DSpace Angular :: Browsing by Author "Valenti, E."

Browsing by Author "Valenti, E."

Now showing 1 - 20 of 37

A new distance to the Brick, the dense molecular cloud G0.253+0.016
(2021) Zoccali, M.; Valenti, E.; Surot, F.; Gonzalez, O. A.; Renzini, A.; Valenzuela Navarro, A.
We analyse the near-infrared colour-magnitude diagram of a field including the giant molecular cloud G0.253+0.016 (a.k.a. The Brick) observed at high spatial resolution, with HAWK-I@VLT. The distribution of red clump stars in a line of sight crossing the cloud, compared with that in a direction just beside it, and not crossing it, allow us to measure the distance of the cloud from the Sun to be 7.20, with a statistical uncertainty of +/- 0.16 and a systematic error of +/- 0.20 kpc. This is significantly closer than what is generally assumed, i.e. that the cloud belongs to the near side of the central molecular zone, at 60 pc from the Galactic centre. This assumption was based on dynamical models of the central molecular zone, observationally constrained uniquely by the radial velocity of this and other clouds. Determining the true position of the Brick cloud is relevant because this is the densest cloud of the Galaxy not showing any ongoing star formation. This puts the cloud off by one order of magnitude from the Kennicutt-Schmidt relation between the density of the dense gas and the star formation rate. Several explanations have been proposed for this absence of star formation, most of them based on the dynamical evolution of this and other clouds, within the Galactic centre region. Our result emphasizes the need to include constraints coming from stellar observations in the interpretation of our Galaxy's central molecular zone.
Comparing bulge RR Lyrae stars with bulge giants: Insight from 3D kinematics
(2024) Carvajal, J. Olivares; Zoccali, M.; De Leo, M.; Ramos, R. Contreras; Quezada, C.; Rojas-Arriagada, A.; Valenti, E.; Albarracin, R.; Navarro, A. Valenzuela
Context. The structure and kinematics of the old component of the Galactic bulge are still a matter of debate. It is clear that the bulk of the bulge as traced by red clump stars includes two main components, which are usually identified as the metal-rich and metal-poor components. They have different shapes, kinematics, mean metallicities, and alpha-element abundances. It is our current understanding that they are associated with a bar and a spheroid, respectively. On the other hand, RR Lyrae variables trace the oldest population of the bulge. While it would be natural to think that they follow the structure and kinematics of the metal-poor component, the data analysed in the literature show conflicting results. Aims. We aim to derive a rotation curve for bulge RR Lyrae stars in order to determine that the old component traced by these stars is distinct from the two main components observed in the Galactic bulge. Methods. This paper combines APOGEE-2S spectra with OGLE-IV light curves, near-infrared photometry, and proper motions from the VISTA Variables in the V & iacute;a L & aacute;ctea survey for 4193 RR Lyrae stars. Six-dimensional phase-space coordinates were used to calculate orbits within an updated Galactic potential and to isolate the stars. Results. The stars that stay confined within the bulge represent 57% of our sample. Our results show that bulge RR Lyrae variables rotate more slowly than metal-rich red clump stars and have a lower velocity dispersion. Their kinematics is compatible with them being the low-metallicity tail of the metal-poor component. We confirm that a rather large fraction of halo and thick disc RR Lyrae stars pass by the bulge within their orbits, increasing the velocity dispersion. A proper orbital analysis is therefore critical to isolate bona fide bulge variables. Finally, bulge RR Lyrae seem to trace a spheroidal component, although the current data do now allow us to reach a firm conclusion about the spatial distribution.
Comparing the properties of the X-shaped bulges of NGC 4710 and the Milky Way with MUSE
(2016) Rejkuba, M.; Valenti, E.; Zoccali, Manuela; Coccato, L.; Minniti, D.; Ness, M.; Gonzalez, O.; Gadotti, D.; Debattista, V.
Discovery of RR lyrae stars in the nuclear bulge of the Milky Way
(2016) Minniti, D.; Ramos, R. C.; Zoccali, Manuela; Rejkuba, M.; González, O. A.; Valenti, E.; Gran, F.
