Stacking spectra in protoplanetary disks: detecting intensity profiles from hidden molecular lines in HD 163296
- Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)
- European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany)
- Department of Astronomy, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 Indonesia (Indonesia)
We introduce a new stacking method in Keplerian disks that (1) enhances signal-to-noise ratios (S/Ns) of detected molecular lines and (2) makes visible otherwise-undetectable weak lines. Our technique takes advantage of the Keplerian rotational velocity pattern. It aligns spectra according to their different centroid velocities at their different positions in a disk and stacks them. After aligning, the signals are accumulated in a narrower velocity range as compared to the original line width without alignment. Moreover, originally correlated noise becomes decorrelated. Stacked and aligned spectra thus have a higher S/N. We apply our method to Atacama Large Millimeter/Submillimeter Array (ALMA) archival data of DCN (3–2), DCO{sup +} (3–2), N{sub 2}D{sup +} (3–2), and H{sub 2}CO (3{sub 0,3}–2{sub 0,2}), (3{sub 2,2}–2{sub 2,1}), and (3{sub 2,1}–2{sub 2,0}) in the protoplanetary disk around HD 163296. As a result, (1) the S/Ns of the originally detected DCN (3–2), DCO{sup +} (3–2), H{sub 2}CO (3{sub 0,3}–2{sub 0,2}), and N{sub 2}D{sup +} (3–2) lines are boosted by a factor of ≳4–5 at their spectral peaks, implying one order of magnitude shorter integration times to reach the original S/N; and (2) the previously undetectable spectra of the H{sub 2}CO (3{sub 2,2}–2{sub 2,1}) and (3{sub 2,1}–2{sub 2,0}) lines are materialized at more than 3σ. These dramatically enhanced S/Ns allow us to measure intensity distributions in all lines with high significance. The principle of our method can be applied not only to Keplerian disks but also to any systems with ordered kinematic patterns.
- OSTI ID:
- 22868387
- Journal Information:
- Astrophysical Journal, Vol. 832, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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