La Silla Quest Rr Lyrae Star Survey: Region I

Zinn, R.; Horowitz, Benjamin; Vivas, A. Katherina; Baltay, C.; Ellman, N.; Hadjiyska, E.; Rabinowitz, D.; Miller, L.

doi:10.1088/0004-637x/781/1/22

Cited by 71 publications

(115 citation statements)

References 143 publications

(269 reference statements)

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“…Thus, there is not a clear excess of RRLS that can be readily associated with this stream from an old wrap. A similar conclusion on the lack of strong evidence for a stream stripped between 3.2 to 5 Gyr ago was made by Zinn et al (2014) based on the spatial distribution of a larger sample of RR Lyrae stars.…”

Section: Comparison With Sgr Modelssupporting

confidence: 72%

“…With a σ of 116 km s −1 (Brown et al 2010) for the distribution of the radial velocities of halo stars, the value of v max encloses 2.2σ of the distribution. On the other hand, the number of RRLS farther away than 60 kpc from the galactic center is very low (Sesar et al 2007;Zinn et al 2014) and thus it is an appropriate value for (3d) max . For the weight in the (3d) distance we only took into account the error in distance along the line of sight since the errors in position of the stars (less than 1 ) are negligible compared with the typical separation between stars in a pair (a few degrees).…”

Section: Group Finding Algorithmmentioning

confidence: 99%

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A comprehensive view of the Virgo stellar stream

Duffau

Vivas

Zinn

et al. 2014

A&A

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To explore the complex halo substructure that has been reported in the direction of the Virgo constellation, radial velocities and metallicities have been measured for 82 RR Lyrae stars (RRLS) that were identified by the QUEST survey. These stars are distributed over 90 square degrees of the sky, and lie from 4 to 23 kpc from the Sun. Using an algorithm for finding groups in phase space and modeling the smooth halo component in the region, we identified the 5 most significant RRLS groups, some of which were previously known or suspected. We have examined the SEKBO and the Catalina catalog of RRLS (with available spectroscopic measurements), as well as the bright QUEST RRLS sample, the catalog of Red Giant stars from the Spaghetti survey, and three recent catalogs of blue horizontal branch (BHB) stars, for stars that may be related to the QUEST RRLS groups. The most significant group of RRLS is the Virgo stellar stream (VSS) identified here as group A, which is composed of at least 10 RRLS and 3 BHB stars. It has a mean distance of 19.6 kpc and a mean radial velocity V gsr = 128 km s −1 , as estimated from its RRLS members. With the revised velocities reported here, there is no longer an offset in velocity between the RRLS in the VSS and the prominent peak in the velocities of main-sequence turnoff stars reported by other researchers in the same direction and at a similar distance (known as S297+63-20.5). The location in phase space of two other groups (F and H) suggests a possible connection with the VSS, which cannot be discarded at this point, although the turnoff colors of the VSS and group H, as identified from other works, suggest they might be composed of different populations. Two more groups, B and D, are found at mean distances of 19.0 and 5.7 kpc, and mean radial velocities of V gsr = −94 and 32 km s −1 . The latter is the more numerous in terms of total members, as well as the more extended in RA. A comparison with the latest model of the disruption of the Sagittarius dwarf, indicates that none of the above groups is related to it. Rather than being the result of a single accretion event, the excess of stars observed in Virgo appears to be composed of several halo substructures along the same line of sight.

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Section: Comparison With Sgr Modelssupporting

confidence: 72%

Section: Group Finding Algorithmmentioning

confidence: 99%

A comprehensive view of the Virgo stellar stream

Duffau

Vivas

Zinn

et al. 2014

A&A

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“…We draw 10,000 samples from a Poisson distribution with λ = 0.13 and find that 12% of our samples contain one field RR Lyrae star and only 1% of samples contain two or more field RR Lyrae stars. If we instead use the broken power-law fit from Zinn et al (2014) for the RR Lyrae star density profile, we find a RR Lyrae star halo density of ∼ 10 -4.5 kpc -3 at the distance of Hercules, resulting in 4% of our Poisson samples containing one field RR Lyrae star, and only 8 of our 10,000 samples containing more than one field RR Lyrae star. This shows that the probability of there being a field RR Lyrae star in our search volume is low, but not insignificant, while the probability of more than one field RR Lyrae star being present is very low.…”

