Browsing by Author "Vivas, A. Katherina"

Now showing 1 - 5 of 5
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    Deep drilling in the time domain with DECam: survey characterization
    (2023) Graham, Melissa L.; Knop, Robert A.; Kennedy, Thomas D.; Nugent, Peter E.; Bellm, Eric; Catelan, Márcio; Patel, Avi; Smotherman, Hayden; Soraisam, Monika; Stetzler, Steven; Aldoroty, Lauren N.; Awbrey, Autumn; Baeza-Villagra, Karina; Bernardinelli, Pedro H.; Federica Bianco, Federica; Brout, Dillon; Clarke, Riley; Clarkson, William I.; Collett, Thomas; Davenport, James R.; Fu, Shenming; Gizis, John E.; Heinze, Ari; Hu, Lei; Jha, Saurabh W.; Jurić, Mario; Kalmbach, J. Bryce; Kim, Alex; Lee, Chien-Hsiu; Lidman, Chris; Magee, Mark; Martínez-Vázquez, Clara E.; Matheson, Thomas; Narayan, Gautham; Palmese, Antonella; Phillips, Christopher A.; Rabus, Markus; Rest, Armin; Rodríguez-Segovia, Nicolás; Street, Rachel; Vivas, A. Katherina; Wang, Lifan; Wolf, Nicholas; Yang, Jiawen
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    DISENTANGLING THE VIRGO OVERDENSITY WITH RR LYRAE STARS
    (IOP PUBLISHING LTD, 2016) Vivas, A. Katherina; Zinn, Robert; Farmer, John; Duffau, Sonia; Ping, Yiding
    We use a combination of spatial distribution and radial velocity to search for halo substructures in a sample of 412 RR Lyrae stars (RRLSs) that covers a. region of similar to 525 square degrees. of the Virgo overdensity (VOD) and spans distances from the Sun from 4 to 75 kpc. With a friends-of-friends algorithm we identified six high-significance groups of RRLSs in phase space, which we associate mainly with the VOD and with the Sagittarius stream. Four other groups were also flagged as less significant overdensities. Three high-significance and three. lower-significance groups have distances between similar to 10 and 20 kpc, which places them in the distance range attributed by others to the VOD. The largest of these is the Virgo stellar stream. at 19 kpc, which has 18 RRLSs, a factor of two increase over the number known previously. While these VOD groups are distinct according to our selection criteria, their overlap in position and distance. and, in a few cases, similarity in radial velocity are suggestive that they may not all stem from separate accretion events. Even so, the VOD appears to be caused by more than one overdensity. The Sagittarius (Sgr). stream is a very obvious feature in the background of the VOD at a mean distance of 44 kpc. Two additional high-significance. groups were detected at distances >40 kpc. Their radial velocities and locations differ from the expected path of the Sgr debris in this part of the sky, and they are likely to be remnants of other accretion events.
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    RR Lyrae stars as tracers of halo substructures
    (2017) Duffau, Sonia; Vivas, A. Katherina; Navarrete, Camila; Carballo-Bello, Julio; Hajdu, Gergel; Catelan, Marcio
    Three RR Lyrae overdensity candidates in the southern sky have been studied using low resolution spectra obtained with the Goodman spectrograph at SOAR. We search for unidentified velocity peaks indicative of the possible presence of streams within the overdensities. Our results suggest that all three overdensities present an excess of radial velocity signal at high mean radial velocities which cannot be explained as a contribution from any known Galactic component....
