恆星生成速率(SFR)是規範恆星形成理論之關鍵指標。精確的年輕恆星物體(YSO)分類對於得到準確恆星生成速率是不可或缺的。我們構建了一道分類流水線利用多波段光度測量來分辨主序後星、恆星、星系與年輕恆星物體。根據先前觀測或理論仔細的定義主序後星、恆星、星系之物體稠密區域，物體落在餘下區域即為YSO。與傳統使用雙色圖及顏色-星等圖分類法相比，新的分類
方法利用物體自然定義邊界而非人為判斷。應用此分類流水線至兩個史匹哲遺留計畫︰從分子核心至行星生成盤、古爾德帶探測(GB)的目錄，移除了849個先前方法識別之YSO並新識別出3925個YSO（佔先前方法YSO之126%）。應用此分類流水線至史匹哲強化影像目錄，我們識別了36804個年輕恆星物體，移除了31650個由機器學習方法(Chiu et al. 2021)識別之YSO並 新識別出14009個YSO。以上與先前方法之巨大的差異來自於兩點︰(1)先前的恆星樣本中有來自點擴散方程擬合的巨大的光度誤差(2)新的主序後星分類。然而多數第一類及平坦類YSO維持不變，除了在GB目錄中增加了20%，先前的重大差異主要來自主序後星以及第三類YSO，並不影響SFR之計算。我們的YSO分類流水線可以直接應用於將來的詹姆斯·韋伯太空望遠鏡之觀測，將提供在當前樣本不足之高密度分子雲區更多的資料。

Star formation rate is a key indicator to constrain star formation theories. To obtain an accurate star formation rate, precise classification of young stellar objects (YSO) is indispensable.
In this work, we construct a classification pipeline to classify evolved stars, stars, galaxies, and YSOs, solely based on their photometry measurements from multiple bands. We carefully define the object-populated regions for evolved stars, stars, and galaxies based on previous observations or theoretical models. Then, we identify sources as YSOs, if they do not fall in the evolved star, star, and galaxy regions. Compared to the traditional methods that generally use CCD or CMD to classify objects, the advantage of our method is that boundaries are defined naturally with object samples instead of defined artificially with different considerations. We apply this pipeline to catalogs obtained by two Spitzer Legacy Programs: From Molecular Cores to Planet Forming Disks (c2d) and Gould Belt's Survey (GB), which removes 849 previously identified YSOs and identifies 3925 new YSOs which is 126\% of previous identified YSOs. Applying our pipeline to the Spitzer Enhanced Imaging Products (SEIP) which includes all available Spitzer detections, we identify 36804 YSOs in total, which removes 31650 YSOs identified by previous machine learning results (Chiu et al. 2021) and identifies 14009 new YSOs. The huge difference between our identification and previous studies comes from two reasons: (1) large photometry errors caused by PSF fitting in previous star samples and (2) a new evolved stars object type is introduced. Nevertheless, most of class I and flat sources remain unchanged except in the GB regions where we find 20\% more class I and flat sources; a major difference occurs in the identification of stars, evolved stars, and class III YSOs which do not affect the star formation rate calculations. Our new pipeline for YSO identification can be directly applied to the upcoming JWST measurements, providing a better determination of star formation rates in high-density molecular clouds that currently has incomplete YSO samples.

