Browsing by Author "Lane, R. R."

Now showing 1 - 8 of 8
  • Thumbnail Image
    Item
    A Chemical and Kinematical Analysis of the Intermediate-age Open Cluster IC 166 from APOGEE and Gaia DR2
    (2018) Schiappacasse-Ulloa, J.; Tang, B.; Fernandez-Trincado, J. G.; Zamora, O.; Geisler, D.; Frinchaboy, P.; Schultheis, M.; Dell'Agli, F.; Villanova, S.; Masseron, T.; Meszaros, Sz; Souto, D.; Hasselquist, S.; Cunha, K.; Smith, V. V.; Garcia-Hernandez, D. A.; Vieira, K.; Robin, A. C.; Minniti, D.; Zasowski, G.; Moreno, E.; Perez-Villegas, A.; Lane, R. R.; Ivans, I. I.; Pan, K.; Nitschelm, C.; Santana, F. A.; Carrera, R.; Roman-Lopes, A.
  • No Thumbnail Available
    Item
    Are the Milky Way and Andromeda unusual? A comparison with Milky Way and Andromeda analogues
    (2020) Boardman, N.; Zasowski, G.; Newman, J. A.; Andrews, B.; Fielder, C.; Bershady, M.; Brinkmann, J.; Drory, N.; Krishnarao, D.; Lane, R. R.; Mackereth, T.; Masters, K.; Stringfellow, G. S.
    Our Milky Way provides a unique test case for galaxy evolution models because of our privileged position within the Milky Way's disc. This position also complicates comparisons between the Milky Way and external galaxies, due to our inability to observe the Milky Way from an external point of view. Milky Way analogue galaxies offer us a chance to bridge this divide by providing the external perspective that we otherwise lack. However, overprecise definitions of 'analogue' yield little-to-no galaxies, so it is vital to understand which selection criteria produce the most meaningful analogue samples. To address this, we compare the properties of complementary samples of Milky Way analogues selected using different criteria. We find the Milky Way to be within 1 sigma of its analogues in terms of star formation rate and bulge-to-total ratio in most cases, but we find larger offsets between the Milky Way and its analogues in terms of disc scale length; this suggests that scale length must be included in analogue selections in addition to other criteria if the most accurate analogues are to be selected. We also apply our methodology to the neighbouring Andromeda galaxy. We find analogues selected on the basis of strong morphological features to display much higher star formation rates than Andromeda, and we also find analogues selected on Andromeda's star formation rate to overpredict Andromeda's bulge extent. This suggests both structure and star formation rate should be considered when selecting the most stringent Andromeda analogues.
  • Thumbnail Image
    Item
    CAPOS: The bulge Cluster APOgee Survey. I. Overview and initial ASPCAP results
    (2021) Geisler, D.; Villanova, S.; O'Connell, J. E.; Cohen, R. E.; Moni Bidin, C.; Fernández-Trincado, J. G.; Muñoz, C.; Minniti, D.; Zoccali, M.; Rojas-Arriagada, A.; Contreras Ramos, R.; Catelan, Márcio; Mauro, F.; Cortés, C.; Ferreira Lopes, C. E.; Arentsen, A.; Starkenburg, E.; Martin, N. F.; Tang, B.; Parisi, C.; Alonso-García, J.; Gran, F.; Cunha, K.; Smith, V.; Majewski, S. R.; Jönsson, H.; García-Hernández, D. A.; Horta, D.; Mészáros, S.; Monaco, L.; Monachesi, A.; Muñoz, R. R.; Brownstein, J.; Beers, T. C.; Lane, R. R.; Barbuy, B.; Sobeck, J.; Henao, L.; González-Díaz, D.; Miranda, R. E.; Reinarz, Y.; Santander, T. A.