Galactic bulge population II Cepheids in the VVV survey: period-luminosity relations and a distance to the Galactic centre
(2017) Bhardwaj, A.; Rejkuba, M.; Minniti, D.; Surot, F.; Valenti, E.; Zoccali, Manuela; Gonzalez, O.; Romaniello, M.; Kanbur, S.; Singh, H.
Interstellar extinction curve variations towards the inner Milky Way : a challenge to observational cosmology
(2016) Nataf, D.; Gonzalez, O.; Casagrande, L.; Zasowski, G.; Wegg, C.; Wolf, C.; Kunder, A.; Alonso, J.; Minniti, D.; Zoccali, Manuela; Saito, R.; Valenti, E.; Rejkuba, M.; Poleski, R.; Pietrzynski, G.; Skowron, J.
Mapping the stellar age of the Milky Way bulge with the VVV I. The method
(2019) Surot, F.; Valenti, E.; Hidalgo, S.L.; Zoccali, Manuela; Sokmen, E.; Rejkuba, M.; Minniti, D.; Gonzalez, O.A.; Cassisi, S.; Renzini, O.; Weiss, A.
Mapping the stellar age of the Milky Way bulge with the VVV II. Deep JK_s catalog release based on PSF photometry
(2019) Surot, F.; Valenti, E.; Hidalgo, S. L.; Zoccali, M.; Gonzalez, O. A.; Sokmen, E.; Minniti, D.; Rejkuba, M.; Lucas, P. W.
Context. The bulge represents the best compromise between old and massive Galactic components, and as such its study is a valuable opportunity to understand how the bulk of the Milky Way formed and evolved. In addition, being the only bulge in which we can individually resolve stars in all evolutionary sequences, the properties of its stellar content provide crucial insights into the formation of bulges.
Mapping the stellar age of the Milky Way bulge with the VVV III. High-resolution reddening map
(2020) Surot, F.; Valenti, E.; Gonzalez, O. A.; Zoccali, M.; Sokmen, E.; Hidalgo, S. L.; Minniti, D.
Context. A detailed study of the Galactic bulge stellar population necessarily requires an accurate representation of the interstellar extinction, particularly toward the Galactic plane and center, where severe and differential reddening is expected to vary on sub-arcmin scales. Although recent infrared surveys have addressed this problem by providing extinction maps across the whole Galactic bulge area, dereddened color-magnitude diagrams near the plane and center appear systematically undercorrected, prompting the need for higher resolution. These undercorrections affect any stellar study sensitive to color (e.g., star formation history analyses via color-magnitude diagram fitting), either making them inaccurate or limiting them to small and relatively stable extinction windows where this value is low and better constrained.Aims. This study is aimed at providing a high-resolution (2 arcmin to similar to 10 arcsec) color excess map for the VVV bulge area in J-K-s color.Methods. We used the MW-BULGE-PSFPHOT catalogs, sampling similar to 300 deg(2) across the Galactic bulge (|l| < 10 degrees and -10 degrees< b< 5 degrees) to isolate a sample of red clump and red giant branch stars, for which we calculated the average J-K-s color in a fine spatial grid in (l, b) space.Results. We obtained an E(J-K-s) map spanning the VVV bulge area of roughly 300 deg(2), with the equivalent of a resolution between similar to 1 arcmin for bulge outskirts (l< 6 degrees) to below 20 arcsec within the central |l| < 1 degrees, and below 10 arcsec for the innermost area (|l| < 1 degrees and |b| < 3 degrees).
