The VLT-FLAMES Tarantula Survey

Abstract

Context. The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. Aims. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Methods. Spectra of over 800 early-type stars from the Very Large Telescope Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614 Å and -in a smaller region near the central cluster R 136 -neutral sodium (the Na i D doublet); we also measured the DIBs at 5780 and 5797 Å.Results. The maps show strong 4428 and 6614 Å DIBs in the quiescent cloud complex to the south of 30 Dor but weak absorption in the harsher environments to the north (bubbles) and near the OB associations. The Na maps show at least five kinematic components in the LMC and a shell-like structure surrounding R 136, and small-scale structure in the Milky Way. The strengths of the 4428, 5780, 5797 and 6614 Å DIBs are correlated, also with Na absorption and visual extinction. The strong 4428 Å DIB is present already at low Na column density but the 6614, 5780 and 5797 Å DIBs start to be detectable at subsequently larger Na column densities. Conclusions. The carriers of the 4428, 6614, 5780 and 5797 Å DIBs are increasingly prone to removal from irradiated gas. The relative strength of the 5780 and 5797 Å DIBs clearly confirm the Tarantula Nebula as well as Galactic high-latitude gas to represent a harsh radiation environment. The resilience of the 4428 Å DIB suggests its carrier is large, compact and neutral. Structure is detected in the distribution of cool-warm gas on scales between one and >100 pc in the LMC and as little as 0.01 pc in the Sun's vicinity. Stellar winds from the central cluster R 136 have created an expanding shell; some infalling gas is also detected, reminiscent of a galactic "fountain".

The VMC survey

“…We see the young stars have similar reddening to the RC stars and use them to examine the relationship between A V and DIB equivalent width using data from the FLAMES Tarantula survey (van Loon et al 2013) finding similar results to what they found when using O-and B-type stars. This shows it is possible to use other populations to supplement the reddening map.…”

“…The K s passband curve begins before the K passband, finishes before it and the overall width is nearly identical. The extinction coefficients do vary slightly with spectral type (van Loon et al 2003). This variance is small in the NIR (0.004 mag from A0 to M10 star in the J band).…”

“…Another comparison that can be made is with the DIBs analysed in van Loon et al (2013). They have compared DIB equivalent widths (combining the Galactic and LMC components) to A V measured from the VFTS sample (which mostly contains Oand B-type stars).…”

“…The dust-to-gas ratio in a galaxy is mainly correlated with metallicity (Franco & Cox 1986); some additional variance is linked to the mass outflow rate (Lisenfeld & Ferrara 1998). The Very Large Telescope FLAMES Tarantula Survey (VFTS) has used diffuse interstellar bands (DIBs) as a measurement of the environments in the Tarantula Nebula (van Loon et al 2013).…”

A CATALOG OF 1.5273 μm DIFFUSE INTERSTELLAR BANDS BASED ON APOGEE HOT TELLURIC CALIBRATORS

“…Most measured DIBs have a Galactic origin. Still, they have also been detected in the Magellanic clouds, M31 and M33 (Ehrenfreund et al 2002;Welty et al 2006;Cordiner et al 2008aCordiner et al , 2008bCordiner et al , 2011van Loon et al 2013) and in a few line of sights toward e.g., starburst galaxies or in SNe Ia spectra (Sollerman et al 2005;Cox & Patat 2008;Heckman & Lehnert 2000;Phillips et al 2013). Recently a DIB gradient was established for the first time in a 160 Mpc distant galaxy (Monreal-Ibero et al 2015).…”