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					Why, How, and How we Figure Out

Where New Stars Form
Alyssa A. Goodman
Harvard-Smithsonian Center for Astrophysics

cfa-www.harvard.edu/~agoodman
          Glossary                                   Extinction
for Alyssa Goodman’s Talk
         12/12/02

 Extinction--the degree of “blackness”
    on the sky caused by dust between
    background objects and an observer
                                                     Emission

 Emission--photons produced by some
   physical process

 Absorption--removal of photons by
    some physical process
                                                     Spectral line
 Spectral line--emission or absorption
    over a very narrow wavelength
                                         Intensity
    range, caused by a change in the
    quantum mechanical state of a
    particular atom or molecule

                                                                  "Velocity"
Star Formation




         (a.k.a. GMC or Cloud Complex)
 Barnard’s
Interstellar
  Medium
   “Barnard’s Method”: Star Counting



 Counts of stars per
  unit area measure
  how much material
  must be producing
  obscuration, gives
  “extinction.”




                           Observations by Alves, Lada & Lada
 Barnard’s
Interstellar
  Medium
80 years
 after
Barnard
80 years
 after
Barnard
 HST, IRAS
(Earth Orbit)                                          SIRTF
                                                     (Sun Orbit)

    Telescopes Used in Our Mapping of the ISM

                FCRAO & CfA       IRAM 30-m           Nagoya 4-m
                   (Mass.)          (Spain)             (Japan)
 JCMT
(Hawaii)


 KPNO 12-m          Arecibo
   & HHT          (Puerto Rico)
  (Arizona)

     NTT, VLT
      (Chile)                                 ATCA+Parkes
                                               (Australia)
Dust Emits, as well as Absorbs, Photons




       Barnard’s Optical                IRAS Satellite Observation,
    Photograph of Ophiuchus                         1983


 Remember: Cold (10K) dust glows, like a blackbody, in the far-infrared.
  Absorption, Scattering, Emission & Extinction


                                    Absorber    “Absorption”




                                    Scatterer    “Scattering”



Emitter
                                                 “Emission”


          Note: Absorption + Scattering = “Extinction”
Multiwavelength Milky Way


                            O
Thermal
  Dust
Emission
 in the
 Orion
  Star-
Forming
 Region
  Absorption, Scattering, Emission & Extinction


                                    Absorber    “Absorption”




                                    Scatterer    “Scattering”



Emitter
                                                 “Emission”


          Note: Absorption + Scattering = “Extinction”
   Wavelength Dependence of
          Extinction
short wavelength, e.g. optical
                            “Dust
                                     Light is “Extinguished”
                            Grain”   & Does not Reach Us


long wavelength, e.g. near-IR



                                     Light Goes Right by
                   “Dust
                   Grain”            & Reaches Us
Bok Globule (Core)
  Optical




    Seeing “through” the Clouds
Near-Infrared
                 B68 obscuring, glowing & moving
 Optical                                            Dust Emission                C18O
 Image




            Extinc                         Emission from                         Emission from
Coordinated tion
                                           Glowing Dust
            Molecular-Probe Line, Extinction &
                                                                                 Molecular Gas
Thermal Emission Observations of Barnard 68                                                  Radial Density
This figure highlights the work of Senior Collaborator                                  Profile, with Critical
João Alves and his collaborators. The top left panel                                          Bonnor-Ebert
shows a deep VLT image (Alves, Lada & Lada 2001).                   NICER                         Sphere Fit
The middle top panel shows the 850 m continuum                     Extinction
emission (Visser, Richer & Chandler 2001) from the dust
                                                                    Map
causing the extinction seen optically. The top right panel
highlights the extreme depletion seen at high extinctions
in C18O emission (Lada et al. 2001). The inset on the
bottom right panel shows the extinction map derived from
applying the NICER method applied to NTT near-infrared
observations of the most extinguished portion of B68.
The graph in the bottom right panel shows the incredible
radial-density profile derived from the NICER extinction
map (Alves, Lada & Lada 2001). Notice that the fit to
this profile shows the inner portion of B68 to be
essentially a perfect critical Bonner-Ebert sphere
             Pillars of Creation




Contours show Molecular Spectral-Line (CO) E




                                         M. Pound 1998
       Molecular Clouds: Where Stars Form




 The Oschin telescope,
48-inch aperture wide-
field Schmidt camera at
        Palomar
                            Red Plate, Digitized Palomar Observatory Sky Surve
Radio Spectral-line Observations of Interstellar Clouds
                                       Spectral Line Observations
     Tutorial:
   Velocity from
   Spectroscopy



                                                       Observed Spectrum

        Telescope                   1.5

       Spectrometer
                                     1.0
                        Intensity



