This is a repository copy of The VLT-FLAMES Tarantula Survey XI. A census of the hot luminous stars and their feedback in 30 Doradus. White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/120563/ Version: Accepted Version Article: Doran, E.I., Crowther, P.A., de Koter, A. et al. (16 more authors) (2013) The VLT-FLAMES Tarantula Survey XI. A census of the hot luminous stars and their feedback in 30 Doradus. Astronomy and Astrophysics, 558. A134. ISSN 0004-6361 https://doi.org/10.1051/0004-6361/201321824 Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. 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Schneider12, W. D. Taylor5, J. Th. van Loon16, and J. S. Vink9 (Affiliations can be found after the references) Accepted: 5 August 2013 ABSTRACT Aims. We compile the first comprehensive census of hot luminous stars in the 30 Doradus (30 Dor) star forming region of the Large Magellanic Cloud. We investigate the stellar content and spectroscopic completeness of early type stars within a 10arcmin (150pc) radius of the central cluster, R136. Estimates were made of the integrated ionising luminosity and stellar wind luminosity. These values were used to re-assess the star formation rate (SFR) of the region and determine the ionising photon escape fraction. Methods. Stars were selected photometrically and combined with the latest spectral classifications. Stellar calibrations and models were applied to obtain physical parameters and wind properties. Their integrated properties were then compared to global observations from ultra-violet (UV) to far-infrared (FIR) imaging as well as the population synthesis code, Starburst99. Results. The census identified 1145 candidate hot luminous stars of which > 700 were considered genuine early type stars that contribute to feedback. We assess the spectroscopic completeness to reach 85% in outer regions (> 5 pc) but fall to 35% in the vicinity of R136, giving a total of 500 hot luminous stars with spectroscopy. Only 31 W-R and Of/WN stars were included, but their contribution to the integrated ionising luminosity and wind luminosity was ∼ 40% and ∼ 50%, respectively. Similarly, stars with Minit > 100 M⊙ (mostly H-rich WN stars) also showed high contributions to the global feedback, ∼ 25% in both cases. Such massive stars are not accounted for by the current Starburst99 code, which was found to underestimate the integrated ionising luminosity and wind luminosity of R136 by a factor ∼ 2 and ∼ 9, respectively. The census −1 inferred a SFR for 30 Dor of 0.073±0.04 M⊙ yr . This was generally higher than that obtained from some popular SFR calibrations but still showed good consistency with the far-UV luminosity tracer and the combined Hα and mid-infrared tracer, but only after correcting for Hα extinction. The +55 global ionising output was also found to exceed that measured from the associated gas and dust, suggesting that ∼ 6−6 % of the ionising photons escape the region. Conclusions. When studying the most luminous star forming regions, it is essential to include their most massive stars if one is to determine a reliable energy budget. The large ionising outputs of these stars increase the possibility of photon leakage. If 30 Dor is typical of other large star forming regions, estimates of the SFR will be underpredicted if this escape fraction is not accounted for. Key words. Stars: early-type – Stars: Wolf-Rayet – Stars: massive – Galaxies: open clusters and associations: individual: Tarantula Nebula (30 Doradus) – Galaxies: star clusters: individual: RMC 136 – Galaxies: star formation 1. Introduction tiple ages; from areas of ongoing star formation (Brandner et al. 2001; Walborn et al. 2013) to older (∼ 20 − 25 Myr) supergiants The Tarantula Nebula (NGC 2070, 30 Doradus - hereafter “30 in the Hodge 301 cluster (Grebel & Chu 2000). Dor”) in the Large Magellanic Cloud (LMC) is optically the brightest H ii region in the Local Group (Kennicutt 1984). It has been subject to numerous ground-based photometric and spec- More recently, the VLT-Flames Tarantula Survey (VFTS, see troscopic studies, displaying an abundance of hot massive stars Evans et al. 2011, hereafter, Paper I) has provided unprecedented (Melnick 1985; Schild & Testor 1992; Parker 1993; Walborn multi-epoch spectroscopic coverage of the massive star popula- & Blades 1997). Hubble Space Telescope observations later re- tion. The VFTS greatly extends our sampling of massive stars vealed their high concentration in the more crowded central clus- at different luminosities and temperatures, which are unobtain- arXiv:1308.3412v1 [astro-ph.SR] 15 Aug 2013 ter, R136 (Hunter et al. 1995; Massey & Hunter 1998), also be- able from distant galaxies. In particular, it allows several topics lieved to be the home of stars with masses > 150 M⊙ (Crowther to be assessed including: stellar multiplicity (Sana et al. 2013a); et al. 2010). Roughly a third of the LMC Wolf-Rayet (W-R) stars rotational velocity distributions (Dufton et al. 2013 & Ram´ırez- compiled in Breysacher et al. (1999) are contained within the 30 Agudelo et al. in prep); the dynamics of the region and R136 Dor nebular region of N157 (Henize 1956), with several found (Henault-Brunet´ et al. 2012b). In this paper we look at 30 Dor within R136 itself. The stellar population of 30 Dor spans mul- in a broader context. Prior to the VFTS, < 20% of massive stars within the central 10 arcmin ≈ 150 pc (adopting a distance ⋆ Based on observations collected at the European Southern modulus to the LMC of 18.49 ± 0.047 mag i.e. a distance of Observatory under program ID 182.D-0222 ≈ 49.97±1.11 kpc, Pietrzynski´ et al. 2013) had a known spectral ⋆⋆ Complete versions of Tables D.1 & D.2 are available in elec- type (SpT). As we will show, this spectroscopic completeness is tronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr improved to ∼ 85% by the VFTS, enabling us to compile the (130.79.128.5) or at ftp://astro.shef.ac.uk/pub/eid first robust census of the hot luminous stars in 30 Dor. 1 E. I. Doran et al.: The VLT-FLAMES Tarantula Survey XI. A census of the hot luminous stars in 30 Doradus Its close proximity and low foreground extinction, combined & Dessart (1998) compiled a list of the hot luminous stars in the with its rich source of hot luminous stars, make 30 Dor the inner 10 pc of 30 Dor and found the W-R stars to play a key role ideal laboratory for studying starburst environments in the dis- in the overall feedback. We extend their study to a larger radius, tant universe. In more distant cases, however, stars cannot be employing updated stellar calibrations and models to determine individually resolved and starburst regions can only be studied whether the W-R star contribution still remains significant. via their integrated properties. This census provides us with a Population synthesis codes can predict observable properties spectral inventory for an archetypal starburst, along with esti- of extragalactic starbursts, and 30 Dor equally serves as a test mates of the stellar feedback. Here, we focus on radiative and bed for these. Direct comparisons to the stellar content and feed- mechanical feedback, to which hot luminous stars greatly con- back in similar luminous star forming regions is relatively un- tribute, especially prior to core-collapse supernova explosions. studied. The R136 cluster is believed to be at a pre-supernova Their high luminosities and temperatures provide a plethora of age and so has largely preserved its initial mass function (IMF), extreme UV (EUV) photons (Q0), that ionise the surrounding although mass-loss and binary effects may have affected this to 4 gas to produce H ii regions. Meanwhile, their strong stellar winds some extent. Its high mass (Mcl . 5.5 × 10 M⊙, Hunter et al. lead to a high wind luminosity (LSW), capable of sweeping up 1995) also ensures that its upper mass function (MF) is suffi- the ISM into bubbles, even prior to the first supernovae (Chu & ciently well populated, hence ideal to test synthetic predictions Kennicutt 1994). R136 itself, appears to show evidence of such of the stellar feedback. Comparisons to the entire 30 Dor region effects through an expanding shell (e.g. van Loon et al. 2013). are less straight forward given its non-coevality, but can still be Individual analyses are currently underway of all the VFTS made by adopting an average age for 30 Dor.