    Context. Bulge globular clusters (BGCs) are exceptional tracers of the formation and chemodynamical evolution of this oldest Galactic component. However, until now, observational difficulties have prevented us from taking full advantage of these powerful Galactic archeological tools. Aims: CAPOS, the bulge Cluster APOgee Survey, addresses this key topic by observing a large number of BGCs, most of which have only been poorly studied previously. Even their most basic parameters, such as metallicity, [α/Fe], and radial velocity, are generally very uncertain. We aim to obtain accurate mean values for these parameters, as well as abundances for a number of other elements, and explore multiple populations. In this first paper, we describe the CAPOS project and present initial results for seven BGCs. Methods: CAPOS uses the APOGEE-2S spectrograph observing in the H band to penetrate obscuring dust toward the bulge. For this initial paper, we use abundances derived from ASPCAP, the APOGEE pipeline. Results: We derive mean [Fe/H] values of −0.85 ± 0.04 (Terzan 2), −1.40 ± 0.05 (Terzan 4), −1.20 ± 0.10 (HP 1), −1.40 ± 0.07 (Terzan 9), −1.07 ± 0.09 (Djorg 2), −1.06 ± 0.06 (NGC 6540), and −1.11 ± 0.04 (NGC 6642) from three to ten stars per cluster. We determine mean abundances for eleven other elements plus the mean [α/Fe] and radial velocity. CAPOS clusters significantly increase the sample of well-studied Main Bulge globular clusters (GCs) and also extend them to lower metallicity. We reinforce the finding that Main Bulge and Main Disk GCs, formed in situ, have [Si/Fe] abundances slightly higher than their accreted counterparts at the same metallicity. We investigate multiple populations and find our clusters generally follow the light-element (anti)correlation trends of previous studies of GCs of similar metallicity. We finally explore the abundances of the iron-peak elements Mn and Ni and compare their trends with field populations. Conclusions: CAPOS is proving to be an unprecedented resource for greatly improving our knowledge of the formation and evolution of BGCs and the bulge itself....
  • No Thumbnail Available
    Item
    From the bulge to the outer disc: monospace StarHorse monospace stellar parameters, distances, and extinctions for stars in APOGEE DR16 and other spectroscopic surveys
    (2020) Queiroz, A. B. A.; Anders, F.; Chiappini, C.; Khalatyan, A.; Santiago, B. X.; Steinmetz, M.; Valentini, M.; Miglio, A.; Bossini, D.; Barbuy, B.; Minchev, I; Minniti, D.; Garcia Hernandez, D. A.; Schultheis, M.; Beaton, R. L.; Beers, T. C.; Bizyaev, D.; Brownstein, J. R.; Cunha, K.; Fernandez-Trincado, J. G.; Frinchaboy, P. M.; Lane, R. R.; Majewski, S. R.; Nataf, D.; Nitschelm, C.; Pan, K.; Roman-Lopes, A.; Sobeck, J. S.; Stringfellow, G.; Zamora, O.
    We combine high-resolution spectroscopic data from APOGEE-2 survey Data Release 16 (DR16) with broad-band photometric data from several sources as well as parallaxes from Gaia Data Release 2 (DR2). Using the Bayesian isochrone-fitting code StarHorse, we derived the distances, extinctions, and astrophysical parameters for around 388 815 APOGEE stars. We achieve typical distance uncertainties of similar to 6% for APOGEE giants, similar to 2% for APOGEE dwarfs, and extinction uncertainties of similar to 0.07 mag, when all photometric information is available, and similar to 0.17 mag if optical photometry is missing. StarHorse uncertainties vary with the input spectroscopic catalogue, available photometry, and parallax uncertainties. To illustrate the impact of our results, we show that thanks to Gaia DR2 and the now larger sky coverage of APOGEE-2 (including APOGEE-South), we obtain an extended map of the Galactic plane. We thereby provide an unprecedented coverage of the disc close to the Galactic mid-plane (|Z(Gal)| < 1 kpc) from the Galactic centre out to R-Gal20 kpc. The improvements in statistics as well as distance and extinction uncertainties unveil the presence of the bar in stellar density and the striking chemical duality in the innermost regions of the disc, which now clearly extend to the inner bulge. We complement this paper with distances and extinctions for stars in other public released spectroscopic surveys: 324 999 in GALAH DR2, 4 928 715 in LAMOST DR5, 408 894 in RAVE DR6, and 6095 in GES DR3.