Mass accretion rates from multiband photometry in the Carina Nebula : The case of Trumpler 14
(2015) Beccari, G.; De Marchi, G.; Panagia, N.; Valenti, E.; Carraro, G.; Romaniello, M.; Zoccali, Manuela; Weidner, Carsten
MOONS: The New Multi-Object Spectrograph for the VLT
(2020) Cirasuolo, M.; Fairley, A.; Rees, P.; González, O. A.; Taylor, W.; Maiolino, R.; Afonso, J.; Evans, C.; Flores, H.; Lilly, S.; Oliva, E.; Paltani, S.; Vanzi, L.; Abreu, M.; Accardo, M.; Adams, N.; Álvarez Méndez, D.; Amans, J. -P.; Amarantidis, S.; Atek, H.; Atkinson, D.; Banerji, M.; Barrett, J.; Barrientos, F.; Bauer, F.; Beard, S.; Béchet, C.; Belfiore, A.; Bellazzini, M.; Benoist, C.; Best, P.; Biazzo, K.; Black, M.; Boettger, D.; Bonifacio, P.; Bowler, R.; Bragaglia, A.; Brierley, S.; Brinchmann, J.; Brinkmann, M.; Buat, V.; Buitrago, F.; Burgarella, D.; Burningham, B.; Buscher, D.; Cabral, A.; Caffau, E.; Cardoso, L.; Carnall, A.; Carollo, M.; Castillo, R.; Castignani, G.; Catelan, Márcio; Cicone, C.; Cimatti, A.; Cioni, M. -R. L.; Clementini, G.; Cochrane, W.; Coelho, J.; Colling, M.; Contini, T.; Contreras, R.; Conzelmann, R.; Cresci, G.; Cropper, M.; Cucciati, O.; Cullen, F.; Cumani, C.; Curti, M.; Da Silva, A.; Daddi, E.; Dalessandro, E.; Dalessio, F.; Dauvin, L.; Davidson, G.; de Laverny, P.; Delplancke-Ströbele, F.; De Lucia, G.; Del Vecchio, C.; Dessauges-Zavadsky, M.; Di Matteo, P.; Dole, H.; Drass, H.; Dunlop, J.; Dünner, R.; Eales, S.; Ellis, R.; Enriques, B.; Fasola, G.; Ferguson, A.; Ferruzzi, D.; Fisher, M.; Flores, M.; Fontana, A.; Forchi, V.; Francois, P.; Franzetti, P.; Gargiulo, A.; Garilli, B.; Gaudemard, J.; Gieles, M.; Gilmore, G.; Ginolfi, M.; Gomes, J. M.; Guinouard, I.; Gutierrez, P.; Haigron, R.; Hammer, F.; Hammersley, P.; Haniff, C.; Harrison, C.; Haywood, M.; Hill, V.; Hubin, N.; Humphrey, A.; Ibata, R.; Infante, L.; Ives, D.; Ivison, R.; Iwert, O.; Jablonka, P.; Jakob, G.; Jarvis, M.; King, D.; Kneib, J. -P.; Laporte, P.; Lawrence, A.; Lee, D.; Li Causi, G.; Lorenzoni, S.; Lucatello, S.; Luco, Y.; Macleod, A.; Magliocchetti, M.; Magrini, L.; Mainieri, V.; Maire, C.; Mannucci, F.; Martin, N.; Matute, I.; Maurogordato, S.; McGee, S.; Mcleod, D.; McLure, R.; McMahon, R.; Melse, B. -T.; Messias, H.; Mucciarelli, A.; Nisini, B.; Nix, J.; Norberg, P.; Oesch, P.; Oliveira, A.; Origlia, L.; Padilla, N.; Palsa, R.; Pancino, E.; Papaderos, P.; Pappalardo, C.; Parry, I.; Pasquini, L.; Peacock, J.; Pedichini, F.; Pello, R.; Peng, Y.; Pentericci, L.; Pfuhl, O.; Piazzesi, R.; Popovic, D.; Pozzetti, L.; Puech, M.; Puzia, T.; Raichoor, A.; Randich, S.; Recio-Blanco, A.; Reis, S.; Reix, F.; Renzini, A.; Rodrigues, M.; Rojas, F.; Rojas-Arriagada, Á.; Rota, S.; Royer, F.; Sacco, G.; Sanchez-Janssen, R.; Sanna, N.; Santos, P.; Sarzi, M.; Schaerer, D.; Schiavon, R.; Schnell, R.; Schultheis, M.; Scodeggio, M.; Serjeant, S.; Shen, T. -C.; Simmonds, C.; Smoker, J.; Sobral, D.; Sordet, M.; Spérone, D.; Strachan, J.; Sun, X.; Swinbank, M.; Tait, G.; Tereno, I.; Tojeiro, R.; Torres, M.; Tosi, M.; Tozzi, A.; Tresiter, E.; Valenti, E.; Valenzuela Navarro, Á.; Vanzella, E.; Vergani, S.; Verhamme, A.; Vernet, J.; Vignali, C.; Vinther, J.; Von Dran, L.; Waring, C.; Watson, S.; Wild, V.; Willesme, B.; Woodward, B.; Wuyts, S.; Yang, Y.; Zamorani, G.; Zoccali, M.; Bluck, A.; Trussler, J.
