arXiv subjects

Camila Navarrete

Publications and source records attributed to Camila Navarrete.

26 records · Page 2Linked to original sources

arXiv2018

Stellar streams around the Magellanic Clouds in 4D

We carried out a spectroscopic follow-up program of the four new stellar stream candidates detected by Belokurov & Koposov (2016) in the outskirts of the Large Magellanic Cloud (LMC) using FORS2 (VLT). The medium-resolution spectra were used to measure the line-of-sight velocities, estimate stellar metallicities and to classify stars into Blue Horizontal Branch (BHB) and Blue Straggler (BS) stars. Using the 4-D phase-space information, we attribute approximately one half of our sample to the Magellanic Clouds, while the rest is part of the Galactic foreground. Only two of the four stream candidates are confirmed kinematically. While it is impossible to estimate the exact levels of MW contamination, the phase-space distribution of the entire sample of our Magellanic stars matches the expected velocity gradient for the LMC halo and extends as far as 33 deg (angular separation) or 29 kpc from the LMC center. Our detections reinforce the idea that the halo of the LMC seems to be larger than previously expected, and its debris can be spread in the sky out to very large separations from the LMC center. Finally, we provide some kinematic evidence that many of the stars analysed here have likely come from the Small Magellanic Cloud.

astro-ph.GA↗

arXiv2017

The globular cluster NGC7492 and the Sagittarius tidal stream: together but unmixed

We have derived from VIMOS spectroscopy the radial velocities for a sample of 71 stars selected from CFHT/Megacam photometry around the Galactic globular cluster NGC7492. In the resulting velocity distribution, it is possible to distinguish two relevant non-Galactic kinematic components along the same line of sight: a group of stars at $\langle{v_{\rm r}}\rangle \sim 125$km s$^{-1}$ which is compatible with the velocity of the old leading arm of the Sagittarius tidal stream, and a larger number of objects at $\langle{v_{\rm r}}\rangle \sim -110$km s$^{-1}$ that might be identified as members of the trailing wrap of the same stream. The systemic velocity of NGC7492 set at $v_{\rm r} \sim -177$km s$^{-1}$ differs significantly from that of both components, thus our results confirm that this cluster is not one of the globular clusters deposited by the Sagittarius dwarf spheroidal in the Galactic halo, even if it is immersed in the stream. A group of stars with $ \sim -180$km s$^{-1}$ might be comprised of cluster members along one of the tidal tails of NGC7492.

astro-ph.GA↗

arXiv2017

Tails and streams around the Galactic globular clusters NGC1851, NGC1904, NGC2298 and NGC2808

We present DECam imaging for the peculiar Galactic globular clusters NGC1851, NGC1904 (M79), NGC2298 and NGC2808. Our deep photometry reveals that all the clusters have an important contribution of stars beyond their King tidal radii and present tails with different morphologies. We have also explored the surroundings of the clusters where the presence of the Canis Major overdensity and/or the low Galactic latitude Monoceros ring at d~8kpc is evident. A second stellar system is found at d~17kpc and spans at least 18deg x 15deg in the sky. As one of the possible scenarios to explain that feature, we propose that the unveiled system is part of Monoceros explained as a density wave moving towards the outer Milky Way. Alternatively, the unveiled system might be connected with other known halo substructures or associated with the progenitor dwarf galaxy of NGC1851 and NGC1904, which are widely considered accreted globular clusters.

astro-ph.GA↗

arXiv2017

Pulsating stars in $ω$ Centauri: Near-IR properties and period-luminosity relations

$ω$ Centauri (NGC~5139) contains many variable stars of different types, including the pulsating type II Cepheids, RR Lyrae and SX Phoenicis stars. We carried out a deep, wide-field, near-infrared (IR) variability survey of $ω$ Cen, using the VISTA telescope. We assembled an unprecedented homogeneous and complete $J$ and $K_{\rm S}$ near-IR catalog of variable stars in the field of $ω$ Cen. In this paper we compare optical and near-IR light curves of RR Lyrae stars, emphasizing the main differences. Moreover, we discuss the ability of near-IR observations to detect SX Phoenicis stars given the fact that the amplitudes are much smaller in these bands compared to the optical. Finally, we consider the case in which all the pulsating stars in the three different variability types follow a single period-luminosity relation in the near-IR bands.

