Outer-Disk Populations in NGC 7793: Evidence for Stellar Radial Migration

Radburn-Smith, David J.; Roškar, Rok; Debattista, Victor P.; Dalcanton, Julianne J.; Streich, David; Jong, Roelof S. de; Vlajić, Marija; Holwerda, Benne W.; Purcell, Chris W.; Dolphin, Andrew E.; Zucker, D. B.

doi:10.1088/0004-637x/753/2/138

Cited by 85 publications

(94 citation statements)

References 58 publications

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“…This is in good agreement with observations as shown e.g. for NGC 4244 by de Jong et al (2007), for NGC 7793 by Radburn-Smith et al (2012) and for our Galaxy e.g. by Sale et al (2010), and by references therein.…”

Section: Profiles Of Type Ii: General Considerations and Trends With supporting

confidence: 94%

Dynamical modelling of galactic disc outskirts

Athanassoula

2016

Proc. IAU

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Abstract. I review briefly some dynamical models of structures in the outer parts of disc galaxies, including models of polar rings, tidal tails and bridges. I then discuss the density distribution in the outer parts of discs. For this, I compare observations to results of a model in which the disc galaxy is in fact the remnant of a major merger, and find good agreement. This comparison includes radial profiles of the projected surface density and of stellar age, as well as time evolution of the break radius and of the inner and outer disc scale lengths. I also compare the radial projected surface density profiles of dynamically motivated mono-age populations and find that, compared to older populations, younger ones have flatter density profiles in the inner region and steeper in the outer one. The break radius, however, does not vary with stellar age, again in good agreement with observations.

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Section: Profiles Of Type Ii: General Considerations and Trends With supporting

confidence: 94%

Dynamical modelling of galactic disc outskirts

Athanassoula

2016

Proc. IAU

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“…Pannuti et al (2011) discuss an interaction between SDIG and NGC 7793 as a plausible way to explain this asymmetry in the X-ray sources, although they do not regard it as strong a possibility. Radburn-Smith et al (2012) discuss that the detected stellar radial migration in NGC 7793 may also be due to a past interaction event having occurred in NGC 7793. While the deprojected distance of SDIG shows its current location and its actual orbit remains unknown (e.g.…”

Section: Summary and Discussionmentioning

confidence: 89%

“…the neighbouring galaxy producing the maximum tidal action (Karachentsev et al 2004). NGC 7793 is a spiral galaxy and stellar population analyses of several halo and disk fields detect a metallicity gradient (Vlajic et al 2011), as well as indications for substantial stellar radial migration (Radburn-Smith et al 2012). The SFH of a halo field in NGC 7793 indicates that a burst of star formation has occurred within the last 20 Myr and with an amplitude three times that of the average SFR, most likely associated with the spiral arm feature contaminating the halo field (Dalcanton et al 2012, Figs.…”

Section: Summary and Discussionmentioning

confidence: 99%

The star formation history of the Sculptor dwarf irregular galaxy

Lianou

Cole

2012

A&A

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Aims. We study the resolved stellar populations and derive the star formation history of the Sculptor dwarf irregular galaxy (SDIG), a gas-rich dwarf galaxy member of the NGC 7793 subgroup in the Sculptor group of galaxies. Methods. We constructed a colour−magnitude diagram (CMD) using archival observations from the Hubble Space Telescope/Advanced Camera for Surveys in order to examine the stellar content of SDIG, as well as the spatial distribution of stars selected within different stellar evolutionary phases. We derived the star formation history of SDIG using a maximum-likelihood fit to the CMD. Results. The CMD shows that SDIG contains stars from 10 Myr to several Gyr old, as revealed from the main sequence, blue loop, luminous asymptotic giant branch, and red giant branch stars. The young stars with ages less than ∼250 Myr show a stellar spatial distribution confined to the central regions of SDIG, and additionally the young main sequence stars exhibit an off-centre density peak. The intermediate-age and older stars as traced by the red giant branch stars are more spatially extended. SDIG is dominated by intermediate-age stars with an average age of 6.4 +1.6 −1.4 Gyr. The average metallicity inferred from the CMD modelling is [M/H] ≈ −1.5 dex. SDIG has a star formation history consistent with a constant star formation rate, except for ages younger than ≈200 Myr. The lifetime average star formation rate is 1.3 +0.4 −0.3 × 10 −3 M yr −1 . More recently than 100 Myr, there has been a burst of star formation at a rate ∼2-3 times higher than the average star formation rate. The inferred recent star formation rate from CMD modelling, 2.7(±0.5) × 10 −3 M yr −1 , is higher than inferred from the Hα flux of the galaxy; we interpret this to mean that the upper end of the initial mass function is not being fully sampled due to the low star formation rate. Additionally, an observed lack of bright blue stars in the CMD could indicate a downturn in star formation rate on 10 7 -yr timescales. A previous star formation enhancement appears to have occurred between 600−1100 Myr ago, with amplitude similar to the most recent 100 Myr. Older bursts of similar peak star formation rate and duration would not be resolvable with these data. The observed enhancements in star formation suggest that SDIG is able to sustain a complex star formation history without the effect of gravitational interactions with its nearest massive galaxy. Integrating the star formation rate over the entire history of SDIG yields a total stellar mass equal to 1.77 +0.71 −0.72 × 10 7 M , and a current V-band stellar mass-to-light ratio equal to 3.2 M /L .

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“…Bakos et al (2008) claimed that a break is only due to a change in stellar populations and that the mass profile is unbroken, but this is in contrast to results from the GHOSTS survey (de Jong et al 2007;Radburn-Smith et al 2012), which show breaks in star counts of different populations. The break in simulations is also connected to a steepening of the stellar mass profile (Roškar et al 2008;Sánchez-Blázquez et al 2009).…”

Section: Radial Structure Of Disksmentioning

confidence: 82%

“…This agrees with earlier 19 Or from color gradients, but degeneracies between age, metallicity, and extinction effects make an interpretation of these gradients ambiguous. observations by de Jong et al (2007) and Radburn-Smith et al (2012). The conclusion that a constant break radius favors a dynamical origin of the break (de Jong et al 2007) was questioned by Roškar et al (2008).…”

Section: Breaksmentioning

confidence: 99%

Extragalactic archeology with the GHOSTS Survey

Streich

Jong

Bailin

et al. 2015

A&A

Self Cite

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Aims. We study the individual evolution histories of three nearby low-mass edge-on galaxies (IC 5052, NGC 4244, and NGC 5023). Methods. Using resolved stellar populations, we constructed star count density maps for populations of different ages and analyzed the change of structural parameters with stellar age within each galaxy. Results. We do not detect a separate thick disk in any of the three galaxies, even though our observations cover a wider range in equivalent surface brightness than any integrated light study. While scale heights increase with age, each population can be well described by a single disk. Two of the galaxies contain a very weak additional component, which we identify as the faint halo. The mass of these faint halos is lower than 1% of the mass of the disk. The three galaxies show low vertical heating rates, which are much lower than the heating rate of the Milky Way. This indicates that heating agents, such as giant molecular clouds and spiral structure, are weak in low-mass galaxies. All populations in the three galaxies exhibit no or only little flaring. While this finding is consistent with previous integrated light studies, it poses strong constraints on galaxy simulations, where strong flaring is often found as a result of interactions or radial migration.

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Outer-Disk Populations in NGC 7793: Evidence for Stellar Radial Migration

Cited by 85 publications

References 58 publications

Dynamical modelling of galactic disc outskirts

Dynamical modelling of galactic disc outskirts

The star formation history of the Sculptor dwarf irregular galaxy

Extragalactic archeology with the GHOSTS Survey

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