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3.3. A gallery of follow-up results

In this section we show some of the submm-selected galaxies with the most complete and comprehensive follow-up information, including all three with confirmed redshifts (Figs. 14, 18 and 19). To reveal more of the diversity of counterparts to the SCUBA galaxies, we also show a relatively strong radio source with a faint red K-band counterpart (Fig. 17), two K appeq 19.5 galaxies, one a formal ERO and the other with very red colors (Smail et al., 1999; Figs. 16 and 20), which are likely to be the correct counterpart on the grounds of the relatively low surface density of EROs; and a mm-continuum source located by the OVRO MMA at the position of a SCUBA-selected galaxy, with a very faint K-band counterpart observed using the NIRC instrument on the Keck telescope (Frayer et al., 2000; Fig. 15). Similar enigmatic faint red galaxies have been reported as counterparts to well-located submm-selected galaxies from other submm surveys by Gear et al. (2000) and Lutz et al. (2001), while Dannerbauer et al. (2002) do not find counterparts to three well-located MAMBO galaxies to a 3-sigma limit of Ks = 21.9.

The galaxies shown in Figs. 14 - 20 are certainly an unrepresentative sample of submm-selected galaxies, missing galaxies that are either intrinsically very faint at other wavelengths or lie at the highest redshifts. It is to be hoped that within the next few years, deep follow-up observations, especially near-IR ground-based observations 14 and mid-IR observations using SIRTF will reveal the nature of the majority of submm-selected galaxies. 15

Figure 14

Figure 14. Multi-waveband images of SMM J02399-0136 (23 mJy; Ivison et al., 1998; Frayer et al., 1998). The format of this figure is the template for those that follow. Note that these multiwaveband figures are presented in order of reducing 850-µm flux density, without correcting for gravitational lensing amplification. The leftmost panel shows black contours of 850-µm emission superimposed on a grayscale I-band image. The second panel shows black contours of faint 1.4-GHz radio emission superimposed on a K-band image. These two left-hand images are both 30 arcsec on a side. The third panel shows a 10-arcsec zoom of the K-band image (from UKIRT unless otherwise stated; Smail et al., 2002). The rightmost panel shows a B-band CFHT image in this figure; in the figures that follow this panel shows an HST image. Here and in the figures that follow, white contours are added to show contrast in saturated regions of the grayscale. North is up and East is to the left. SMM J02399-0136 is a merging galaxy with a confirmed optical/radio counterpart, and a CO redshift z = 2.808: see Vernet and Cimatti (2001) for a new high-quality spectrum showing Lyman-alpha emission from this galaxy extended over 12 arcsec.

Figure 15

Figure 15. Images of SMM J00266+1708 (18.6 mJy; Frayer et al., 2000). The left-hand K-band image is from UKIRT; the right-hand K-band image is from Keck-NIRC. The K-band detection is located at the position of the very red galaxy M12 in a 1.1-mm continuum image obtained using the OVRO MMA.

Figure 16

Figure 16. Images of SMM J09429+4658 (17.2 mJy), an ERO counterpart (Smail et al., 1999). Faint radio emission and extended, rather bright K-band emission make this a good candidate for the source of the submm emission. H1 is a low-redshift spiral galaxy in the foreground of Abell 851.

Figure 17

Figure 17. Multi-waveband images of SMM J14009+0252 (14.5 mJy), the bright radio-detected submm galaxy Abell 1835 (Fig. 1; Ivison et al., 2000). Two faint near-IR counterparts can be seen in the K-band image. Of these, J5 is extremely red, has no counterpart in the HST-F702W image, and is aligned accurately with the centroid of the radio emission.

Figure 18

Figure 18. Multi-waveband images of SMM J14011+0252 (12.3 mJy; Ivison et al., 2000, 2001). This complex merging system has a confirmed optical/radio counterpart, and a CO redshift z = 2.565 (Frayer et al., 1999). High-resolution CO and radio images are presented in Ivison et al. (2001). Note that the Northern extension of J1 is extremely red, and is close to the centroid of the radio emission. J2 is blue, while J1 is red. The complexity of this system is a caution against simple treatment of extinction as a uniform screen in submm galaxies: for a detailed discussion see Goldader et al. (2002) and references therein.

Figure 19

Figure 19. Multi-waveband images of SMM J02399-0134 (11.0 mJy; Kneib et al., 2002). This ring galaxy has a confirmed optical/radio counterpart, and a CO redshift z = 1.06. Its low redshift accounts for its very bright K-band image and mid-IR ISO detection at 15 µm. The other galaxy in the K-band image is a member of Abell 370.

Figure 20

Figure 20. Images of SMM J04431+0210 (7.2 mJy), a very red counterpart (Smail et al., 1999). A tentative Halpha redshift of z = 2.5 is determined from a near-IR Keck-NIRSPEC observation. Unlike SMM J09429+4658 this galaxy has no radio emission.

14 Near-IR imaging to 2sigma K appeq 24 of all of the SCUBA Lens Survey submm galaxies is underway using the NIRC camera at the Keck telescopes: see Fig. 15. Back.

15 More information about this sample can be found in the catalog paper of the SCUBA Lens Survey (Smail et al., 2002 and references therein). Back.

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