MOONS is the new Multi-Object Optical and Near-infrared Spectrograph currently under construction for the Very Large Telescope (VLT) at ESO. This remarkable instrument combines, for the first time, the collecting power of an 8-m telescope, 1000 fibres with individual robotic positioners, and both low- and high-resolution simultaneous spectral coverage across the 0.64-1.8 μm wavelength range. This facility will provide the astronomical community with a powerful, world-leading instrument able to serve a wide range of Galactic, extragalactic and cosmological studies. Construction is now proceeding full steam ahead and this overview article presents some of the science goals and the technical description of the MOONS instrument. More detailed information on the MOONS surveys is provided in the other dedicated articles in this Messenger issue....
NEW DENSITY PROFILE AND STRUCTURAL PARAMETERS OF THE COMPLEX STELLAR SYSTEM TERZAN 5
(2010) Lanzoni, B.; Ferraro, F. R.; Dalessandro, E.; Mucciarelli, A.; Beccari, G.; Miocchi, P.; Bellazzini, M.; Rich, R. M.; Origlia, L.; Valenti, E.; Rood, R. T.; Ransom, S. M.
Terzan 5 is a globular cluster-like stellar system in the Galactic bulge which has been recently found to harbor two stellar populations with different iron content and probably different ages. This discovery suggests that Terzan 5 may be the relic of a primordial building block that contributed to the formation of the Galactic bulge. Here we present a re-determination of the structural parameters (center of gravity, density and surface brightness profiles, total luminosity, and mass) of Terzan 5, as obtained from the combination of high-resolution (ESO-MAD and Hubble Space Telescope ACS-WFC) and wide-field (ESO-WFI) observations. We find that Terzan 5 is significantly less concentrated and more massive than previously thought. Still it has the largest collision rate of any stellar aggregate in the Galaxy. We discuss the impact of these findings on the exceptional population of millisecond pulsars harbored in this stellar system.
New near-infrared JHK_s light-curve templates for RR Lyrae variables
(2019) Braga, V. F.; Stetson, P. B.; Bono, G.; Dall'Ora, M.; Ferraro, I; Fiorentino, G.; Iannicola, G.; Inno, L.; Marengo, M.; Neeley, J.; Beaton, R. L.; Buonanno, R.; Calamida, A.; Ramos, R. Contreras; Chaboyer, B.; Fabrizio, M.; Freedman, W. L.; Gilligan, C. K.; Johnston, K., V; Lub, J.; Madore, B. F.; Magurno, D.; Marconi, M.; Marinoni, S.; Marrese, P. M.; Mateo, M.; Matsunaga, N.; Minniti, D.; Monson, A. J.; Monelli, M.; Nonino, M.; Persson, S. E.; Pietrinferni, A.; Sneden, C.; Storm, J.; Walker, A. R.; Valenti, E.; Zoccali, M.
We provide homogeneous optical (UBVRI) and near-infrared (NIR, JHK) time series photometry for 254 cluster (omega Cen, M 4) and field RR Lyrae (RRL) variables. We ended up with more than 551 000 measurements, of which only 9% are literature data. For 94 fundamental (RRab) and 51 first overtones (RRc) we provide a complete optical/NIR characterization (mean magnitudes, luminosity amplitudes, epoch of the anchor point). The NIR light curves of these variables were adopted to provide new light-curve templates for both RRc and RRab variables. The templates for the J and the H bands are newly introduced, together with the use of the pulsation period to discriminate among the different RRab templates. To overcome subtle uncertainties in the fit of secondary features of the light curves we provide two independent sets of analytical functions (Fourier and periodic Gaussian series). The new templates were validated by using 26 omega Cen and Bulge RRLs. We find that the difference between the measured mean magnitude along the light curve and the mean magnitude estimated by using the template on a single randomly extracted phase point is better than 0.01 mag (sigma = 0.04 mag). We also validated the template on variables for which at least three phase points were available, but without information on the phase of the anchor point. We find that the accuracy of the mean magnitudes is also similar to 0.01 mag (sigma = 0.04 mag). The new templates were applied to the Large Magellanic Cloud (LMC) globular cluster Reticulum and by using literature data and predicted PLZ relations we find true distance moduli mu = 18.47 +/- 0.10 (rand.) +/- 0.03 (syst.) mag (J) and 18.49 +/- 0.09 +/- 0.05 mag (K). We also used literature optical and mid-infrared data and we found a mean mu of 18.47 +/- 0.02 +/- 0.06 mag, suggesting that Reticulum is similar to 1 kpc closer than the LMC.
