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 sq .
deg .
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 by Prior et al .
2009 , and Drake et al .
2013 ) , as well as the bright QUEST RRLS sample ( Vivas et al .
in prep .
) , the catalogs of blue horizontal branch ( BHB ) stars compiled by Sirko et al ( 2004 ) and Brown et al ( 2008 , 2010 ) and the catalog of Red Giant stars from the Spaghetti survey , for stars that may be related to the QUEST RRLS groups .
The most significant group of RRLS is the Virgo Stellar Stream ( VSS , first reported by Duffau et al 2006 ) 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 Newberg et al ( 2007 ) in the same direction and at a similar distance ( S297+63-20.5 ) .
The location in phase space of two other groups ( F and H ) suggests a possible connection with the VSS , which can not be discarded at this point , although the turnoff colors of the VSS and group H , as identified from Newberg et al .
2007 , 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 .