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Register a new userThe star cluster Collinder 232 in the Carina complex and its relation to Trumpler 14/16
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Carraro Giovanni dr
Publication date
2004
fields
Physics
and research's language is
English
Authors
Giovanni Carraro
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In this paper we present and analyze new CCD $UBVRI$ photometry down to $V approx$ 21 in the region of the young open cluster Collinder 232, located in the Carina spiral arm, and discuss its relationship to Trumpler 14 and Trumpler 16, the two most prominent young open clusters located in the core of NGC 3372 (the Carina Nebula). First of all we study the extinction pattern in the region. We find that the total to selective absorption ratio $R_V$ differs from cluster to cluster, being $3.48pm0.11$, $4.16pm0.07$ and $3.73pm0.01$ for Trumpler 16, Trumpler 14 and Collinder 232, respectively. Then we derive individual reddenings and intrinsic colours and magnitudes using the method devised by Romaniello et al. (2002). Ages, age spreads and distances are then estimated by comparing the Colour Magnitude Diagrams and the Hertzsprung-Russel diagram with post and pre-main sequence tracks and isochrones. We find that Trumpler 14 and Collinder 232 lie at the same distance from the Sun (about 2.5 kpc), whereas Trumpler 16 lies much further out, at about 4 kpc from the Sun. As for the age, we find that Trumpler 16 is older than both Trumpler 14 and Collinder 232. For all the clusters we indicate the existence of a significant age dispersion, whose precise value is hampered by our inability to properly distinguish members from non-members. We finally suggest that Collinder 232 is a physical aggregate and provide estimates of its basic parameters.
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Using offset-corrected Gaia-EDR3 parallax measurements and spectrophotometric methods, we have determined distances for 69 massive stars in the Carina OB1 association and associated clusters: Trumpler 16 (21 stars), Trumpler 14 (20 stars), Trumpler 15 (3 stars), Bochum 11 (5 stars), and South Pillars region (20 stars). Past distance estimates to the Carina Nebula range from 2.2 to 3.6 kpc, with uncertainties arising from photometry and anomalous dust extinction. The EDR3 parallax solutions show considerable improvement over DR2, with typical errors $sigma_{varpi}/varpi approx$~3-5%. The O-type stars in the Great Carina Nebula lie at essentially the same distance ($2.35pm0.08$ kpc), quoting mean and rms variance. The clusters have distances of $2.32pm0.12$ kpc (Tr 16), $2.37pm0.15$ kpc (Tr 14), $2.36pm0.09$ kpc (Tr 15), and $2.33pm0.12$ kpc (Bochum 11) in good agreement with the $eta$ Car distance of around 2.3 kpc. O-star proper motions suggest internal (2D) velocity dispersions $sim4$ km/s for Tr 14 and Tr 16. Reliable distances allow estimates of cluster sizes, stellar dynamics, luminosities, and fluxes of photoionizing radiation incident on photodissociation regions in the region. We estimate that Tr 14 and Tr 16 have half-mass radii $r_h = 1.5-1.8$ pc, stellar crossing times $t_{rm cr} = r_h/v_m approx 0.7-0.8$ Myr, and two-body relaxation times $t_{rh} approx 40-80$ Myr. The underlying velocity dispersion for Tr 14, if a bound cluster, would be $v_m approx 2.1^{+0.7}_{-0.4}$ km/s for $N = 7600^{+5800}_{-2600}$ stars. With the higher dispersions of the O-stars, mass segregation might occur slowly, on times scales of 3-6~Myr.
Trumpler 16 is a well--known rich star cluster containing the eruptive supergiant $eta$ Carinae and located in the Carina star-forming complex. In the context of the Chandra Carina Complex Project, we study Trumpler 16 using new and archival X-ray data. A revised X-ray source list of the Trumpler 16 region contains 1232 X-ray sources including 1187 likely Carina members. These are matched to 1047 near-infrared counterparts detected by the HAWK-I instrument at the VLT allowing for better selection of cluster members. The cluster is irregular in shape. Although it is roughly circular, there is a high degree of sub-clustering, no noticeable central concentration and an extension to the southeast. The high--mass stars show neither evidence of mass segregation nor evidence of strong differential extinction. The derived power-law slope of the X-ray luminosity function for Trumpler 16 reveals a much steeper function than the Orion Nebula Cluster implying different ratio of solar- to higher-mass stars. We estimate the total Trumpler 16 pre-main sequence population to be > 6500 Class II and Class III X-ray sources. An overall K-excess disk frequency of ~ 8.9% is derived using the X-ray selected sample, although there is some variation among the sub-clusters, especially in the Southeastern extension. X-ray emission is detected from 29 high--mass stars with spectral types between B2 and O3.
