The assembly of the Milky Way and its satellite galaxies

Smith, M. C.; Okamoto, Sakurako; Yuan, H.-B.; Liu, Xiao Wei

doi:10.1088/1674-4527/12/8/008

Cited by 10 publications

(15 citation statements)

References 146 publications

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“…The survey contains the LAMOST ExtraGAlactic Survey (LEGAS) and the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE: Deng et al 2012;Smith et al 2012), which itself is composed of three separate surveys with different input catalogues and selection functions.…”

Section: Lamostmentioning

confidence: 99%

Effects of the selection function on metallicity trends in spectroscopic surveys of the Milky Way

Nandakumar

Schultheis

Hayden

et al. 2017

A&A

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Context. Large spectroscopic Galactic surveys imply a selection function in the way they performed their target selection. Aims. We investigate here the effect of the selection function on the metallicity distribution function (MDF) and on the vertical metallicity gradient by studying similar lines of sight using four different spectroscopic surveys (APOGEE, LAMOST, RAVE, and Gaia-ESO), which have different targeting strategies and therefore different selection functions. Methods. We use common fields between the spectroscopic surveys of APOGEE, LAMOST, RAVE (ALR) and APOGEE, RAVE, Gaia-ESO (AGR) and use two stellar population synthesis models, GALAXIA and TRILEGAL, to create mock fields for each survey. We apply the selection function in the form of colour and magnitude cuts of the respective survey to the mock fields to replicate the observed source sample. We make a basic comparison between the models to check which best reproduces the observed sample distribution. We carry out a quantitative comparison between the synthetic MDF from the mock catalogues using both models to understand the effect of the selection function on the MDF and on the vertical metallicity gradient. Results. Using both models, we find a negligible effect of the selection function on the MDF for APOGEE, LAMOST, and RAVE. We find a negligible selection function effect on the vertical metallicity gradients as well, though GALAXIA and TRILEGAL have steeper and shallower slopes, respectively, than the observed gradient. After applying correction terms on the metallicities of RAVE and LAMOST with respect to our reference APOGEE sample, our observed vertical metallicity gradients between the four surveys are consistent within 1σ. We also find consistent gradient for the combined sample of all surveys in ALR and AGR. We estimated a mean vertical metallicity gradient of −0.241 ± 0.028 dex kpc −1 . There is a significant scatter in the estimated gradients in the literature, but our estimates are within their ranges. Conclusions. We have shown that there is a negligible selection function effect on the MDF and the vertical metallicity gradients for APOGEE, RAVE, and LAMOST using two stellar population synthesis models. Therefore, it is indeed possible to combine common fields of different surveys in studies using MDF and metallicity gradients provided their metallicities are brought to the same scale.

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Section: Lamostmentioning

confidence: 99%

Effects of the selection function on metallicity trends in spectroscopic surveys of the Milky Way

Nandakumar

Schultheis

Hayden

et al. 2017

A&A

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“…We also incorporate the [Fe/H] dependence given in their equation (A2), where we use the metallicity determined from the SDSS spectra. Smith et al (2012) noted that the turn-off correction of Ivezić et al (2008) is not ideal for general disk stars. They concluded that for the magnitude range 0.3 < (g − i) 0 < 0.6 a better choice is to have no turn-off correction and to simply increase the uncertainty (equation A1 of Smith et al 2012).…”

Section: Distancesmentioning

confidence: 99%

“…Combining the uncertainty in the Ivezić et al (2008) relation with the error on [Fe/H], Smith et al (2012) found that for their Stripe 82 sample the median distance error was 10.7%. Therefore in our current work we simplify our calculation by assuming all stars have a distance error of 10%.…”

Section: Distancesmentioning

confidence: 99%

Red Runaways Ii: Low-Mass Hills Stars in SDSS Stripe 82

Zhang

Smith

Carlin

2016

ApJ

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Stars ejected from the Galactic centre can be used to place important constraints on the Milky Way potential. Since existing hypervelocity stars are too distant to accurately determine orbits, we have conducted a search for nearby candidates using full three-dimensional velocities. Since the efficacy of such studies are often hampered by deficiencies in proper motion catalogs, we have chosen to utilize the reliable, high-precision SDSS Stripe 82 proper motion catalog. Although we do not find any candidates which have velocities in excess of the escape speed, we identify 226 stars on orbits that are consistent with Galactic centre ejection. This number is significantly larger than what we would expect for halo stars on radial orbits and cannot be explained by disk or bulge contamination. If we restrict ourselves to metal-rich stars, we find 29 candidates with [Fe/H] > −0.8 dex and 10 with [Fe/H] > −0.6 dex. Their metallicities are more consistent with what we expect for bulge ejecta, and so we believe these candidates are especially deserving of further study. We have supplemented this sample using our own radial velocities, developing an algorithm to use proper motions for optimizing candidate selection. This technique provides considerable improvement on the blind spectroscopic sample of SDSS, being able to identify candidates with an efficiency around 20 times better than a blind search.

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“…The photometric part of the survey has led to the discovery of a host of new streams and dwarf galaxies, including a new population of ultra-faint dwarf galaxies (see Belokurov 2013 for a recent review). Furthermore it has spurred on many different analyses on the state of the disk both through its photometry and spectroscopy (for example, see review articles by Ivezić et al 2012 andSmith et al 2012).…”

Section: The Sdss Surveymentioning

confidence: 99%

Tidal Streams in the Local Group and Beyond

Newberg¹,

Carlin²

2016

Astrophysics and Space Science Library

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The stellar debris structures that have been discovered around the Milky Way and other galaxies are thought to be formed from the disruption of satellite stellar systems-dwarf galaxies or globular clusters-by galactic tidal fields. The total stellar mass in these structures is typically tiny compared to the galaxy around which they are found, and it is hence easy to dismiss them as inconsequential. However , they are remarkably useful as probes of a galaxy's history (as described in this chapter) and mass distribution (covered in a companion chapter in this volume). This power is actually a consequence of their apparent insignificance: their low contribution to the overall mass makes the physics that describes them both elegant and simple and this means that their observed properties are relatively easy to understand and interpret.

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The assembly of the Milky Way and its satellite galaxies

Cited by 10 publications

References 146 publications

Effects of the selection function on metallicity trends in spectroscopic surveys of the Milky Way

Effects of the selection function on metallicity trends in spectroscopic surveys of the Milky Way

Red Runaways Ii: Low-Mass Hills Stars in SDSS Stripe 82

Tidal Streams in the Local Group and Beyond

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