{"title":"Median Statistics Estimate of the Distance to M87","authors":"Nicholas Rackers, Sofia Splawska, Bharat Ratra","doi":"10.1088/1538-3873/ad220e","DOIUrl":null,"url":null,"abstract":"de Grijs & Bono compiled 211 independent measurements of the distance to galaxy M87 in the Virgo cluster from 15 different tracers and reported 31.03 ± 0.14 mag as the arithmetic mean of a subset of this compilation as the best estimate of the distance. We compute three different central estimates—the arithmetic mean, weighted mean, and the median—and corresponding statistical uncertainty for the full data set as well as three sub-compilations. We find that for all three central estimates the error distributions show that the data sets are significantly non-Gaussian. As a result, we conclude that the median is the most reliable of the three central estimates, as median statistics do not assume Gaussianity. We use median statistics to determine the systematic error on the distance by analyzing the scatter in the 15 tracer subgroup distances. From the 211 distance measurements, we recommend a summary M87 distance modulus of <inline-formula>\n<tex-math>\n<?CDATA ${31.08}_{-0.04}^{+0.05}$?>\n</tex-math>\n<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>31.08</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>0.04</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.05</mml:mn></mml:mrow></mml:msubsup></mml:math>\n<inline-graphic xlink:href=\"paspad220eieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\n</inline-formula> (statistical) <inline-formula>\n<tex-math>\n<?CDATA ${}_{-0.06}^{+0.04}$?>\n</tex-math>\n<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>0.06</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.04</mml:mn></mml:mrow></mml:msubsup></mml:math>\n<inline-graphic xlink:href=\"paspad220eieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\n</inline-formula> (systematic) mag, or combining the two errors in quadrature <inline-formula>\n<tex-math>\n<?CDATA ${31.08}_{-0.07}^{+0.06}$?>\n</tex-math>\n<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>31.08</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>0.07</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.06</mml:mn></mml:mrow></mml:msubsup></mml:math>\n<inline-graphic xlink:href=\"paspad220eieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\n</inline-formula> mag, rounded to 16.4 ± 0.5 Mpc, all at 68.27% significance.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.3000,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Publications of the Astronomical Society of the Pacific","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1088/1538-3873/ad220e","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ASTRONOMY & ASTROPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
de Grijs & Bono compiled 211 independent measurements of the distance to galaxy M87 in the Virgo cluster from 15 different tracers and reported 31.03 ± 0.14 mag as the arithmetic mean of a subset of this compilation as the best estimate of the distance. We compute three different central estimates—the arithmetic mean, weighted mean, and the median—and corresponding statistical uncertainty for the full data set as well as three sub-compilations. We find that for all three central estimates the error distributions show that the data sets are significantly non-Gaussian. As a result, we conclude that the median is the most reliable of the three central estimates, as median statistics do not assume Gaussianity. We use median statistics to determine the systematic error on the distance by analyzing the scatter in the 15 tracer subgroup distances. From the 211 distance measurements, we recommend a summary M87 distance modulus of 31.08−0.04+0.05 (statistical) −0.06+0.04 (systematic) mag, or combining the two errors in quadrature 31.08−0.07+0.06 mag, rounded to 16.4 ± 0.5 Mpc, all at 68.27% significance.
期刊介绍:
The Publications of the Astronomical Society of the Pacific (PASP), the technical journal of the Astronomical Society of the Pacific (ASP), has been published regularly since 1889, and is an integral part of the ASP''s mission to advance the science of astronomy and disseminate astronomical information. The journal provides an outlet for astronomical results of a scientific nature and serves to keep readers in touch with current astronomical research. It contains refereed research and instrumentation articles, invited and contributed reviews, tutorials, and dissertation summaries.