The Next Generation Virgo Cluster Survey. Xix. Tomography of Milky Way Substructures in the NGVS Footprint

Lokhorst, Deborah; Starkenburg, Else; McConnachie, Alan W.; Navarro, Julio F.; Ferrarese, Laura; Côté, Patrick; Liu, Chengze; Peng, Eric W.; Gwyn, Stephen; Cuillandre, Jean-Charles; Guhathakurta, Puragra

doi:10.3847/0004-637x/819/2/124

Cited by 13 publications

(14 citation statements)

References 101 publications

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“…The footprint was chosen to be accessible from both hemispheres for the spectroscopic follow-up and to include a variety of known stellar halo substructures. It includes a portion of the Sagittarius stream and of the Virgo overdensity (see Belokurov et al 2006a;Lokhorst et al 2016, for an SDSS map of these regions), along with 3 globular clusters (NGC5904/M5, Pal 5, and Pal 14), most of the Pal 5 stellar stream and 3 faint dwarf galaxies (Boötes I, Boötes II, and Hercules). Furthermore, it covers 17 SEGUE spectroscopic fields that we use to calibrate the CaHK -to-[Fe/H] relation.…”

Section: Observations and Coveragementioning

confidence: 99%

The Pristine survey – I. Mining the Galaxy for the most metal-poor stars

Starkenburg

Martín

Youakim

et al. 2017

Monthly Notices of the Royal Astronomical Society

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213

219

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We present the Pristine survey, a new narrow-band photometric survey focused on the metallicity-sensitive Ca H & K lines and conducted in the northern hemisphere with the wide-field imager MegaCam on the Canada-France-Hawaii Telescope (CFHT). This paper reviews our overall survey strategy and discusses the data processing and metallicity calibration. Additionally we review the application of these data to the main aims of the survey, which are to gather a large sample of the most metal-poor stars in the Galaxy, to further characterise the faintest Milky Way satellites, and to map the (metal-poor) substructure in the Galactic halo. The current Pristine footprint comprises over 1,000 deg 2 in the Galactic halo ranging from b ∼ 30 • to ∼ 78 • and covers many known stellar substructures. We demonstrate that, for SDSS stellar objects, we can calibrate the photometry at the 0.02-magnitude level. The comparison with existing spectroscopic metallicities from SDSS/SEGUE and LAMOST shows that, when combined with SDSS broad-band g and i photometry, we can use the CaHK photometry to infer photometric metallicities with an accuracy of ∼0.2 dex from [Fe/H] = −0.5 down to the extremely metal-poor regime ([Fe/H] < −3.0). After the removal of various contaminants, we can efficiently select metal-poor stars and build a very complete sample with high purity. The success rate of uncovering [Fe/H] SEGUE < −3.0 stars among [Fe/H] Pristine < −3.0 selected stars is 24% and 85% of the remaining candidates are still very metal poor ([Fe/H]< −2.0). We further demonstrate that Pristine is well suited to identify the very rare and pristine Galactic stars with [Fe/H] < −4.0, which can teach us valuable lessons about the early Universe. . The observations at the Canada-France-Hawaii Telescope were performed with care and respect from the summit of Maunakea which is a significant cultural and historic site.†

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Section: Observations and Coveragementioning

confidence: 99%

The Pristine survey – I. Mining the Galaxy for the most metal-poor stars

Starkenburg

Martín

Youakim

et al. 2017

Monthly Notices of the Royal Astronomical Society

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213

219

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“…Pristine survey targets were cross-matched with SDSS photometry to obtain ugri broad-band magnitudes used for colour temperature determinations and point source identification. Additional selection criteria were adopted, as described by Youakim et al (2017), including the removal of non-star contaminants (based on SDSS and CaHK flags), white dwarf contaminants (removing SDSS u − g > 0.6, Lokhorst et al 2016), variability flags from Pan-STARRS1 photometry (Hernitschek et al 2016), and the quality of SDSS gri-band photometry. The SDSS gri-band photometry was further used for a colour selection, where 0.25 < (g − i) o < 1.5 and 0.15 < (g − r) o < 1.2 correspond to the temperature range 4200 K < T eff < 6500 K, covering the tip of the red giant branch and the cooler main sequence to the main sequence turnoff.…”

Section: Target Selectionmentioning

confidence: 99%

The Pristine survey – IX. CFHT ESPaDOnS spectroscopic analysis of 115 bright metal-poor candidate stars

