The hidden past of M92: Detection and characterization of a newly formed 17° long stellar stream using the Canada-France Imaging Survey
Guillaume F. Thomas, Jaclyn Jensen, Alan McConnachie, Patrick Côté, Kim Venn, Nicolas Longeard, Raymond Carlberg, Scott Chapman, Jean-Charles Cuillandre, Benoit… 展开作者
Guillaume F. Thomas, Jaclyn Jensen, Alan McConnachie, Patrick Côté, Kim Venn, Nicolas Longeard, Raymond Carlberg, Scott Chapman, Jean-Charles Cuillandre, Benoit Famaey, Laura Ferrarese, Stephen Gwyn, François Hammer, Rodrigo A. Ibata, Khyati Malhan, Nicolas F. Martin, Simona Mei, Julio F. Navarro, Céline Reylé, Else Starkenburg
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14 pages, 8 figures. Accepted for publication in ApJ
We present an analysis of the structure, kinematics and orbit of a newly found stellar stream emanating from the globular cluster M92 (NGC 6341). This stream was discovered in an improved matched-filter map of the outer Galaxy, based on a "color-color-magnitude" diagram, created using photometry from the Canada-France Imaging Survey (CFIS) and the Pan-STARRS 1 3$π$ survey (PS1). We find the stream to have a length of 17° (2.5 kpc at the distance of M92), a width dispersion of $0.29$°(42 pc) and a stellar mass of $[3.17 \pm{0.89}] \times 10^{4} $ M$_\odot$ ($10 \%$ of the stellar mass of the current main body of M92). We examine the kinematics of main sequence, red giant and blue horizontal branch stars belonging to the stream and that have proper motion measurements from the second data release of Gaia. N-body simulations suggest that the stream was likely formed very recently (during the last $\sim 500$ Myr) forcing us to question the orbital origin of this ancient, metal-poor globular cluster.
We present imaging and spectroscopic observations for six quasars at z>5.9 discovered by the Canada-France High-z Quasar Survey (CFHQS). The CFHQS contains sub-surveys with a range of flux and area combinations to sample a wide range of quasar luminosities at z~6. The new quasars have luminosities 10 to 75 times lower than the most luminous SDSS quasars at this redshift. The least luminous quasar, CFHQS J0216-0455 at z=6.01, has absolute magnitude M_1450=-22.21, well below the likely break in the luminosity function. This quasar is not detected in a deep XMM-Newton survey showing that optical …
We present the kinematics of Blue Straggler (BS) stars identified in the Canada-France-Imaging-Survey (CFIS), covering 4000 deg$^2$ on the sky in the $u$-band. The BS sample, characterised through CFIS and Pan-STARRS photometry, has been kinematically decomposed into putative halo and disc populations after cross-matching with Gaia astrometry and SDSS/SEGUE/LAMOST spectroscopy. This decomposition clearly reveals the strong flaring of the outer Milky Way disc. In particular, we show that we can detect this flaring up to a vertical height of $|Z| \simeq 8$ kpc at a Galactocentric distance of $R\…
The Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) represents the most powerful weak lensing survey carried out to date. The CFHTLenS (Canada-France-Hawaii Telescope Lensing Survey) team was formed in 2008 to analyse the data from the CFHTLS focussing on a rigorous treatment of systematic effects in shape measurements and photometric redshifts. Here we review the technical challenges that we faced in analysing these data and their solutions which set the current standard for weak lensing analyses. We also present some science highlights that were made possible by this effort including c…
We present optical spectroscopy for 18 halo white dwarfs identified using photometry from the Canada-France Imaging Survey and Pan-STARRS1 DR1 3$π$ survey combined with astrometry from Gaia DR2. The sample contains 13 DA, 1 DZ, 2 DC, and two potentially exotic types of white dwarf. We fit both the spectrum and the spectral energy distribution in order to obtain the temperature and surface gravity, which we then convert into a mass, and then an age, using stellar isochrones and the initial-to-final mass relation. We find a large spread in ages that is not consistent with expected formation scen…
The Canada-France Imaging Survey (CFIS) will map the northern high Galactic latitude sky in the $u$-band ("CFIS-u", 10,000$\, {\rm deg^2}$) and in the $r$-band ("CFIS-r", 5,000$\, {\rm deg^2}$), enabling a host of stand-alone science investigations, and providing some of the ground-based data necessary for photometric redshift determination for the Euclid mission. In this first contribution we present the $u$-band component of the survey, describe the observational strategy, and discuss some first highlight results, based on approximately one third of the final area. We show that the Galactic …
We present the stellar density profile of the outer halo of the Galaxy traced over a range of Galactocentric radii from $15< R_{GC} < 220$ kpc by blue horizontal branch (BHB) stars. These stars are identified photometrically using deep $u-$band imaging from the new Canada-France-Imaging-Survey (CFIS) that reaches 24.5 mag. This is combined with $griz$ bands from Pan-STARRS 1 and covers a total of $\sim4000$ deg$^2$ of the northern sky. We present a new method to select BHB stars that has low contamination from blue stragglers and high completeness. We use this sample to measure and parameteriz…
As the remnants of stars with initial masses $\lesssim$ 8 M$_{\odot}$, white dwarfs contain valuable information on the formation histories of stellar populations. In this paper, we use deep, high-quality, u-band photometry from the Canada France Imaging Survey (CFIS), griz photometry from Pan-STARRS 1 (PS1), as well as proper motions from Gaia DR2, to select 25,156 white dwarf candidates over $\sim$4500 deg$^2$ using a reduced proper motion diagram. We develop a new white dwarf population synthesis code that returns mock observations of the Galactic field white dwarf population for a given st…
