Probing Circumstellar Molecular Gas in the o StarForming

Probing Circumstellar Molecular Gas in the o Star-Forming Region BD +40 4124 Murad Hamidouche, Shiya Wang, Leslie W. Looney University of Illinois at Urbana-Champaign

Outline n n Studying the effects of clusters on lowmass stars Probing the circumstellar molecular gas in the cluster The physical conditions of the gas and the state of the cluster Implications

Understanding our Sun? • It is becoming clear from short-lived isotopes (e. g. 60 Fe and 26 Al) in the early solar nebula that the Sun probably formed nearby a massive star < 2 pc (Looney et al. 2006) • This is not surprising, as most stars form in groups or clusters (e. g. Lada & Lada 2004). • Clearly massive stars effect the birth and evolution of nearby low-mass stars. But by how much? HST image of Trapezium in Orion • Hard question– just beginning to well understand isolated lowmass stars.

o Why study BD +40 4124? • Start with easier to understand small clusters around intermediate-mass stars. • BD +40 o 4124 is a perfect system – small, loose cluster at 1000 pc • 25 low mass systems within 0. 15 pc. BD +40 o 4124 V 1318 Cyg N S V 1686 Cyg • Associated with 300 M of clumpy, dense molecular gas. • V 1318 Cyg binary system : a low mass star and an intermediate-mass young Herbig Ae/Be star → nearly simultaneous intermediate and low mass star formation? K-band image (Hillenbrand et al. 1995)

Probing the Molecular Gas • BIMA interferometric observation (high and low resolution) → CS(2 -1) overlaid on H-Band adaptive optics (Davies et al. 2001) • Significant CS emission with long ridge structure morphology

Comparison of Dust and Gas • SCUBA 850 micron images of region, similar in morphology. • Besides, CS emission traces more dense regions than sub-mm • 22 sources (Hillenbrand et al. 1995) YSO.

Spatial Density of the Young Stars • 80% of the stars are closely associated with dense gas : Embedded sources have a larger preference for the dense regions • Embedded objects more likely to be near a massive star. • Some gas clumps without known embedded stars (probably a young hidden population)

Spatial Density of the Young Stars • Larger number of massive stars than one would expect from IMF. • A very deeply embedded population would rectify somewhat • Regardless, 100% of known population has IR excess ( YSO) • High and low mass star formation on quick timescales

When did each star form ? • From the PMS stars’ age within 1 Myrs • This implies that low-mass and higher mass stars coevolved • Unlike the proposed case in the Eagle nebula where higher mass stars triggering low-mass stars (Hester et al. 1996)

Dust Continuum Emission V 1318 Cyg 3 2 1 • At Dust lowemission resolution, is resolved the threeatmain highcontinuum resolution peaks coincide with the → fit CS asemission a Gaussian peaks 3000 exactly. x 1500 AU • Optically thin with 25 K temperature, estimated M=2 M M 1=4 M , M 2=0. 6 M , M 3=1. 4 M • What is this structure?

Dust Continuum Emission V 1318 Cyg • The offset is slightly significant but fits quite well the VLA position of a water maser (accuracy of 0. 1 ) • We suggest that there is a very young, deeply embedded intermediate or low-mass star in the system ?

The physical conditions of the gas BD +40 o 4124 Overlay of CS CS C B A 2 K J I F E D A 1 • Assume : LTE, constant temperature and density with CS in a LVG model, kinetic temperature = 15 -30 K the best fit to the fluxes : Ncs = 1. 6 × 1013 – 1014 cm-2 • Assume: CS/H 2 ~ 10 -9 the mass of clumps: A 2 : 0. 9 – 1. 7 M ; B : 0. 5 – 1. 3 M ; D : 0. 5 – 1. 4 M ; F : 0. 3 – 0. 9 M ; H : 0. 2 – 0. 8 M

CS C B A 2 C I K J F The kinematics of clumps – cloud-cloud collision ? D E D A 1 E

Conclusions n CS traces the dense cores → Possible site of star formation ~10 emission peaks/clumps ¨ → Perhaps new forming stars or embedded protostars ¨ n The strongest emission is associated with V 1318 Cyg binary system → The peak is located near the southern star ¨ → Maybe a very young and deeply embedded intermediate protostar ¨ n Varying peak systemic velocities of remnant clouds → Suggestive of two cloud cores colliding ¨ → Would explain the high efficiency of star formation ¨