Venn

Kielty

Sestito

et al. 2019

Monthly Notices of the Royal Astronomical Society

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A chemo-dynamical analysis of 115 metal-poor candidate stars selected from the narrow-band Pristine photometric survey is presented based on CFHT highresolution ESPaDOnS spectroscopy. We have discover 28 new bright (V < 15) stars with [Fe/H]< −2.5 and 5 with [Fe/H]< −3.0 for success rates of 40% (28/70) and 19% (5/27), respectively. A detailed model atmospheres analysis is carried out for the 28 new metal-poor stars. Stellar parameters were determined from SDSS photometric colours, Gaia DR2 parallaxes, MESA/MIST stellar isochrones, and the initial Pristine survey metallicities, following a Bayesian inference method. Chemical abundances are determined for 10 elements (Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Y, Ba). Most stars show chemical abundance patterns that are similar to the normal metal-poor stars in the Galactic halo; however, we also report the discoveries of a new r-process rich star, a new CEMP-s candidate with [Y/Ba]>0, and a metal-poor star with very low [Mg/Fe]. The kinematics and orbits for all of the highly probable metal-poor candidates are determined by combining our precision radial velocities with Gaia DR2 proper motions. Some stars show unusual kinematics for their chemistries, including planar orbits, unbound orbits, and highly elliptical orbits that plunge deeply into the Galactic bulge (R peri < 0.5 kpc); also, eight stars have orbital energies and actions consistent with the Gaia-Enceladus accretion event. This paper contributes to our understanding of the complex chemo-dynamics of the metal-poor Galaxy, and increases the number of known bright metal-poor stars available for detailed nucleosynthetic studies.

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“…The line of sight towards the core of Virgo crosses the Milky Way halo in the direction of the Virgo Stellar Overdensity (VSO) and of a major stream of the Sagittarius dwarf galaxy (Jerjen et al 2013;Durrell et al 2014;Lokhorst et al 2016). In the range of g-band magnitudes we have selected, bright blue stars are thought to belong mostly to the VSO, while fainter ones belong to the Sagittarius stream.…”

Section: Real Patterns In the Stellar Colorsmentioning

confidence: 99%

The Next Generation Virgo Cluster Survey (NGVS). XXXII. A Search for Globular Cluster Substructures in the Virgo Galaxy Cluster Core

Powalka¹,

Puzia

Lançon³

et al. 2018

ApJ

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Substructure in globular cluster (GC) populations around large galaxies is expected in galaxy formation scenarios that involve accretion or merger events, and it has been searched for using direct associations between GCs and structure in the diffuse galaxy light, or with GC kinematics. Here, we present a search for candidate substructures in the GC population around the Virgo cD galaxy M87 through the analysis of the spatial distribution of the GC colors. The study is based on a sample of ∼ 1800 bright GCs with high-quality u, g, r, i, z, K s photometry, selected to ensure a low contamination by foreground stars or background galaxies. The spectral energy distributions of the GCs are associated with formal estimates of age and metallicity, which are representative of its position in a 4-D color-space relative to standard single stellar population models. Dividing the sample into broad bins based on the relative formal ages, we observe inhomogeneities which reveal signatures of GC substructures. The most significant of these is a spatial overdensity of GCs with relatively young age labels, of diameter ∼ 0.1 deg (∼ 30 kpc), located to the south of M87. The significance of this detection is larger than about 5σ after accounting for estimates of random and systematic errors. Surprisingly, no large Virgo galaxy is present in this area, that could potentially host these GCs. But candidate substructures in the M87 halo with equally elusive hosts have been described based on kinematic studies in the past. The number of GC spectra available around M87 is currently insufficient to clarify the nature of the new candidate substructure.

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The Next Generation Virgo Cluster Survey. Xix. Tomography of Milky Way Substructures in the NGVS Footprint

Cited by 13 publications

References 101 publications

The Pristine survey – I. Mining the Galaxy for the most metal-poor stars

The Pristine survey – I. Mining the Galaxy for the most metal-poor stars

The Pristine survey – IX. CFHT ESPaDOnS spectroscopic analysis of 115 bright metal-poor candidate stars

The Next Generation Virgo Cluster Survey (NGVS). XXXII. A Search for Globular Cluster Substructures in the Virgo Galaxy Cluster Core

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