  • No Thumbnail Available
    Item
    H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia
    (2019) Fernandez-Trincado, J. G.; Zamora, O.; Souto, Diogo; Cohen, R. E.; Agli, F. Dell; Garcia-Hernandez, D. A.; Masseron, T.; Schiavon, R. P.; Meszaros, Sz; Cunha, K.; Hasselquist, S.; Shetrone, M.; Schiappacasse Ulloa, J.; Tang, B.; Geisler, D.; Schleicher, D. R. G.; Villanova, S.; Mennickent, R. E.; Minniti, D.; Alonso-Garcia, J.; Manchado, A.; Beers, T. C.; Sobeck, J.; Zasowski, G.; Schultheis, M.; Majewski, S. R.; Rojas-Arriagada, A.; Almeida, A.; Santana, F.; Oelkers, R. J.; Longa-Pena, P.; Carrera, R.; Burgasser, A. J.; Lane, R. R.; Roman-Lopes, A.; Ivans, I. I.; Hearty, F. R.
    We present an elemental abundance analysis of high-resolution spectra for five giant stars spatially located within the innermost regions of the bulge globular cluster NGC 6522 and derive Fe, Mg, Al, C, N, O, Si, and Ce abundances based on H-band spectra taken with the multi-object APOGEE-north spectrograph from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. Of the five cluster candidates, two previously unremarked stars are confirmed to have second-generation (SG) abundance patterns, with the basic pattern of depletion in C and Mg simultaneous with enrichment in N and Al as seen in other SG globular cluster populations at similar metallicity. In agreement with the most recent optical studies, the NGC 6522 stars analyzed exhibit (when available) only mild overabundances of the s-process element Ce, contradicting the idea that NGC 6522 stars are formed from gas enriched by spinstars and indicating that other stellar sources such as massive AGB stars could be the primary polluters of intra-cluster medium. The peculiar abundance signatures of SG stars have been observed in our data, confirming the presence of multiple generations of stars in NGC 6522.
  • No Thumbnail Available
    Item
    Milky Way analogues in MaNGA: multiparameter homogeneity and comparison to the Milky Way
    (2020) Boardman, N.; Zasowski, G.; Seth, A.; Newman, J.; Andrews, B.; Bershady, M.; Bird, J.; Chiappini, C.; Fielder, C.; Fraser-McKelvie, A.; Jones, A.; Licquia, T.; Masters, K. L.; Minchev, I; Schiavon, R. P.; Brownstein, J. R.; Drory, N.; Lane, R. R.
    The Milky Way provides an ideal laboratory to test our understanding of galaxy evolution, owing to our ability to observe our Galaxy over fine scales. However, connecting the Galaxy to the wider galaxy population remains difficult, due to the challenges posed by our internal perspective and to the different observational techniques employed. Here, we present a sample of galaxies identified as Milky Way analogues on the basis of their stellar masses and bulge-to-total ratios, observed as part of the Mapping Nearby Galaxies at Apache Point Observatory survey. We analyse the galaxies in terms of their stellar kinematics and populations as well as their ionized gas contents. We find our sample to contain generally young stellar populations in their outskirts. However, we find a wide range of stellar ages in their central regions, and we detect central active galactic nucleus-like or composite-like activity in roughly half of the sample galaxies, with the other half consisting of galaxies with central star-forming emission or emission consistent with old stars. We measure gradients in gas metallicity and stellar metallicity that are generally flatter in physical units than those measured for the Milky Way; however, we find far better agreement with the Milky Way when scaling gradients by galaxies' disc scale lengths. From this, we argue much of the discrepancy in metallicity gradients to be due to the relative compactness of the Milky Way, with differences in observing perspective also likely to be a factor.
  • Thumbnail Image
    Item
    SDSS-IV MaNGA: spatially resolved star formation histories in galaxies as a function of galaxy mass and type
    (OXFORD UNIV PRESS, 2017) Goddard, D.; Thomas, D.; Maraston, C.; Westfall, K.; Etherington, J.; Riffel, R.; Mallmann, N. D.; Zheng, Z.; Argudo Fernandez, M.; Lian, J.; Bershady, M.; Bundy, K.; Drory, N.; Law, D.; Yan, R.; Wake, D.; Weijmans, A.; Bizyaev, D.; Brownstein, J.; Lane, R. R.; Maiolino, R.; Masters, K.; Merrifield, M.; Nitschelm, C.; Pan, K.; Roman Lopes, A.; Storchi Bergmann, T.; Schneider, D. P.