                                     0.5


                                     0.0



                                    -0.5
All thanks to Doppler
                                           100   150    200       250      300   350   400

                                                              "Velocity"
     Tutorial:
   Velocity from
   Spectroscopy



                                                       Observed Spectrum

        Telescope                   1.5

       Spectrometer
                                     1.0
                        Intensity



                                     0.5


                                     0.0



                                    -0.5
All thanks to Doppler
                                           100   150    200       250      300   350   400

                                                              "Velocity"
Radio Spectral-line Observations of Interstellar Clouds
                                       Spectral Line Observations
Radio Spectral-line Observations of Interstellar Clouds




                        Radio Spectral-Line Survey




                                                     Alves, Lada & Lada 19
Velocity as a "Fourth" Dimension
                          Spectral Line Observations




                                               Loss of
                                               1
                                               dimension

                  No loss of
 Mountain Range   informatio
                       n
                Star Velocity Information
           Utility of Formation 101
                                 "Cores" and
                                   Outflows




                                               1 pc
 Studies of Cloud
                               Studies of
 Turbulence
               Molecular or      Infall,
               Dark Clouds     Outflow &
                                Rotation
                                  Jets and
                                    Disks
         Extrasolar System




                              Studies of
   Detection of               Disk & Jet
    Planets by                 Motions
Variations in Star’s
Molecular Spectral Line Mapping
                              1950     1960           1970          1980         1990   2000

                                  8
                             10                                               Product
                                      That’s a one-thousand-fold
                                  7   “improvement” in 20 years.                           10
                                                                                                4

                             10




                                                                                                    Nchannels, S/N in 1 hour, N
(S/N)*N pixels *N channels




                                  6
                             10                                                                 3
                                                                                           10

                             10
                                  5       Nchannels

                                                                                                2
                                                                           S/N             10
                                  4
                             10


                                  3




                                                                                                                               pixels
                             10                                                                 1
                                                                           Npixels         10

                                  2
                             10
                                                                                                0
                                                                                           10

                              1950     1960           1970          1980         1990   2000

                                                             Year
          Star Formation 101
                     "Cores" and
                       Outflows




                                   1 pc
      Molecular or
      Dark Clouds



                      Jets and
                        Disks
Extrasolar System
                       “Giant” Outflows




See references in H. Arce’s Thesis 2001
          “Giant”
        Herbig-Haro
         Flow from
          PV Ceph


                              1 pc




mage from Reipurth, Bally & Devine 1997
    PV Ceph

  Episodic ejections
from a precessing or
 wobbling moving
       source




 Goodman & Arce 2002
      PV Ceph is
      moving at
      ~10 km s-1




Goodman & Arce 2002
Truth?: Part 1
Part II
Star Formation
     >>101

•MHD turbulence gives
“t=0” conditions; Jeans
mass=1 Msun
•50 Msun, 0.38 pc, navg=3 x
105 ptcls/cc
•forms ~50 objects
•T=10 K
•SPH, no B or L, G
•movie=1.4 free-fall times
  Bate, Bonnell & Bromm
           2002
                                                                                         Nagahama et al. 1998 13CO (1-0) Survey

                                                                                    Molecular Line
           Putting in All                                                           Map

            Together:
       The “Uncoordination”
             Problem
                                                 2MASS/NICER Extinction Map of Orion
                                                                                             1:50
   50
                                    1 pc
   55
                                                                                             2:00

2:00



   05                                                                                           10


   10


                                                                                                20
   15



   20
                                                                                                      1 pc
                                                                                                30
   25

             SCUBA
   30

        40    5:41:00     20        40   42:00                                                  40   SCUBA
                        R.A. (2000)

                                                                                                      42:00   30         41:00   30    5:40:00
                                                                                                                   R.A. (2000)
             Johnstone et al. 2001                          Lombardi & Alves 2001                              Johnstone et al. 2001
The
COordinated
Molecular
Probe
Line                  COMPLETE
Extinction        sampling as a path to missing truths
Thermal
Emission
Survey
         Alyssa A. Goodman, Principal Investigator (CfA)
                    João Alves (ESA, Germany)
                      Héctor Arce (Caltech)
                   Paola Caselli (Arcetri, Italy)
                James DiFrancesco (HIA, Canada)
                   Mark Heyer (UMASS/FCRAO)
                  Doug Johnstone (HIA, Canada)
                 Scott Schnee (CfA, PhD student)
                    Mario Tafalla (OAS, Spain)
                    Tom Wilson (MPIfR/SMTO)
The                       SIRTF’s
SIRTF
Legacy                  1st Plan for
Survey                 Star-Forming
                          Regions
    “From Molecular Cores to Planet-Forming Disks”
         Neal J. Evans, II, Principal Investigator (U. Texas)
                          Lori E. Allen (CfA)
                    Geoffrey A. Blake (Caltech)
                     Paul M. Harvey (U. Texas)
                David W. Koerner (U. Pennsylvania)
                     Lee G. Mundy (Maryland)
                        Philip C. Myers (CfA)
            Deborah L. Padgett (SIRTF Science Center)
                    Anneila I. Sargent (Caltech)
                       Karl Stapelfeldt (JPL)
                  Ewine F. van Dishoeck (Leiden)
SIRTF Legacy Survey

