STUDY OF THE W40 STAR-FORMING REGION BASED ON OBSERVATIONS BY THE WISE INFRARED SPACE TELESCOPE

The study of the mechanisms of star formation and evolution is based on comprehensive research into interstellar regions, including the analysis and identification of young stellar objects (YSOs). The identification of young stellar objects by their radiation at various wavelengths in the infrared range is a relatively recent development - the first studies in this field appeared only at the end of the 20th century. The development of this field has been made possible by improvements in observation techniques and data processing methods, the acquisition of more reliable characteristics of stellar sources, and the creation of catalogs containing extensive arrays of information about cosmic objects. In this study, the star-forming region W40 of the Aquilla molecular cloud was investigated in the infrared wavelength range to detect previously unidentified young stellar objects at various stages of evolution. Identification was carried out using two approaches: photometric criteria and spectral indices. This made it possible to more reliably identify the evolutionary stages of 37 newly discovered and previously unexplored YSO candidates (5 objects of class I, 2 objects of class II, 4 objects – class “transitional disks” and 26 objects — class III), which indicates an active and ongoing process of star formation in W40.

1. Lada, C.J. Star formation: from OB associations to protostars. IAU Symposium, 115, 1–17 (1987). https://doi.org/10.1017/S0074180900094766

2. Allen, L.E., et al. Initial results from the Spitzer Young Stellar Cluster Survey. Astrophysical Journal Supplement Series, 154 (1), 367–373 (2004). https://doi.org/10.1086/422823

3. Gutermuth, R.A., et al. The Spitzer Gould Belt Survey of large nearby interstellar clouds: discovery of a dense embedded cluster in the Serpens–Aquila Rift. Astrophysical Journal, 673 (2), L151–L154 (2008). https://doi.org/10.1086/528710

4. Koenig, X.P., and Leisawitz, D.V. A classification scheme for young stellar objects using the Widefield Infrared Survey Explorer AllWISE catalog: revealing low-density star formation in the outer Galaxy. Astrophysical Journal, 791 (2), 131 (2014). https://doi.org/10.1088/0004-637X/791/2/131

5. Fischer, W.J., et al. A WISE census of young stellar objects in Canis Major. Astrophysical Journal, 827 (2), 96 (2016). https://doi.org/10.3847/0004-637X/827/2/96

6. Manapbaeva, A.B., Esimbek, J., Alimgazinova, N.Sh., Kyzgarina, M.T., and Atamurat, A.B. N22 shan kopirshikteri zhanyndagy zhas zhuldyz obektilerin anyqtau. Izvestija Nacional’noj Akademii Nauk Respubliki Kazahstan. Serija Fiz-Mat, 3 (337), 96–105 (2021). (in Kazakh). https://doi.org/10.32014/2021.2518-1726.51

7. Nazar, A.B., Manapbaeva, A.B., Alimgazinova, N.Sh., Kyzgarina, M.T., and Demessinova, A.M. Identification of young star objects near dust bubble N10. Recent Contributions to Physics, 4 (83), 13–20 (2022). https://doi.org/10.26577/RCPh.2022.v83.i4.02

8. Alimgazinova, N.Sh., Sharipbay, N.A., Kyzgarina, M.T., Manapbaeva, A.B., Turekhanova, K.M., Omar, A.Zh., Demessinova, A.M., and Alibek, A.A. Study of the N126 dust bubble in the infrared wavelength range. Recent Contributions to Physics, 2, 19–26 (2024). https://doi.org/10.26577/RCPh.2024v89i2-03

9. Alimgazinova, N.Sh. Young stellar objects in the region of dust bubble N1. Recent Contributions to Physics, 1 (92), 50–60 (2025). https://doi.org/10.26577/RCPh20259215

10. Reipurth, B., et al. Handbook of Star Forming Regions. Volume I: The Northern Sky (San Francisco, CA: Astronomical Society of the Pacific, 2008), 1023 p. ISBN: 978-1-58381-670-7

11. Komesh, T., Esimbek, J., Baan, W., Zhou, J., Li, D., Wu, G., He, Y., Sailanbek, S., Tang, X., and Manapbayeva, A. H₂CO and H110α observations toward the Aquila Molecular Cloud. The Astrophysical Journal, 874 (2), 172 (2019). https://doi.org/10.3847/1538-4357/ab0ae3

12. Tursun, K., Esimbek, J., Henkel, C., Tang, X., Wu, G., Li, D., et al. Ammonia observations towards the Aquila Rift cloud complex. Astronomy & Astrophysics, 643, A178 (2020). https://doi.org/10.1051/0004-6361/202037659