Contents
Abstract (Chinese) . . . . . . . . . . . . . . . . . . . . . . . . I
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . IV
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . VIII
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . XII
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Source of Data . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1 c2d . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.2 Gould Belt’s Survey (GB) . . . . . . . . . . . . . . . . . . 5
2.1.3 SEIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.4 UKIDSS . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.5 SIMBAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.6 NED . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Data Preparation . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.1 c2d and GB Catalogs in This Work . . . . . . . . . . . . . . 8
2.2.2 SEIP Catalog in This Work . . . . . . . . . . . . . . . . . 9
3 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1 Multi-dimensional Magnitude Space . . . . . . . . . . . . . . 12
3.1.1 Finding Object-populated Region Boundary . . . . . . . . . . 14
3.2 Pre-classification Pipeline . . . . . . . . . . . . . . . . . 15
3.2.1 Unknown, Faint, Bright Object Classifier . . . . . . . . . . 16
3.3 Main Classification Pipeline . . . . . . . . . . . . . . . . . 17
3.3.1 Binning Process . . . . . . . . . . . . . . . . . . . . . . 18
3.3.2 Evolved Star Classifier . . . . . . . . . . . . . . . . . . 18
3.3.3 Star Classifier . . . . . . . . . . . . . . . . . . . . . . 19
3.3.4 Galaxy Classifier . . . . . . . . . . . . . . . . . . . . . 20
3.3.5 Re-classification Process . . . . . . . . . . . . . . . . . 22
3.4 Post-classification Pipeline for YSO . . . . . . . . . . . . . 23
3.4.1 Nearby Galaxy Classifier . . . . . . . . . . . . . . . . . . 23
3.5 Appendix: Object Samples . . . . . . . . . . . . . . . . . . . 24
3.5.1 Binned Multi-dimensional Magnitude Space . . . . . . . . . . 24
3.5.2 Object SED Samples in this work . . . . . . . . . . . . . . 24
3.5.3 Object Samples in Magnitude-magnitude Diagram . . . . . . . 28
4 Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.1 Spectroscopically Confirmed YSO catalogs . . . . . . . . . . . 29
4.1.1 Comparison of An et al. (2011) [1] . . . . . . . . . . . . . 30
4.1.2 Comparison of Furlan et al. (2016) [8] . . . . . . . . . . . 30
4.2 c2d catalog . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.1 Comparison of Evans et al. (2007) [5] . . . . . . . . . . . 32
4.2.2 Comparison of Hsieh & Lai (2013) [14] . . . . . . . . . . . 34
4.3 GB catalog . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.3.1 Comparison of Dunham et al. (2015) [4] . . . . . . . . . . . 35
4.4 SEIP Catalog . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.4.1 Comparison of SCAO (Chiu et al. 2021 [3]) . . . . . . . . . 37
4.4.2 Comparison of Marton et al. (2019) [20] . . . . . . . . . . 38
4.4.3 Comparison of SPICY (Kuhn et al. 2021 [17]) . . . . . . . . 39
4.5 YSO Cross-matched with NED Galaxy . . . . . . . . . . . . . . 40
4.6 Appendix: Online Data . . . . . . . . . . . . . . . . . . . . 42
5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.1 YSO Class Distribution . . . . . . . . . . . . . . . . . . . . 45
5.1.1 YSO Class Distribution in c2d Catalog . . . . .. . . . . . . 46
5.1.2 YSO Class Distribution in GB Catalog . . . . . . . . . . . . 47
5.1.3 YSO Class Distribution in SEIP Catalog . . . . . . . . . . . 49
5.2 Star Formation in c2d and GB Regions . . . . . . . . . . . . . 50
5.2.1 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . 53
6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

[1] Deokkeun An, Solange V. Ram ́ırez, Kris Sellgren, Richard G. Arendt,
A. C.Adwin Boogert, Thomas P. Robitaille, Mathias Schultheis, Angela S.
Cotera, Howard A. Smith, and Susan R. Stolovy. Massive young stellar objects in the Galactic center. I. Spectroscopic identification from Spitzer infrared spectrograph observations. Astrophysical Journal, 736(2), 8 2011.
[2] M. Casali. Widefield IR Imaging at Dome C. EAS Publications Series, 25:201–208, 2007.
[3] Y. L. Chiu, C. T. Ho, D. W. Wang, and S. P. Lai. Searching for young stellar objects through SEDs by machine learning. Astronomy and Computing, 36:100470, 7 2021.
[4] Michael M. Dunham, Lori E. Allen, Neal J. Evans, Hannah Broekhoven-Fiene, Lucas A. Cieza, James Di Francesco, Robert A. Gutermuth, Paul M. Harvey, Jennifer Hatchell, Amanda Heiderman, Tracy L. Huard, Doug Johnstone, Jason M. Kirk, Brenda C. Matthews, Jennifer F. Miller, Dawn E. Peterson, and Kaisa E. Young. YOUNG STELLAR OBJECTS IN THE GOULD BELT. The Astrophysical Journal Supplement Series, 220(1):11, 9 2015.
[5] Harvey M. P. Evans, N. J. and M. M. Dunham. Final Delivery of Data from the c2d Legacy Project: IRAC and MIPS.
[6] Neal J. Evans, Lori E. Allen, Geoffrey A. Blake, A. C. A. Boogert, Tyler Bourke, Paul M. Harvey, J. E. Kessler, David W. Koerner, Chang Won Lee, Lee G. Mundy, Philip C. Myers, Deborah L. Padgett, K. Pontoppidan, Anneila I. Sargent, Karl R. Stapelfeldt, Ewine F. van Dishoeck, Chadwick H. Young, and Kaisa E. Young. From Molecular Cores to Planet-forming Disks: An SIRTF Legacy Program. Publications of the Astronomical Society of the Pacific, 115(810):965–980, 8 2003.
