Star formation in the Local Group

Program lead: Guido de Marchi (ESA)

Program duration: 15 hours

This short NIRSpec GTO program will showcase the multi-object spectroscopy (MOS) capabilities of NIRSpec for stellar studies. We will obtain medium- and high-resolution spectroscopy of hundreds of known pre-main sequence (PMS) stars of different ages, hosted in massive starburst clusters located in different environments (metallicity) in the Local Group. The target clusters are NGC 3603 in the Galaxy, 30 Dor in the Large Magellanic Cloud (LMC), and NGC 346 in the Small Magellanic Cloud (SMC). These PMS stars have been identified photometrically as objects with strong Hα excess emission and equivalent width exceeding 20 Å, and as such appear to be actively accreting from a circumstellar disc. While for many of these objects comparison with isochrones indicates young ages of the order of a few Myr, a large number of them appear older than 20Myr, suggesting that in these environments accretion onto PMS stars lasts longer than in small nearby Galactic star forming regions. The proposed NIRSpec observations will allow us to obtain accurate accretion luminosities, mass accretion rates, and infalling gas kinematics for all these stars, both young and old, from the analysis of several hydrogen recombination lines (Paα, Brβ, Br γ). The ultimate scientific goal of this project is to understand the very nature of the mass accretion process, and how it depends on the mass, age, and metallicity of the individual objects. This study is unique since existing spectroscopy of PMS stars is so far limited to the solar neighborhood and no information exists for starburst clusters or non-solar metallicity.

Observations and targets:

NGC3603

~1.8ks (on-source) MOS observations in the F170LP/G235H configuration and for 3 different sets of targets (3 different MSA configurations and pointings). Observations based on existing source catalogs.

NGC 2070 (30 Dor)

~8.4ks (on-source) MOS observations in the F170LP/G235M  (2 different MSA configurations and pointing) plus F170LP/G235H for one MSA configuration. Observations based on existing source catalogs.

NGC 346

These observations conducted in collaboration with the team of M. Meixner will involve the use of NIRCam, MIRI and NIRSpec. The NIRSpec MOS observations will be obtained in two phases. During the first phase, the NIRSpec MOS observations will draw their targets from existing catalogs and new NIRCam and MIRI imaging will be obtained. In the second phase, the MOS observations will draw their targets from the catalogs generated using the NIRCam and MIRI imaging.

We will typically spend ~9.3ks (on-source) for MOS observations in the F170LP/G235M  (2 different MSA configurations and pointing) plus F170LP/G235H for one MSA configuration.

Each time NIRSpec MOS is used, we will obtain parallel NIRCam imaging.

CAUTION: the observing strategy and the pointings described here are not yet completely frozen and are subject to change between now and the submission of the consolidated observation proposal files in November 2017 when the official cycle-1 APT software version will become available.

Presentations: