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The O star hinterland of the Galactic starburst, NGC 3603
No full textThe very bright and compact massive young cluster, NGC 3603, has been cited as an example of a starburst in the Milky Way and compared with the much-studied R136/30 Doradus region in the Large Magellanic Cloud. Here we build on the discovery by Mohr-Smith et al. (2017) of a large number of reddened O stars around this cluster. We construct a list of 288 candidate O stars with proper motions, in a region of sky spanning 1.5 × 1.5 square degrees centered on NGC 3603, by cross-matching the Mohr-Smith et al. (2017) catalogue with Gaia DR2 (Gaia Collaboration et al. 2018). This provides the basis for a first comprehensive examination of the proper motions of these massive stars in the halo of NGC 3603, relative to the much better studied central region. We identify up to 11 likely O star ejections – 8 of which would have been ejected between 0.60 and 0.95 Myr ago (supporting the age of ~1 Myr that has been attributed to the bright cluster centre). Seven candidate ejections are arranged in a partial ring to the south of the cluster core spanning radii of 9–18 arcmin (18–36 pc if the cluster is 7 kpc away). We also show that the cluster has a halo of a further ~100 O stars extending to a radius of at least 5 arcmin, adding to the picture of NGC 3603 as a scaled down version of the R136/30 Dor region
Infrared observations of NGC 3603
No full textWe have performed deep Ks-band observations of the starburst region NGC 3603
with the infrared camera ISAAC mounted on the VLT Antu.
The total area covered by our data stretches from the NGC 3603 starburst cluster towards
the south up to a maximal distance of about 370\hbox{^{\prime\prime}} (~12 pc).
This enables us to reconsider and redetermine the radial extent of the cluster which is
found to be about 150\hbox{^{\prime\prime}}
± 15\hbox{^{\prime\prime}} (~5 pc), exceeding previous
estimates by a factor of 2.5.
King model fits are used to disentangle the count statistics of cluster stars from those
of field stars.
With knowledge of the cluster radius we then construct and analyze the Ks-band
luminosity function (KLF) of the NGC 3603 starburst cluster.
The KLF for cluster radii >30\hbox{^{\prime\prime}} is rising down to the completeness limit of our
study at Ks ~ 17–175, corresponding to 1 Myr old cluster
members of ~ 0.5 \cal M\hbox{_{\odot}}.
For the range of intermediate luminosity stars we obtain a KLF slope of
α
= 0.35 ± 0.02 which is consistent with a Miller-Scalo type initial mass
function (IMF) of a ~1 Myr old stellar cluster
if one assumes a power-law index of β ~ 2 for the mass-luminosity relation of
both intermediate mass main sequence stars and low mass pre-main sequence stars.
At the high luminosity end the observed KLF likely flattens (α ~ 0.2), being
consistent with a Salpeter type IMF for NGC 3603's massive main sequence stars
Block Card 3603 Wyckliffe Parkway
No full textThis image was produced by the Auditor's Office in Lucas County, Ohio for tax assessment purposes. Associated dates are approximate. Descriptive terms related to this photograph include: English Cottage Style | Dwelling | 3603 Wycliffe Parkway (Toledo, Ohio) | Extension of Forest View Addition (Toledo, Ohio) | Deveaux Area (Toledo, Ohio) | West Toledo (Toledo, Ohio
Block Card 3603 Hoiles Avenue
No full textThis image was produced by the Auditor's Office in Lucas County, Ohio for tax assessment purposes. Associated dates are approximate. Descriptive terms related to this photograph include: Dwelling (Toledo, Ohio) | Folk House Style | West Toledo (Toledo, Ohio) | Homewood Park (Toledo, Ohio) | Willys Park area (Toledo, Ohio) | 3603 Hoiles Avenue (Toledo, Ohio
Block Card 3603 Hazelhurst Avenue
No full textThis image was produced by the Auditor's Office in Lucas County, Ohio for tax assessment purposes. Associated dates are approximate. Descriptive terms related to this photograph include: Dwelling (Toledo, Ohio) | Box bay | Craftsman Style | Homewood Park Extension (Toledo, Ohio) | Willys Park area (Toledo, Ohio) | West Toledo (Toledo, Ohio) | 3603 Hazelhurst Avenue (Toledo, Ohio) | Folk House Styl
Infrared observations of NGC 3603
No full textIn the framework of a multi-wavelengths study of NGC 3603 we have performed near and mid
infrared imaging to investigate the nature and the evolutionary status of the highly reddened
sources NGC 3603 IRS 9A–C.
These sources are located on the OB cluster facing side of the massive molecular cloud core
NGC 3603 MM 2 and were apparently only recently revealed from most of their natal environment
by strong stellar winds and energetic radiation originating from the nearby high mass cluster
stars.
On the basis of the steeply rising spectral energy distributions and the large near and mid
infrared excess emission we conclude that IRS 9A–C represent (the brightest members of) a
sparse association of high mass protostars, solely embedded in the gravitationally bound
material of their circumstellar envelopes but largely blown free from gas + dust of
the pristine molecular cloud core.
Fitting blackbody functions to the overall spectral energy distribution at near and mid
infrared wavelengths we identify two dust components at temperatures of 250 K and 1150 K
for IRS 9A and 250 K and 700–750 K for IRS 9B / 9C.
