Abstract. The region of M 17 has been imaged at 10.5 and 20.0 µm with the groundbased infrared camera MANIAC. In addition to a prominent diffuse emission bar (4. 5×0. 3) extending southeast to northwest at the interface between the H ii region and the southwestern molecular cloud, the mosaic of 133 single frames at each wavelength revealed 22 compact sources. One of these sources is the Kleinmann-Wright-Object and another was previously identified as the ultra-compact H ii region M 17-UC1. Combining the N-band and Q-band data with near infrared data yielded spectral energy distributions that classifies all sources to be of Class I. The observed luminosities were between 55 and 4775 L , which suggests that these sources represent the youngest generation of massive early type stars in M 17 and are surrounded by relics of their protostellar clouds. The morphology of the 10.5 and 20.0 µm emission towards some of the sources reveals flattened structures and may be the first evidence of the presence of circumstellar disks around massive stars.

We used the near-IR imager/spectrograph LUCIFER mounted on the Large Binocular Telescope (LBT) to image, with sub-arcsec seeing, the local dwarf starburst NGC 1569 in the JHK bands and HeI 1.08µm, [FeII] 1.64µm and Brγ narrow-band filters. We obtained high-quality spatial maps of HeI 1.08µm,[FeII] 1.64µm and Brγ emission across the galaxy, and used them together with HST /ACS images of NGC 1569 in the Hα filter to derive the two-dimensional spatial map of the dust extinction and surface star formation rate density. We show that dust extinction (as derived from the Hα/Brγ flux ratio) is rather patchy and, on average, higher in the North-West (NW) portion of the galaxySimilarly, the surface density of star formation rate (computed from either the dereddened Hα or dereddened Brγ image) peaks in the NW region of NGC 1569, reaching a value of about 4 × 10 −6 M ⊙ yr −1 pc −2 . The total star formation rate as estimated from the integrated, dereddened Hα (or, alternatively, Brγ) luminosity is about 0.4 M ⊙ yr −1 , and the total supernova rate from the integrated, dereddened [FeII] 1.64µm luminosity is about 0.005 yr −1 (assuming a distance of 3.36 Mpc). The azimuthally averaged [FeII] 1.64µm/Brγ flux ratio is larger at the edges of the central, gas-deficient cavities (encompassing the super star clusters A and B) and in the galaxy outskirts. If we interpret this line ratio as the ratio between the average past star formation (as traced by supernovae) and on-going activity (represented by OB stars able to ionize the interstellar medium), it would then indicate that star formation has been quenched within the central cavities and lately triggered in a ring around them. The number of ionizing hydrogen and helium photons as computed from the integrated, dereddened Hα and HeI 1.08µm luminosities suggests that the latest burst of star formation occurred about 4 -5 -Myr ago and produced new stars with a total mass of ≃1.8 × 10 6 M ⊙ .

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The LUCIFER MOS unit has been designed to exchange long-slit and multi-slit masks between two mask storage cabinets and the focal plane area. In combination with auxiliary cryostats, the MOS unit also permits the exchange of cold mask cabinets between LUCIFER and the auxiliary cryostats. Main functional components of the MOS unit are: a focal plane interface accepting the active mask, a mask handling unit transporting the masks between the focal plane mount and their storage locations, a stationary and an exchangeable cabinet holding 10 longslit and 23 multi-slit masks respectively, the translation drives for the exchangeable cabinet and the mask handling unit, and the mask locking unit securing the masks in their cabinets. For mask cabinet exchange, the LUCIFER cryostat as well as the auxiliary cryostats are equipped with 32 cm clear diameter gate valves. A test cryostat has been built to test all MOS unit functions at LN 2 temperature. Most of the MOS unit components have been completed. System tests at ambient have started. First results are presented.