The age calibration of integrated ultraviolet colors and young stellar clusters in the Large Magellanic Cloud

Barbero, Javier; Brocato, E.; Cassatella, A.; Castellani, V.; Geyer, E. H.

doi:10.1086/168448

Cited by 6 publications

(17 citation statements)

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“…12 compares the UV two-colours diagram (C(15−31) vs. C(18−28)) presented in the already quoted paper by Barbero et al (1990) with analogous results, but obtained from the present computations over the relevant range of ages (t ≤ 1 Gyr). The time evolution of the diagrams appear in rather good agreement, supporting the scenario discussed in that paper.…”

Section: Comparison With Previous Models and To Lmc Clusterssupporting

confidence: 74%

“…Moreover, a not negligible aspect is that the MS phase is also the most populated evolutionary phase (thanks to the large Hburning timescales), making this indicator the best choice also for statistical reasons. Barbero et al (1990) presented a two UV colour diagram (C(15−31) vs. C(18−25)) based on the photometric bands explored by the ANS-satellite, showing a fair correlation with the age. More recently, Cassatella et al (1996) proved that ages obtained with these integrated UV colours are consistent with ages derived by isochrone fittings for a sample of LMC clusters.…”

Section: The Theoretical Backgroundmentioning

confidence: 99%

“…In a previous work (Barbero et al 1990) we collected evolutionary tracks from several papers in the literature to present an age calibration of integrated UV colours of young stellar clusters in the Large Magellanic Clouds. In that paper we found a rather satisfactory agreement between theoretical predictions and observation.…”

Section: Introductionmentioning

confidence: 99%

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Predicted HST FOC and broad band colours for young and intermediate simple stellar populations

Brocato

Castellani

Raimondo

et al. 1999

Astron. Astrophys. Suppl. Ser.

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Abstract. This paper presents theoretical HST and broad band colours from population synthesis models based on an homogeneous set of stellar evolutionary tracks as computed under canonical (no overshooting) assumptions, covering the range of cluster ages from t = 8 Myr to t = 5 Gyr for three different metallicities (Z = 0.02, 0.006, and 0.001). Statistical fluctuations in the cluster population have been investigated, assessing the predicted fluctuations of the various colours as a function of the cluster integrated absolute magnitude. We show that the red leak in HST UV filters deeply affects the predicted fluxes and colours. However, we find that for F152M − F307M ≤ 0.5 and for F170M − F278M ≤ 0.5 (which means ages lower than 1 Gyr) the HST UV colours can still be used to infer reliable indications on the age of distant clusters. Moreover, one finds that the age calibration of these colours is scarcely affected by the amount of original helium or by the assumed IMF. On this basis, we present a calibration of the HST UV two-colours (F152M − F307M vs. F170M − F278M) in terms of cluster ages for the three above quoted metallicities. We suggest the combined use of HST UV colours and IR colours (V − K in particular) to disentangle the metallicity-age effect in integrated colours of young stellar populations (t ≤ 1 Gyr).

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Section: Comparison With Previous Models and To Lmc Clusterssupporting

confidence: 74%

Section: The Theoretical Backgroundmentioning

confidence: 99%

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Predicted HST FOC and broad band colours for young and intermediate simple stellar populations

Brocato

Castellani

Raimondo

et al. 1999

Astron. Astrophys. Suppl. Ser.

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“…In the calibration by Barbero et al (1990), NGC 1978 was found to be over a magnitude brighter at 1550 A than expected for a 2 Gyr cluster, but a magnitude fainter than the metal-poor, blue horizontal branch clusters. Barbero et al {1990) were unable to draw The full width of the image is 2:8; North is 127° clockwise from vertical, East is to the upper right. Note the effect that the filter vignette pattern has had on the comers of the three WF chips.…”

Section: Introductionmentioning

confidence: 70%

“…The IUE short wavelength (1550 A) data suffered from poor signal-to-noise, and its radial extent did not seem to correlate well with that of the longer wavelength light (Cassatella et al 1987). In the calibration by Barbero et al (1990), NGC 1978 was found to be over a magnitude brighter at 1550 A than expected for a 2 Gyr cluster, but a magnitude fainter than the metal-poor, blue horizontal branch clusters. Barbero et al {1990) were unable to draw The full width of the image is 2:8; North is 127° clockwise from vertical, East is to the upper right.…”

Section: Introductionmentioning

confidence: 84%

Far-Ultraviolet Imaging of the Large Magellanic Cloud Populous Cluster NGC 1978 with WFPC2

Cole¹,

Mould²,

Gallagher³

et al. 1997

The Astronomical Journal

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We have imaged the ~2.2 billion-year-old Large Magellanic Cloud populous cluster NGC 1978 in the far-ultraviolet and visible with the second Wide Field/Planetary Camera {WFPC2) on the Hubble Space Telescope. The far-ultraviolet images show a sparse stellar field with little apparent density enhancement in the cluster core. The visible images are dominated by the cluster's first-ascent and second-ascent red giants, which are completely invisible to the far-ultraviolet filter. No evidence for a hot horizontal branch population of core-helium-burning stars is seen; nor is there any apparent indication of a significant blue straggler population. These results suggest that the presence of a rich, young population of field stars in the NGC 1978 region is responsible for the unusual location of the cluster in the integrated light color-color plots produced by IUE.

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Star Clusters in M33. III. The Youngest Population

Chandar¹,

Bianchi²,

Ford³

et al. 1999

PUBL ASTRON SOC PAC

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We investigate the properties of young (¹108 yr) M33 star clusters from the samples presented in the Ðrst two papers of this series using far-UV photometry. Previously, UBV colors were used to derive cluster ages, luminosities, and masses, assuming an extinction interpolated from neighboring stars. Fifteen of 44 clusters imaged in the Hubble Space T elescope WFPC2 with the F170W Ðlter are detected. The far-UV magnitudes provided by this Ðlter are used to rederive young cluster ages by comparing integrated photometry with stellar evolutionary models. Overall, we Ðnd ages consistent with those from our second paper from UBV photometry. However, the addition of the F170W Ñux provides three major improvements over previous work : (1) This band is more sensitive to the temperature range of clusters younger than D108 yr. (2) UBV colors for young clusters with contaminated V -band Ñuxes (from red supergiants or from line emission by surrounding excited gas) provide only an upper age limit. The addition of the far-UV Ñux allows us to extract precise ages. (3) Far-UV Ñux helps to constrain cluster extinction.New theoretical ratios are presented for cluster ages between 4 ] 106 and 1010 yr and metallicities M/L V of (Z \ 0.02, Y \ 0.28), (Z \ 0.008, Y \ 0.25), (Z \ 0.004, Y \ 0.24), (Z \ 0.001, Y \ 0.23), and (Z \ 0.0004, Y \ 0.23), extracted from the recent models of C. Chiosi. These values are used to M/L V estimate cluster masses from derived ages and measured luminosities. We Ðnd young clusters to have masses in the range 6 ] 102È2 ] 104These values are smaller than the most massive old clusters in M33 M _ . (which have masses up to a few times 105 in the sample presented in our second paper. M _ ) ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ

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The age calibration of integrated ultraviolet colors and young stellar clusters in the Large Magellanic Cloud

Cited by 6 publications

References 0 publications

Predicted HST FOC and broad band colours for young and intermediate simple stellar populations

Predicted HST FOC and broad band colours for young and intermediate simple stellar populations

Far-Ultraviolet Imaging of the Large Magellanic Cloud Populous Cluster NGC 1978 with WFPC2

Star Clusters in M33. III. The Youngest Population

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