Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/research/workshops/2012/ALMA/Schnee_ALMAWorkshop2012_cores.pdf Дата изменения: Tue Mar 20 07:03:40 2012 Дата индексирования: Tue Feb 5 13:32:11 2013 Кодировка: Поисковые слова: molecular cloud

Characterizing Low Mass Cores in Nearby Molecular Clouds
Sco: Schnee (NRAO) Australian ALMA Community Workshop February 7, 2012


Collaborators
· · · · · · · · James Di Francesco Melissa Enoch Rachel Friesen Alyssa Goodman Doug Johnstone Stella Offner Sarah Sadavoy Lisa Wei


Related QuesQons
1. At what stage during star formaQon does fragmentaQon begin? 2. How smooth is the mass distribuQon within starless cores? 3. How can one find deeply embedded protostars?


Samples
1. 11 of the brightest (at 1mm) starless cores in Perseus molecular cloud
­ Starless status based on Spitzer NIR MIR data ­ Chosen from Enoch et al. (2006; 2008) Bolocam 1.1mm survey of Perseus ­ Observed with CARMA D&E array + SZA
· 3mm conQnuum

­ Follow up observaQons with CARMA, SMA, Spitzer
· Spectral line, 70 m conQnuum, 1.3mm conQnuum


Perbo58 as a Protostar
Greyscale and Green contours: 1.3mm conQnuum emission Red and blue contours: Red and blue shided 12CO (2 1) emission (0.3 7.3 & 7.3 14.3 km/s)

(Dunham, Chen, Arce, Bourke, Schnee, & Enoch 2011)


Perbo45 as a Protostar
Color scale ­ VLSR of SiO (2 1) emission Red contour: 3mm conQnuum Black contours: 850 micron SCUBA map

(Schnee et al. 2012)


Perbo45 as a Protostar
Color scale ­ FWHM of N2H+ (1 0) Red contour: 3mm conQnuum Black contours: 850 micron SCUBA map

(Schnee et al. 2012)


Samples
2. 5 most Jeans unstable starless cores in Perseus and Ophiuchus
­ Starless status based on Spitzer NIR MIR data ­ 1.3mm conQnuum, 12CO (2 1), 13CO (2 1), C18O (2 1), N2D+ (3 2) ­ SMA subcompact observaQons ­ Chosen from Sadavoy et al. (2010)


J033217 as a Protostar
12CO

and conQnuum

C18O and conQnuum

Black: 1.3mm conQnuum (0.1 ­ 0.5 mJy/beam) Red: 12CO (2 1) Tint 9 km/s v 18 km/s Blue: 12CO (2 1) Tint 2 km/s v 5 km/s Color contours at 3, 6, ..., 21 K km/s

Black: C18O Tint in intervals of 2 K km/s Color: C18O VLSR



(Schnee et al. in prep)


Conclusions from ConQnuum Survey
· Of the 11 brightest "starless" cores in Perseus
­ 2/11 single peak conQnuum detecQons ­ Both detecQons are protostellar

· Of 5 most Jeans unstable "starless" cores in Ophiuchus and Perseus
­ 1/5 detecQon rate ­ Protostellar source


Conclusions from ConQnuum Survey
· The majority of starless cores have no observaQonal evidence of sub structure or fragmentaQon · EsQmate that 5 20% of "starless" cores in Perseus are actually protostars
­ ~100 starless cores and 50 protostars in Perseus

· Spitzer observaQons alone are not enough to determine if a core is starless


SimulaQons of Turbulent FragmentaQon in Starless Cores
Simulated CARMA D array observaQons

(Offner, Capodilupo, Schnee, & Goodman 2011)


SimulaQons of Turbulent FragmentaQon in Starless Cores
Simulated ALMA Full Science + ACA observaQons

(Offner, Capodilupo, Schnee, & Goodman 2011)


Final Thoughts
· The observaQonal data do not yet support the theory that fragmentaQon begins in the starless stage · Turbulent fragmentaQon theory suggests that ALMA, combining the main (12m) array with the ACA (7m & total power), can detect fragmentaQon in starless cores · ALMA will surely find many low luminosity protostars in the process


The End
Thank you for your Qme!


CARMA & SZA 3mm ConQnuum

0.01 pc

(Schnee et al. 2010)


3mm derived ProperQes of Starless Cores

1. 2. 3. 4. 5.



Offset from (0,0) posiQon given in Enoch et al. (2006) Derived from Gaussian fit to flux distribuQon Deconvolved using the synthesized beam For non detecQons, 3 upper limits to a point source are given Does not include SZA data, so some 3mm emission is resolved out

(Schnee et al. 2010)


Perbo58 as a FHSC?

(Enoch et al. 2010)


1mm derived ProperQes of Starless Cores

(Schnee et al. 2010)


850m derived ProperQes of Starless Cores

(Sadavoy et al. 2010)


Ophiuchus Cores

Grey scale: Spitzer 8m map Contours SCUBA 850m map in steps of 0.2 Jy/beam (Sadavoy et al. 2010)


Perseus Cores

Grey scale: Spitzer 8m map Contours SCUBA 850m map in steps of 0.2 Jy/beam (Sadavoy et al. 2010)


Jeans Instability of Cores


3mm ConQnuum Flux Profiles
n(r) = n0/[1 + (r/r0)]

(Schnee et al. 2010)