The Cygnus X Protostellar Luminosity Function | SOFIA Science Center Skip to main content Search × About SOFIA SOFIA Overview Why SOFIA? Science Team Science and Management Team Postdoctoral Astronomers SOFIA Senior Leadership Advisory Groups German SOFIA Science Working Group (GSSWG) SOFIA Users Group (SUG) SOFIA International Summit (SIS) SOFIA NASA Observatory and Program Assessment Council (SNOPAC) SOFIA Science Council (SSC) Steering Documents Contact Privacy Policy and Credits Careers Social Media Announcements Proposing & Observing Proposal Calls Cycle 10 Cycle 10 Overview Cycle 10 Complementary Sky Positions Director's Discretionary Time Director's Discretionary Time Overview DDT Approved Programs SOFIA Archival Research Program SOFIA Archival Research Program Overview SOFIA Synergies with JWST and ALMA SARP Selected Proposals Flash Calls Current Observing Cycle Cycle 9 Overview Cycle 9 Complementary Sky Positions Cycle 9 Flight Series Cycle 9 Selected Proposals Cycle 9 Dual Anonymous Review Cycle 9 Instructions Past Observing Cycles Cycle 8 Cycle 8 Overview Cycle 8 Selected Proposals Cycle 8 Flight Series Cycle 8 Complementary Sky Positions Cycle 8 Instructions Cycle 7 Cycle 7 Overview Cycle 7 Selected Proposals Cycle 7 Flight Plans Cycle 7 Instructions Cycle 6 Cycle 6 Overview Cycle 6, Phase I Cycle 6, Phase II Cycle 6 Schedule and Flight Plans Cycle 6 Selected Proposals Cycle 5 Cycle 5 Overview Cycle 5 Flight Plans Cycle 5, Phase I Cycle 5, Phase II Cycle 5 Results Cycle 4 Cycle 4 Overview Cycle 4 Flight Plans Cycle 4, Phase I Cycle 4, Phase II SOFIA Cycle 4 Results Cycle 3 Cycle 3 Overview Cycle 3, Phase I Cycle 3 Phase II SOFIA Cycle 3 Results Cycle 3 Flight Plans Cycle 2 Cycle 2 Overview SOFIA Cycle 2 Results SOFIA Cycle 2 Approved Programs SOFIA Cycle 2 Programs in Do If Time Category Cycle 1 Cycle 1 Overview SOFIA Cycle 1 US Queue Results SOFIA Cycle 1 US Approved Programs Basic Science Basic Science Overview Basic Science Call for Proposal Results Short Science Short Science Overview Instructions for downloading SOFIA Short Science I data Proposal Documents Proposal Tools Current Cycle Flight Plans Access Proposals (DCS) Flying on SOFIA Data Science Archive Legacy Programs Multi-observatory Programs Green Bank Observatory/SOFIA Joint Observations HST/SOFIA Joint Observations JWST Early Release Science Program Selected Highlights of the Data Archive Data Pipelines Data Analysis Data Processing Instruments SOFIA Instruments Suite SOFIA Telescope EXES FIFI-LS FORCAST FPI+ GREAT HAWC+ Guider Cameras Water Vapor Monitor Instrument Development SOFIA Science Instrument Development Overview Instrument Roadmap Report Workshop: Building the 2020-2025 Instrument Roadmap Building the SOFIA Instrument Roadmap Workshop II Retired Instruments AIRES CASIMIR FLITECAM HIPO SAFIRE Publications Information for Authors SOFIA Refereed Papers SOFIA Published Papers SOFIA Paper Preprints Science Presentation Materials Promote your Result in a SOFIA Science Spotlight SOFIA Science Newsletter Science Results Archive Theses PhD Theses Master's Theses Best Paper and Best Thesis SOFIA Conference Publications SOFIA Blog Events All Events Recorded Talks SOFIA Summer Series 2022 SOFIA School 2022 SOFIA at the 240th AAS Meeting Lake Arrowhead 2022 Colloquia Tele-Talks Upcoming Tele-Talks Past Tele-Talks Meetings and Workshops Multimedia Media Portal SOFIA Blog SOFIA YouTube Channel Image Galleries Image Use Policy Public Engagement Materials Search Website The Cygnus X Protostellar Luminosity Function Breadcrumb Home Publications Science Results Archive Zoom Zoom 6/22/2022 By Yingjie Cheng and Joan Schmelz Paper: Completing the Protostellar Luminosity Function in Cygnus-X with SOFIA/FORCAST Imaging Cheng, Yingjie, et al., 2022/05, MNRAS, 512, 960. Large infrared surveys of molecular clouds have shown consistently that low-mass protostars are less luminous than expected from traditional star-formation models. The solution to this so-called ‘luminosity problem’ would shed light on some fundamental problems like the time required for a low-mass star to form. Since different star formation theories predict different protostellar luminosity functions, probing a large, unbiased sample of protostars could address these issues. Such a study hinges critically on obtaining a complete census of young stellar objects and extending their spectral energy distribution coverage through mid-infrared wavelengths. The Cygnus X complex, one