We present the chemical distribution of the Milky Way, based on 2,900$\, {\rm deg^2}$ of $u$-band photometry taken as part of the Canada-France Imaging Survey. When complete, this survey will cover 10,000$\, {\rm deg^2}$ of the Northern sky. By combing the CFHT $u$-band photometry together with SDSS and Pan-STARRS $g,r,$ and $i$, we demonstrate that we are able to measure reliably the metallicities of individual stars to $\sim 0.2$ dex, and hence additionally obtain good photometric distance estimates. This survey thus permits the measurement of metallicities and distances of the dominant main…
Brightest cluster galaxies (BCGs) are very massive elliptical galaxies found at the centers of clusters. Their study gives clues on the formation and evolution of the clusters in which they are embedded. We analysed here in a homogeneous way the properties of a sample of more than one thousand BCGs in the redshift range 0.15 < z < 0.7, based on images from the Canada France Hawaii Telescope Legacy Survey. Based on the cluster catalogue of 1371 clusters by Sarron et al. (2018), we applied our automatic BCG detection algorithm and identified successfully 70% of the BCGs in our sample. We analyse…
We present a new fully data-driven algorithm that uses photometric data from the Canada-France-Imaging-Survey (CFIS; $u$), Pan-STARRS 1 (PS1; $griz$), and Gaia ($G$) to discriminate between dwarf and giant stars and to estimate their distances and metallicities. The algorithm is trained and tested using the SDSS/SEGUE spectroscopic dataset and Gaia photometric/astrometric dataset. At [Fe/H]$<-1.2$, the algorithm succeeds in identifying more than 70% of the giants in the training/test set, with a dwarf contamination fraction below 30% (with respect to the SDSS/SEGUE dataset). The photometric me…
Context. Thanks to recent and ongoing large scale surveys, hundreds of brown dwarfs have been discovered in the last decade. The Canada-France Brown Dwarf Survey is a wide-field survey for cool brown dwarfs conducted with the MegaCam camera on the Canada-France-Hawaii Telescope telescope. Aims. Our objectives are to find ultracool brown dwarfs and to constrain the field brown-dwarf luminosity function and the mass function from a large and homogeneous sample of L and T dwarfs. Methods. We identify candidates in CFHT/MegaCam i' and z' images and follow them up with pointed near infrared (NIR) i…
We investigate the characteristics of the thick disk in the Canada - France - Hawaii - Telescope Legacy Survey (CFHTLS) fields, complemented at bright magnitudes with Sloan Digital Sky Survey (SDSS) data. The ([Fe/H], Z) distributions are derived in the W1 and W3 fields, and compared with simulated maps produced using the Besançon model. It is shown that the thick disk, represented in star-count models by a distinct component, is not an adequate description of the observed ([Fe/H], Z) distributions in these fields.
Knowledge of the mass function in open clusters constitutes one way to constrain the formation of low-mass stars and brown dwarfs as does the knowledge of the frequency of multiple systems and the properties of disks. The aim of the project is to determine the shape of the mass function in the low-mass and substellar regimes in the pre-main sequence (27 Myr) cluster IC4665, which is located at 350 pc from the Sun. We have cross-matched the near-infrared photometric data from the Eighth Data Release of the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey with previous optical da…
The early-type galaxy NGC 5195 (alternatively known as M51b) possesses extended gas features detected in multi-wavelength, postulated to be associated with previous activities of the central supermassive black hole (SMBH). Using integral field spectroscopic observations from the Canada-France-Hawaii Telescope (CFHT)/SITELLE, we report on the discovery of a new large-scale ionized gas structure traced by [O III], [N II], and H$α$ line emission, extending to $\sim10\rm\,kpc$ from the nucleus of NGC 5195. Its bipolar morphology, emission line ratio diagnostics, and comparison with the X-ray image…
The whole Sloan Digital Sky Survey (SDSS, 14,555 deg^2 has been searched for intergalactic globular clusters (IGCs) in the Local Group (LG). Using optical, infrared, and ultraviolet photometric selection criteria and photometric redshifts, the 2.1x10^8 of objects in the SDSS Galaxy Catalogue were reduced to only 183,791 brighter than r_o = 19 that might be GCs. Visual examination of their SDSS images recovered 84 percent of the confirmed GCs in M31 and M33 and yielded 17 new GC candidates, 5 of them of high confidence, which we could confirm as GCs in MegaPrime images from the Canada, France, …
The recently re-discovered open cluster Stock 2, located roughly 375 pc away and about 400 Myr old, has the potential to be an exciting new testbed for our understanding of stellar evolution. We present results from a spectroscopic campaign to characterize stars near the cluster's main-sequence turnoff; our goal is to identify candidate chemically peculiar stars among the cluster's A stars. We obtained echelle spectra for 64 cluster members with ESPaDOnS on the 3.6-m Canada-France-Hawaii Telescope, Mauna Kea Observatory, USA, and for six stars with SOPHIE on the 1.93-m telescope at the Observa…
Deep imaging, that is imaging capable of capturing very low surface brightness extended objects, is a quickly growing field of extragalactic astronomy. Not only can new types of faint objects be discovered, but deep images of bright galaxies are very valuable, too, since they reveal faint signs of past galaxy collisions, the tidal features. Such "archeological" record can be exploited for investigating how galaxies formed. In the MATLAS survey, we obtained extremely deep images of 177 nearby massive elliptical and lenticular galaxies using the 3.5m Canada-France-Hawaii Telescope. In our contri…
