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$\begin{figure} \par\includegraphics[width=11.2cm,clip]{7631f1.eps}\end{figure}$ Figure 1: Map of the VIMOS observations in the Centaurus cluster. Dots are all photometrically selected compact object candidates from the VIMOS pre-images. Open circles mark the 386 compact objects with measured radial velocities (out of 405 for which slits had been allocated). Filled (green) circles indicate the 27 compact objects with radial velocities in the range of the Centaurus cluster ( $1750<v_{\rm rad}<5550$ km s^-1, see Fig. 3). Filled (green) circles with red dots indicate objects with radial velocity above 4000 km s^-1, hence members of the Cen45 sub-cluster. Blue asterisks indicate the locations of 13 dwarf elliptical galaxies included in this study. The golden asterisks indicate the location of NGC 4696 and NGC 4709, the central galaxies of the Cen30 and Cen45 components. The dotted red rectangle indicates the central FORS pointing of our deep photometric Centaurus cluster study (see text and Mieske et al. 2005).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{7631f2.eps}\end{figure}$ Figure 2: Example excerpts of two reduced spectra of Centaurus compact objects. The dashed ticks at the top mark the correspondingly red-shifted regions of the Mgb and Fe5270 Lick indices. Left: object CCOS J1248.54-4119.64, with a S/N around 45. Right: object CCOS J1248.74-4118.95, with a S/N around 18.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{7631f3.eps}\end{figure}$ Figure 3: Radial velocity histogram of all observed sources. The green dashed lines mark the limits applied for Centaurus cluster membership selection (40 Centaurus cluster members, including 13 dEs). The two vertical ticks mark the radial velocities of NGC 4696 ( $\sim$ 3000 km s^-1) and NGC 4709 ( $\sim$ 4500 km s^-1).
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{7631f4.eps}\end{figure}$ Figure 4: Colour-magnitude diagram in VR of the sources from Fig. 1, excluding the dwarf elliptical galaxies.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{7631f5.eps}\end{figure}$ Figure 5: Cumulative magnitude distribution of Centaurus compact objects. Dashed lines indicate the cumulative magnitude distribution of assumed Gaussian Globular Cluster Luminosity Functions with three different widths $\sigma$ : from top to bottom 1.4, 1.3, and 1.2 mag. The assumed turnover magnitude is M_V=-7.4 mag. The KS-test probabilities with which the measured compact object distribution is drawn from the Gaussians are 21% ( $\sigma =1.4$ mag), 11% ( $\sigma =1.3$ mag) and 2% ( $\sigma =1.2$ mag).
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In the text

$\begin{figure} \par\mbox{\includegraphics[width=4.2cm,clip]{7631f6a.eps}\hspace*{2mm} \includegraphics[width=4.2cm,clip]{7631f6b.eps} } \end{figure}$ Figure 6: Comparison of cumulative radial distributions of various object samples. Left panel: Centaurus compact objects are indicated by the (blue) solid histogram. The sample of 13 dwarf ellipticals is indicated by the (black) dotted histogram. For this plot, the radial distance was calculated with respect to NGC 4696 for the Cen30 members and with respect to NGC 4709 for the Cen45 members. The samples of compact objects and dEs have identical parent distributions at the 0.2% confidence level according to a KS-test. Right panel: the short dashed red line is the distribution of GC candidates around NGC 4696 from Mieske et al. (2005), see Fig. 1. The long dashed blue histogram is the distribution of compact objects restricted to the same field as the GC candidate sample. According to a KS test, both samples stem at 98% probability from the same parent distribution.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{7631f7.eps}\end{figure}$ Figure 7: Comparison between measured and literature Lick index values for the four Lick standard stars included in our observations. Index ${\rm \langle Fe\rangle }$ is indicated by green solid squares, Mgb by black asterisks. Literature data is from Worthey et al. (1994). The dashed line indicates the identity.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{7631f8.eps}\end{figure}$ Figure 8: Lick index ${\rm \langle Fe\rangle }$ plotted vs. Mgb. Large, green filled circles are Centaurus compact objects with S/N>30, small green filled circles those with S/N<30. At the top, the left error bar indicates the average statistical uncertainty of our (green) data points, while the right error bar indicates the global uncertainty of our Lick calibration (see text). Sources surrounded by a solid square indicate those with HST imaging available (see Sect. 4.5). The source with an attached error bar is the most extended of those compact objects (see Sect. 4.5). Asterisks indicate values for central regions of dwarf elliptical galaxies, comprising the 13 Centaurus cluster dEs included in our study, and Fornax and Virgo dEs from Geha et al. (2003). Blue open circles are Virgo UCDs from Evstigneeva et al. (2007). Magenta open circles are the Fornax UCDs (Mieske et al. 2006a). The solid (dashed) lines indicate SSP models by Thomas et al. (2003) for an assumed age of 12 Gyr (4 Gyr) and the three indicated [ $\alpha$ /Fe] values. Metallicities are from bottom to top -2.25 to 0.67 dex.
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In the text

