CCCP Papers in ApJS Vol. 194 No. 1 (Special Issue), May 2011

The following 16 papers constitute a Special Issue of ApJ Supplements (Volume 194, Number 1) on the Chandra Carina Complex Project (CCCP).  Listed are the paper first authors, titles, brief non-technical descriptions, the full manuscripts as PDF files, and links to the papers on astro-ph.

1. Townsley et al., "An Introduction to the Chandra Carina Complex Project"

We mapped the Great Nebula in Carina with the Advanced CCD Imaging Spectrometer (ACIS) instrument on the Chandra X-ray Observatory, finding over 12,000 young stars and diffuse X-ray emission across the field.  This paper describes how we set up the survey and organized the project, shows some general results, and describes some unusual and unexpected X-ray sources revealed by this project. 

Published version (ADS)
full-resolution PDF  arXiv1102.4779 

2. Broos et al., "A Catalog of Chandra X-ray Sources in the Carina Nebula"

We present a catalog of all (>14,000) X-ray point sources detected in the CCCP.  We describe the data reduction and analysis procedures performed on the X-ray observations, including calibration and cleaning of the X- ray event data, point source detection, and source extraction.  Counterparts to the X-ray sources are identified in a variety of visual, near-infrared, and mid-infrared surveys. The X-ray and infrared source properties presented here form the basis of many CCCP studies of the young stellar populations in Carina.

Published version (ADS)
full-resolution PDF  arXiv1102.5121

3. Getman et al., "Source Contamination in X-ray Studies of Star-Forming Regions: Application to the Chandra Carina Complex Project"

This work describes simulations of X-ray-emitting source populations that will appear in Chandra X-ray Observatory studies along the Galactic Plane. The effort is particularly relevant to discriminating young stars in star-forming regions from unrelated older Galactic stars and extragalactic sources.  When applied to the large field covered by the Chandra Carina Complex Project, the simulations predict a total of about 5000 contaminating sources spread evenly across the survey area.  The field is so big, though, that this amounts to a prediction of <300 contaminants for each ACIS pointing.

Published version (ADS)
full-resolution PDF  arXiv1102.5122

4. Broos et al., "A Naive Bayes Source Classifier for X-ray Sources"

Since not all X-ray sources in the direction of the Carina Nebula are young stars in the Carina star-forming complex (some are unrelated foreground or background objects, as described above), it is important to use everything we know about the CCCP X-ray sources to decide which of them are young stars.  We assign Carina membership probabilities to individual sources based on source location (proximity to known clusters), X-ray properties, and visual/infrared properties.  For the particular membership criterion we adopted, 75% of CCCP sources are classified as members (young stars in the Carina complex), 11% are classified as contaminants, and 14% remain unclassified because we lack information on them.  The resulting sample of stars likely to be Carina members is used in several other CCCP studies.

Published version (ADS)
full-resolution PDF  arXiv1102.5120

5. Gagne' et al., "Carina OB Stars: X-ray Signatures of Wind Shocks and Magnetic Fields"

We have compiled a database of 200 known massive stars in the Chandra Carina Complex Project survey area with infrared, optical, and X-ray data for each star.  We identify massive stars that are significantly brighter or fainter in X-rays than expected, or whose X-ray spectra indicate that they are extremely hot.  Among these we identify two very massive stars (>~10 times the mass of the sun) that might have strong magnetic fields and over a dozen stars ~7-10 times more massive than the sun; one of these appears to be quite young, still encircled by a disk of dust and gas left over from its formation.  Among the 11 known massive binary systems (two massive stars in orbit around each other), we also find a possible anti-correlation between the time it takes to complete one orbit and X-ray shock temperature.  If the anti-correlation is confirmed, the X-rays could be used to learn about the mechanism that accelerates the winds of very massive stars.

Published version (ADS)
full-resolution PDF  arXiv1103.1149
ob200 data

6. Povich et al., "Candidate X-ray Emitting OB Stars in Carina Identified Via Infrared Spectral Energy Distributions"

The Great Nebula in Carina, easily visible to the naked eye from the Southern Hemisphere, is the most famous massive star factory in the sky.  In spite of decades of intense scrutiny, perhaps as few as half of the high-mass stars in this nebula have been identified.  Using a combination of X-ray and infrared observations, we find 94 new candidate hot stars in the nebula, each of them 15 to 100 times more massive than our Sun.

Published version (ADS)
full-resolution PDF  arXiv1102.5366

7. Naze' et al., "Global X-ray Properties of the O and B Stars in Carina"

Hot, massive stars are rare objects - therefore they are not so well known. In CCCP, an exceptional number of 129 such stars has been detected. This has enabled us to triple the number of Carina massive stars studied in detail. It is quite impressive that most of the hottest stars show nearly identical behaviours. This challenges theory: for example, contrary to common belief, most binaries are not brighter than single stars - the expected collision between the two stellar winds is thus not as strong as predicted.

Published version (ADS)
full-resolution PDF  arXiv1103.0101

8. Parkin et al., "X-ray Emission from the Double-binary OB-Star System QZ Car (HD 93206)"

QZ Car resides within the Great Carina Nebula and is a multiple star system consisting of two massive star binaries.  The observations of QZ Car obtained as part of the CCCP provide an unsurpassed view of its X-ray emission. Our analysis indicates that the bulk of the X-rays originate from a region of shocked plasma residing between the two binary systems, and also gives evidence for ongoing mass transfer in the less massive binary.

