45677'

The eagle has landed!
(Hill, Motte, Didelon et al. In prep) ALMA targets $4%3/' &877'

9:;5'<-=' >277'


APOD! !
· http://apod.nasa.gov/apod /ap120203.html!


Summary !
· Initial resul promising · Stars form · Ridges are ts from the HOBYS key program are for star formation studies.! in filaments.! super-filaments, of high column density.!
23

­ ~100Av (1 x 10

· High resolution, multi-wavelength Herschel obser vations cover the peak of emission of prestellar cores.!
­ Constraining evolutionary diagrams (L:M)!

­ High mass stars preferentially form in ridges!

cm-2)!

· Identifying class-0 like high mass progenitors and massive dense cores.!


The Niche of Herschel -1 !
· 5 wavelength bands to characterise SEDs !!
­ Characterise evol parameters, e.g. lum, mass, ! ­ - Identify the earliest! ­ precursors of high-mass!
· ! ! ! ! ! ! ! ! stars !

­ ­ ­ evolution
·

- Alternatively identify a! spectrum of sources! from all stages of evolution!
- Characterize SF sequence.!

·

!


The niche of herschel -2 !
· Fragmentation studies!
­ Cores or clumps?! ­ Hill ATCA, 3/7mm!


Courtesy T.Csengeri.


A pathfinder for ALMA !
· HOBYS identifies the best locations for ALMA studies!
­ Filaments, ridges, protostars, prestellar cores! ­ Can identify and characterise sites forming high-mass star forming cores in advance! · ALMA: fragmentation -> individual star-forming cores, spectral lines, chemical evolution etc.! · High resolution velocity information ­ Ridge Vela C, 3D cavity M16, examine scenarios from PDFs! ­ With PACS resolution & with SPIRE bands!

· Strong complementarity!

· HOBYS traces diffuse extended emission which ALMA can not!
­ Provides info. re. cloud structure & star ­forming environments! ­ On large scales!.!