Stars, Star Clusters, and Dust in NGC 3077

Davidge, T. J.

doi:10.1086/382096

Cited by 11 publications

(29 citation statements)

References 71 publications

(169 reference statements)

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“…The stellar contents of the star clusters and thin-disk field are discussed in x 3, while the thick-disk and halo regions are discussed in x 4. Figure 6 is in many respects similar to the CMDs of the NGC 55 fields studied by Davidge (1998), one of which overlaps with the area observed with the CFHTIR. In particular, the prominent vertical sequence in the Davidge (1998) CMDs have a peak K-band brightness and J À K color that matches the CMD in the right-hand panel of Figure 6.…”

Section: Photometric Measurements and Analysis Strategysupporting

confidence: 71%

“…The (i 0 ; r 0 À i 0 ) CMD of the thin disk is dominated by RGB and AGB stars, with the RGB tip near i 0 ¼ 23:1 (x 4.2); the properties of the RGB in the thin disk are not discussed here because of the crowded nature of this part of the GMOS image, and a detailed discussion of the RGB in NGC 55 is deferred to x 4.2. However, it is worth noting that the color of the RGB in the thin-disk portion of the Davidge (2004), while the open triangles are SB(s)m galaxies in the 2MASS Large Galaxy Atlas (Jarrett et al 2003); the colors of the latter objects were computed from their total J, H, and K brightnesses. The reddening vector has a length that corresponds to A V ¼ 1 mag.…”

Section: The Thin Disk As Imaged With Gmosmentioning

confidence: 99%

“…Following Davidge (2003), the r 0 À i 0 colors and i 0 brightnesses were transformed into R À I and I, where R and I are in the Kron-Cousins system, using relations from Fukugita et al (1996) and the relation between V À I and R À I for solar neighborhood giants from Bessell (1979). Bolometric magnitudes were then computed using I-band bolometric corrections for AGB stars from Bessell & Wood (1984).…”

Section: The Thin Disk As Imaged With Gmosmentioning

confidence: 99%

“…A population of C stars was identified, and Pritchet et al (1987) computed a distance modulus of 25:7AE 0:1 based on the mean I-band magnitude of these objects. Davidge (1998) used infrared images to investigate the bright red stellar content in two NGC 55 disk fields. A prominent AGB sequence was detected, and the peak AGB brightness was found to be consistent with an age <0.1 Gyr.…”

Section: Introductionmentioning

confidence: 99%

“…A prominent AGB sequence was detected, and the peak AGB brightness was found to be consistent with an age <0.1 Gyr. A population of red supergiants (RSGs) with K ¼ 15 was also found, from which Davidge (1998) computed a distance modulus of 26:0.…”

Section: Introductionmentioning

confidence: 99%

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The Disk and Extraplanar Regions of NGC 55

Davidge

2005

ApJ

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The stellar content of the nearby SB(s)m galaxy NGC 55 is investigated using images obtained with the Gemini South and Canada-France-Hawaii telescopes. The (K, H À K ) and (K, J À K ) color-magnitude diagrams (CMDs) of stars near the plane of the disk reveal signatures of large-scale star formation during recent and intermediate epochs in the form of red supergiants (RSGs) with M K ¼ À11:5, and an asymptotic giant branch (AGB) that peaks near M K ¼ À10. Comparisons with stellar evolution models suggest that the brightest RSGs have an age near 8 Myr. A well-defined plume, which stellar evolution models suggest contains stars with masses near the RSG-AGB transition, is detected in CMDs constructed both from infrared and visible wavelength observations. It is concluded that star formation in the thin disk of NGC 55 has occurred at a significant rate for at least the past 0.1-0.2 Gyr, and this is consistent with other indicators. The near-infrared spectral energy distribution of the integrated light near the center of the galaxy is consistent with that in other Magellanic irregular galaxies, indicating that the star-forming history of NGC 55, when averaged over timescales of 0.1-1 Gyr, has likely not been peculiar when compared with other late-type systems. Evidence is also presented that the disk contains a large population of old [log (t yr ) $ 10] stars, and it is argued that a stable disk has been in place in NGC 55 for a significant fraction of the age of the universe. At projected distances in excess of 2 kpc off of the disk plane, the brightest AGB stars have ages 10 þ3 À2 Gyr. Thus, despite indications that dust and gas are present in the envelope surrounding the NGC 55 disk, the AGB content suggests that recently formed stars do not occur in large numbers in the extraplanar region. The (r 0 À i 0 ) colors of the RGB in the extraplanar region are consistent with [Fe/H] between À2.2 and À0.7, with the majority of stars having ½Fe=H > À1:2, and the mean metallicity inferred from the RGB color does not change with distance above the disk plane. Thus, the stellar component in the extraplanar envelope is well mixed, at least in terms of metallicity. The mean metallicity of RGB stars is in excellent agreement with that measured in the extraplanar H ii regions EHR 1 and 2, suggesting that the age-metallicity relation in this part of NGC 55 has been flat for at least a few Gyr. Finally, the RGB tip occurs near i 0 ¼ 23:1 in the extraplanar region, and a distance modulus of 26.5 is computed from this feature.

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Section: Photometric Measurements and Analysis Strategysupporting

confidence: 71%

Section: The Thin Disk As Imaged With Gmosmentioning

confidence: 99%

Section: The Thin Disk As Imaged With Gmosmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Disk and Extraplanar Regions of NGC 55

Davidge

2005

ApJ

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Tracing the stellar halo of an early type galaxy out to 25 effective radii

Rejkuba

2015

Proc. IAU

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We have used ACS and WFC3 cameras on board HST to resolve stars in the halo of NGC 5128 out to 140 kpc (25 effective radii, R eff ) along the major axis and 70 kpc (13 R eff ) along the minor axis. This dataset provides an unprecedented radial coverage of stellar halo properties in any galaxy. Color-magnitude diagrams clearly reveal the presence of the red giant branch stars belonging to the halo of NGC 5128 even in the most distant fields. The V-I colors of the red giants enable us to measure the metallicity distribution in each field and so map the metallicity gradient over the sampled area. The stellar metallicity follows a shallow gradient and even out at 140 kpc (25 R eff ) its median value does not go below [M/H]∼-1 dex. We observe significant field-to-field metallicity and stellar density variations. The star counts are higher along the major axis when compared to minor axis field located 90 kpc from the galaxy centre, indicating flattening in the outer halo. These observational results provide new important constraints for the assembly history of the halo and the formation of this gE galaxy.

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Globular clusters and the Mira period-luminosity relation

Feast

Whitelock

Menzies

2002

Monthly Notices of the Royal Astronomical Society

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A globular cluster distance scale based on Hipparcos parallaxes of subdwarfs has been used to derive estimates of MK for cluster Miras, including one in the Small Magellanic Cloud (SMC) globular cluster NGC 121. These lead to a zero‐point of the Mira infrared period–luminosity (PL) relation, PL(K), in good agreement with that derived from Hipparcos parallaxes of nearby field Miras. The mean of these two estimates together with data on LMC Miras yields a Large Magellanic Cloud (LMC) distance modulus of in evident agreement with a metallicity‐corrected Cepheid modulus . The use of luminous asymptotic giant branch (AGB) stars as extragalactic population indicators is also discussed.

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Stars, Star Clusters, and Dust in NGC 3077

Cited by 11 publications

References 71 publications

The Disk and Extraplanar Regions of NGC 55

The Disk and Extraplanar Regions of NGC 55

Tracing the stellar halo of an early type galaxy out to 25 effective radii

Globular clusters and the Mira period-luminosity relation

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