DOES THE MILKY WAY OBEY SPIRAL GALAXY SCALING RELATIONS?

作者：Licquia Timothy C^*; Newman Jeffrey A; Bershady Matthew A

来源：Astrophysical Journal, 2016, 833(2): 220.

DOI：10.3847/1538-4357/833/2/220

• galaxies: fundamental parameters
• Galaxy: disk
• Galaxy: fundamental parameters
• methods: statistical

It is crucial to understand how the Milky Way (MW), the galaxy we can study in the most intimate detail, fits in among other galaxies. Key considerations include the Tully-Fisher relation (TFR)-i.e., the tight correlation between luminosity (L) and rotational velocity (V-rot)-and the three-dimensional luminosity-velocity-radius (LVR) scaling relation. Several past studies have characterized the MW as a 1-1.5 sigma outlier to the TFR. This study re-examines such comparisons using new estimates of MW properties that are robust to many of the systematic uncertainties that have been a problem in the past and are based on assumptions consistent with those used for other spiral galaxies. Comparing to scaling relations derived from modern extragalactic data, we find that our Galaxy's properties are in excellent agreement with TFRs defined using any Sloan Digital Sky Survey-filter absolute magnitude, stellar mass, or baryonic mass as the L proxy. We next utilize disk scale length (R-d) measurements to extend this investigation to the LVR relation. Here we find that our Galaxy lies farther from the relation than similar to 90% of other spiral galaxies, yielding similar to 9.5 sigma evidence that it is unusually compact for its L and V-rot (based on MW errors alone), a result that holds for all of the L proxies considered. The expected Rd for the MW from the LVR relation is similar to 5 kpc, nearly twice as large as the observed value, with error estimates placing the two in tension at the similar to 1.4 sigma level. The compact scale length of the Galactic disk could be related to other ways in which the MW has been found to be anomalous.

• 出版日期2016-12-20