            Perseus Molecular Cloud Complex
            (one of 5 similar regions to be fully
            mapped in far-IR by SIRTF Legacy)
          SIRTF Legacy Survey


                          MIRAC Coverage




2 degrees ~ 10 pc
                                                                        5 degrees (~tens of
                                                                               pc)



COMPLETE, Part 1
                                                             SIRTF Legacy
                                                             Coverage of
Observations:                                                Perseus
   2003--    Mid- and Far-IR SIRTF Legacy Observations: dust temperature and column

      >10-degree scale
   density maps ~5 degrees mapped with ~15" resolution (at 70 m)
   2002-- NICER/2MASS Extinction Mapping: dust column density maps ~5 degrees mapped
   with ~5' resolution


     Near-IR Extinction,
   2003-- SCUBA Observations: dust column density maps, finds all "cold" source               ~20"
   resolution on all AV>2”
   2002-- FCRAO/SEQUOIA         13CO   and   13CO     Observations: gas temperature, density and
   velocity information ~40" resolution on all AV>1

      Molecular Line and
Science:
   –Combined Thermal Emission data: dust spectral-energy distributions, giving emissivity,
   Tdust and Ndust

    Dust Emission Surveys
   –Extinction/Thermal Emission inter-comparison: unprecedented constraints on dust
   properties and cloud distances, in addition to high-dynamic range Ndust map
   –Spectral-line/Ndust Comparisons Systematic censes of inflow, outflow & turbulent

    of Perseus, Ophiuchus
   motions enabled
   –CO maps in conjunction with SIRTF point sources will comprise YSO outflow census
                                                                                         (Lee, Myers & Tafalla 2001).
COMPLETE,
  Part 2
 (2003-5)
                                          FCRAO N2H+ map with CS spectra superimposed.


Observations, using target list generated from Part 1:
  <arcminute-scale core
    NICER/8-m/IR camera Observations: best density profiles for dust
    associated with "cores". ~10" resolution

   maps to get density &
    FCRAO + IRAM N2H+ Observations: gas temperature, density and
    velocity information for "cores” ~15" resolution
Science:
   velocity structure all
    Multiplicity/fragmentation studies
    Detailed modeling of pressure structure on <0.3 pc scales

  the way from >10 pc to
    Searches for the "loss" of turbulent energy (coherence)



          0.01 pc
                         Is this Really Possible Now?

                     3                                                  A V~5 mag, Resolution~1'
               10
                             1 day for a                                A V~30 mag, Resolution~10"
                            13CO map then                               13
                                                                            CO Spectra for 32 Positions          1 Week
                     2
               10                                                       in a Dark Cloud (S/N~3)
                                                                         Sub-mm Map of a Dense Core
                                                                                                                 1 Day
                                                                        at 450 and 850    m
                     1
               10
Time (hours)




                     0
               10                                                                                                1 Hour

                                                                                              NICER/8-m          1 Minute
                    -1
               10
                                                                                              SEQUOIA+

                    -2
               10                                                   1 minute for a            SCUBA-2
                                                                    13CO map now


                    -3
               10
                                                                                                                 1 Second
                    -4                             NICER/2MASS
               10                                                       NICER/SIRTF

                     1980      1985         1990    1995         2000        2005         2010            2015

                                                           Year
             COMPLETE Preview:
Discovery of a Heated Dust Ring in Ophiuchus




                                        2 pc




                                Goodman, Li & Schnee 20
…and the famous “1RXS
J162554.5-233037” is right
in the Middle !?




                  2 pc
The “COMPLETE” Truth about Star
       Formation, c. 2005

     Statistical Evaluation of Outflows’ Role

  Evaluation of Constructive/Destructive Role of

                  Explosions/Winds

             Tracking down progeny
Why, How, and How we Figure Out

Where New Stars Form
Alyssa A. Goodman
Harvard-Smithsonian Center for Astrophysics

cfa-www.harvard.edu/~agoodman

				
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posted:8/4/2011
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