detecting dark clouds in the galactic plane with 2mass data by : luis mercado
DESCRIPTION
Detecting Dark Clouds in the Galactic Plane with 2MASS data By : Luis Mercado. In collaboration with the part of GLIMPSE team (Christer Watson, Ed Churchwell and Bob Benjamin). Introduction / Background. What are Dark Clouds and why study them? Optically thick at visual and IR wavelengths - PowerPoint PPT PresentationTRANSCRIPT
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Detecting Dark Clouds in the Galactic Plane with
2MASS dataBy : Luis Mercado
In collaboration with the part of GLIMPSE team (Christer Watson, Ed Churchwell and Bob Benjamin)
![Page 2: Detecting Dark Clouds in the Galactic Plane with 2MASS data By : Luis Mercado](https://reader036.vdocuments.net/reader036/viewer/2022062520/56815911550346895dc63d0e/html5/thumbnails/2.jpg)
Introduction / Background
• What are Dark Clouds and why study them?– Optically thick at visual and IR
wavelengths– Star Formation Regions– GLIMPSE & SIRTF
• Infrared Surveys– MSX (8 micron) – Showed dark clouds
to be thicker than previously believed– 2MASS – 2 Micron All-Sky Survey
![Page 3: Detecting Dark Clouds in the Galactic Plane with 2MASS data By : Luis Mercado](https://reader036.vdocuments.net/reader036/viewer/2022062520/56815911550346895dc63d0e/html5/thumbnails/3.jpg)
2MASS Database
• Imaged entire sky in near infrared with J, H & K filters
• Used data to produce point source catalog with over 300 million sources
• Our selection criteria:– Artifact flags– Magnitude errors < 0.15 mags– Mag limits:
• 14.3 for H, 13.5 for K
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Our Technique
• H-K grid – pixels represent average color excess over a radius of 1.2’
• Stellar density grid – pixels represent number of stars over radius of 1.2’
• Unsharp Masking – used Gaussian to smooth image and create contrast image
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Contrast =Image - Background_____________________
Background
Smoothing Process
1.2’ radius for image
2.0’ radius for smoothing
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Our Technique
• H-K grid – pixels represent average color excess over a radius of 1.2’
• Stellar density grid – pixels represent number of stars over radius of 1.2’
• Unsharp Masking – used Gaussian to smooth image and create contrast image
• Best technique: product of color and density contrasts
![Page 7: Detecting Dark Clouds in the Galactic Plane with 2MASS data By : Luis Mercado](https://reader036.vdocuments.net/reader036/viewer/2022062520/56815911550346895dc63d0e/html5/thumbnails/7.jpg)
What it all looks like…
H-Kave from l = 10°-15° H-Kave contrast
K stellar density K-density contrast
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Above: Product of density and color contrast.
Below:MSX image of same field (l = 10°15°).Notice the correlation between the dark blue objects on the contrast plot and high absorption areas (dark clouds) in the MSX image.
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2MASS three color image of test field.Also plotted are contours obtained from our selection method for the corresponding area.
![Page 10: Detecting Dark Clouds in the Galactic Plane with 2MASS data By : Luis Mercado](https://reader036.vdocuments.net/reader036/viewer/2022062520/56815911550346895dc63d0e/html5/thumbnails/10.jpg)
Results / Conclusions
• Dark Clouds are identifiable with 2MASS data– Found technique that proves this– Color excess and stellar density are both
used as indicators– 380 dark clouds were detected in
l = 10°- 40° range with our technique
• Since we only see foreground stars, information about the clouds is limited
![Page 11: Detecting Dark Clouds in the Galactic Plane with 2MASS data By : Luis Mercado](https://reader036.vdocuments.net/reader036/viewer/2022062520/56815911550346895dc63d0e/html5/thumbnails/11.jpg)
What Now?
• Develop catalogue of Dark Clouds for publishing
• Present work at AAS meeting• Use data on future research missions
such as SIRTF
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THE END
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Problems
Left: Histogram of # of dark clouds detected vs. galactic longitude. Notice a rise in detections at high longitudes, opposite to what would be expected
Right: Plot of noise and density versus longitude. Notice the similar behavior. It turns out noise seems to be proportional to the density, but in an unexpected way.