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arXiv2017

The discovery of tidal tails around the globular cluster NGC 7492 with Pan-STARRS1

We report the discovery of tidal tails around the Galactic globular cluster NGC 7492, based on the Data Release 1 of the Pan-STARRS 1 survey. The tails were detected with a version of the matched filter technique applied to the $(g-r,r)$ and $(g-i,i)$ color-magnitude diagrams. Tidal tails emerging from the cluster extend at least $\sim$3.5 degrees in the North-East to South-East direction, equivalent to $\sim1.5$ kpc in projected length.

astro-ph.GA↗

arXiv2017

FSR 1716: A new Milky Way Globular Cluster confirmed using VVV RR Lyrae stars

We use deep multi-epoch near-IR images of the VISTA Variables in the Vía Láctea (VVV) Survey to search for RR Lyrae stars towards the Southern Galactic plane. Here we report the discovery of a group of RR Lyrae stars close together in VVV tile d025. Inspection of the VVV images and PSF photometry reveals that most of these stars are likely to belong to a globular cluster, that matches the position of the previously known star cluster FSR\,1716. The stellar density map of the field yields a $>100$ sigma detection for this candidate globular cluster, that is centered at equatorial coordinates $RA_{J2000}=$16:10:30.0, $DEC_{J2000}=-$53:44:56; and galactic coordinates $l=$329.77812, $b=-$1.59227. The color-magnitude diagram of this object reveals a well populated red giant branch, with a prominent red clump at $K_s=13.35 \pm 0.05$, and $J-K_s=1.30 \pm 0.05$. We present the cluster RR Lyrae positions, magnitudes, colors, periods and amplitudes. The presence of RR Lyrae indicates an old globular cluster, with age $>10$ Gyr. We classify this object as an Oosterhoff type I globular cluster, based on the mean period of its RR Lyrae type ab, $ =0.540$ days, and argue that this is a relatively metal-poor cluster with $[Fe/H] = -1.5 \pm 0.4$ dex. The mean extinction and reddening for this cluster are $A_{K_s}=0.38 \pm 0.02$, and $E(J-K_s)=0.72 \pm 0.02$ mag, respectively, as measured from the RR Lyrae colors and the near-IR color-magnitude diagram. We also measure the cluster distance using the RR Lyrae type ab stars. The cluster mean distance modulus is $(m-M)_0 = 14.38 \pm 0.03$ mag, implying a distance $D = 7.5 \pm 0.2$ kpc, and a Galactocentric distance $R_G=4.3$ kpc.

astro-ph.GA↗

arXiv2016

A fork in the Sagittarius trailing debris

We take advantage of the deep and wide coverage of the VST ATLAS survey to study the line-of-sight structure of the Sagittarius stellar stream in the Southern hemisphere, only ~40° away from the progenitor. We use photometrically selected Sub-Giant Branch (SGB) stars to reveal a complex debris morphology of the trailing arm and detect at least two clear peaks in the SGB distance modulus distribution. The separation between the two line-of-sight components is at least 5 kpc at the edge of the VST ATLAS footprint, but appears to change along the stream, which allows us to conclude that these detections correspond to two physically independent stellar structures, rather than a mix of co-distant stellar populations within a single stream. Our discovery of a fork in the Sgr trailing arm is verified using Blue Horizontal Branch stars and our distance measurements are calibrated using RR Lyrae stars from the Catalina Real-Time Transient Survey. Comparing with numerical simulations of the Sgr dwarf disruption, the more distant of the two components in the fork matches perfectly with the track of the trailing debris. However, no obvious counterpart exists in the simulation for the closer line-of-sight component.

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arXiv2015

The Kapteyn moving group is not tidal debris from $ω$ Centauri

The Kapteyn moving group has been postulated as tidal debris from $ω$ Centauri. If true, members of the group should show some of the chemical abundance patterns known for stars in the cluster. We present an optical and near-infrared high-resolution, high-S/N spectroscopic study of 14 stars of the Kapteyn group, plus 10 additional stars (the $ω$ Cen-group) that, while not listed as members of the Kapteyn group as originally defined, have been nevertheless associated dynamically with $ω$ Centauri. Abundances for Na, O, Mg, Al, Ca and Ba were derived from the optical spectra, while the strength of the chromospheric He I 10830 Å line is studied as a possible helium abundance indicator. The resulting Na-O and Mg-Al patterns for stars of the combined Kapteyn and $ω$ Cen-group samples do not resemble those of $ω$ Centauri, and are not different from those of field stars of the Galactic halo. The distribution of equivalent widths of the He I 10830 Å line is consistent with that found among non-active field stars. Therefore, no evidence is found for second-generation stars within our samples, which most likely rules out a globular-cluster origin. Moreover, no hint of the unique Ba-overabundance at the metal-rich end, well-established for $ω$ Centauri stars, is seen among stars of the combined samples. Because this specific Ba pattern is present in $ω$ Centauri irrespective of stellar generation, this would rule out the possibility that our entire sample might be composed of only first generation stars from the cluster. Finally, for the stars of the Kapteyn group, the possibility of an origin in the hypothetical $ω$ Centauri's parent galaxy is disfavored by the different run of $α$-elements with metallicity between our targets and stars from present-day dwarf galaxies.

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