Astron. Astrophys. 364, 683-688 (2000)

1. Introduction

Massive YSOs are protostars (Palla & Stahler 1993) which are either surrounded by ultracompact HII regions or will eventually be hot enough to produce HII regions. They are mostly found buried deep inside clouds of gas and dust. The major difficulties in the study of massive YSOs are (a) there are fewer massive YSOs compared to low-mass YSOs and most of them are at a distance greater than 1 kpc from the Sun and b) most massive YSOs suffer large extinction (Av 10) and hence are difficult to study in the optical wavelengths. However, they can be studied in the radio and infrared wavelengths. Further, it is possible to study the environment of these objects with seeing limited spatial resolution in the near-infrared using array detectors like NICMOS.

Recent studies by Churchwell (1997) revealed that massive YSOs undergo similar bipolar outflows like the low-mass YSOs, but the rate of mass outflow is larger by orders of magnitude (3). Similarly luminosities of massive YSOs are also higher. The total mass locked in the outflow is often found to be larger than the central star. Churchwell (1997) proposed that the larger outflow mass could be due to the in-falling matter directly diverted into the bipolar jets. It is clear from earlier works (Shepherd & Churchwell 1996; Churchwell 1997; Hartquist & Dyson 1997; Hunter et al. 1997) that the impact of outflows from massive YSOs shapes the history of star-formation in the parent molecular cloud.

We have started a NIR observational program on studies of regions of massive star formation. This is our first paper in the series. In this paper we study the massive and luminous YSO IRAS 05361+3539 and the star formation in the neighborhood using 2MASS (The Two Micron All Sky Survey) data and new NIR observations from Mt. Abu, India. The region so far is not very well studied. IRAS source 05361+3539 (G173.58 +2.45) was studied in the millimeter lines (¹²CO and ¹³CO) by Shepherd & Churchwell (1996). The source is situated at a kinematic distance of 1.8 kpc (Wouterloot & Brand 1989). Earlier, Wouterloot et al. (1988) detected H₂O maser from the source. The source is embedded inside a large molecular cloud. The FIR fluxes meet the conditions of Wood & Churchwell (1989) for UCHII regions and total FIR fluxes correspond to a B2.5 central star. Shepherd & Churchwell (1996) found bipolar flows in the ¹²CO velocity map with high velocities (up to -27.1 km/s in the blue shifted lobe) with a total mass of 32 locked in the outflow. They estimated from the IRAS fluxes the central star mass to be 7.

In Sect. 2 we present the observations and data reduction procedures, Sect. 3 deals with results and discussion and we summarize our conclusions in Sect. 4.

© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001
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