13. Komesh, T., Baan, W., Esimbek, J., Zhou, J., Li, D., Wu, G., He, Y., Rosli, Z., and Ibraimov, M. Studies of the distinct regions due to CO selective dissociation in the Aquila molecular cloud. Astronomy & Astrophysics, 644, A46 (2020). https://doi.org/10.1051/0004-6361/202038632

14. Bontemps, S., et al. The Herschel first look at protostars in the Aquila Rift. Astronomy & Astrophysics, 518, L85 (2010). https://doi.org/10.1051/0004-6361/201014661

15. Kirk, H., Myers, P.C., Bourke, T.L., et al. Filamentary accretion flows in the embedded Serpens South protocluster. Astrophysical Journal, 766 (2), 115 (2013). https://doi.org/10.1088/0004-637X/766/2/115

16. Könyves, V., André, P., Menʼshchikov, A., et al. A census of dense cores in the Aquila Cloud Complex: SPIRE/PACS observations from the Herschel Gould Belt Survey. Astronomy & Astrophysics, 584, A91 (2015). https://doi.org/10.1051/0004-6361/201525861

17. Straižys, V., Černis, K., and Bartašiūtė, S. Interstellar extinction in the direction of the Aquila Rift. Astronomy & Astrophysics, 405 (2), 585–590 (2003). https://doi.org/10.1051/0004-6361:20030599

18. Dzib, S., et al. VLBA determination of the distance to nearby star-forming regions. IV. A preliminary distance to the proto-Herbig Ae/Be star EC 95 in the Serpens Core. Astrophysical Journal, 718 (2), 610–619 (2010). https://doi.org/10.1088/0004-637X/718/2/610

19. Ortiz-León, G.N., Dzib, S.A., and Kounkel, M.A. The Gould’s Belt Distances Survey (GOBELINS). Astrophysical Journal, 834 (2), 143 (2017). https://doi.org/10.3847/1538-4357/834/2/143

20. Ortiz-León, G.N., Loinard, L., Dzib, S.A., et al. Gaia-DR2 confirms VLBA parallaxes in Ophiuchus, Serpens, and Aquila. Astrophysical Journal Letters, 869 (2), L33 (2018). https://doi.org/10.48550/arXiv.1812.02360

21. Anderson, A.R., Williams, J.P., van der Marel, N., et al. Protostellar and protoplanetary disk masses in the Serpens region. Astrophysical Journal, 938 (1), 55 (2022). https://doi.org/10.48550/arXiv.2204.08731

22. André, P., Men’shchikov, A., et al. From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from the Herschel Gould Belt Survey. Astronomy & Astrophysics, 518, L102 (2010). https:// doi.org/10.1051/0004-6361/201014666

23. Pokhrel, R., Megeath, S.T., et al. Extension of HOPS out to 500 pc (eHOPS). I. Identification and modeling of protostars in the Aquila molecular clouds. Astrophysical Journal Supplement Series, 266 (2), 32 (2023). https://doi.org/10.3847/1538-4365/acbfaс

24. Spitzer Heritage Archive. Available at: http://sha.ipac.caltech.edu/applications/Spitzer/SHA (accessed March 13, 2026).

25. Smith, J., et al. Infrared sources and excitation of the W40 complex. Astrophysical Journal, 291, 571–580 (1985). https://doi.org/10.1086/163097

26. Komesh, T., Garay, G., Henkel, C., Omar, A., Estalella, R., Assembay, Z., et al. Infall motions in the hot core associated with the hypercompact H II region G345.0061+01.794 B. The Astrophysical Journal, 967 (1), 15 (2024). https://doi.org/10.3847/1538-4357/ad3e7b

27. Shen, H., Esimbek, J., Henkel, C., Li, D.L., Zhou, J.J., He, Y.X., Tang, X.D., Wu, G., Komesh, T., Tursun, K., Zhou, D.D., Ma, Y., Sailanbek, S., and Berdikhan, D. Triggered and dispersed under feedback of super H II region W4. Astronomy & Astrophysics, 693, A21 (2025). https://doi.org/10.1051/0004-6361/202450914

28. Omar, A., Abdirakhman, A., Alimgazinova, N., Kyzgarina, M., Naurzbayeva, A., Islyam, Z., Turekhanova, K., Demessinova, A., and Manapbayeva, A. ALMA Observations of G333.6–0.2: Molecular and Ionized Gas Environment. Galaxies, 13 (4), 73 (2025). https://doi.org/10.3390/galaxies13040073