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    RR Lyrae Stars Belonging to the Candidate Globular Cluster Patchick 99
    (2024) Butler, Evan; Kunder, Andrea; Prudil, Zdenek; Covey, Kevin R.; Ball, Macy; Campos, Carlos; Gollnick, Kaylen; Carvajal, Julio Olivares; Hughes, Joanne; Devine, Kathryn; Johnson, Christian I.; Vivas, A. Katherina; Rich, R. Michael; Joyce, Meridith; Simion, Iulia T.; Marchetti, Tommaso; Koch-Hansen, Andreas J.; Clarkson, William I.; Kuss, Rebekah
    Patchick 99 is a candidate globular cluster located in the direction of the Galactic bulge, with a proper motion almost identical to the field and extreme field star contamination. A recent analysis suggests it is a low-luminosity globular cluster with a population of RR Lyrae stars. We present new spectra of stars in and around Patchick 99, targeting specifically the three RR Lyrae stars associated with the cluster as well as the other RR Lyrae stars in the field. A sample of 53 giant stars selected from proper motions and a position on the color-magnitude diagram are also observed. The three RR Lyrae stars associated with the cluster have similar radial velocities and distances, and two of the targeted giants also have radial velocities in this velocity regime and [Fe/H] metallicities that are slightly more metal-poor than the field. Therefore, if Patchick 99 is a bona fide globular cluster, it would have a radial velocity of -92 +/- 10 km s-1, a distance of 6.7 +/- 0.4 kpc (as determined from the RR Lyrae stars), and an orbit that confines it to the inner bulge.
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    The One-hundred-deg2 DECam Imaging in Narrowbands (ODIN): Survey Design and Science Goals
    (2024) Lee, Kyoung-Soo; Gawiser, Eric; Park, Changbom; Yang, Yujin; Valdes, Francisco; Lang, Dustin; Ramakrishnan, Vandana; Moon, Byeongha; Firestone, Nicole; Appleby, Stephen; Artale, Maria Celeste; Andrews, Moira; Bauer, Franz; Benda, Barbara; Broussard, Adam; Chiang, Yi-Kuan; Ciardullo, Robin; Dey, Arjun; Farooq, Rameen; Gronwall, Caryl; Guaita, Lucia; Huang, Yun; Hwang, Ho Seong; Im, Sang Hyeok; Jeong, Woong-Seob; Karthikeyan, Shreya; Kim, Hwihyun; Kim, Seongjae; Kumar, Ankit; Nagaraj, Gautam R.; Nantais, Julie; Padilla, Nelson; Park, Jaehong; Pope, Alexandra; Popescu, Roxana; Schlegel, David; Seo, Eunsuk; Singh, Akriti; Song, Hyunmi; Troncoso, Paulina; Vivas, A. Katherina; Zabludoff, Ann; Zenteno, Alfredo
    We describe the survey design and science goals for One-hundred-deg(2) DECam Imaging in Narrowbands (ODIN), a NOIRLab survey using the Dark Energy Camera (DECam) to obtain deep (AB similar to 25.7) narrowband images over an unprecedented area of sky. The three custom-built narrowband filters, N419, N501, and N673, have central wavelengths of 419, 501, and 673 nm and respective FWHM of 7.5, 7.6, and 10.0 nm, corresponding to Ly alpha at z = 2.4, 3.1, and 4.5 and cosmic times of 2.8, 2.1, and 1.4 Gyr, respectively. When combined with even deeper, public broadband data from the Hyper Suprime-Cam, DECam, and in the future, the Legacy Survey of Space and Time, the ODIN narrowband images will enable the selection of over 100,000 Ly alpha-emitting (LAE) galaxies at these epochs. ODIN-selected LAEs will identify protoclusters as galaxy overdensities, and the deep narrowband images enable detection of highly extended Ly alpha blobs (LABs). Primary science goals include measuring the clustering strength and dark matter halo connection of LAEs, LABs, and protoclusters, and their respective relationship to filaments in the cosmic web. The three epochs allow for the redshift evolution of these properties to be determined during the period known as Cosmic Noon, where star formation was at its peak. The narrowband filter wavelengths are designed to enable interloper rejection and further scientific studies by revealing [O II] and [O III] at z = 0.34, Ly alpha and He II 1640 at z = 3.1, and Lyman continuum plus Ly alpha at z = 4.5. Ancillary science includes similar studies of the lower-redshift emission-line galaxy samples and investigations of nearby star-forming galaxies resolved into numerous [O III] and [S II] emitting regions.