Stellar Parameters and Radial Velocities of Hot Stars in the Carina Nebula

Abstract

The Carina Nebula is an active star forming region in the southern sky that is of particular interest due to the presence of a large number of massive stars in a wide array of evolutionary stages. Here we present the results of the spectroscopic analysis of 82 B-type stars and 33 O-type stars that were observed in 2013 and 2014. For 82 B-type stars without line blending, we fit model spectra from the Tlusty BSTAR2006 grid to the observed profiles of Hγ and He λλ 4026, 4388, and 4471 to measure the effective temperatures, surface gravities, and projected rotational velocities. We also measure the masses, ages, radii, bolometric luminosities, and distances of these stars. From the radial velocities measured in our sample, we find 31 single lined spectroscopic binary candidates. We find a high dispersion of radial velocities among our sample stars, and we argue that the Carina Nebula stellar population has not yet relaxed and become virialized. the mass, radius, and age. We also compare our results with any shared stars in past studies. Section 4 discusses the radial velocities and distances of the stars in our sample. OBSERVATIONSObservations of the stars were made at the Anglo-Australian Telescope (AAT) over the course of two runs in March 2013 and April 2014. The observations of these stars are described in greater detail by Alexander et al. (2016). We chose two different wavelength regions, 3925-4210Å (2013) and 4235-4510Å (2014), to cover many useful H and He lines for analysis. As the target spectra were vertically stacked on the imaging plane, distortions in the imaging plane meant that the exact spectral coverage varied among the targets and sky spectra. During our first day of observations in 2014, we used a slightly different range (4200-4475Å) for some of our exposures, but we found that this omitted the He I λ4471 line for some of our targets due to variable dispersion across the chip.The raw spectra were reduced using the dohydra package of IRAF and a custom IDL code for sky subtraction to account for the changing wavelength coverage across the CCD. Due to the variable dusty nature of the Carina Nebula, sometimes the average sky spectrum is too strong or too weak in comparison to our targets, which results in contamination of the Balmer line cores for some of our stars.Bright stars in our 2013 data generally have a signal-to-noise ratio (S/N) of 50-120, while the faint stars have a S/N of 30-70. The bright stars in our 2014 data have a S/N of 100-200, while the faint stars have a S/N of 120-210. The signal-to-noise of our 2013 data was low because our observing time was cut short due to wildfires in the area. We used two different fiber configurations for the bright versus the faint stars and observed them with different exposure times, which is how we achieved marginally better S/N for the fainter stars. Our measurements of S/N for each star are listed in Table 1.

A Gaia view of the two OB associations Cygnus OB2 and Carina OB1: the signature of their formation process

“…We studied the internal structure and kinematics of the two OB associations Cyg OB2 and Car OB1 in the Galaxy using the high-precision astrometric data from Gaia DR2 (Gaia Collaboration et al 2018) and RVs from previous studies (Kiminki et al 2007;Damiani et al 2017;Hanes et al 2018). From the distribution of distances, we concluded that these associations are genuine structures rather than a line-ofsight coincidence of several stellar groups.…”

Carina’s pillars of destruction: the view from ALMA

“…the mean of the intensity weighted velocity map of the pillar). Plotted on the same colour scale are the radial velocities of the surrounding O stars taken from the 2014 epoch measurements of Hanes et al (2018), and Table 2 of Kiminki & Smith (2018), where the colour reflects the mean measured radial velocity for each star. The radial velocities of the stars are plotted on the same colour scale as the CO to highlight which ones are more likely to be influencing the observed molecular gas (i.e.…”

“…The pillars sample the 'Southern Pillars', 'Northern Pillars', and the 'Southwestern Pillars' complexes as defined in Hartigan et al (2015), and in the following we use their pillar Table 4 of Hanes et al (2018) and Table 2 of Kiminki & Smith (2018). The colours of the star markers corresponds to their radial velocities of those stars.…”

“…expansion), or that we are seeing one edge more in projection than the other. If we assume the cloud is expanding, given that the velocity difference between the cloud edge in Pillar 20 (-10 km s −1 ) and Pillar 22 (-6 km s −1 ) is 4 km s −1 , and that the projected separation is 0.12 pc, the cloud has been expanding for roughly 30 000 years, a much shorter timescale than the age of the cluster embedded within it (see the discussion in Hanes et al 2018).…”

Detection of new O-type stars in the obscured stellar cluster Tr 16-SE in the Carina Nebula with KMOS

“…The Carina Nebula, at a distance of ≈ 2.3 kpc (see Smith & Brooks 2008, for a review), is one of the most massive and active star forming regions in our Galaxy and harbors a large population of high-mass stars (M ≥ 8 M ). With 70 optically identified O-type stars, three known Wolf-Rayet (WR) stars, and η Car with its companion (see Smith 2006;Alexander et al 2016;Hanes et al 2018), the currently known population comprises 75 stars with masses above 18 M . These massive stars constitute a large OB association, in which Tr 14, 15, and 16 are the most prominent open clusters in optical images.…”