Section: Tidal Destruction Of Herculesmentioning

confidence: 84%

“…We adopt the amplitudes from Musella et al (2012) for the variables characterized in that work. RR Lyrae stars from the La Silla-QUEST survey (Zinn et al 2014) a These stars fell in chip gaps in our DECam discovery data.…”

Section: The Rr Lyrae Star Demographics Of Herculesmentioning

confidence: 99%

Mapping the Tidal Destruction of the Hercules Dwarf: A Wide-field DECam Imaging Search for RR Lyrae Stars

Garling

Willman

Sand

et al. 2018

ApJ

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We investigate the hypothesized tidal disruption of the Hercules ultra-faint dwarf galaxy (UFD). Previous tidal disruption studies of the Hercules UFD have been hindered by the high degree of foreground contamination in the direction of the dwarf. We bypass this issue by using RR Lyrae stars, which are standard candles with a very low field-volume density at the distance of Hercules. We use wide-field imaging from the Dark Energy Camera on CTIO to identify candidate RR Lyrae stars, supplemented with observations taken in coordination with the Beijing-Arizona Sky Survey on the Bok Telescope. Combining color, magnitude, and light-curve information, we identify three new RR Lyrae stars associated with Hercules. All three of these new RR Lyrae stars lie outside its published tidal radius. When considered with the nine RR Lyrae stars already known within the tidal radius, these results suggest that a substantial fraction of Hercules' stellar content has been stripped. With this degree of tidal disruption, Hercules is an interesting case between a visibly disrupted dwarf (such as the Sagittarius dwarf spheroidal galaxy) and one in dynamic equilibrium. The degree of disruption also shows that we must be more careful with the ways we determine object membership when estimating dwarf masses in the future. One of the three discovered RR Lyrae stars sits along the minor axis of Hercules, but over two tidal radii away. This type of debris is consistent with recent models that suggest Hercules' orbit is aligned with its minor axis.

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“…Simple cuts on lightcurve parameters (Henze, Meusinger & Pietsch 2008, Graczyk & Eyer 2010 as well as advanced machine learning techniques (Feeney et al 2005) can be used to select lightcurves of a known shape from a large photometric data set. A pre-selection based on colour can be used to reduce the number of candidates when searching for variables of a specific type (Kinemuchi et al 2006, Tisserand et al 2013, Zinn et al 2014, Ordoñez & Sarajedini 2016, Moretti et al 2016.…”

mentioning

confidence: 99%

Comparative performance of selected variability detection techniques in photometric time series data

Sokolovsky

Gavras

Karampelas

et al. 2016

Mon. Not. R. Astron. Soc.

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Photometric measurements are prone to systematic errors presenting a challenge to lowamplitude variability detection. In search for a general-purpose variability detection technique able to recover a broad range of variability types including currently unknown ones, we test 18 statistical characteristics quantifying scatter and/or correlation between brightness measurements. We compare their performance in identifying variable objects in seven time series data sets obtained with telescopes ranging in size from a telephoto lens to 1 m-class and probing variability on time-scales from minutes to decades. The test data sets together include lightcurves of 127539 objects, among them 1251 variable stars of various types and represent a range of observing conditions often found in ground-based variability surveys. The real data are complemented by simulations. We propose a combination of two indices that together recover a broad range of variability types from photometric data characterized by a wide variety of sampling patterns, photometric accuracies and percentages of outlier measurements. The first index is the interquartile range (IQR) of magnitude measurements, sensitive to variability irrespective of a time-scale and resistant to outliers. It can be complemented by the ratio of the lightcurve variance to the mean square successive difference, 1/η, which is efficient in detecting variability on time-scales longer than the typical time interval between observations. Variable objects have larger 1/η and/or IQR values than non-variable objects of similar brightness. Another approach to variability detection is to combine many variability indices using principal component analysis. We present 124 previously unknown variable stars found in the test data.

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La Silla Quest Rr Lyrae Star Survey: Region I

Cited by 71 publications

References 143 publications

A comprehensive view of the Virgo stellar stream

A comprehensive view of the Virgo stellar stream

Mapping the Tidal Destruction of the Hercules Dwarf: A Wide-field DECam Imaging Search for RR Lyrae Stars

Comparative performance of selected variability detection techniques in photometric time series data

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