The Intermediate Stellar Mass Population in R136 Determined from Hubble Space Telescope Planetary Camera 2 Images

Hunter, Deidre A.; Shaya, E.; Holtzman, Jon A.; Light, R. M.; O'Neil, Earl J.; Lynds, Roger

doi:10.1086/175950

Cited by 195 publications

(312 citation statements)

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“…This implication has an important consequence for understanding the early dynamical evolution of star clusters since it suggests that mass segregation in young clusters (the necessary condition for effective production of runaway OB stars) should be primordial rather than caused by the Spitzer instability. For example, R136 was found to already be mass-segregated at its age of about 2 Myr or younger (Campbell et al 1992;Hunter et al 1995;Brandl et al 1996;de Grijs et al 2002). But the Spitzer instability could be a very fast ( < ∼ 0.5 Myr) process if the birth cluster is very dense (e.g.…”

Section: Discussionmentioning

confidence: 99%

Massive runaway stars in the Large Magellanic Cloud

Gvaramadze

Kroupa

Pflamm-Altenburg

2010

A&A

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The origin of massive field stars in the Large Magellanic Cloud (LMC) has long been an enigma. The recent measurements of large offsets (∼100 km s −1 ) between the heliocentric radial velocities of some very massive (O2-type) field stars and the systemic LMC velocity provides a possible explanation of this enigma and suggests that the field stars are runaway stars ejected from their birthplaces at the very beginning of their parent cluster's dynamical evolution. A straightforward way to prove this explanation is to measure the proper motions of the field stars and to show that they are moving away from one of the nearby star clusters or OB associations. This approach is, however, complicated by the long distance to the LMC, which makes accurate proper motion measurements difficult. We used an alternative approach for solving the problem (first applied for Galactic field stars), based on the search for bow shocks produced by runaway stars. The geometry of detected bow shocks would allow us to infer the direction of stellar motion, thereby determining their possible parent clusters. In this paper we present the results of a search for bow shocks around six massive field stars that have been proposed as candidate runaway stars. Using archival Spitzer Space Telescope data, we found a bow shock associated with one of our programme stars, the O2 V((f*)) star BI 237, which is the first-ever detection of bow shocks in the LMC. Orientation of the bow shock suggests that BI 237 was ejected from the OB association LH 82 (located at 120 pc in projection from the star). A by-product of our search is the detection of bow shocks generated by four OB stars in the field of the LMC and an arc-like structure attached to the candidate luminous blue variable R81 (HD 269128). The geometry of two of these bow shocks is consistent with the possibility that their associated stars were ejected from the 30 Doradus star-forming complex. We discuss implications of our findings for the problem of the origin of runaway stars and the early dynamical evolution of star clusters.

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Section: Discussionmentioning

confidence: 99%

Massive runaway stars in the Large Magellanic Cloud

Gvaramadze

Kroupa

Pflamm-Altenburg

2010

A&A

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“…Imagesharpening techniques such as speckle interferometry (Weigelt & Baier 1985) revealed that this object had many individual A&A 602, A56 (2017) stars, however, which ere coined the R 136a Weigelt components. R 136a was clearly resolved into hundreds of sources by the Hubble Space Telescope (HST, Hunter et al 1995;Campbell et al 1992), which opened routes to better study each of Weigelt components at various wavelengths and resolutions. More recent multiconjugate adaptive optics instruments (AO, Campbell et al 2010) on the VLT attempted to better resolve the core of R 136 with relative success.…”