Published version (ADS)
full-resolution PDF  arXiv1103.0794

9. Feigelson et al., "X-ray Star Clusters in the Carina Complex"

Using brighter CCCP sources, we mapped the star clusters across ~150 lightyears of the Carina Complex.  Several distinct types of clusters are present:  rich clusters dominated by massive stars (Tr 14, 15, and 16), small groups associated with triggered star formation in the cold clouds that surround the main clusters, and a widely-distributed population likely from earlier generations of star formation.

Published version (ADS)
full-resolution PDF  arXiv1103.0802

10. Preibisch et al., "Infrared Properties of the X-ray-emitting Young Stellar Objects in the Carina Nebula" 

We used the results of a  very deep near-infrared survey, obtained with the European Southern Observatory 8-meter Very Large Telescope, to identify the infrared counterparts of Chandra X-ray sources in the Carina Nebula.  Since our infrared images are much deeper and cover a larger area than all other existing similar data sets, our catalog of more than 600,000 infrared sources provided counterparts to 90% of all Chandra sources in the common field of view.  The infrared data are used to determine basic parameters of the X-ray-detected young stars, such as stellar mass, age, extinction, and the degree to which they still possess circumstellar disks, remnants of the material from which the stars formed.

Published version (ADS)
full-resolution PDF  arXiv1103.2052

11. Wang et al., "A Chandra ACIS Study of the Young Star Cluster Trumpler 15 in Carina and Correlation with Near-infrared Sources"

The CCCP Tr15 study finds evidence that Trumpler 15, which was thought to be a background cluster, is physically related to other Carina clusters but older.  The majority of the stars here have no dusty disks that emit strong infrared emission, and the most massive stars may have already gone through big explosions, the final stages of their evolution.

Published version (ADS)
full-resolution PDF  arXiv1103.0785

12. Wolk et al., "The Chandra Carina Complex Project View of Trumpler 16"

Trumpler 16 is one of the three great/massive clusters of young stars in the Carina nebula.  The cluster is unusual.  Most massive clusters, including the other two in this area, are regular in shape with the massive stars in the center and fewer stars as you move away from the center.  Trumpler 16 is more like a blueberry muffin - with a few pockets with more stars (blueberries) than in other regions and with the massive stars much more mixed around than in "normal" clusters.  Despite this unusual arrangement, the relative numbers of each type of star are the same as in the other clusters. 

Published version (ADS)
full-resolution PDF  arXiv1103.1126

13. Evans et al., "Low Mass Companions of B Stars in Trumpler 16 in the Carina Nebula"

Intermediate-mass stars called "B stars" (with ~5 times the mass of the sun) do not produce X-rays, except possibly in very rare cases when they have magnetic fields.  However, low-mass stars at the same age as the B stars in the young cluster Tr 16 are copious X-ray producers; sometimes these low-mass stars orbit the B stars and are called "companions".  It is important to know the fraction of B stars with low-mass companions  in order to learn how these stars form, but that number is difficult to determine.  We have used the Chandra X-ray observations of Tr 16 to determine the fraction of intermediate-mass B stars which are detected in X-rays, and hence have low-mass companions, to be ~39%.

Published version (ADS)
full-resolution PDF  arXiv1103.1344

14. Povich et al., "A Pan-Carina YSO Catalog: Intermediate-Mass Young Stellar Objects in the Carina Nebula Identified Via Mid-Infrared Excess Emission"

Using infrared observations of the Great Nebula in Carina, we found nearly 1500 young stars with disks. One-third were also detected by the Chandra X-ray Observatory, and their properties suggest that we need to revise our understanding of how X-rays are produced by young stars more massive than the Sun.

Published version (ADS)
full-resolution PDF  arXiv1103.2060
Table 2
Table 3

15. Townsley et al., "The Chandra Carina Complex Project: Deciphering the Enigma of Carina’s Diffuse X-ray Emission"

The Carina Nebula shows bright diffuse X-ray emission, which is now easier to study because Chandra has resolved out so many point sources; in this paper, we remove those point sources and carefully characterize and map the X-ray properties of the remaining diffuse emission.  This diffuse emission shows evidence for hot plasma interacting with cold molecular material, revealing how cold gas and dust get destroyed by powerful stellar winds and exploding stars inside a star-forming region.

Published version (ADS)
full-resolution PDF   arXiv1103.0764
diffuse spectra  

16. Townsley et al., "The Integrated Diffuse X-ray Emission of the Carina Nebula Compared to Other Massive Star-forming Regions"

Carina's diffuse X-ray emission is bright and complex; we divided it up into small regions and mapped the X-ray properties of those regions in the paper described above.  Here, we combine all the diffuse X-ray emission from Carina to imagine what the complex might look like if it was farther away (where we couldn't see it so well) and we compare the properties of that combined diffuse emission to the combined diffuse emission in other famous massive star-forming regions.  We find that these other regions have diffuse X-ray emission that is similar to Carina's, but not exactly the same.  Most regions show evidence for hot plasma destroying cold gas and dust as we saw in Carina.  Some regions also show more energetic diffuse X-ray emission, evidence that a massive star might have exploded recently there.

Published version (ADS)
full-resolution PDF  arXiv1103.1606

Related Meeting Presentations

The Chandra Carina Complex Project (CCCP): Introduction and Diffuse X-ray Emission (poster at 12 Years of Science With Chandra meeting, May 2011)

The Chandra Carina Complex Project: Finding Oases in the “X-Ray Desert” of Intermediate-Mass Stars (poster at 12 Years of Science With Chandra meeting, May 2011)
AAS Meeting, May 2011

Press Release (AAS meeting, May 2011)

talk (Leisa Townsley)

talk (Matt Povich)

talk (Junfeng Wang)