[7] Neal J. Evans, Michael M. Dunham, Jes K. Jørgensen, Melissa L. Enoch, Bruno Mer ́ın, Ewine F. van Dishoeck, Juan M. Alcal ́a, Philip C. Myers, Karl R. Stapelfeldt, Tracy L. Huard, Lori E. Allen, Paul M. Harvey, Tim van Kempen, Geoffrey A. Blake, David W. Koerner, Lee G. Mundy, Deborah L. Padgett, and Anneila I. Sargent. THE SPITZER c2d LEGACY RESULTS: STAR-FORMATION RATES AND EFFICIENCIES; EVOLUTION AND LIFETIMES. The Astrophysical Journal Supplement Series, 181(2):321–350, 4 2009.
[8] E. Furlan, W. J. Fischer, B. Ali, A. M. Stutz, T. Stanke, J. J. Tobin, S. T. Megeath, M. Osorio, L. Hartmann, N. Calvet, C. A. Poteet, J. Booker, P. Manoj, D. M. Watson, and L. Allen. THE HERSCHEL ORION PROTOSTAR SURVEY: SPECTRAL ENERGY DISTRIBUTIONS AND FITS USING A GRID OF PROTOSTELLAR MODELS. The Astrophysical Journal Supplement Series, 224(1):5, 5 2016.
[9] Wilking B. A. Andre P. Young E. T. Lada C. J. Greene, T. P. Further
mid-infrared study of the rho Ophiuchi cloud young stellar population: Luminosities and masses of pre-main-sequence stars. 434(2):614–626, 1994.
[10] Paul Harvey, Bruno Merin, Tracy L. Huard, Luisa M. Rebull, Nicholas Chapman, Neal J. Evans II, and Philip C. Myers. The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. IX. The Serpens YSO Population as Observed with IRAC and MIPS. The Astrophysical Journal, 663(2):1149–1173, 7 2007.
[11] Amanda Heiderman, Neal J. Evans, Lori E. Allen, Tracy Huard, and Mark Heyer. THE STAR FORMATION RATE AND GAS SURFACE DENSITY RELATION IN THE MILKY WAY: IMPLICATIONS FOR EXTRAGALACTIC STUDIES. The Astrophysical Journal, 723(2):1019, 10 2010.
[12] P. C. Hewett, S. J. Warren, S. K. Leggett, and S. T. Hodgkin. The UKIRT Infrared Deep Sky Survey ZY JHK photometric system: passbands and synthetic colours. Monthly Notices of the Royal Astronomical Society, 367(2):454–468, 4 2006.
[13] S. T. Hodgkin, M. J. Irwin, P. C. Hewett, and S. J. Warren. The UKIRT wide field camera ZYJHK photometric system: Calibration from 2MASS. Monthly Notices of the Royal Astronomical Society, 394(2):675-692, 2009.
[14] Tien Hao Hsieh and Shih Ping Lai. Populations of young stellar objects in nearby molecular clouds. Astrophysical Journal, Supplement Series, 205(1), 2013.
[15] Robert C. Kennicutt, Jr. The Global Schmidt Law in Star-forming Galaxies. The Astrophysical Journal, 498(2):541–552, 5 1998.
[16] J. Koornneef. Near-infrared photometry. II - Intrinsic colours and the absolute calibration from one to five micron. Astronomy and Astrophysics, 128(1):84–93, 11 1983.
[17] Michael A. Kuhn, Rafael S. de Souza, Alberto Krone-Martins, Alfred Castro-Ginard, Emille E. O. Ishida, Matthew S. Povich, Lynne A. Hillenbrand, and for the COIN Collaboration. SPICY: The Spitzer/IRAC Candidate YSO Catalog for the Inner Galactic Midplane. The Astrophysical Journal Supplement Series, 254(2):33, 6 2021.
[18] A. Lawrence, S. J. Warren, O. Almaini, A. C. Edge, N. C. Hambly, R. F. Jameson, P. Lucas, M. Casali, A. Adamson, S. Dye, J. P. Emerson, S. Foucaud, P. Hewett, P. Hirst, S. T. Hodgkin, M. J. Irwin, N. Lodieu, R. G. McMahon, C. Simpson, I. Smail, D. Mortlock, and M. Folger. The UKIRT infrared deep sky survey (UKIDSS). Monthly Notices of the Royal Astronomical Society, 379(4):1599–1617, 2007.
