Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 1 Robert Estalella, Aina Palau, Maite Beltrán (UB) Paul T. P. Ho (CfA), Henrik Beuther (MPIfA) IRAS , a puzzling massive star-forming region UNIVERSITAT DE BARCELONA

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 2 Introduction: modes of star formation Observationally, there are two modes of star formation in molecular clouds: clustered mode (e.g. Orion) isolated mode (e.g. HHL 73) (Megeath et al. 2005) (Anglada et al. 1997) Likely phenomena in clustered mode: ● interaction between sources ● outflows ● mergings of cloud cores ● compression front from high-mass stars

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 3 Introduction: the big question Nobody knows (up to now) the answer, but we can gain insight by: ● characterizing different cluster environments in their first stages of formation, and ● studying the interaction between the members of these environments Approach and strategy ● detect low-mass condensations:high sensitivity ● first evolutionary stages:mm/submm range ● high-mass star-forming regions farther away than 1 kpc: angular resolution: 2''-5'' Why do stars preferently form closely packed rather than in isolation? Source selected from a sample of massive star-forming regions: IRAS

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 4 ● 3200 L ⊙ at 1.4 kpc in Cygnus OB2 ● 3 bright IR stars, brightest infrared source IRS 3 coincident with a weak cm source ● IRS 1: the most luminous and embedded object of the association? ● N-S bipolar outflow (single dish) 0.05 pc IRAS MASS composite J, H, K image

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 5 Continuum results (1 mm SMA) cm source (white): associated with IRS 3 1 mm emission (brown): 3 condensations: ● west: mm1-mm4, ~4 M ⊙ ● east: mm7, ~0.5 M ⊙ ● north: mm6/IRS 1, ~ M ⊙ mm5/IRS 1N? grey scale: 2MASS J image

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 6 CO (2-1) results (SMA) Low velocity: associated with IRS 1, two elongated structures at both sides of IRS 3 High velocity: bipolar molecular outflow in the east-west direction driven by IRS 1. No evidence of large-scale north-south outflow high vel IRS 1 is at the center of symmetry of the outflow low vel grey scale: H 2 cont + line at 2.12 µ m (Kumar et al. 2002)

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 7 The bipolar outflow CO emission with IRAM 30 m (Beuther et al. 2002) Large-scale blue lobe resolved out by the SMA Parameters of the outflow discovered toward IRS 1 compared to other outflows: extended emission CO(2-1) IRAM 30m Parameters of IRS 1 outflow in between low-mass and high-mass outflows high mass low mass

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 8 Cavity created by IRS 3 Observations suggest that IRS 3 is blowing up a shell of surrounding material, and that the dust condensations at both sides of IRS 3 are the result of accumulation of mass.  IRS 3 Snowplow model from Anglada et al. (1995) R shell = 0.07 pc v shell = 2 km/s P ext  (3.3 km/s) 2 n 0 = 2300 cm -3 t wind = 10 4 yr R max = 0.08 pc assumptions:Derived param.: low res CO low vel CO cont 1mm

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November 23 9 The nature of IRS 1 IRS 1: ● 2MASS very bright magnitudes ● strong IR excess ● circumstellar mass at 1 mm ● outflow parameters SED for IRS 1 typical of Class I: ● 1-2 µ m: steep >0 profile ● µ m: >0 profile ● Comparison with other SEDs of Class I sources of different luminosities scaled to the distance of IRAS IRS 1 is an intermediate-mass Class I source (but the circumstellar mass is low) Is IRS 1 a high-mass B0 star? (too luminous) Is IRS 1 a high-mass protostar? (too low circumstellar mass) Is IRS 1 a low/intermediate-mass protostar? (IRS 13) 960 L ⊙ (IRS 14) 250 L ⊙ (IRAS ) 4 L ⊙

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November Star formation: interactions, initial conditions The most massive source has faint mm emission associated Other sources around it: different properties at different wavelengths This suggests continuous star formation, and since N s (IR) > N s (mm), that t life (IR) > t life (mm) IRS 3 IRS 1 IRS 3 is driving a cavity and accumulating the surrounding material in the walls Interaction between sources could have triggered star formation in some cases IRS 1 and IRS 3 could have formed simultaneously (IRS 3 may have not triggered the formation of IRS 1) Initial conditions are required to explain the overall spatial distribution of the sources

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November Number of mm sources vs IR sources Median number of mm sources around high-mass protostars: 5 Median number of IR sources around high-mass stars: 15 Palau 2006, PhD thesis Beuther & Schilke 2004 Cesaroni 1999 Why? Summary of high-mass protostellar objects observed with enough sensitivity to detect low-mass condensations (< 1 M ⊙ ) in the mm range, up to 2006: (based on very poor statistics!) See Aina’s presentation Sensitivity problem? Enough resolution and u-v coverage? Massive enough regions? Protostars already formed around the high-mass protostar? Is star formation a continuous process?

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November Conclusions IRAS is a cluster environment with a variety of sources. IRS 1, an intermediate-mass Class I source, driving an east-west bipolar CO(2-1) outflow. IRS 3, seems to drive an expanding shell pushing out the dust condensations detected at both sides of this source. Our observations suggest that star formation in this cluster environments is a continuous process. Interaction seems to be important in massive star-forming regions, but initial conditions must be important as well to determine the final distribution of young stellar objects in the cluster environment.

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November Date: 2003 August 3 (still not completed), first SMA observation with 6 antennas! Hybrid compact/extended configuration (baselines from 13 to 120 m) CO(2-1), spectral resolution: 1.06 km/s Continuum at 230 GHz (1.3 mm); bandwidth 1 GHz per sideband; rms= 2 mJy/beam Angular resolution: ~3''. Primary beam FWHM 45'' Passband calibration: Uranus and Neptune. Phase calibration: Flux calibration (~20%): Uranus SMA observations of IRAS SubMillimeter Array (SAO, ASIAA)

Mini Workshop on Star Formation and Astrochemistry. Barcelona, 2006 November Sources in different evolutionary stages ● no infrared emission ● strong mm emission, ~1 M ⊙ ● no signs of star formation ● visible at optical wavelengths ● brightest infrared source in the field ● cm source  UCHII region, B2 star ● no dust, no CO emission main-sequence star, end accretion phase ● infrared 2MASS source, strong IR excess ● mm source, ~0.5 M ⊙, intermediate-mass ● driving molecular outflow accretion phase, Class I starless cores? IRS3 IRS1 ● infrared 2MASS source, strong IR excess ● mm source, ~0.6 M ⊙ accretion phase IRS1N