of the most active nearby star-formation regions, is a promising laboratory for this study. The huge protostar sample as well as the wide range of star-forming environments set the stage for not only completing the aggregate protostellar luminosity function, but also testing how it is affected by natal environment. Over 21,000 point sources have already been detected and identified as young stellar objects within Cygnus X as part of the Spitzer Extended Solar Neighborhood Archive, which provides uniformly produced mosaics, source catalogues, and corresponding completeness maps. However, the capacity of Spitzer to constrain the luminosity of bright sources is largely inhibited by confusion and saturation in its MIPS 24 μm data. In order to obtain the luminosities of bright, closely clustered protostars and in turn complete the luminosity coverage, new observations with the Faint Object InfraRed CAmera for the SOFIA Telescope (FORCAST) instrument on SOFIA are required. Since the FORCAST beam is much cleaner than the MIPS beam at large radii, its sensitivity gain for bright sources and nebulosity is frequently superior to MIPS. By combining bright protostars identified by FORCAST with the existing Spitzer catalogue, the coverage and luminosity estimates of bright protostars are greatly improved. Furthermore, differences among model predictions are best tested at the high luminosity end, so including the FORCAST data makes the comparison between observations and theories much more feasible. An empirical relationship based on the mid-infrared spectral index and the mid-infrared luminosity is used to derive the bolometric luminosities of identified protostars. Then the protostellar luminosity function is simply the probability density distribution of the bolometric luminosities of all detected protostars. After accounting for possible contamination and incompleteness, the protostellar luminosity function in Cygnus X is well described by a power-law function with an index of around −0.5. Previous work argued that the protostellar luminosity function in Cygnus X varies within molecular complexes and depends on the local environment in which protostars form. The improved sample results indicate that the protostellar luminosity function shows no dependence on temperature, but exhibits some excess at higher luminosities in regions of high stellar or gas density. These results are consistent with previous studies. Researchers compared the observed protostellar luminosity function with predictions from three different models. The isothermal-sphere model assumes that gas accretes from an isothermal gas sphere on to the protostar at a constant rate determined by temperature. The turbulent-core model describes high-mass star formation in which stars form from turbulently supported cores within a gravitationally bound clump of gas. In the competitive-accretion model, stars accrete gas in the same gravitational potential until exhausted or ejected, so the accretion rate of each protostar depends on its mass and location within the clump of gas. The isothermal-sphere model does not reproduce the observed data. The lack of dependence on the gas temperature further supports the rejection of this model. Both the turbulent-core and competitive-accretion models fit the data well for constant accretion rates, but appear to over-predict the low-luminosity end and under-predict the high-luminosity end in regions of higher gas density. This may be an indication that episodic accretion as seen by SOFIA is an important aspect of star formation. For More Information For more information about SOFIA, visit: NASA SOFIA website • DLR website For information about SOFIA's science mission and scientific instruments, visit: SOFIA Science Center website • DSI website Science Results Archive 2004 (4) 2010 (2) 2011 (22) 2012 (16) 2013 (12) 2014 (20) 2015 (15) 2016 (14) 2017 (14) 2018 (14) 2019 (13) 2020 (12) 2021 (16) 2022 (6) Quick Links Subscribe to Newsletter Quick Guide Proposal Documents Current Flight Plans Data Archive Help-Desk Quick Links Science Center Careers Subscribe to email announcements Current Flight Plans Contact SOFIA Science Help Desk Proposal Documents Data Archive Latest Tweets Tweets by SOFIAtelescope Tweets by SOFIAtelescope Leadership Ed Stanton, NASA Project Manager Naseem Rangwala, NASA Project Scientist Margaret Meixner, USRA Science Mission Operations Director Image Image Image Image facebook twitter youtube instagram
