Two Distant Halo Velocity Groups Discovered by the Palomar Transient Factory

Sesar, Branimir; Cohen, Judith G.; Levitan, David; Grillmair, Carl J.; Jurić, Mario; Kirby, Evan N.; Laher, Russ R.; Ofek, E. O.; Surace, J.; Prince, Thomas A.

doi:10.1088/0004-637x/755/2/134

Cited by 22 publications

(41 citation statements)

References 65 publications

(105 reference statements)

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“…The radial velocity curves of RRL depend on the mode of pulsation and the amplitude of of the light variation. Sesar et al (2012) combined the RVs from high resolution spectra of several bright RRab to obtain template radial velocity curves at several wavelengths. We chose the curve based on the Hγ line (see Figure 1 of Sesar et al 2012) as it was near the center of our spectrum, and we scaled its RV amplitude using the photometric amplitude (∆V = Vmin − Vmax) of each RRL from Table 2 and Equation 5 of Sesar et al (2012).…”

Section: Radial Velocity Measurementsmentioning

confidence: 99%

“…For each RRL, we performed a least-squares fit between the observed RV and phase data, and the scaled RV template, yielding a systemic, center-ofmass velocity for the pulsating star, vCM . Sesar et al (2012) noted an uncertainty of σv γ ≈ 13 km s −1 in vCM due to the uncertainty in the phase on the template at which the systemic velocity occurs. RRc variables have much smaller RV amplitudes than RRab, and the precise form of RV curve is less critical.…”

Section: Radial Velocity Measurementsmentioning

confidence: 99%

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Local RR Lyrae stars: native and alien

Zinn

Chen

Layden

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Measurements of [Fe/H] and radial velocity are presented for 89 RR Lyrae (RRL) candidates within 6 kpc of the Sun. After the removal of two suspected non-RRL, these stars were added to an existing database, which yielded 464 RRL with [Fe/H] on a homogeneous scale. Using data from the Gaia satellite (Data Release 2), we calculated the positions and space velocities for this sample. These data confirm the existence of a thin-disc of RRL with [α/Fe]∼ solar. The majority of the halo RRL with large total energies have near zero angular momenta about the Z axis. Kinematically these stars closely resemble the Gaia-Sausage/Gaia-Enceladus stars that others have proposed are debris from the merger of a large galaxy with the Milky Way. The metallicity and period distributions of the RRL and their positions in the period-amplitude diagram suggest that this disrupted galaxy was as massive as the Large Magellanic Cloud and possibly greater.

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Section: Radial Velocity Measurementsmentioning

confidence: 99%

Section: Radial Velocity Measurementsmentioning

confidence: 99%

Local RR Lyrae stars: native and alien

Zinn

Chen

Layden

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Details for this calculation are given in Section 5.3 of Sesar et al (2012). Since typical v r amplitudes over the period for RR Lyr stars of Hα are…”

Section: Radial Velocity Measurementsmentioning

confidence: 99%

The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility*

Cohen

Sesar

Bahnolzer³

et al. 2017

ApJ

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RR Lyrae stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way (MW). This is because they are easy to find in the light-curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112RR Lyr stars beyond 50 kpc in the outer halo of the MW, excluding the Sgr streams, for which we have obtained moderate-resolution spectra with Deimos on the Keck II Telescope. Four of these have distances exceeding 100 kpc. These were selected from a much larger set of 447candidate RR Lyr stars that were datamined using machine-learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112RR Lyr stars we determine the radial velocity dispersion in the outer halo of the MW to be ∼90 km s −1 at 50kpc, falling to about 65 km s −1 near 100kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as r 4 -.

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“…A number of stellar streams, moving and kinematic groups were identified in our Galaxy (Zuckerman & Song 2004;Helmi 2008;Klement et al 2009;Sesar et al 2012, and references therein). Some of them are suspected to originate from accreted satellites.…”

Section: Introductionmentioning

confidence: 99%

Stellar substructures in the solar neighbourhood

Stonkutė

Tautvaišienė

Nordström

et al. 2013

A&A

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Context. The evolution of chemical elements in a galaxy is linked to its star formation history. Variations in star formation history are imprinted in the relative abundances of chemical elements produced in different supernova events and asymptotic giant branch stars. Aims. We determine detailed elemental abundances of s-and r-process elements in stars belonging to Group 3 of the Geneva-Copenhagen survey and compare their chemical composition with Galactic disc stars. The aim is to look for possible chemical signatures that might give information about the formation history of this kinematic group of stars, which is suggested to correspond to remnants of disrupted satellites. Methods. High-resolution spectra were obtained with the FIES spectrograph at the Nordic Optical Telescope, La Palma, and were analysed with a differential model atmosphere method. Comparison stars were observed and analysed with the same method. Results. Abundances of chemical elements produced mainly by the s-process are similar to those in the Galactic thin-disc dwarfs of the same metallicity, while abundances of chemical elements produced predominantly by the r-process are overabundant. The similar elemental abundances are observed in Galactic thick-disc stars. Conclusions. The chemical composition together with the kinematic properties and ages of stars in Group 3 of the Geneva-Copenhagen survey support a gas-rich satellite merger scenario as the most likely explanation for the origin. The similar chemical composition of stars in Group 3 and the thick-disc stars might suggest that their formation histories are linked.

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Two Distant Halo Velocity Groups Discovered by the Palomar Transient Factory

Cited by 22 publications

References 65 publications

Local RR Lyrae stars: native and alien

Local RR Lyrae stars: native and alien

The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility*

Stellar substructures in the solar neighbourhood

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