分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Context: A variety of formation models for dwarf spheroidal (dSph) galaxies have been proposed in the literature, but generally they have not been quantitatively compared with observations. Aims: We search for chemodynamical patterns in our observational data set and compare the results with mock galaxies consisting of pure random motions, and simulated dwarfs formed via the dissolving star cluster and tidal stirring models. Methods: We made use of a new spectroscopic data set for the Milky Way dSph Leo I, combining 288 stars observed with Magellan/IMACS and existing Keck/DEIMOS data, to provide velocity and metallicity measurements for 953 Leo I member stars. We used a specially developed algorithm called Beacon to detect chemo-kinematical patterns in the observed and simulated data. Results: After analysing the Leo I data, we report the detection of 14 candidate streams of stars that may have originated in disrupted star clusters. The angular momentum vectors of these streams are randomly oriented, consistent with the lack of rotation in Leo I. These results are consistent with the predictions of the dissolving cluster model. In contrast, we find fewer candidate stream signals in mock data sets that lack coherent motions ~99% of the time. The chemodynamical analysis of the tidal stirring simulation produces streams that share a common orientation of their angular momenta, which is inconsistent with the Leo I data. Conclusions: Even though it is very difficult to distinguish which of the detected streams are real and which are only noise, we can be certain that there are more streams detected in the observational data of Leo I than expected in pure random data.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
C. López-Sanjuan
H. Vázquez Ramió
K. Xiao
H. Yuan
J. M. Carrasco
J. Varela
D. Cristóbal-Hornillos
P. -E. Tremblay
A. Ederoclite
A. Marín-Franch
A. J. Cenarro
P. R. T. Coelho
S. Daflon
A. del Pino
H. Domínguez Sánchez
J. A. Fernández-Ontiveros
A. Hernán-Caballero
F. M. Jiménez-Esteban
J. Alcaniz
R. E. Angulo
摘要： We present the photometric calibration of the twelve optical passbands for the Javalambre Photometric Local Universe Survey (J-PLUS) third data release (DR3), comprising 1642 pointings of two square degrees each. We selected nearly 1.5 million main sequence stars with a signal-to-noise ratio larger than ten in the twelve J-PLUS passbands and available low-resolution (R = 20-80) spectrum from the blue and red photometers (BP/RP) in Gaia DR3. We compared the synthetic photometry from BP/RP spectra with the J-PLUS instrumental magnitudes, after correcting for the magnitude and color terms between both systems, to obtain an homogeneous photometric solution for J-PLUS. To circumvent the current limitations in the absolute calibration of the BP/RP spectra, the absolute color scale was derived using the locus of 109 white dwarfs closer than 100 pc with a negligible interstellar extinction. Finally, the absolute flux scale was anchored to the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) photometry in the r band. The precision of the J-PLUS photometric calibration, estimated from duplicated objects observed in adjacent pointings and by comparison with the spectro-photometric standard star GD 153, is ~12 mmag in u, J0378, and J0395; and ~7 mmag in J0410, J0430, g, J0515, r, J0660, i, J0861, and z. The estimated accuracy in the calibration along the surveyed area is better than 1% for all the passbands. The Gaia BP/RP spectra provide a high-quality, homogeneous photometric reference in the optical range across the full-sky, in spite of their current limitations as an absolute reference. The calibration method for J-PLUS DR3 reaches an absolute precision and accuracy of 1% in the twelve optical filters within an area of 3284 square degrees.
点击量
待评议
点击量
下载量
评论