    We study the internal gradients of stellar population propertieswithin 1.5 R-e for a representative sample of 721 galaxies, with stellar masses ranging between 10(9)M circle dot and 10(11.5)M circle dot from the SDSS-IV MaNGA Integral-Field-Unit survey. Through the use of our full spectral fitting code FIREFLY, we derive light-and mass-weighted stellar population properties and their radial gradients, as well as full star formation and metal enrichment histories. We also quantify the impact that different stellar population models and full spectral fitting routines have on the derived stellar population properties and the radial gradient measurements. In our analysis, we find that age gradients tend to be shallow for both early-type and late-type galaxies. Mass-weighted age gradients of early-types arepositive (similar to 0.09 dex/Re) pointing to ` outsidein' progression of star formation, while late-type galaxies have negative light-weighted age gradients (similar to-0.11 dex/R-e), suggesting an ` inside-out' formation of discs. We detect negative metallicity gradients in both early-and late-type galaxies, but these are significantly steeper in late-types, suggesting that the radial dependence of chemical enrichment processes and the effect of gas inflow and metal transport are far more pronounced in discs. Metallicity gradients of both morphological classes correlate with galaxy mass, with negative metallicity gradients becoming steeper with increasing galaxy mass. The correlation with mass is stronger for late-type galaxies, with a slope of d(del[Z/H])/d(logM) similar to -0.2 +/- 0.05, compared to d(del[Z/H])/d(logM) similar to -0.05 +/- 0.05 for early-types. This result suggests that the merger history plays a relatively small role in shaping metallicity gradients of galaxies.
  • No Thumbnail Available
    Item
    The Milky Way bar and bulge revealed by APOGEE and Gaia EDR3
    (2021) Queiroz, A. B. A.; Chiappini, C.; Perez-Villegas, A.; Khalatyan, A.; Anders, F.; Barbuy, B.; Santiago, B. X.; Steinmetz, M.; Cunha, K.; Schultheis, M.; Majewski, S. R.; Minchev, I; Minniti, D.; Beaton, R. L.; Cohen, R. E.; da Costa, L. N.; Fernandez-Trincado, J. G.; Garcia-Hernandez, D. A.; Geisler, D.; Hasselquist, S.; Lane, R. R.; Nitschelm, C.; Rojas-Arriagada, A.; Roman-Lopes, A.; Smith, V; Zasowski, G.
    We investigate the inner regions of the Milky Way using data from APOGEE and Gaia EDR3. Our inner Galactic sample has more than 26 500 stars within |X-Gal|< 5 kpc, |Y-Gal|< 3.5 kpc, |Z(Gal)|< 1 kpc, and we also carry out the analysis for a foreground-cleaned subsample of 8000 stars that is more representative of the bulge-bar populations. These samples allow us to build chemo-dynamical maps of the stellar populations with vastly improved detail. The inner Galaxy shows an apparent chemical bimodality in key abundance ratios [alpha/Fe], [C/N], and [Mn/O], which probe different enrichment timescales, suggesting a star formation gap (quenching) between the high- and low-alpha populations. Using a joint analysis of the distributions of kinematics, metallicities, mean orbital radius, and chemical abundances, we can characterize the different populations coexisting in the innermost regions of the Galaxy for the first time. The chemo-kinematic data dissected on an eccentricity-|Z|(max) plane reveal the chemical and kinematic signatures of the bar, the thin inner disc, and an inner thick disc, and a broad metallicity population with large velocity dispersion indicative of a pressure-supported component. The interplay between these different populations is mapped onto the different metallicity distributions seen in the eccentricity-|Z|(max) diagram consistently with the mean orbital radius and V-phi distributions. A clear metallicity gradient as a function of |Z|(max) is also found, which is consistent with the spatial overlapping of different populations. Additionally, we find and chemically and kinematically characterize a group of counter-rotating stars that could be the result of a gas-rich merger event or just the result of clumpy star formation during the earliest phases of the early disc that migrated into the bulge. Finally, based on 6D information, we assign stars a probability value of being on a bar orbit and find that most of the stars with large bar orbit probabilities come from the innermost 3 kpc, with a broad dispersion of metallicity. Even stars with a high probability of belonging to the bar show chemical bimodality in the [alpha/Fe] versus [Fe/H] diagram. This suggests bar trapping to be an efficient mechanism, explaining why stars on bar orbits do not show a significant, distinct chemical abundance ratio signature.