Australia Telescope National Facility

Total Magnitudes of Virgo Galaxies. I.
Construction of a Self-consistent Reference Dataset
Spanning 8th to 18th mag.
Christopher Ke-shih Young
, PASA, 18 (2), in press.

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Title/Abstract Page: Total Magnitudes of Virgo
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Intermediate galaxy sample (14th-12th mag.)

**Table 2:** New
B_t=U_t-(U-B) estimates (bold type) for galaxies with published (U-B) colours for which the VPC's photometry was saturated in B_J but unsaturated in U
Designation	VCC type/	U_t	U₂₅-U_t	(U-B)	$\sigma_{(U-B)}$	aperture	(U-B)	B_t
VPC/other	membership	(mag.)	(mag.)	(mag.)	(mag.)	(arcsec)	source	(mag.)
178/NGC 4305	Sa/M	13.54	0.61	0.30	0.1	142.7	SV96	13.24
328/NGC 4352	S0/M	13.87	0.37	0.39	0.03	34.5	RC3e	13.48
				0.40	0.06	$\infty$	RC3T
532/NGC 4431	dS0/M	14.43	0.33	0.43	0.07	$\infty$	RC3T	14.00
544/NGC 4436	dE-dS0/M	14.49	0.38	0.30	0.05	40.6	RC3e	14.19
				0.29	0.07	$\infty$	RC3T
665/NGC 4468	S0-Sa/M	14.16	0.40	0.33	0.1	89.3	SV96	13.83
				0.34	0.02	54.7	RC3e
				0.33	0.03	$\infty$	RC3T
778/NGC 4491	SBa	13.89	0.19	0.25	0.1	89.3	SV96	13.64
820/NGC 4497	SB0-SBa/M	13.79	0.23	0.34	0.1	89.3	SV96
				0.29	0.06	62.8	RC3e	13.50
				0.25	0.06	$\infty$	RC3T
838/IC 797	SBc/M	13.83	0.11	-0.05	0.1	89.3	SV96	13.88
855/NGC 4506	S(pec)/M	13.94	0.42	0.23	0.1	142.7	SV96	13.71
865/IC 3470	dE/M	15.18	0.21	0.36	0.1	32.0	WT73	14.82
885/IC 3481	E(pec)/B	14.54	0.86	0.55	0.04	25.6	RC3e	13.99
				0.51	0.04	$\infty$	RC3T
918/IC 3499	E-S0/M	14.74	0.17	0.25	0.05	$\infty$	RC3T	14.49
948/NGC 4531	Sa(pec)/M	12.90	0.26	0.32	0.1	142.7	SV96	12.58

Notes: (1) Membership assignments are based on radial velocities: M (for member) if less than 3500 km ${\rm s}^{-1}$ ; otherwise B (for background). (2) The sources of (U-B) measurements are: WT73 for Tifft (1973); RC3 for de Vaucouleurs et al. (1991) (e for effective colour, T for total colour); and SV96 for Schröder & Visvanathan (1996). When the (U-B) values listed are simply those corresponding to the largest aperture quoted by a particular source,
$\sigma_{(U-B)}$ has been arbitrarily set to 0.1 mag. (3) The quantity `aperture' is strictly only applicable to the SV96 and WT73 measurements. In the case of the RC3e measurements, the quoted values are the effective diameters (A_e/arcsec in the notation of the RC3). Although the RC3T measurements are based on extrapolations to infinite radial distances, they may suffer from systematic errors as demonstrated by Young et al. (1998). The new B_t values are therefore only based on RC3T measurements when alternative measurements are unavailable. (4) In order to minimise possible errors due to colour gradients not being taken into account, the new B_t value for NGC 4468 was based on the aperture measurement made with the largest aperture. In the case of NGC 4497 however, owing to considerable scatter in the published (U-B) measurements, a median (U-B) value was adopted instead.

In the light of the high level of consistency found between B_t values derived from the VPC's U and B_J-band photometry for faint objects, another literature search was conducted for (U-B) colours for those 48 objects with unsaturated U-band but saturated B_J-band photometry. The apparent brightnesses of these galaxies lie within the range

$16.72 \geq U_t \geq 12.90$ mag. Those 13 objects for which colours could be found are listed in Table 2, together with newly derived B_t estimates for them.

Next Section: Bright galaxy sample (14th-8th
Title/Abstract Page: Total Magnitudes of Virgo
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Contents Page: Volume 18, Number 2

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