Observed kinematics of the Milky Way nuclear stellar disk region
(2024) Zoccali, M.; Rojas-Arriagada, A.; Valenti, E.; Ramos, R. Contreras; Valenzuela-Navarro, A.; Salvo-Guajardo, C.
Context. The nuclear region of the Milky Way, within approximately -1 degrees < l < +1 degrees and -0.3 degrees < b < +0.3 degrees (i.e., |l|< 150 pc, |b|< 45 pc), is believed to host a nuclear stellar disk, co-spatial with the gaseous central molecular zone. Previous kinematical studies detected faster rotation for the stars belonging to the nuclear stellar disk, compared to the surrounding regions. Aims. We analyze the rotation velocity of stars at the nuclear stellar disk, and compare them with its analog in a few control fields just outside this region. We limit our analysis to stars in the red clump of the color magnitude diagram, in order to be able to relate their mean de-reddened luminosity with distance along the line of sight. Methods. We used a proper motion catalog, obtained from point spread function photometry on VISTA variables in the V & iacute;a L & aacute;ctea images, to construct maps of the transverse velocity for these stars. We complemented our analysis with radial velocities from the 17th data release of the APOGEE survey. Results. We find that the main difference between the nuclear stellar disk region and its surroundings is that at the former we see only stars moving eastward, which we believe are located in front of the Galactic center. On the contrary, in every other direction, we see the brightest red clump stars moving eastward, and the faintest ones moving westward, as expected for a rotating disk. We interpret these observations as being produced by the central molecular zone, hiding stars behind itself. What we observe is compatible with being produced by just the absence of the component at the back, without requiring the presence of a cold, fast rotating disk. This component is also not clearly detected in the newest release of the APOGEE catalog. In other words, we find no clear signature of the nuclear stellar disk as a distinct kinematical component. Conclusions. This work highlights the need for nearby control fields when attempting to characterize the properties of the nuclear stellar disk, as the different systematics affecting this region, compared to nearby ones, might introduce spurious results. Deep, wide field and high resolution photometry of the inner 4 deg of the Milky Way is needed in order to understand the structure and kinematics of this very unique region of our Galaxy.
On the Use of Field RR Lyrae as Galactic Probes. II. A New ΔS Calibration to Estimate Their Metallicity*
(2021) Crestani, J.; Fabrizio, M.; Braga, V. F.; Sneden, C.; Preston, G.; Ferraro, I.; Iannicola, G.; Bono, G.; Alves-Brito, A.; Nonino, M.; D'Orazi, V.; Inno, L.; Monelli, M.; Storm, J.; Altavilla, G.; Chaboyer, B.; Dall'Ora, M.; Fiorentino, G.; Gilligan, C.; Grebel, E. K.; Lala, H.; Lemasle, B.; Marengo, M.; Marinoni, S.; Marrese, P. M.; Martinez-Vazquez, C. E.; Matsunaga, N.; Mullen, J. P.; Neeley, J.; Prudil, Z.; da Silva, R.; Stetson, P. B.; Thevenin, F.; Valenti, E.; Walker, A.; Zoccali, M.
