TY - JOUR
T1 - Planetary nebulae as standard candles. X. Tests in the coma I region
AU - Jacoby, George H.
AU - Ciardullo, Robin
AU - Harris, William E.
N1 - Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 1996
Y1 - 1996
N2 - We present the results of an [O III] λ5007 survey for planetary nebulae (PNs) in three galaxies of the Coma I group: NGC 4278 (Hubble type E1), NGC 4494 (E1), and NGC 4565 (edge-on Sb). Using the planetary nebula luminosity function (PNLF), we derive distances to NGC 4494 (12.8 ± 0.9 Mpc), NGC 4565 (10.5-1.0+0.8 Mpc), and NGC 4278 (10.2-1.0+0.7 Mpc). The larger distance for NGC 4494 is significant beyond the 99% confidence level when the common systematic errors in all three distances are removed. This agrees with the results of the globular cluster luminosity function and surface brightness fluctuation methods, both of which place NGC 4565 in front of NGC 4494. The large separation is also consistent with the results of Virgocentric flow models, which predict triple-valued solutions to the Hubble flow in that direction. Our planetary nebula survey of the small elliptical NGC 4278 also reveals two [O III] λ5007 sources more luminous than the nominal limit of the PNLF. Both objects can be excluded a priori from the list of PN candidates: one is quite bright in Hα, the other is marginally resolved. Nevertheless, the existence of these objects in an otherwise normal elliptical galaxy poses a potential problem for the PNLF technique. We discuss the possible origins of objects brighter than the PNLF cutoff and consider one way in which their existence might be incorporated into PNLF distance measurements.
AB - We present the results of an [O III] λ5007 survey for planetary nebulae (PNs) in three galaxies of the Coma I group: NGC 4278 (Hubble type E1), NGC 4494 (E1), and NGC 4565 (edge-on Sb). Using the planetary nebula luminosity function (PNLF), we derive distances to NGC 4494 (12.8 ± 0.9 Mpc), NGC 4565 (10.5-1.0+0.8 Mpc), and NGC 4278 (10.2-1.0+0.7 Mpc). The larger distance for NGC 4494 is significant beyond the 99% confidence level when the common systematic errors in all three distances are removed. This agrees with the results of the globular cluster luminosity function and surface brightness fluctuation methods, both of which place NGC 4565 in front of NGC 4494. The large separation is also consistent with the results of Virgocentric flow models, which predict triple-valued solutions to the Hubble flow in that direction. Our planetary nebula survey of the small elliptical NGC 4278 also reveals two [O III] λ5007 sources more luminous than the nominal limit of the PNLF. Both objects can be excluded a priori from the list of PN candidates: one is quite bright in Hα, the other is marginally resolved. Nevertheless, the existence of these objects in an otherwise normal elliptical galaxy poses a potential problem for the PNLF technique. We discuss the possible origins of objects brighter than the PNLF cutoff and consider one way in which their existence might be incorporated into PNLF distance measurements.
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U2 - 10.1086/177122
DO - 10.1086/177122
M3 - Article
AN - SCOPUS:21344454066
SN - 0004-637X
VL - 462
SP - 1
EP - 12
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1 PART I
ER -