HST Survey of the Mid-UV Morphology of Nearby Galaxies

Windhorst, R. A., Taylor, V. A., Jansen, R. A., Odewahn, S. C., Chiarenza, C. A., Conselice, C., de Grijs, R., de Jong, R. S., MacKenty, J., Eskridge, P. B., Frogel, J. A., Gallagher III, J. S., Hibbard, J., Matthews, L., & O'Connell, R. W. 2002, ApJS, 143, 113

Fig: NGC6782: (left) F255W, (middle) F300W, (right) F814W

We present a systematic imaging survey of 37 nearby galaxies observed with the Hubble Space Telescope (HST) Wide Field and Planetary Camera 2 (WFPC2) in the mid-UV F300W filter, centered at 2930A, as well as in the I-band (F814W) filter at 8230A. Eleven of these galaxies were also imaged in the F255W filter, centered at 2550A. Our sample is carefully selected to include galaxies of sufficiently small radius and high predicted mid-UV surface brightness to be detectable with WFPC2 in one orbit, and covers a wide range of Hubble types and inclinations. The mid-UV (2000-3200A) spans the gap between ground-based UBVR(IJHK) images, which are available or were acquired for the current study, and far-UV images available from the Astro/UIT missions for 15 galaxies in our sample. The first qualitative results from our study are:
(1) Early-type galaxies show a significant decrease in surface brightness going from the red to the mid-UV, reflecting the absence of a dominant young stellar population, and in some cases the presence of significant (central) dust lanes. Galaxies that are early-types in the optical show a variety of morphologies in the mid-UV that can lead to a different morphological classification, although not necessarily as later-type. Some early-type galaxies become dominated by a blue nuclear feature or a point source in the mid-UV, e.g., due to the presence of a Seyfert nucleus or a LINER. This is in part due to our mid-UV surface brightness selection, but it also suggests that part of the strong apparent evolution of weak AGN in early-type galaxies may be due to surface brightness dimming of their UV-faint stellar population, which renders the early-type host galaxies invisible at intermediate to higher redshifts.
(2) About half of the mid-type spiral and star-forming galaxies appear as a later morphological type in the mid-UV, as ASTRO/UIT also found primarily in the far-UV. Sometimes these differences are dramatic (e.g., NGC6782 shows a spectacular ring of hot stars in the mid-UV). However, not all mid-type spiral galaxies look significantly different in the mid-UV. Their mid-UV images show a considerable range in the scale and surface brightness of individual star-forming regions. Almost without exception, the mid-type spirals in our sample have their small bulges bisected by a dust-lane, which often appears to be connected to the inner spiral arm structure.
(3) The majority of the heterogeneous subset of late-type, irregular, peculiar and merging galaxies display F300W morphologies that are similar to those seen in F814W, but with important differences due to recognizable dust-features absorbing the bluer light, and due to hot stars, star-clusters, and star-formation "ridges" that are bright in the mid-UV. Less than one third of the galaxies classified as late-type in the optical appears sufficiently different in the mid-UV to result in a different classification.
Our HST mid-UV survey of nearby galaxies shows that -- when observed in the rest-frame mid-UV -- early- to mid-type galaxies are more likely to be misclassified as later types than late-type galaxies are to be misclassified as earlier types. This is because the later type galaxies are dominated by the same young and hot stars in all filters from the mid-UV to the red, and so have a smaller "morphological K-correction" than true earlier type galaxies. The morphological K-correction can thus explain part, but certainly not all of the excess faint blue late-type galaxies seen in deep HST fields.
Links to project pages:

Figures from paper:
Links to jpgs of Figures 3.xx (F300W & F814W; F255W if present):

  1. figure 3a: CGCG 097-094; NGC 1398
  2. figure 3b: NGC 4478
  3. figure 3c: NGC 3516; UGC 3426 (Mrk 3)
  4. figure 3d: UGC 08823 (Mrk279); NGC 3921 (Arp 224, Mrk 430)
  5. figure 3e: UGC 05101; UGC 08696 (Mrk 273)
  6. figure 3f: NGC 2551
  7. figure 3g: NGC 6753
  8. figure 3h: NGC 7769
  9. figure 3i: NGC 3310 (Arp 217)
  10. figure 3j: NGC 7685
  11. figure 3k: NGC 6782
  12. figure 3l: UGC 10043; UGC 06697
  13. figure 3m: IC 3949
  14. figure 3n: ESO 033-G022; IC 4393
  15. figure 3o: MCG+03-30-071; MCG+06-24-047
  16. figure 3p: UGC 05028/9 (Arp 200, Mrk 111)
  17. figure 3q: NGC 3860B; ESO 418-G008
  18. figure 3r: NGC 1510
  19. figure 3s: NGC 5253; NGC 1140 (Mrk 1063)
  20. figure 3t: UGC 05626
  21. figure 3u: UGC 09855; NGC 6789
  22. figure 3v: Mrk 66; UGC 05189
  23. figure 3w: NGC 3690/IC 694 (Arp 299)
  24. figure 3x: UGC 06527 (Arp 322, Mrk 176); UGC 08335 (Arp 238)
  25. figure 3y: IC 2184 (Mrk 8); NGC 5278/9 (Arp 239, Mrk 271)