We performed the largest and most homogeneous spectroscopic survey of field RR Lyraes (RRLs). We secured 6300 high-resolution (HR, R similar to 35,000) spectra for 143 RRLs (111 fundamental, RRab; 32 first-overtone, RRc). The atmospheric parameters were estimated by using the traditional approach and the iron abundances were measured by using an LTE line analysis. The resulting iron distribution shows a well-defined metal-rich tail approaching solar iron abundance. This suggests that field RRLs experienced a complex chemical enrichment in the early halo formation. We used these data to develop a new calibration of the Delta S method. This diagnostic, based on the equivalent widths of Ca ii K and three Balmer (H-delta,H-gamma,H-beta) lines, traces the metallicity of RRLs. For the first time, the new empirical calibration: (i) includes spectra collected over the entire pulsation cycle; (ii) includes RRc variables; (iii) relies on spectroscopic calibrators covering more than three dex in iron abundance; and (iv) provides independent calibrations based on one/two/three Balmer lines. The new calibrations were applied to a data set of both SEGUE-SDSS and degraded HR spectra totalling 6451 low-resolution (R similar to 2000) spectra for 5001 RRLs (3439 RRab, 1562 RRc). This resulted in an iron distribution with a median eta = -1.55 0.01 and sigma = 0.51 dex, in good agreement with literature values. We also found that RRc are 0.10 dex more metal-poor than RRab variables, and have a distribution with a smoother metal-poor tail. This finding supports theoretical prescriptions suggesting a steady decrease in the RRc number when moving from metal-poor to metal-rich stellar environments.
On the Use of Field RR Lyrae as Galactic Probes. III. The α-element Abundances*
(2021) Crestani, J.; Braga, V. F.; Fabrizio, M.; Bono, G.; Sneden, C.; Preston, G.; Ferraro, I.; Iannicola, G.; Nonino, M.; Fiorentino, G.; Thevenin, F.; Lemasle, B.; Prudil, Z.; Alves-Brito, A.; Altavilla, G.; Chaboyer, B.; Dall'Ora, M.; D'Orazi, V.; Gilligan, C.; Grebel, E. K.; Koch-Hansen, A. J.; Lala, H.; Marengo, M.; Marinoni, S.; Marrese, P. M.; Martinez-Vazquez, C.; Matsunaga, N.; Monelli, M.; Mullen, J. P.; Neeley, J.; da Silva, R.; Stetson, P. B.; Salaris, M.; Storm, J.; Valenti, E.; Zoccali, M.
We provide the largest and most homogeneous sample of alpha-element (Mg, Ca, Ti) and iron abundances for field RR Lyrae (RRLs; 162 variables) by using high-resolution spectra. The current measurements were complemented with similar abundances available in the literature for 46 field RRLs brought to our metallicity scale. We ended up with a sample of old (t >= 10 Gyr), low-mass stellar tracers (208 RRLs: 169 fundamental, 38 first overtone, and 1 mixed mode) covering 3 dex in iron abundance (-3.00 <= [Fe/H] <= 0.24). We found that field RRLs are similar to 0.3 dex more alpha poor than typical halo tracers in the metal-rich regime ([Fe/H] >= -1.2), while in the metal-poor regime ([Fe/H] <= -2.2) they seem to be on average similar to 0.1 dex more alpha enhanced. This is the first time that the depletion in alpha elements for solar iron abundances is detected on the basis of a large, homogeneous, and coeval sample of old stellar tracers. Interestingly, we also detected a close similarity in the [alpha/Fe] trend between alpha-poor, metal-rich RRLs and red giants (RGs) in the Sagittarius dwarf galaxy as well as between alpha-enhanced, metal-poor RRLs and RGs in ultrafaint dwarf galaxies. These results are supported by similar elemental abundances for 46 field horizontal branch stars. These stars share with RRLs the same evolutionary phase and the same progenitors. This evidence further supports the key role that old stellar tracers play in constraining the early chemical enrichment of the halo and, in particular, in investigating the impact that dwarf galaxies have had in the mass assembly of the Galaxy.
On the Use of Field RR Lyrae as Galactic Probes. V. Optical and Radial Velocity Curve Templates
(2021) Braga, V. F.; Crestani, J.; Fabrizio, M.; Bono, G.; Sneden, C.; Preston, G. W.; Storm, J.; Kamann, S.; Latour, M.; Lala, H.; Lemasle, B.; Prudil, Z.; Altavilla, G.; Chaboyer, B.; Dall'Ora, M.; Ferraro, I; Gilligan, C. K.; Fiorentino, G.; Iannicola, G.; Inno, L.; Kwak, S.; Marengo, M.; Marinoni, S.; Marrese, P. M.; Martinez-Vazquez, C. E.; Monelli, M.; Mullen, J. P.; Matsunaga, N.; Neeley, J.; Stetson, P. B.; Valenti, E.; Zoccali, M.
