C.B. Ivers, Foran High School, Milford, Connecticut M. Booker, Robinson Secondary School, Fairfax, Virginia M. Piper, Lincoln Way High School / Adler Planetarium, Chicago, Illinois L. Powers, Bozeman High School, Bozeman, Montana Babar Ali, Caltech, Pasadena, California S. Wolk, SUNY Long island, New York Student Contributors: Robinson Secondary School: Casey Hughes, Alex Huynh, James Mangahas, Rachel Otto, Brandy Skaddan, Paola Vidal We gratefully acknowledge funding via Bozeman High School: Hannah Cebulla, Madeline Kelly, Brittany Suisse Foran High School: Jessica Johnson, Catria Gadwah-Meaden NASA Astrophysics Data Program funds and NASA/IPAC Archive Outreach funds. Thesis: NGC 281: A Tale of Two Populations East: formation Do differences in star West: Star formation is formation triggers produce is thought to be East West triggered by triggered by lateral different protostars? A typical source: A typical source: compression of gas. Radiation Driven • cocoon-like envelope • located along ionization front Implosion (RDIs, • aligned along filament or pillar Motivation, Methodology: Megeath & Wilson 1997, AJ, • 118 visual candidates 114, 3). • 58 after further vetting A variety of trigger mechanisms are seen to cause the onset of star • 70 visual candidates Final Results formation (SF) in the . Larson, R.B. 2003, Rept. Prog. Phys, 66, 1651 • 31 after further • 7 Yes sources NGC 281 is an unusual case in vetting • 51 Maybes which two separate triggers Final Results appear to be responsible for SF Photometry Details: in the same cloud. • 8 Yes sources • 23 Maybes We were limited to aperture Guetter & Turner 1997, AJ, 113, 6 . photometry only. Combined PACS 70 We used the Aperture We used Herschel to map (blue), 100 (green) Photometry Tool . and 160 (red) micron NGC 281 in the far-IR image of NGC 281 http://www.aperturephotometry.org from Herschel We cannot reliably determine (70, 100, 160 m). µ backgrounds for 160 µm channel with aperture Source ID and Photometry photometry. Herschel observations allow Visual identification from 24, 70, and 100 micron us to identify and measure FITS images along with values of full-width half Yes Maybe Not a Source Consequently, 160 µm maxima (FWHM) and x-y aperture slices from photometry was dropped brightnesses of the youngest NGC 281 as seen in X-ray and photometry data led to the determination of a select from further analysis. protostars infrared. group of protostar candidates in each region.

Star Formation: Results: Conclusions: In the earliest stages of their development, are enshrouded by dust and gas. East and West side comparison • We did not find any systematic differences in proto-stellar populations between the East and West groups. • However, our experiment is sensitive only to the Comparison of NGC 281 protostars with a grid of high-luminosity protostars. Differences may yet radiative transfer models based on physical exist in the low luminosity protostars. characteristics of protostars. Cartoon from Greene, American Scientist, Jul-Aug 2001 Both East and West protostars have mass infall rates -5 The youngest consistent with model values less than 10 Mʘ/yr. Comparison to models and Orion A&B. protostars are most No protostars are unambiguously consistent with • Protostars in NGC 281 appear to have low mass easily identified in high mass infall rates. infall rates, and are bluer than protostars in Orion. the far-IR and sub- • We offer three scenarios to explain these results: mm because the bulk Model SED with peak at 70 • Protostars in NGC 281 are at a later evolutionary of their emission is in µm and protostar geometry The East and West populations occupy the stage compared to those in Orion. those wavelengths. Credit: Elise Furlan • It is possible that only the lowest luminosity proto-

Source 5 East same region of the color-color plot. A lack stars (not detected here) are at an earlier Typical source 16 evolutionary state compared to Orion and the SED in NGC 281 14 y = 16.018x - 21.278 of difference may signify lack of 12 models. Rising SEDs 10 8 evolutionary differences in the accretion towards the mid- 6 • Protostellar evolution is faster in NGC 281 IR mean our 4 Both East and West sources are bluer than compared to Orion. 2 rates, or ages of the two groups. sources are at 0 protostars found in the prolific star-forming 1 1.2 1.4 1.6 1.8 2 2.2 2.4 region of the Orion . class 0 or 1 stage Log λ (µm)