The Local Group Dwarf Irregular Galaxy NGC 6822.II.The Old and Intermediate -Age Star Formation History

Gallart, Carme; Aparicio, A.; Bertelli, G.; Chiosi, C.

doi:10.1086/118154

Cited by 121 publications

(145 citation statements)

References 0 publications

Supporting

Mentioning

132

Contrasting

Unclassified

Order By: Relevance

“…Hodge (1980) found evidence that a relatively large amount of star formation occurred in the central region of NGC 6822, between 75 and 100 Myr ago. Gallart et al (1996) showed that the star formation increased by a factor of 2-6 between 100 and 200 Myr ago. de Blok & Walter (2000) also suggested that an HI interaction some 100 Myr ago gave birth to the current star formation.…”

Section: Discussionmentioning

confidence: 99%

Long period variable survey in NGC 6822

Battinelli

Demers

2010

A&A

View full text Add to dashboard Cite

Context. The star-formation history of the intermediate-age population of the Local Group dwarf irregular galaxy NGC 6822 may have been influenced by the often discussed interaction with its HI cloud that might have produced the present polar-ring structure. Aims. We investigate the period distribution of the Mira variables in the central region and the spheroid of NGC 6822. Methods. We use the new wide-field near-infrared imager CPAPIR to acquire K s images of a 32 × 32 area, which includes a good part of the eastern spheroid of NGC 6822. Results. Periods could be determined for 45 cyclic and semi-regular variables brighter than K = 17. The vast majority of the variables have ages between 1 and 3 Gyr. Conclusions. The period distribution of the long period variables may reflect the proposed interaction with the HI cloud that produces the polar ring.

show abstract

Section: Discussionmentioning

confidence: 99%

Long period variable survey in NGC 6822

Battinelli

Demers

2010

A&A

View full text Add to dashboard Cite

show abstract

“…This general technique has become increasingly well developed since its first conception about 20 years ago (Tosi et al 1989), with several mathematical and statistical approaches that are now thoroughly described in the literature. Useful descriptions of these methods are given at length in, for example, Gallart et al (1996), Hernandez et al (1999), Harris & Zaritsky (2001), Dolphin (2002), Aparicio & Gallart (2004), Aparicio & Hidalgo (2009) and Tolstoy et al (2009), and we will not discuss these in detail here. Our approach is very much as is done in the codes described in those papers.…”

Section: Synthetic Cmd Simulatormentioning

confidence: 99%

How old are the stars in the halo of NGC 5128 (Centaurus A)?

Rejkuba¹,

Harris

Greggio

et al. 2011

A&A

View full text Add to dashboard Cite

Context. NGC 5128 (Centaurus A) is, at the distance of just 3.8 Mpc, the nearest easily observable giant elliptical galaxy. Therefore it is the best target to investigate the early star formation history of an elliptical galaxy. Aims. Our aims are to establish when the oldest stars formed in NGC 5128, and whether this galaxy formed stars over a long period. Methods. We compare simulated colour−magnitude diagrams with the deep ACS/HST photometry. The simulations assume in input either the observed metallicity distribution function, based on the colour distribution of the upper red giant branch stars, or the closed box chemical enrichment. Simulations are constructed for single age bursts using BASTI evolutionary isochrones; more complex star formation histories are constructed as well by combining several individual simulations. Comparisons with data are made by fitting the whole colour−magnitude diagram as well as the the luminosity functions in V and I band. In addition we inspect carefully the red clump and asymptotic giant branch bump luminosities and number counts, since these features are the primary constraints on the ages of the observed stars. Results. We find that that the observed colour−magnitude diagram can be reproduced satisfactorily only by simulations that have the bulk of the stars with ages in excess of ∼10 Gyr, and that the alpha-enhanced models fit the data much better than the solar scaled ones. Data are not consistent with extended star formation over more than 3−4 Gyr. Two burst models, with 70−80% of the stars formed 12 ± 1 Gyr ago and with 20−30% younger contribution with 2−4 Gyr old stars provide the best agreement with the data. The old component spans the whole metallicity range of the models (Z = 0.0001−0.04), while for the young component the best fitting models indicate higher minimum metallicity (∼1/10−1/4 Z ). Conclusions. The bulk of the halo stars in NGC 5128 must have formed at redshift z > ∼ 2 and the chemical enrichment was very fast, reaching solar or even twice-solar metallicity already for the ∼11−12 Gyr old population. The minor young component, adding ∼20−30% of the stars to the halo, and contributing less than 10% of the mass, may have resulted from a later star formation event ∼2−4 Gyr ago.

show abstract

“…While H i extends 30 to the NW and SE of the galaxy, the big H i hole is devoid of dust emission. The star formation history of NGC 6822 began 12-15 Gyr ago and has been quiescent until about 0.6-1 Gyr ago (Gallart et al 1996;Wyder 2001). Bianchi et al (2001) found very young stellar populations (<10 Myr) in the star-forming regions Hubble V and X.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Herschelphotometric observations of the nearby low metallicity irregular galaxy NGC 6822

Galametz¹,

Madden²,

Galliano³

et al. 2010

A&A

View full text Add to dashboard Cite

We present the first Herschel PACS and SPIRE images of the low-metallicity galaxy NGC 6822 observed from 70 to 500 μm and clearly resolve the H ii regions with PACS and SPIRE. We find that the ratio 250/500 is dependent on the 24 μm surface brightness in NGC 6822, which would locally link the heating processes of the coldest phases of dust in the ISM to the star formation activity. We model the SEDs of some regions H ii regions and less active regions across the galaxy and find that the SEDs of H ii regions show warmer ranges of dust temperatures. We derive very high dust masses when graphite is used in our model to describe carbon dust. Using amorphous carbon, instead, requires less dust mass to account for submm emission due to its lower emissivity properties. This indicates that SED models including Herschel constraints may require different dust properties than commonly used. The global G/D of NGC 6822 is finally estimated to be 186, using amorphous carbon.

show abstract

The Local Group Dwarf Irregular Galaxy NGC 6822.II.The Old and Intermediate -Age Star Formation History

Cited by 121 publications

References 0 publications

Long period variable survey in NGC 6822

Long period variable survey in NGC 6822

How old are the stars in the halo of NGC 5128 (Centaurus A)?

Herschelphotometric observations of the nearby low metallicity irregular galaxy NGC 6822

Contact Info

Product

Resources

About