A Survey of Orion A with XMM and Spitzer: SOXS

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A Survey of Orion A with XMM and Spitzer SOXS
Scott Wolk Harvard-Smithsonian Center for
Astrophysics
In collaboration with Tom Megeath, Lori Allen,
John Bally, Luisa Rebull Marc Gange, Guisi
Micela, Salvo Sciortino, Lee Hartman, Fred
Walter, John Stuaffer, Joanna Olivaria and Rob
Gutermuth
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Goals for the SOXS

• Multi-wavelength observations are providing a
  wealth of information on the distribution and
  motions of stars, protostars, and cores in giant
  molecular clouds.
• These data are an essential constraint on models
  of the formation and evolution of clusters.
• Identify the PMS stars without disks - A full
  cluster census.
• Study the relative importance of clustered and
  isolated star formation.
• Examine the effect of environment on star
  formation and disk evolution.
• Study Transition disk timescales
• Effect of X-rays, especially flares on planet
  forming disks.

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Orion A
CO/Optical map from CfA mm group
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Orion A
Orion B

• 105 M? molecular cloud
• One of the nearest regions of clustered star
  formation
• One of the most active regions of distributed
  (i.e. isolated) star formation within 500 pc.

Orion Nebula
Orion A
13CO 2.6 mm Bally et al.
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Orion A

• 105 M? molecular cloud
• One of the nearest regions of clustered star
  formation.
• One of the most active regions of distributed
  (i.e. isolated) star formation within 500 pc.

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The Spitzer Survey of Orion A

• The Spitzer survey shows that the Orion Nebula
  Cluster is the most concentrated region of star
  formation in the cloud.
• Spitzer found 1000 young low mass stars with
  disks and protostars in the ONC.

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The Spitzer Survey of Orion A

• In addition, the survey finds 700 young stars and
  140 protostars south of the ONC.
• These young stars are found in much different
  environment than that found in the ONC either in
  small clusters of 10-50 stars or in relative
  isolation.
• These stars have formed in environments without
  the strong UV radiation and dense clustering
  found in the
• ONC.

A significant fraction of the stars are in a
distributed component parsecs away from the
massive OB stars.
Megeath et al. in prep.
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The Spitzer Survey of Orion A
White contours AV 3 (Orion) Dots young
stars with IR-excess Colors other than green
indicate clusters of more than 10.
Megeath et al. in prep.
There is no clear border between clustered and
distributed stars Embedded clusters are not
isolated, well defined objects
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By the Numbers

• 1161 X-ray sources in the 9 fields
• Nearly 100,000 IRAC sources in those fields.
• About 140 Class I Sources in those fields
• About 550 Class II sources are in the 9 fields.
• About 220 (45) of the Class II sources were
  detected by XMM.
• Of the 1161 X-ray sources, 882 have counterparts
  in the Spitzer Survey.

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Contaminationby Background X-ray Sources
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Filtering the Contaminants
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Colors of X-ray Sources
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L1641 S
L1641S, the DL Ori group and the HBC 498
cluster R,G,B 24,5.8, 3.6 ?m
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L1641 S
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L1641 N
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Stellar Content of Orion A
Class 0/I II III total
X-Ray Sources lt10 220 420-550 780
Spitzer Sources 140 550 1050-1375 1740-2065

• This is the total for the 9 fields.
• It should be revised upward
• Minor incompleteness of IRAC.
• Some incompleteness in cloud coverage in current
  XMM survey.

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Caveats

• Need to really work field by field
• Need to account for contamination from Orion 1A
• Should be small
• Examine influence of ??Ori.

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Status

• Survey Completed March 2008
• Of the 1161 X-ray sources, 882 have counterparts
  in the Spitzer Survey.
• About 563 have IRAC colors consistent with Class
  III sources
• 99 have colors consistent with agn
• 221 have colors consistent with CII.
• The total number of stars in the 9 fields of
  Orion A is about 2100.
• The Class III sources appear more dispersed than
  the Class II sources.

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Why Bother Looking at Young Stars in X-rays?
Young stars are X-ray bright HMS- High energy
wind shocks? LMS- Despite pedestrian 5000K,
temperatures they have hot corona. Insight into
the interior workings of LMS. To identify young
stars. After stars lose their disks X-ray surveys
are the only way to find young stellar
objects This has allowed us to understand the
history of star formation in the galaxy. Direct
observation of material accreting onto very young
stars. X-rays are probably responsible for rapid
heating of protoplanetary disks.
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COUP study of the ONC

• 850 ks
• 13 papers in the APJSupp
• 465 refereed citations
• 6 Refereed Papers since
• XEST - 11 paper AA special edition on Taurus
  SFR.
• So arent we done?

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Orion AOB stars
Orion B

• 105 M? molecular cloud
• One of the nearest regions of clustered star
  formation
• One of the most active regions of distributed
  (i.e. isolated) star formation within 500 pc.

Orion Nebula
Orion A
13CO 2.6 mm Bally et al.
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The Spitzer Survey of Orion A

• The Spitzer survey shows that the Orion Nebula
  Cluster is the most concentrated region of star
  formation in the cloud.
• Spitzer 1000 young low mass stars with disks and
  protostars in the ONC.

L1641 N V 380 L1641 C HBC 498 L1641 S
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OB STARS