Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userStellar Population Challenge: analysis of M67 with the VO
113
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
In this poster we present the analysis of the CMD of M67 (proposed in the Stellar Population Challenge) performed with VO applications. We found that, although the VO environment is still not ready to perform a complete analysis, its use provides highly useful additional information for the analysis. Thanks to the current VO framework, we are able to identify stars in the provided CMD that are not suitable for isochrone fitting. Additionally, we can complete our knowledge of this cluster extending the analysis to IR colors, which were not provided in the original data but that are available thanks to the VO. On the negative side, we find it difficult to access theoretical data from VO applications, so, currently, it is not possible to perform completely the analysis of the cluster inside the VO framework. However it is expected that the situation will improve in a near future.
rate research
Read More
The spatial distributions of the mean luminosity-weighted stellar age, metallicity, and alpha/Fe ratio along both photometric axes of two nearby elliptical galaxies have been obtained using Lick index measurements on long slit spectra in order to reconstruct the star formation history in their kinematically distinct subsystems. Lick indexes were compared with those of single-aged stellar population (SSP) models. A population synthesis method was also applied in order to help disentangling the age-metallicity degeneracy. The stars characteristics are associated with their kinematics: they are older and alpha-enhanced in the not rotating bulge of NGC 1052 and counter rotating core of NGC 7796, while they show a strong spread of alpha/Fe and age along the rotating disk of NGC 1052 and an outwards radial decreasing of them outside the core of NGC 7796.
We present and analyse 120 spectroscopic binary and triple cluster members of the old (4 Gyr) open cluster M67 (NGC 2682). As a cornerstone of stellar astrophysics, M67 is a key cluster in the WIYN Open Cluster Study (WOCS); radial-velocity (RV) observations of M67 are ongoing and extend back over 45 years, incorporating data from seven different telescopes, and allowing us to detect binaries with orbital periods <~10^4 days. Our sample contains 1296 stars (604 cluster members) with magnitudes of 10 <= V <= 16.5 (about 1.3 to 0.7 Msolar), from the giants down to ~4 mag below the main-sequence turnoff, and extends in radius to 30 arcminutes (7.4 pc at a distance of 850 pc, or ~7 core radii). This paper focuses primarily on the main-sequence binaries, but orbital solutions are also presented for red giants, yellow giants and sub-subgiants. Out to our period detection limit and within our magnitude and spatial domain, we find a global main-sequence incompleteness-corrected binary fraction of 34% +/- 3%, which rises to 70% +/- 17% in the cluster center. We derive a tidal circularization period of P_circ = 11.0 +1.1 -1.0 days. We also analyze the incompleteness-corrected distributions of binary orbital elements and masses. The period distribution rises toward longer periods. The eccentricity distribution, beyond P_circ, is consistent with a uniform distribution. The mass-ratio distribution is also consistent with a uniform distribution. Overall, these M67 binaries are closely consistent with similar binaries in the galactic field, as well as the old (7 Gyr) open cluster NGC 188. WIYN Open Cluster Study. 83.
The open cluster M67 offers the unique opportunity to measure rotation periods for solar-age stars across a range of masses, potentially filling a critical gap in the understanding of angular momentum loss in older main sequence stars. The observation of M67 by NASA K2 Campaign 5 provided light curves with high enough precision to make this task possible, albeit challenging, as the pointing instability, 75d observation window, crowded field, and typically low-amplitude signals mean determining accurate rotation periods on the order of 25 - 30d is inherently difficult. Lingering, non-astrophysical signals with power at >25d found in a set of Campaign 5 A and F stars compounds the problem. To achieve a quantitative understanding of the best-case scenario limits for reliable period detection imposed by these inconveniences, we embarked on a comprehensive set of injection tests, injecting 120,000 sinusoidal signals with periods ranging from 5 to 35d and amplitudes from 0.05% to 3.0% into real Campaign 5 M67 light curves processed using two different pipelines. We attempted to recover the signals using a normalized version of the Lomb-Scargle periodogram and setting a detection threshold. We find that while the reliability of detected periods is high, the completeness (sensitivity) drops rapidly with increasing period and decreasing amplitude, maxing at 15% recovery rate for the solar case (i.e. 25d period, 0.1% amplitude). This study highlights the need for caution in determining M67 rotation periods from Campaign 5 data, but this can be extended to other clusters observed by K2 and, soon, TESS.
We have developed an analytical method to investigate the stellar populations in a galaxy using the broad-band colours. The method enables us to determine the relative contribution, spatial distribution and age for different stellar populations and gives a hint about the dust distribution in a galaxy. We apply this method to the irregular galaxy NGC 3077, using CCD images in U, B, V and R filters.
3D spectroscopy produces hundreds of spectra from which maps of the characteristics of stellar populations (age-metallicity) and internal kinematics of galaxies can be derived. We carried on simulations to assess the reliability of inversion methods and to define the requirements for future observations. We quantify the biases and show that to minimize the errors on the kinematics, age and metallicity (in a given observing time) the size of the spatial elements and the spectral dispersion should be chosen to obtain an instrumental velocity dispersion comparable to the physical dispersion.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