29. Pirogov, L., et al. Molecular-line and continuum study of the W40 cloud. Monthly Notices of the Royal Astronomical Society, 436, 3186–3199 (2013). https://doi.org/10.1093/mnras/stt1802

30. Su, Y., et al. Local molecular gas toward the Aquila Rift region. Astrophysical Journal, 893 (2), 91 (2020). https://doi.org/10.3847/1538-4357/ab7fff

31. Mallick, M., et al. The W40 region in the Gould Belt: An embedded cluster and H II region at the junction of filaments. Astrophysical Journal, 779 (2), 113 (2013). https://doi.org/10.1088/0004-637X/779/2/113

32. VizieR Catalog. URL: https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=II/246 (accessed March 13, 2026).

33. AllWISE Data Release (Cutout). URL: https://vizier.cds.unistra.fr/viz-bin/VizieR-3?-source=II/328/allwise (accessed March 13, 2026).

34. Kang, S.-J., Kerton, C.R., Choi, M., and Kang, M. A comparative observational study of YSO classification in four small star-forming H II regions. Astrophysical Journal, 845 (1), 21 (2017). https://doi.org/10.3847/1538-4357/aa7da3

35. Koenig, X.P., and Leisawitz, D.V. A classification scheme for young stellar objects using the Widefield Infrared Survey Explorer AllWISE catalog: revealing low-density star formation in the outer Galaxy. Astrophysical Journal, 791 (2), 131 (2014). https://doi.org/10.1088/0004-637X/791/2/131

36. Greene, T.P., Wilking, B.A., André, P., Young, E.T., and Lada, C.J. Further mid-infrared study of the ρ Ophiuchi cloud young stellar population: Luminosities and masses of pre-main-sequence stars. Astrophysical Journal, 434, 614–626 (1994). https://doi.org/10.1086/174763

37. SIMBAD Astronomical Database. URL: https://simbad.u-strasbg.fr/simbad/ (accessed March 13, 2026).

38. NASA/IPAC Infrared Science Archive (IRSA). URL: https://irsa.ipac.caltech.edu/frontpage/ (accessed March 13, 2026).

39. Komesh, T., et al. ALMA observations of the environments of G333.0162+00.7615. Proceedings of the International Astronomical Union, 17 (S373), 35–38 (2021). https://doi.org/10.1017/S1743921323000121

40. Assembay, Z., et al. ALMA observations of the environments of G301.1364-00.2249 A. Proceedings of the International Astronomical Union, 18 (S380), 204–206 (2022). https://doi.org/10.1017/S1743921323002624

41. Pokhrel, R., Megeath, S.T., Gutermuth, R., et al. Extension of HOPS out to 500 parsecs (eHOPS). I. Identification and modeling of protostars in the Aquila molecular clouds. Astrophysical Journal Supplement Series, 266 (2), 32 (2023). https://doi.org/10.48550/arXiv.2209.12090

42. Abdullayev, Z., Komesh, T., Grossan, B., Abdikamalov, E., Maksut, Z., Krugov, M., Myrzakul, S., et al. Early-time optical spectral shape measurements of GRB 200925B. Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias), 59, 109–113 (2025). https://doi.org/10.22201/ia.14052059p.2025.59.20

43. Könyves, V. The Aquila prestellar core population revealed by Herschel. Astronomy & Astrophysics, 518, L106 (2010). https://doi.org/10.1051/0004-6361/201014689

44. Strom, K.M., Strom, S.E., Edwards, S., Cabrit, S., Skrutskie, M.F., et al. Circumstellar material associated with solar-type pre-main-sequence stars: A possible constraint on the timescale for planet building. Astronomical Journal, 97 (5), 1451–1470 (1989). https://doi.org/10.1086/115085

45. Marton, G., Verebélyi, E., Kiss, C., and Smidla, J. Newly identified YSO candidates towards the LDN 1188. Astronomische Nachrichten, 334 (9), 924–927 (2013). https://doi.org/10.1002/asna.201311960

46. Straižys, V., Černis, K., and Bartasiūtė, S. Interstellar extinction in the direction of the Aquila Rift. Astronomy & Astrophysics, 405 (2), 585–590 (2003). https://doi.org/10.1051/0004-6361:20030599

47. Robitaille, V.P., Whitney, B.A., Indebetouw, R., Wood, K., and Denzmore, P. Interpreting spectral energy distributions from young stellar objects. II. Fitting observed SEDs using a large grid of precomputed models. Astrophysical Journal Supplement Series, 169 (2), 328–352 (2007). https://doi.org/10.1086/512039