TY - JOUR

T1 - A census of young stellar objects in two line-of-sight star-forming regions toward IRAS 22147+5948 in the outer Galaxy

AU - Karska, Agata

AU - Koprowski, Maciej

AU - Solarz, Aleksandra

AU - Szczerba, Ryszard

AU - Sewilo, Marta

AU - Siodmiak, Natasza

AU - Elia, Davide

AU - Gawronski, Marcin

AU - Grzesiak, Konrad

AU - Yung, Bosco H. K.

AU - Fischer, William J.

AU - Kristensen, Lars E.

PY - 2022/7/25

Y1 - 2022/7/25

N2 - Context. Star formation in the outer Galaxy, namely, outside of the Solar circle, has not been extensively studied in part due to the low CO brightness of the molecular clouds linked with the negative metallicity gradient. Recent infrared surveys provide an overview of dust emission in large sections of the Galaxy, but they suffer from cloud confusion and poor spatial resolution at far-infrared wavelengths.Aims. We aim to develop a methodology to identify and classify young stellar objects (YSOs) in star-forming regions in the outer Galaxy and use it to resolve a long-standing disparity in terms of the distance and evolutionary status of IRAS 22147+5948.Methods. We used a support vector machine learning algorithm to complement standard color-color and color-magnitude diagrams in our search for YSOs in the IRAS 22147 region, based on publicly available data from the Spitzer Mapping of the Outer Galaxy survey. The agglomerative hierarchical clustering algorithm was used to identify clusters. Then the physical properties of individual YSOs were calculated. The distances were determined using CO 1-0 from the Five College Radio Astronomy Observatory survey.Results. We identified 13 Class I and 13 Class II YSO candidates using the color-color diagrams, along with an additional 2 and 21 sources, respectively, using the applied machine learning techniques. The spectral energy distributions of 23 sources were modeled with a star and a passive disk, corresponding to Class II objects. The models of three sources include envelopes that are typical for Class I objects. The objects were grouped into two clusters located at a distance of similar to 2.2 kpc and 5 clusters at similar to 5.6 kpc. The spatial extent of CO, radio continuum, and dust emission confirms the origin of YSOs in two distinct star-forming regions along a similar line of sight.Conclusions. The outer Galaxy may serve as a unique laboratory for exploring star formation across environments, on the condition that complementary methods and ancillary data are used to properly account for cloud confusion and distance uncertainties.

AB - Context. Star formation in the outer Galaxy, namely, outside of the Solar circle, has not been extensively studied in part due to the low CO brightness of the molecular clouds linked with the negative metallicity gradient. Recent infrared surveys provide an overview of dust emission in large sections of the Galaxy, but they suffer from cloud confusion and poor spatial resolution at far-infrared wavelengths.Aims. We aim to develop a methodology to identify and classify young stellar objects (YSOs) in star-forming regions in the outer Galaxy and use it to resolve a long-standing disparity in terms of the distance and evolutionary status of IRAS 22147+5948.Methods. We used a support vector machine learning algorithm to complement standard color-color and color-magnitude diagrams in our search for YSOs in the IRAS 22147 region, based on publicly available data from the Spitzer Mapping of the Outer Galaxy survey. The agglomerative hierarchical clustering algorithm was used to identify clusters. Then the physical properties of individual YSOs were calculated. The distances were determined using CO 1-0 from the Five College Radio Astronomy Observatory survey.Results. We identified 13 Class I and 13 Class II YSO candidates using the color-color diagrams, along with an additional 2 and 21 sources, respectively, using the applied machine learning techniques. The spectral energy distributions of 23 sources were modeled with a star and a passive disk, corresponding to Class II objects. The models of three sources include envelopes that are typical for Class I objects. The objects were grouped into two clusters located at a distance of similar to 2.2 kpc and 5 clusters at similar to 5.6 kpc. The spatial extent of CO, radio continuum, and dust emission confirms the origin of YSOs in two distinct star-forming regions along a similar line of sight.Conclusions. The outer Galaxy may serve as a unique laboratory for exploring star formation across environments, on the condition that complementary methods and ancillary data are used to properly account for cloud confusion and distance uncertainties.

KW - stars: formation

KW - ISM: molecules

KW - ISM: individual objects: IRAS 22147+5948

KW - PARSEC EVOLUTIONARY TRACKS

KW - GALACTIC-PLANE SURVEY

KW - MOLECULAR CLOUDS

KW - MILKY-WAY

KW - HERSCHEL-PACS

KW - MASSIVE STARS

KW - SOLAR CIRCLE

KW - LEGACY

KW - PROTOSTARS

KW - EMISSION

U2 - 10.1051/0004-6361/202141676

DO - 10.1051/0004-6361/202141676

M3 - Journal article

VL - 663

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - 133

ER -