Section: Introductionmentioning

confidence: 99%

Uncrowding R 136 from VLT/SPHERE extreme adaptive optics

Khorrami

Vakili

Lanz

et al. 2017

A&A

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This paper presents the sharpest near-IR images of the massive cluster R 136 to date, based on the extreme adaptive optics of the SPHERE focal instrument implemented on the ESO Very Large Telescope and operated in its IRDIS imaging mode. The crowded stellar population in the core of the R 136 starburst compact cluster remains still to be characterized in terms of individual luminosities, age, mass and multiplicity. SPHERE/VLT and its high contrast imaging possibilities open new windows to make progress on these questions. Stacking-up a few hundreds of short exposures in J and Ks spectral bands over a field of view (FoV) of 10.9 × 12.3 centered on the R 136a1 stellar component, enabled us to carry a refined photometric analysis of the core of R 136. We detected 1110 and 1059 sources in J and Ks images respectively with 818 common sources. Thanks to better angular resolution and dynamic range, we found that more than 62.6% (16.5%) of the stars, detected both in J and Ks data, have neighbours closer than 0.2 (0.1 ). The closest stars are resolved down to the full width at half maximum (FWHM) of the point spread function (PSF) measured by Starfinder. Among resolved and/or detected sources R 136a1 and R 136c have optical companions and R 136a3 is resolved as two stars (PSF fitting) separated by 59 ± 2 mas. This new companion of R 136a3 presents a correlation coefficient of 86% in J and 75% in Ks. The new set of detected sources were used to re-assess the age and extinction of R 136 based on 54 spectroscopically stars that have been recently studied with HST slit-spectroscopy (Crowther et al. 2016, MNRAS, 458, 624) of the core of this cluster. Over 90% of these 54 sources identified visual companions (closer than 0.2 ). We found the most probable age and extinction for these sources are 1.8 +1.2 −0.8 Myr, A J = (0.45 ± 0.5) mag and A K = (0.2 ± 0.5) mag within the photometric and spectroscopic error-bars. Additionally, using PARSEC evolutionary isochrones and tracks, we estimated the stellar mass range for each detected source (common in J and K data) and plotted the generalized histogram of mass (MF with error-bars). Using SPHERE data, we have gone one step further and partially resolved and studied the initial mass function covering mass range of (3-300) M at the age of 1 and 1.5 Myr. The density in the core of R 136 (0.1-1.4 pc) is estimated and extrapolated in 3D and larger radii (up to 6 pc). We show that the stars in the core are still unresolved due to crowding, and the results we obtained are upper limits. Higher angular resolution is mandatory to overcome these difficulties.

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“…The R136 cluster (< 5 pc) has a mass of 5.5 × 10 4 M (Hunter et al 1995) and an age of 1.5±0.5 Myr (Crowther et al 2016). It contains nine VMS (Crowther et al 2016) inside the half-light radius of 1.7 pc (Hunter et al 1995). Doran et al (2013) find Q(H i)= 7.5 × 10 51 s −1 for the R136 region.…”

Section: Ionizing Fluxesmentioning

confidence: 99%

“…Doran et al (2013) provide a census of the hot luminous stars in R136 and the 30 Dor region of the LMC. The R136 cluster (< 5 pc) has a mass of 5.5 × 10 4 M (Hunter et al 1995) and an age of 1.5±0.5 Myr (Crowther et al 2016). It contains nine VMS (Crowther et al 2016) inside the half-light radius of 1.7 pc (Hunter et al 1995).…”

Section: Ionizing Fluxesmentioning

confidence: 99%

The very massive star content of the nuclear star clusters in NGC 5253

2016

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The blue compact dwarf galaxy NGC 5253 hosts a very young starburst containing twin nuclear star clusters, separated by a projected distance of 5 pc. One cluster (#5) coincides with the peak of the Hα emission and the other (#11) with a massive ultracompact H ii region. A recent analysis of these clusters shows that they have a photometric age of 1 ± 1 Myr, in apparent contradiction with the age of 3-5 Myr inferred from the presence of Wolf-Rayet features in the cluster #5 spectrum. We examine Hubble Space Telescope ultraviolet and Very Large Telescope optical spectroscopy of #5 and show that the stellar features arise from very massive stars (VMS), with masses greater than 100 M , at an age of 1-2 Myr. We further show that the very high ionizing flux from the nuclear clusters can only be explained if VMS are present. We investigate the origin of the observed nitrogen enrichment in the circum-cluster ionized gas and find that the excess N can be produced by massive rotating stars within the first 1 Myr. We find similarities between the NGC 5253 cluster spectrum and those of metal poor, high redshift galaxies. We discuss the presence of VMS in young, star-forming galaxies at high redshift; these should be detected in rest frame UV spectra to be obtained with the James Webb Space Telescope. We emphasize that population synthesis models with upper mass cut-offs greater than 100 M are crucial for future studies of young massive star clusters at all redshifts.

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The Intermediate Stellar Mass Population in R136 Determined from Hubble Space Telescope Planetary Camera 2 Images

Cited by 195 publications

References 0 publications

Massive runaway stars in the Large Magellanic Cloud

Massive runaway stars in the Large Magellanic Cloud

Uncrowding R 136 from VLT/SPHERE extreme adaptive optics

The very massive star content of the nuclear star clusters in NGC 5253

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