Thick disks and halos of spiral galaxies M 81, NGC 55 and NGC 300

Тихонов, Н. А.; Galazutdinova, O. A.; Drozdovsky, I.

doi:10.1051/0004-6361:20047042

Cited by 65 publications

(75 citation statements)

References 86 publications

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“…As a result, the model adopting an inside-out formation scenario (i.e., τ = 0.35r/r d + 2.47 Gyr) and an appropriate gas outflow rate (i.e., b out = 0.9) can successfully reproduce the observed constraints of NGC 300. Our results suggest that NGC 300 likely experiences a rapid growth of its disk and its stellar population is predominately old, consistent with the previous observed results (Butler et al 2004;Tikhonov et al 2005;Gogarten et al 2010).…”

Section: Discussionsupporting

confidence: 92%

The star formation history of low-mass disk galaxies: A case study of NGC 300

Kang

Zhang

Chang

et al. 2015

A&A

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Context. Since NGC 300 is a bulgeless, isolated low-mass galaxy and it has not experienced radial migration during its evolution history, it can be treated as an ideal laboratory to test the simple galactic chemical evolution model. Aims. Our main aim is to investigate the main properties of the star formation history (SFH) of NGC 300 and compare its SFH with that of M 33 to explore the common properties and differences between these two nearby low-mass systems. Methods. We construct a simple chemical evolution model for NGC 300, assuming its disk forms gradually from continuous accretion of primordial gas and including the gas-outflow process. The model allows us to build a bridge between the SFH and observed data of NGC 300, in particular, the present-day radial profiles and global observed properties (e.g., cold gas mass, star formation rate, and metallicity). By means of comparing the model predictions with the corresponding observations, we adopt the classical χ 2 methodology to find out the best combination of free parameters a, b, and b out . Results. Our results show that by assuming an inside-out formation scenario and an appropriate outflow rate, our model reproduces well most of the present-day observational values. The model not only reproduces well the radial profiles, but also the global observational data for the NGC 300 disk. Our results suggest that NGC 300 may experience a rapid growth of its disk. Through comparing the best-fitting, model-predicted SFH of NGC 300 with that of M 33, we find that the mean stellar age of NGC 300 is older than that of M 33 and there is a recent lack of primordial gas infall onto the disk of NGC 300. Our results also imply that the local environment may play a key role in the secular evolution of galaxy disks.

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Section: Discussionsupporting

confidence: 92%

The star formation history of low-mass disk galaxies: A case study of NGC 300

Kang

Zhang

Chang

et al. 2015

A&A

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“…The ACS field is located somewhat beyond the WFPC2 field of Mouhcine et al (2005), which is also shown. The ellipse indicates the 22 (∼25 kpc) extent of M81's thick disk as suggested by Tikhonov et al (2005), inclined at 59 • . The box at the upper center is the location of the deep ACS study by Williams et al (2009) and Dalcanton et al (2009).…”

Section: Introductionmentioning

confidence: 92%

“…The specific pointing was chosen to lie along the southwestern semi-minor axis, beyond the radius suggested as the edge of M81's thick disk (Tikhonov et al 2005), where the surface brightness of M81 is still high enough that we can determine a meaningful metallicity distribution from RGB stars. The left panel of Figure 1 shows the location of our ACS pointing.…”

Section: Observations and Reductionsmentioning

confidence: 99%

DEEPHST/ACS PHOTOMETRY OF THE M81 HALO

Durrell

Sarajedini

Chandar

2010

ApJ

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We present a deep color-magnitude diagram (CMD) for individual stars in the halo of the nearby spiral galaxy M81, at a projected distance of 19 kpc, based on data taken with the Advanced Camera for Surveys on the Hubble Space Telescope (HST). The CMD reveals a red giant branch (RGB) that is narrow and fairly blue, and a horizontal branch that has stars that lie mostly redward of the RR Lyrae instability strip. We derive a mean metallicity of [M/H] = −1.15 ± 0.11 and age of 9 ± 2 Gyr for the dominant population in our field, from the shape of the RGB, the magnitude of the red clump, and the location of the RGB bump. We compare our metallicity and age results with those found previously for stars in different locations within M81 and in the spheroids of other nearby galaxies.

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“…Ever since the existence of a thick disk component was shown by star counts in the Milky Way (Gilmore & Reid 1983) and by stellar luminosity distribution studies of external early-and late-type galaxies (Burstein 1979;Tsikoudi 1979;van der Kruit & Searle 1981a;Shaw & Gilmore 1989;Dalcanton & Bernstein 2002;Pohlen et al 2004;Tikhonov et al 2005), its origin and properties have been the subject of a continuing vigorous debate. The distinctive properties of their stars, e.g.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of thick disks formed through minor mergers: stellar excesses and scale lengths

Matteo

Lehnert

et al. 2011

A&A

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By means of a series of N-body/SPH simulations we investigate the morphological properties of thick stellar disks formed through minor mergers with, e.g. a range of gas-to-stellar mass ratios. We show that the vertical surface density profile of the post-merger thick disk follows a sech function and has an excess in the regions furthest away from the disk mid-plane (z 2 kpc). This stellar excess also follows a sech function with a larger scale height than the main thick disk component (except at large radii). It is usually dominated by stars from the primary galaxy, but this depends on the orbital configuration. Stars in the excess have a rotational velocity lower than that of stars in the thick disk, and they may thus be confused with stars in the inner galactic halo, which can have a similar lag. Confirming previous results, the thick disk scale height increases with radius and the rate of its increase is smaller for more gas rich primary galaxies. On the contrary, the scale height of the stellar excess is independent of both radius and gas fraction. We also find that the post-merger thick disk has a radial scale length which is 10−50% larger than that of the thin disk. Two consecutive mergers have basically the same effect on heating the stellar disk as a single merger of the same total mass, i.e., the disk heating effect of a few consecutive mergers does not saturate but is cumulative. To investigate how thick disks produced through secular processes may differ from those produced by minor mergers, we also simulated gravitationally unstable gas-rich disks ("clumpy disks"). These clumpy disks do not produce either a stellar excess or a ratio of thick to thin disk scale lengths greater than one. Comparing our simulation results with observations of the Milky Way and nearby galaxies shows that our results for minor mergers are consistent with observations of the ratio of thick to thin disk scale lengths and with the "Toomre diagram" (the sum in quadrature of the vertical and radial versus the rotational kinetic energies) of the Milky Way. The simulations of clumpy disks do not show such agreement. We conclude that minor mergers are a viable mechanism for the creation of galactic thick disks and investigating stars at several kpc above the mid-plane of the Milky Way and other galaxies may provide a quantitative method for studying the (minor) merger history of galaxies.

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Thick disks and halos of spiral galaxies M 81, NGC 55 and NGC 300

Cited by 65 publications

References 86 publications

The star formation history of low-mass disk galaxies: A case study of NGC 300

The star formation history of low-mass disk galaxies: A case study of NGC 300

DEEPHST/ACS PHOTOMETRY OF THE M81 HALO

Characteristics of thick disks formed through minor mergers: stellar excesses and scale lengths

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