Comments on Individual Sources

WGAJ0043.3-2638. Since being selected for the DXRBS sample, this source was observed by both Cristiani et al. (1995) and Wolter et al. (1998), both of whom identify it as a broad-emission line AGN at z=1.002. Both this redshift and the redshift we list in Table 3 (z=0.451) have problems reproducing some of the features found in both spectra. For example, if the object is at z=1.002, it is difficult to explain the likely emission line at 4050 Å, which we have classified as Mg II at z=0.451. Further observations are needed to determine the correct redshift of this object. The rest-frame equivalent width of the 4050 Å emission line is 9.6 Å (if z=0.451) or 7.0 Å (if z=1.002), only slightly above the dividing line between BL Lac and FSRQ. Therefore, even though the line is clearly broad (FWHM=3800 km/s), this object is similar to objects such as Mkn 501 and BL Lac which share this property and must be classified as a BL Lac.

WGAJ0100.1-3337. The single emission line, which we classify as Mg II at z=0.875, is clearly broad (FWHM=2900 km/s) but its equivalent width is close to the BL Lac/FSRQ dividing line ($W_\lambda = 9.8$ Å rest-frame). We classify this object as a BL Lac, similarly to WGAJ0043.3-2638 (see above discussion).

WGAJ0204.8+1514. This source, also known as 4C +15.05, has a radio flux > 3 Jy, and was also previously observed by Stickel et al. (1996), who classified the source as an AGN at z=0.833 based upon the identification of two lines as OII $\lambda$3727 and Ne I $\lambda$3833. These lines are also present in our spectrum, as are four other lines (Figure 2). However, the redshift claimed by Stickel et al. (1996) is likely incorrect, as all six lines cannot be accounted for if the redshift is z=0.833. We believe that a better fit is obtained with a redshift z=0.405. This object is also the likely counterpart of the EGRET source 2EG0204+1514 (Thompson et al. 1995; Mattox et al. 1997).

WGAJ0210.0-1004. This object, at z = 1.976, is $\sim 2'$ from MS0207.4-1016, identified by Stocke et al. (1991) as a radio-quiet QSO (F(6 cm) < 0.3 mJy at 3 $\sigma$) at z=1.970. A 6cm VLA survey done during the EMSS project showed that there are two fairly strong radio sources which likely would be in the PMN beam (Stocke, private communication). The stronger source, with a flux of 133 mJy, is at the position of WGAJ0210.0-1004; however, there is another 70 mJy source at a position which is not consistent with either WGAJ0210.0-1004 or MS0207.4-1016. Even with this reduced 6 cm flux, WGAJ0210.0-1004 is still a flat spectrum source ($\alpha_{\rm r} = 0.58$). There is no question about the correctness of either X-ray source identification, since WGACAT lists a 0.01 ct/s X-ray source at a position consistent with MS0207.4-1016 (in addition to WGAJ0210.0-1004). It is possible, however, that X-ray emission from both sources may have contributed to the EMSS X-ray flux. What is particularly interesting is that these two objects are at essentially the same redshift, and are therefore likely associated with one another in a group or cluster of galaxies, since the projected separation between them is 1.6 Mpc.

WGAJ0245.2+1047. This object is difficult to classify because of the large equivalent width of its H$\alpha$ emission line (19.1 Å  rest-frame). However, when combined with its low Ca H & K break strength (C = 0.26) it rests securely in the BL Lac area of the $(W_\lambda,C)$plane as defined by Marchã et al. (1996). We therefore classify this object as a BL Lac.

WGAJ0313.9+4115. The H$\alpha$ emission line in this object's spectrum is not very broad, exhibiting FWHM = 1780 km/s. The rest-frame equivalent width of this line is close to the BL Lac/FSRQ dividing line (13.0 Å rest-frame). The Ca II break strength is 0.38, close to the BL Lac/radio galaxy border we are using. We have classified this object as a BL Lac object, but we note that the $1 \sigma$ errors on our measurement of C are not small enough to exclude the alternate classification as a radio galaxy (Figure 1). A higher signal-to-noise spectrum of this object is clearly necessary to confirm its nature.

WGAJ0340.8-1814. The H$\alpha$ emission line in the spectrum of this object has a rest-frame equivalent width of 16.0 Å, and its Ca II break strength is C=0.40. Thus it is right on the borderline of the BL Lac region of the $(W_\lambda,C)$ plane. We have classified this object as a radio galaxy; however, a higher signal-to-noise spectrum is clearly necessary to confirm its nature.

WGAJ0421.5+1433. Our spectra show no clear lines; however, due to its low signal-to-noise ($\sim 7$), the 2$\sigma$ upper limits that can be placed on its break strength (C<0.30) and equivalent width of emission lines ($W_\lambda < 8.2$ Å) are not very stringent. They are adequate, however, to allow us to classify this object as a BL Lac. Better observations of this source are clearly necessary.

WGAJ0428.8-3805. This object has no detectable emission lines in its spectrum (2 $\sigma$ upper limit = 0.7 Å), and a weak Ca break (C = 0.32). We classify it as a BL Lac object using the Marchã et al. (1996) criteria.