We collected the largest spectroscopic catalog of RR Lyrae (RRLs) including approximate to 20,000 high-, medium-, and low-resolution spectra for approximate to 10,000 RRLs. We provide the analytical forms of radial velocity curve (RVC) templates. These were built using 36 RRLs (31 fundamental-split into three period bins-and five first-overtone pulsators) with well-sampled RVCs based on three groups of metallic lines (Fe, Mg, Na) and four Balmer lines (H- alpha , H- beta , H- gamma , H- delta ). We tackled the long-standing problem of the reference epoch to anchor light-curve and RVC templates. For the V-band, we found that the residuals of the templates anchored to the phase of the mean magnitude along the rising branch are similar to 35% to similar to 45% smaller than those anchored to the phase of maximum light. For the RVC, we used two independent reference epochs for metallic and Balmer lines and we verified that the residuals of the RVC templates anchored to the phase of mean RV are from 30% (metallic lines) up to 45% (Balmer lines) smaller than those anchored to the phase of minimum RV. We validated our RVC templates by using both the single-point and the three phase point approaches. We found that barycentric velocities based on our RVC templates are two to three times more accurate than those available in the literature. We applied the current RVC templates to Balmer lines RVs of RRLs in the globular NGC 3201 collected with MUSE at VLT. We found the cluster barycentric RV of V ( gamma ) = 496.89 +/- 8.37(error) +/- 3.43 (standard deviation) km s(-1), which agrees well with literature estimates.
Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS. III. The first global photometric metallicity map of the Galactic bulge
(2013) González, O.; Rejkuba, M.; Zoccali, Manuela; Valenti, E.; Minniti, D.; Tobar, R.
Reinforcing the link between the double red clump and the X-shaped bulge of the Milky Way
(2015) Gonzalez, O. A.; Zoccali, M.; Debattista, V. P.; Alonso-Garcia, J.; Valenti, E.; Minniti, D.
The finding of a double red clump in the luminosity function of the Milky Way bulge has been interpreted as evidence for an X-shaped structure. Recently, an alternative explanation has been suggested, where the double red clump is an effect of multiple stellar populations in a classical spheroid. In this Letter we provide an observational assessment of this scenario and show that it is not consistent with the behaviour of the red clump across different lines of sight, particularly at high distances from the Galactic plane. Instead, we confirm that the shape of the red clump magnitude distribution closely follows the distance distribution expected for an X-shaped bulge at critical Galactic latitudes. We also emphasize some key observational properties of the bulge red clump that should not be neglected in the search for alternative scenarios.
Spectroscopic analysis of VVV CL001 cluster with MUSE
(2022) Olivares Carvajal, J.; Zoccali, M.; Rojas-Arriagada, A.; Contreras Ramos, R.; Gran, F.; Valenti, E.; Minniti, J. H.
Like most spiral galaxies, the Milky Way contains a population of blue, metal-poor globular clusters and another of red, metal-rich ones. Most of the latter belong to the bulge, and therefore they are poorly studied compared to the blue (halo) ones because they suffer higher extinction and larger contamination from field stars. These intrinsic difficulties, together with a lack of low-mass bulge globular clusters, are reasons to believe that their census is not complete yet. Indeed, a few new clusters have been confirmed in the last few years. One of them is VVV CL001, the subject of the present study. We present a new spectroscopic analysis of the recently confirmed globular cluster VVV CL001, made by means of MUSE@VLT integral field data. Individual spectra were extracted for stars in the VVV CL001 field. Radial velocities were derived by cross-correlation with synthetic templates. Coupled with proper motions from the VVV (VISTA Variables in the Via Lactea) survey, these data allow us to select 55 potential cluster members, for which we derive metallicities using the public code The Cannon. The mean radial velocity of the cluster is V-helio = -324.9 +/- 0.8 km s(-1), as estimated from 55 cluster members. This high velocity, together with a low metallicity [Fe/H] = -2.04 +/- 0.02 dex, suggests that VVV CL001 could be a very old cluster. The estimated distance is d = 8.23 +/- 0.46 kpc, placing the cluster in the Galactic bulge. Furthermore, both its current position and the orbital parameters suggest that VVV CL001 is most probably a bulge globular cluster.

Browsing by Author "Valenti, E."

Results Per Page

Sort Options