$\begin{figure} \par\mbox{\includegraphics[width=7.8cm,clip]{7631f9a.eps}\hspace*{4mm} \includegraphics[width=7.5cm,clip]{7631f9b.eps} } \end{figure}$ Figure 9: Left panel: logarithm of the MgFe line index plotted vs. V for the Centaurus compact objects. The upper x-axis indicates an estimate of the corresponding [Fe/H], accurate to 0.2-0.3 dex, see text. Symbols surrounded by (red) circles indicate Cen45 members. The solid squares indicate spectra with S/N larger than 30. The green asterisk indicates the most extended object among the 8 sources with HST imaging (see text). Right panel: Log (MgFe) plotted vs. V for three samples of compact objects. Green filled circles indicate the Centaurus compact objects from the left panel. Blue open circles are the Virgo UCDs (Evstigneeva et al. 2007). Magenta open circles indicate Fornax compact objects (Mieske et al. 2006a).
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{7631f10.eps}\end{figure}$ Figure 10: Radial velocity histogram of Centaurus compact objects (solid line). The (blue) curve indicates the expected velocity distribution if the Cen30 and Cen45 sample had mean velocities and velocity dispersion identical to the early-type galaxy population in both sub-clusters (Stein et al. 1997). The dotted tick at 4000 km s^-1 indicates the adopted separation between Cen30 and Cen45. The two solid ticks indicate the radial velocities of NGC 4696 (2960 km s^-1, NED) and NGC 4709 (4680 km s^-1, NED). The dashed ticks indicate the $\pm 1$ $\sigma$ range of the measured radial velocities for compact objects in Cen30 and Cen45, respectively. The dotted (green) histogram shows the velocity distribution of the 13 dwarf elliptical galaxies included in our sample.
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In the text

$\begin{figure} \par\includegraphics[width=4cm,clip]{7631f11a.ps}\hspace{-4cm}\pa... ....eps}\hspace{0.2cm} \includegraphics[width=3.5cm,clip]{7631f11d.eps}\end{figure}$ Figure 11: Top: Two $3''\times 2.5''$ HST archival image excerpts of Centaurus compact objects (a total of 9 objects have HST imaging available, see text). The images are from an ACS image in the F435W filter (Proposal 9427, PI Harris) with matched intensity cuts. Object CCOS J1248.74-4118.58 is the largest source of the sample, object CCOS J1248.76-4118.70 the smallest one (see also Fig. 12). Bottom: arbitrarily normalised radial intensity profile of both sources, compared to a stellar PSF (dashed line).
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In the text

$\begin{figure} \par\includegraphics[width=7.2cm,clip]{7631f12.eps}\end{figure}$ Figure 12: HST based half light radius measurements of compact objects in various environments plotted vs. their absolute magnitude M_V. Green filled circles indicate Centaurus compact objects (this paper). The dotted line indicates the resolution limit of the Centaurus ACS images. This value ( $r_{\rm h}\simeq$ 2.5 pc) also corresponds closely to the average GC size. Magenta open circles indicate Fornax compact objects from Mieske et al. (2006a) and Evstigneeva et al. (2007). Blue open circles are Virgo UCDs from Evstigneeva et al. (2007) and Hasegan et al. (2005). Red crosses are the Local Group compact objects $\omega$ Cen (fainter) and G1 (brighter).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{7631f2.eps}\end{figure}$	Figure 2: Example excerpts of two reduced spectra of Centaurus compact objects. The dashed ticks at the top mark the correspondingly red-shifted regions of the Mgb and Fe5270 Lick indices. Left: object CCOS J1248.54-4119.64, with a S/N around 45. Right: object CCOS J1248.74-4118.95, with a S/N around 18.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{7631f3.eps}\end{figure}$	Figure 3: Radial velocity histogram of all observed sources. The green dashed lines mark the limits applied for Centaurus cluster membership selection (40 Centaurus cluster members, including 13 dEs). The two vertical ticks mark the radial velocities of NGC 4696 ( $\sim$ 3000 km s^-1) and NGC 4709 ( $\sim$ 4500 km s^-1).
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{7631f4.eps}\end{figure}$	Figure 4: Colour-magnitude diagram in VR of the sources from Fig. 1, excluding the dwarf elliptical galaxies.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{7631f7.eps}\end{figure}$	Figure 7: Comparison between measured and literature Lick index values for the four Lick standard stars included in our observations. Index ${\rm \langle Fe\rangle }$ is indicated by green solid squares, Mgb by black asterisks. Literature data is from Worthey et al. (1994). The dashed line indicates the identity.
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