Links to jpgs of Figures 4.xx (All Available Bands):

  1. figure 4a: CGCG 097-094
  2. figure 4b: NGC 1398
  3. figure 4c: NGC 4478
  4. figure 4d: NGC 3516
  5. figure 4e: UGC 3426 (Mrk 3)
  6. figure 4f: UGC 08823 (Mrk279)
  7. figure 4g: NGC 3921 (Arp 224, Mrk 430)
  8. figure 4h: UGC 05101
  9. figure 4i: UGC 08696 (Mrk 273)
  10. figure 4j: NGC 2551
  11. figure 4k: NGC 6753
  12. figure 4l: NGC 7769
  13. figure 4m: NGC 3310 (Arp 217)
  14. figure 4n: NGC 7685
  15. figure 4o: NGC 6782
  16. figure 4p: UGC 10043
  17. figure 4q: UGC 06697
  18. figure 4r: IC 3949
  19. figure 4s: ESO 033-G022
  20. figure 4t: IC 4393
  21. figure 4u: MCG+03-30-071
  22. figure 4v: MCG+06-24-047
  23. figure 4w: UGC 05028/9 (Arp 200, Mrk 111)
  24. figure 4x: NGC 3860B
  25. figure 4y: ESO 418-G008
  26. figure 4z: NGC 1510
  27. figure 4aa: NGC 5253
  28. figure 4bb: NGC 1140 (Mrk 1063)
  29. figure 4cc: UGC 05626
  30. figure 4dd: UGC 09855
  31. figure 4ee: NGC 6789
  32. figure 4ff: Mrk 66
  33. figure 4gg: UGC 05189
  34. figure 4hh: NGC 3690/IC 694 (Arp 299)
  35. figure 4ii: UGC 06527 (Arp 322, Mrk 176)
  36. figure 4jj: UGC 08335 (Arp 238)
  37. figure 4kk: IC 2184 (Mrk 8)
  38. figure 4ll: NGC 5278/9 (Arp 239, Mrk 271)

Links arranged by galaxy name (uses older Figures 3.xx and Figures 4.xx):

  1. HTML page showing All Figs 3.xx
  2. HTML page showing All Figs 4.xx
  3. MCG+03-30-71: figure.3.01, figure.4.01
  4. NGC1396: figure.3.02, figure.4.02
  5. NGC4478: figure.3.03, figure.4.03
  6. NGC3516: figure.3.04, figure.4.04a, figure.4.04b
  7. UGC08823: figure.3.05, figure.4.05
  8. UGC03426: figure.3.06, figure.4.06
  9. NGC3921: figure.3.07
  10. UGC05101: figure.3.08, figure.4.08a, figure.4.08b
  11. MRK273: figure.3.09, figure.4.09
  12. NGC2551: figure.3.10, figure.4.10
  13. NGC6753: figure.3.11a, figure.3.11b, figure.4.11
  14. NGC7769: figure.3.12a, figure.3.12b, figure.4.12a
  15. NGC3310: figure.3.13a, figure.3.13b, figure.4.13
  16. UGC12638: figure.3.14, figure.4.14
  17. NGC6782: figure.3.15a, figure.3.15b
  18. UGC10043: figure.3.16, figure.4.16
  19. UGC06697: figure.3.17, figure.4.17
  20. UGC08096: figure.3.18a, figure.3.18b, figure.4.18
  21. ESO033-G22: figure.3.19, figure.4.19
  22. ESO446-G44: figure.3.20, figure.4.20
  23. CGCG97-114: figure.3.21, figure.4.21
  24. MCG+06-24-47: figure.3.22, figure.4.22
  25. UGC05028: figure.3.23a, figure.3.23b
  26. ESO418-008: figure.3.24, figure.4.24
  27. UGC05626: figure.3.25, figure.4.25a, figure.4.25b
  28. NGC5253: figure.3.26, figure.4.26
  29. NGC1140: figure.3.27, figure.4.27
  30. NGC1510: figure.3.28
  31. UGC09855: figure.3.29, figure.4.29
  32. NGC6789: figure.3.30 figure.4.30a, figure.4.30b
  33. MRK66: figure.3.31, figure.4.31
  34. UGC05189: figure.3.32a, figure.3.32b, figure.4.32
  35. MRK8: figure.3.33 figure.4.33a, figure.4.33b
  36. ARP299: figure.3.34a, figure.3.34b, figure.4.34
  37. UGC06527: figure.3.35, figure.4.35
  38. UGC08335: figure.3.36, figure.4.36
  39. UGC08677-8.g: figure.3.37, figure.4.37
Last modified: Thu Aug 11 15:08:30 EDT 2005
Back to home
Maintained by jhibbard @ nrao.edu