From the mid infrared fluxes we deduce lower limits for the gas + dust masses of the
circumstellar envelopes:
\ga0.1 \cal M\hbox{_{\odot}} for IRS 9A and {\ga}3\times10^{-3}
\cal M\hbox{_{\odot}} for IRS 9B / 9C.
Estimates of the total luminosities are on the order of 105
L\hbox{_{\odot}} and
103
L\hbox{_{\odot}} for IRS 9A and IRS 9B / 9C, respectively.
Finally, our interpretation of IRS 9A–C being protostars is supported by recent ATCA data.
The measured 3 cm and 6 cm radio fluxes of IRS 9A can neither be explained by non-thermal
emission nor by thermal dust emission.
From the spectral index ~ 0.3 we conclude that the observed radio
emission is thermal bremsstrahlung and most likely excited externally by ionizing photons
originating from the nearby OB cluster
The origin of very massive stars around NGC 3603
No full textThe formation mechanism of the most massive stars in the Universe remains an unsolved problem. Are they able to form in relative isolation in a manner similar to the formation of solar-type stars, or do they necessarily require a clustered environment? In order to shed light on this important question, we study the origin of two very massive stars (VMS): the O2.5If*/WN6 star RFS7 (∼100 M⊙), and the O3.5If* star RFS8 (∼70 M⊙), found within ∼53 and 58 pc, respectively, of the Galactic massive young cluster NGC 3603, using Gaia data. The star RFS7 is found to exhibit motions resembling a runaway star from NGC 3603. This is now the most massive runaway star candidate known in the Milky Way. Although RFS8 also appears to move away from the cluster core, it has proper-motion values that appear inconsistent with being a runaway from NGC 3603 at the 3σ level (but with substantial uncertainties due to distance and age). Furthermore, no evidence for a bow-shock or a cluster was found surrounding RFS8 from available near-infrared photometry. In summary, whilst RFS7 is likely a runaway star from NGC 3603, making it the first VMS runaway in the Milky Way, RFS8 is an extremely young (∼2 Myr) VMS, which might also be a runaway, but this would need to be established from future spectroscopic and astrometric observations, as well as precise distances. If RFS 8 was still not found to meet the criteria for being a runaway from NGC 3603 from such future data, this would have important ramifications for current theories of massive star formation, as well as the way the stellar initial mass function is sampled
The O star hinterland of the Galactic starburst, NGC 3603
No full textThe very bright and compact massive young cluster, NGC 3603, has been cited as an example of a starburst in the Milky Way and compared with the much-studied R136/30 Doradus region in the Large Magellanic Cloud. Here we build on the discovery by Mohr-Smith et al. of a large number of reddened O stars around this cluster. We construct a list of 288 candidate O stars with proper motions (PMs), in a region of sky spanning 1.5 × 1.5 deg 2 centred on NGC 3603, by cross-matching the Mohr-Smith et al. catalogue with Gaia DR2. This provides the basis for a first comprehensive examination of the PMs of these massive stars in the halo of NGC 3603, relative to the much better studied central region. We identify up to 11 likely O star ejections - 8 of which would have been ejected between 0.60 and 0.95 Myr ago (supporting the age of ∼1 Myr that has been attributed to the bright cluster centre). Seven candidate ejections are arranged in a partial ring to the south of the cluster core spanning radii of 9-18 arcmin (18-36 pc if the cluster is 7 kpc away). We also show that the cluster has a halo of a further ∼100 O stars extending to a radius of at least 5 arcmin, adding to the picture of NGC 3603 as a scaled down version of the R136/30 Dor region
Open Clusters in Carina: NGC 3603, Westerlund 2 and Sher 1
No full textSe presentan observaciones polarimétricas en las bandas U BV RI de estrellas situadas en la dirección de los cúmulos NGC 3603, Westerlund 2 y Sher 1, con el propósito de estudiar las características del polvo entre el Sol y los cúmulos, evidencias polarimétricas de la existencia (o no) de enrojecimiento anómalo en NGC 3603 y en Westerlund 2, y la identificación de estrellas con indicios de polarización intrínseca.
40% de las estrellas observadas en Westerlund 2 presentan indicios de polarización intrínseca, porcentaje similar al encontrado en NGC 6611 y en IC 2944; en cambio, en NGC 3603 es mucho menor. Las eficiencias polarimétricas medias son bajas por la presencia de varias nubes de polvo interestelar entre los objetos y el Sol. Se apoya la existencia de enrojecimiento anómalo en NGC 3603, mientras que en Westerlund 2 existen leves indicios de ello.We present polarimetric observations in the U BV RI bands of stars located in the directions of NGC 3603, Westerlund 2 and Sher 1. Our main objectives are to study the characteristics of the dust lying between the Sun and the clusters, to analyze polarimetric evidence on the existence (or not) of abnormal reddening in NGC 3603 and Westerlund 2; and to identify stars with signatures of intrinsic polarization.
40% of the stars observed in Westerlund 2 display indications of intrinsic polarization, a percentage similar to those found in the open clusters NGC 6611 and IC 2944: but in NGC 3603 it is very small. Mean polarization efficiencies are low, due to the presence of several dust clouds located in the way to the clusters. We are in favor of the existence of abnormal reddening in NGC 3603, while in Westerlund 2 there are only indications.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica
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