WGAJ0449.4-4349. This bright BL Lac object was observed as a target by ROSAT; however, until now it was unidentified. Due to its nonserendipitous observation by ROSAT, we will not include it in computations of the luminosity function. We include it here as it was identified during our observing campaign and there will probably be no other opportunity to discuss it.

WGAJ0500.0-3040. We have termed this object a radio galaxy despite the fact that all of its emission lines have equivalent widths greater than 5 Å (some are as large as 70 Å), since all are relatively narrow (FWHM $\sim 1000-2000$ km/s). However, there is no detectable 4000 Å break in its spectrum, which points to an unusually strong non-thermal contribution.

WGAJ0513.8+0156. The Ca II break strength (C = 0.34) and lack of emission lines (2 $\sigma$ upper limit on $W_\lambda = 1.3$ Å) allow us to classify this object as a BL Lac object. However, the low signal-to-noise of its spectrum blueward of the Ca II break results in a relatively large 1 $\sigma$ error on its break strength, large enough so that we cannot exclude the alternate classification as a radio galaxy (Figure 1). A higher signal-to-noise spectrum of this source is required to confirm its nature.

WGAJ0558.1+5328. The H$\alpha$ emission line in this object's spectrum is not very broad, exhibiting FWHM = 2100 km/s. The equivalent width of this line is close to the BL Lac/FSRQ dividing line (9.8 Å). The Ca II break strength is 0.29. We classify this object as a BL Lac. However, the low signal-to-noise of its spectrum, particularly blueward of the Ca II break ($\sim 5$ compared to $\sim 12-15$ redward of the break) do not quite allow us to exclude the alternate (radio galaxy) classification. A higher signal-to-noise spectrum would clarify this question.

WGAJ0624.7-3230. The emission line and absorption line redshifts of this object are somewhat different (z_abs = 0.252 and z_em = 0.275). Therefore it is likely that the galactic emission in the spectrum is due to a foreground galaxy superposed upon the radio source. The sole emission line has a rest-frame equivalent width of 8.5 Å; slightly over the BL Lac/FSRQ dividing line, but the line is narrow (FWHM = 900 km/s). We are classifying this object as a BL Lac because of its small equivalent-width emission line and low Ca H & K break contrast (C = 0.22).

WGAJ0656.3-2403. There is a possible emission feature in the spectrum of this object at 3845 Å. It is unclear whether this is a real emission line, noise, or a cosmic ray due to the noisiness of the spectrum in this range. The lack of other emission lines in the spectrum and high noise level in the blue make it somewhat doubtful that this feature is truly an emission line. However, if it is due to Mg II emission, the redshift of this object would be z=0.371, and it would be narrow (FWHM = 500 km/s). We classify this object as a BL Lac due to the likely lineless nature of its spectrum, though we note that if the 3845 Å feature is indeed an emission line it exceeds by more than a factor of four the traditional BL Lac/FSRQ dividing line (rest-frame $W_\lambda = 24.5$ Å).

WGAJ0724.3-0715. Despite its faintness, the H $\alpha$ emission line in the spectrum of this object is quite broad (rest-frame $W_\lambda = 30.3$ Å, FWHM = 4000 km/s). We therefore classify it as an FSRQ.

WGAJ0744.8+2920. This object was identified independently by Gregg et al. (1996) as part of the FIRST bright QSO sample, and by Wolter et al. (1998). We confirm both identifications and redshifts; however, a comparison of our spectrum with that given by Wolter et al. reveals a large deficit in the blue in our spectrum. This is most likely due to a combination of instrumental and weather related factors.

WGAJ0816.0-0736. We tentatively classify this object as a BL Lac due to its lack of emission lines and low break strength (C=0.37). However, due to the low signal-to-noise of its spectrum blueward of the Ca II break ($\sim 4$compared to $\sim 20$ at >5000 Å), we cannot exclude the alternative (radio galaxy) classification due to the large 1$\sigma$ error on C (0.18). A higher signal-to-noise spectrum is required to clarify its nature.

WGAJ0900.2-2817. A second spectrum of this object, with much wider wavelength coverage, was obtained in May 1997 at the ESO 2.2m. That spectrum (which will be published in a later paper) confirms the identification of the single line as Mg II $\lambda 2798$.

WGAJ1057.7-7724. The fairly low signal-to-noise spectrum we have ($S/N \sim 7$) places 2 $\sigma$ limits on C and $W_\lambda$ which are sufficient to classify this object as a BL Lac. A higher signal-to-noise spectrum is required to obtain a redshift.

WGAJ1222.6+2934. The fairly low signal-to-noise spectrum we have ($S/N \sim 6$) places 2 $\sigma$ limits on C and $W_\lambda$ which are sufficient to classify this object as a BL Lac. A higher signal-to-noise spectrum is required to obtain a redshift.

WGAJ1525.3+4201. This source was listed as a BL Lac candidate by Ruscica et al. (1996). However, our spectrum shows strong, broad lines, and we identify this object as a quasar at z = 1.189.

WGAJ2317.9-4213. This object is most likely a radio galaxy based upon its strong Ca II break (C=0.52). It is probably associated with a group of galaxies at the same redshift found by the Las Campanas Redshift Survey (Schechtman et al. 1996).

WGAJ2322.0+2114. This object was also observed by Wolter et al. (1998). We confirm both their identification and redshift.