[19] Carol J. Lonsdale, Harding E. Smith, Michael Rowan-Robinson, Jason Surace, David Shupe, Cong Xu, Sebastian Oliver, Deborah Padgett, Fan Fang, Tim Conrow, Alberto Franceschini, Nick Gautier, Matt Griffin, Perry Hacking, Frank Masci, Glenn Morrison, Joanne O’Linger, Frazer Owen, Ismael P ́erez-Fournon, Marguerite Pierre, Rick Puetter, Gordon Stacey, Sandra Castro, Maria Del Carmen Polletta, Duncan Farrah, Tom Jarrett, Dave Frayer, Brian Siana, Tom Babbedge, Simon Dye, Matt Fox, Eduardo Gonzalez-Solares, Malcolm Salaman, Stefano Berta, Jim J. Condon, Herv ́e Dole, and Steve Serjeant. SWIRE: The SIRTF Wide-Area Infrared Extragalactic Survey. Publications of the Astronomical Society of the Pacific, 115(810):897–927, 8 2003.
[20] G Marton, P ́Abrah ́am, E Szegedi-Elek, J Varga, M Kun, ́A K ́osp ́al, E Varga-Vereb ́elyi, S Hodgkin, L Szabados, R Beck, and Cs Kiss. Identification of Young Stellar Object candidates in the Gaia DR2 x AllWISE catalogue with machine learning methods. Monthly Notices of the Royal Astronomical Society, 487(2):2522–2537, 8 2019.
[21] Isa Oliveira, Bruno Mer ́ın, Klaus M. Pontoppidan, Ewine F. Van Dishoeck, Roderik A. Overzier, Jes ́us Hern ́andez, Aurora Sicilia-Aguilar, Carlos Eiroa, and Benjamin Montesinos. OPTICAL CHARACTERIZATION OF A NEW YOUNG STELLAR POPULATION IN THE SERPENS MOLECULAR CLOUD. The Astrophysical Journal, 691(1):672, 1 2009.
[22] L. M. Rebull, D. L. Padgett, C. E. McCabe, L. A. Hillenbrand, K. R. Stapelfeldt, A. Noriega-Crespo, S. J. Carey, T. Brooke, T. Huard, S. Terebey, M. Audard, J. L. Monin, M. Fukagawa, M. G ̈udel, G. R. Knapp, F. Menard, L. E. Allen, J. R. Angione, C. Baldovin-Saavedra, J. Bouvier, K. Briggs, C. Dougados, N. J. Evans, N. Flagey, S. Guieu, N. Grosso, A. M. Glauser, P. Harvey, D. Hines, W. B. Latter, S. L. Skinner, S. Strom, J. Tromp, and S. Wolf. THE TAURUS SPITZER SURVEY: NEW CANDIDATE TAURUS MEMBERS SELECTED USING SENSITIVE MID-INFRARED PHOTOMETRY. The Astrophysical Journal Supplement Series, 186(2):259, 1 2010.
[23] M. F. Skrutskie, R. M. Cutri, R. Stiening, M. D. Weinberg, S. Schneider, J. M. Carpenter, C. Beichman, R. Capps, T. Chester, J. Elias, J. Huchra, J. Liebert, C. Lonsdale, D. G. Monet, S. Price, P. Seitzer, T. Jarrett, J. D. Kirkpatrick, J. E. Gizis, E. Howard, T. Evans, J. Fowler, L. Fullmer, R. Hurt, R. Light, E. L. Kopan, K. A. Marsh, H. L. McCallon, R. Tam, S. Van Dyk, and S. Wheelock. The Two Micron All Sky Survey (2MASS). The Astronomical Journal, 131(2):1163-1183, 2 2006.
[24] Joseph C. Weingartner and B. T. Draine. Dust Grain–Size Distributions and Extinction in the Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud. The Astrophysical Journal, 548(1):296–309, 2 2001.
[25] M. Wenger, F. Ochsenbein, D. Egret, P. Dubois, F. Bonnarel, S. Borde, F. Genova, G. Jasniewicz, S. Lalo ̈e, S. Lesteven, and R. Monier. The SIMBAD astronomical database - The CDS reference database for astronomical objects. Astronomy and Astrophysics Supplement Series, 143(1):9–22, 4 2000.
[26] M. W. Werner, T. L. Roellig, F. J. Low, G. H. Rieke, M. Rieke, W. F. Hoffmann, E. Young, J. R. Houck, B. Brandl, G. G. Fazio, J. L. Hora, R. D. Gehrz, G. Helou, B. T. Soifer, J. Stauffer, J. Keene, P. Eisenhardt, D. Gallagher, T. N. Gautier, W. Irace, C. R. Lawrence, L. Simmons, J. E. Van Cleve, M. Jura, E. L. Wright, and D. P. Cruikshank. The Spitzer Space Telescope Mission. The Astrophysical Journal Supplement Series, 154(1):1–9, 9 2004.