J/ApJ/939/38ivo://CDS.VizieR/J/ApJ/939/38doi:10.26093/cds/vizier.19390038CDSFilion C.Platais I.Wyse R.F.G.Kozhurina-Platais V.2025-02-18T20:14:20Z2024-11-18T08:27:38ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frdwarf-galaxieshst-photometryvisible-astronomyproper-motionsThis paper presents improved constraints on the low-mass stellar initial mass function (IMF) of the Bootes I (Boo I) ultrafaint dwarf galaxy, based on our analysis of recent deep imaging from the Hubble Space Telescope. The identification of candidate stellar members of Boo I in the photometric catalog produced from these data was achieved using a Bayesian approach, informed by complementary archival imaging data for the Hubble Ultra Deep Field. Additionally, the existence of earlier-epoch data for the fields in Boo I allowed us to derive proper motions for a subset of the sources and thus identify and remove likely Milky Way stars. We were also able to determine the absolute proper motion of Boo I, and our result is in agreement with, but completely independent of, the measurement(s) by Gaia. The best-fitting parameter values of three different forms of the low-mass IMF were then obtained through forward modeling of the color-magnitude data for likely Boo I member stars within an approximate Bayesian computation Markov Chain Monte Carlo algorithm. The best-fitting single power-law IMF slope is {alpha}=-1.95_-0.28_^+0.32^, while the best-fitting broken power-law slopes are {alpha}_1_=-1.67_-0.57_^+0.48^ and {alpha}_2_=-2.57_-1.04_^+0.93^. The best-fitting lognormal characteristic mass and width parameters are M_c_=0.17_-0.11_^+0.05^M_{sun}_ and {sigma}=0.49_-0.20_^+0.13^. These broken power-law and lognormal IMF parameters for Boo I are consistent with published results for the stars within the Milky Way, and thus it is plausible that Bootes I and the Milky Way are populated by the same stellar IMF.2022ApJ...939...38Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/939/38CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/350 : Gaia EDR3 (Gaia Collaboration, 2020)J/AJ/136/2321 : Washington photometry of Bootes I stars (Hughes+, 2008)J/ApJ/723/1632 : Abundance spreads in Bootes I and Segue 1 (Norris+, 2010)J/ApJ/736/146 : Radial velocities of stars in Bootes I (Koposov+, 2011)J/MNRAS/439/788 : Stromgren and Washington photometry in Boo I (Hughes+, 2014)J/ApJ/797/115 : HSTPROMO I. Observations and NGC7078 results (Bellini+, 2014)J/ApJ/826/110 : Boo-127 and Boo-980 high-resolution spectra (Frebel+, 2016)J/MNRAS/461/3702 : gi photometry of Bootes I (Roderick+, 2016)J/ApJ/852/49 : Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018)J/AJ/159/272 : Orion Nebula Cluster PMs with HST (Platais+, 2020)J/ApJS/251/2 : CDWFS: Chandra survey in Bootes. I. (Masini+, 2020)J/ApJ/920/92 : VLT Spectroscopy of Ultra-faint Dwarf Gal. (Jenkins+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/939/38https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/939/38http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/939/38https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/939/38https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/939/38http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/939/38GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/939/38/photo (Catalog containing HST photometry in the Vega magnitude system)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/939/38/photo?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/939/38/photo?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/939/38/photo?GETtext/xml+votable180.050000true210.02552314.4772520.005555555555555556Cone search capability for table J/ApJ/939/38/astro (Catalog containing relative proper motions)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/939/38/astro?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/939/38/astro?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/939/38/astro?GETtext/xml+votable180.050000true210.02552303814.4772519980.0055555555555555566/87452.3657755224268815e-19 3.5452907792336973e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/939/38?format=asciiOpticaldefaultJ/ApJ/939/38/photoCatalog containing HST photometry in the Vega magnitude systemPMm[0/1] Bayesian probability of membership from photometrystat.fit.goodnessfloatPNMm[0.001/1] Bayesian probability of non-membership from photometrystat.fit.goodnessfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/30451] Photometric catalog identifiermeta.id;meta.mainintF606W[19.7/30.1] DAOPHOT PSF photometric Vega magnitude in the HST ACS/WFC F606W filtermagphot.mag;em.opt.Rfloate_F606W[0.01/0.6] F606W uncertaintymagstat.errorfloatF814W[18.48/29.1] DAOPHOT PSF photometric Vega magnitude in the HST ACS/WFC F814W filtermagphot.mag;em.opt.Ifloate_F814W[0.007/0.6] F814W uncertaintymagstat.errorfloatshF606W[-4.7/1.9] DAOPHOT sharp statistic in the F606W filterstat.fit.param;em.opt.RfloatshF814W[-3.3/1.6] DAOPHOT sharp statistic in the F814W filterstat.fit.param;em.opt.IfloatRAJ2000[209.93/210.11] Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[14.44/14.6] Declination (J2000)degpos.eq.dec;meta.mainMm[0/1] Flag indicating if source meets all criteria for membership (1=yes, 0=no)meta.code.memberintAstroDisplay data from the astrometric cat. within 0.1"meta.ref.urlintnullableJ/ApJ/939/38/astroCatalog containing relative proper motionsNdel[0/4] Number of deleted datapointsmeta.numberinte_pmRA[0.02/2.5] pmRA uncertaintymas/yrstat.error;pos.pm;pos.eq.rafloatpmDE[-16.2/15.5] Weighted proper motion in Y (pmy)mas/yrpos.pm;pos.eq.decfloate_pmDE[0.02/2.5] pmDE uncertaintymas/yrstat.error;pos.pm;pos.eq.decfloatPhotoDisplay data from the photometric cat. within 0.1"meta.ref.urlintnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1017/2757029] Astrometric catalog IDmeta.id;meta.mainintpmRA[-17/14.5] Weighted proper motion in X (pmx)mas/yrpos.pm;pos.eq.rafloatmag[11.7/27.3] Proxy stellar magnitude (m_astrom_)magphot.magfloatN1[2/8] Number of first-epoch datapointsmeta.numberintN2[1/16] Number of second-epoch datapointsmeta.numberintResmax[0.015/1.1] Largest residual in either proper-motion fitpixstat.fit.residualfloatXpos[43/4113] X-coordinate in ACS/WFC pixels aligned with RApixpos.cartesian.x;instr.detfloatYpos[-119/4211] Y-coordinate in ACS/WFC pixels aligned with DECpixpos.cartesian.y;instr.detfloatRAJ2000[209.93/210.11] Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[14.44/14.6] Declination (J2000)degpos.eq.dec;meta.mainPoint[1/5] Pointing/field center to which source belongs (1, 3 or 5)obs.fieldint