We present the first extensive spectroscopic study of the global population in star clusters Trumpler~16, Trumpler~14 and Collinder~232 in the Carina Nebula, using data from the Gaia-ESO Survey, down to solar-mass stars. In addition to the standard homogeneous Survey data reduction, a special processing was applied here because of the bright nebulosity surrounding Carina stars. We find about four hundred good candidate members ranging from OB types down to slightly sub-solar masses. About one-hundred heavily-reddened early-type Carina members found here were previously unrecognized or poorly classified, including two candidate O stars and several candidate Herbig Ae/Be stars. Their large brightness makes them useful tracers of the obscured Carina population. The spectroscopically-derived temperatures for nearly 300 low-mass members allows the inference of individual extinction values, and the study of the relative placement of stars along the line of sight. We find a complex spatial structure, with definite clustering of low-mass members around the most massive stars, and spatially-variable extinction. By combining the new data with existing X-ray data we obtain a more complete picture of the three-dimensional spatial structure of the Carina clusters, and of their connection to bright and dark nebulosity, and UV sources. The identification of tens of background giants enables us also to determine the total optical depth of the Carina nebula along many sightlines. We are also able to put constraints on the star-formation history of the region, with Trumpler~14 stars found to be systematically younger than stars in other sub-clusters. We find a large percentage of fast-rotating stars among Carina solar-mass members, which provide new constraints on the rotational evolution of pre-main-sequence stars in this mass range.
We investigate the physical conditions of the CO gas near the young star cluster, Trumpler 14 of the Carina Nebula. The observations presented in this work are taken with the Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) onboard the Herschel Space Observatory. Our field of view covers the edge of a cavity carved by Trumpler 14 about $1,mathrm{Myr}$ ago and marks the transition from HII regions to photo-dissociation regions. With the state-of-the-art Meudon PDR code, we successfully derive the physical conditions, which include the thermal pressure ($P$) and the scaling factor of radiation fields ($G_{mathrm{UV}}$), from the observed CO spectral line energy distributions~(SLEDs) in the observed region. The derived $G_{mathrm{UV}}$ values generally show an excellent agreement with the UV radiation fields created by nearby OB-stars and thus confirm that the main excitation source of the observed CO emission are the UV-photons provided by the massive stars. The derived thermal pressure is between $0.5-3,times,10^{8},mathrm{K,cm^{-3}}$ with the highest values found along the ionization front in Car I-E region facing Trumpler 14, hinting that the cloud structure is similar to the recent observations of the Orion Bar. Comparing the derived thermal pressure with the radiation fields, we report the first observationally-derived and spatially-resolved $P sim 2times10^4,G_{mathrm{UV}}$ relationship. As direct comparisons of the modeling results to the observed $^{13}mathrm{CO}$, [OI] $63,mathrm{mu m}$, and [CII] $158,mathrm{mu m}$ intensities are not straightforward, we urge the readers to be cautious when constraining the physical conditions of PDRs with combinations of $^{12}mathrm{CO}$, $^{13}mathrm{CO}$, [CI], [OI] $63,mathrm{mu m}$, and [CII] $158,mathrm{mu m}$ observations.
We present observations of the Trumpler 14/Carina I region carried out using the Stratospheric Terahertz Observatory 2 (STO2). The Trumpler 14/Carina I region is in the west part of the Carina Nebula Complex, which is one of the most extreme star-forming regions in the Milky Way. We observed Trumpler 14/Carina I in the 158 $mu$m transition of [C,{sc ii}] with a spatial resolution of 48$$ and a velocity resolution of 0.17 km s$^{-1}$. The observations cover a 0.25$^circ$ by 0.28$^circ$ area with central position {it l} = 297.34$^circ$, {it b} = -0.60$^circ$. The kinematics show that bright [C,{sc ii}] structures are spatially and spectrally correlated with the surfaces of CO clouds, tracing the photodissociation region and ionization front of each molecular cloud. Along 7 lines of sight that traverse Tr 14 into the dark ridge to the southwest, we find that the [C,{sc ii}] luminosity from the HII region is 3.7 times that from the PDR. In same los we find in the PDRs an average ratio of 1:4.1:5.6 for the mass in atomic gas:dark-CO gas: molecular gas traced by CO. Comparing multiple gas tracers including HI 21cm, [C,{sc ii}], CO, and radio recombination lines, we find that the HII regions of the Carina Nebula Complex are well-described as HII regions with one-side freely expanding towards us, consistent with the champagne model of ionized gas evolution. The dispersal of the GMC in this region is dominated by EUV photoevaporation; the dispersal timescale is 20-30 Myr.
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