Infrared photometry of 487 sources in the inner regions of NGC 5128 (Centaurus A)
- Observatorio Astronomico Cordoba, Laprida 854, 5000 Cordoba, Argentina, and European Southern Observatory, D-85748 Garching bei Muenchen (Germany)
- Lawrence Livermore National Laboratory, MS L-413, P.O. Box 808, Livermore, California 94550 (United States)
We study the sources present in the inner 3 kpc region of NGC 5128 (Cen A), most of which are star clusters of different ages. Photometry of archival Hubble Space Telescope WFPC images (F675W filter) is complemented with IR photometry (JHK{prime} filters) obtained with the IRAC2B infrared array camera at the ESO/MPI 2.2 m telescope. From IR color maps we divide the field into two regions: a clear region outside the dust lane, and an obscured region well inside the dust lane of NGC 5128. In the unreddened region there is a great variety of sources such as globular clusters, star associations, and HII regions. These sources are not individual stars. The vast majority of IR sources in the reddened region, where the dust lane dominates, are not seen at all in the deep HST images. The presence of large amounts of differential extinction makes it difficult to evaluate them. In total, there are 372 objects detected in the inner region of NGC 5128. From them, 125 objects are detected both in IR and HST frames. There are 247 IR sources without optical counterparts (47 in the clear region and 200 in the dust lane). Accounting for the small volume sampled, there must be a total of {approximately}500 sources with K{lt}18 in the dust lane region. The distribution of these sources is rather uniform and not particularly centrally concentrated. This fact suggests that the majority of them are located in a disk, as would be expected if they are young associations or clusters. The degree of background and foreground contamination is evaluated using observations of a nearby field. We found 115 IR sources in this field. The nucleus itself is invisible in deep optical images, but it is clearly identified in the IR. In the region just south of the nucleus the extinction must be larger than A{sub K}=3. In the clear region, where the effect of the dust lane is negligible, we have identified some objects as intermediate-age clusters containing carbon stars. (Abstract Truncated)
- Research Organization:
- Lawrence Livermore National Laboratory
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 548800
- Journal Information:
- Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Journal Issue: 2 Vol. 109; ISSN 0067-0049; ISSN APJSA2
- Country of Publication:
- United States
- Language:
- English
Similar Records
Picture processing analysis of the optical structure of NGC 5128 (Centarurus A)
MAPPING THE SPATIAL DISTRIBUTION OF DUST EXTINCTION IN NGC 959 USING BROADBAND VISIBLE AND MID-INFRARED FILTERS