The IR Stellar Population Around the Galactic Centre

1993 ◽  
pp. 329-330
Author(s):  
A. Ruelas-Mayorga ◽  
P. Teague
Keyword(s):  
Stellar Population ◽  
Galactic Centre

scholarly journals Star formation history and metallicity in the Galactic inner bulge revealed by the red giant branch bump

2018 ◽  
Vol 620 ◽  
pp. A83 ◽  
Author(s):  
F. Nogueras-Lara ◽  
R. Schödel ◽  
H. Dong ◽  
F. Najarro ◽  
A. T. Gallego-Calvente ◽  
...  
Keyword(s):  
Stellar Population ◽  
Milky Way ◽  
Angular Resolution ◽  
Interstellar Extinction ◽  
Star Formation History ◽  
Galactic Centre ◽  
Luminosity Functions ◽  
Formation History ◽  
Red Giant ◽  
The One

Context. The study of the inner region of the Milky Way bulge is hampered by high interstellar extinction and extreme source crowding. Sensitive high angular resolution near-infrared imaging is needed to study stellar populations and their characteristics in such a dense and complex environment. Aims. We aim at investigating the stellar population in the innermost Galactic bulge, to study the star formation history in this region of the Galaxy. Methods. We used the 0.2″ angular resolution JHKs data from the GALACTICNUCLEUS survey to study the stellar population within two 8.0′×3.4′ fields, about 0.6° and 0.4° to the Galactic north of the Milky Way centre and to compare it with the one in the immediate surroundings of Sagittarius A*. We also characterise the absolute extinction and the extinction curve of the two fields. Results. The average interstellar extinction to the outer and the inner field is AKs ∼ 1.20 ± 0.08 mag and ∼1.48 ± 0.10 mag, respectively. We present Ks luminosity functions that are complete down to at least two magnitudes below the red clump (RC). We detect a feature in the luminosity functions that is fainter than the RC by 0.80 ± 0.03 and 0.79 ± 0.02 mag, respectively, in the Ks band. It runs parallel to the reddening vector. We identify the feature as the red giant branch bump. Fitting α-enhanced BaSTI luminosity functions to our data, we find that a single old stellar population of ∼12.8 ± 0.6 Gyr and Z = 0.040 ± 0.003 provides the best fit. Our findings thus show that the stellar population in the innermost bulge is old, similar to the one at larger distances from the Galactic plane, and that its metallicity is about twice solar at distances as short as about 60 pc from the centre of the Milky Way, similar to what is observed at about 500 pc from the Galactic Centre. Comparing the obtained metallicity with previous known values at larger latitudes (|b| > 2°), our results favour a flattening of the gradient at |b| < 2°. As a secondary result we obtain that the extinction index in the studied regions agrees within the uncertainties with our previous value of α = 2.30 ± 0.08 that was derived for the very Galactic centre.

scholarly journals Star formation at the Galactic Centre: coevolution of multiple young stellar discs

2019 ◽  
Vol 490 (4) ◽  
pp. 5820-5831 ◽  
Author(s):  
Alessandra Mastrobuono-Battisti ◽  
Hagai B Perets ◽  
Alessia Gualandris ◽  
Nadine Neumayer ◽  
Anna C Sippel
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Direct Evidence ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Disc ◽  
The Galaxy ◽  
Kinematic Properties

ABSTRACT Studies of the Galactic Centre suggest that in situ star formation may have given rise to the observed stellar population near the central supermassive black hole (SMBH). Direct evidence for a recent starburst is provided by the currently observed young stellar disc (2–7 Myr) in the central 0.5 pc of the Galaxy. This result suggests that star formation in galactic nuclei may occur close to the SMBH and produce initially flattened stellar discs. Here, we explore the possible build-up and evolution of nuclear stellar clusters near SMBHs through in situ star formation producing stellar discs similar to those observed in the Galactic Centre and other nuclei. We use N-body simulations to model the evolution of multiple young stellar discs and explore the potential observable signatures imprinted by such processes. Each of the five simulated discs is evolved for 100 Myr before the next one is introduced in the system. We find that populations born at different epochs show different morphologies and kinematics. Older and presumably more metal-poor populations are more relaxed and extended, while younger populations show a larger amount of rotation and flattening. We conclude that star formation in central discs can reproduce the observed properties of multiple stellar populations in galactic nuclei differing in age, metallicity, and kinematic properties.

scholarly journals Kinematics of the old stellar population at the Galactic centre

2008 ◽  
Vol 492 (2) ◽  
pp. 419-439 ◽  
Author(s):  
S. Trippe ◽  
S. Gillessen ◽  
O. E. Gerhard ◽  
H. Bartko ◽  
T. K. Fritz ◽  
...  
Keyword(s):  
Stellar Population ◽  
Galactic Centre

scholarly journals GALACTICNUCLEUS: A high angular-resolution JHKs imaging survey of the Galactic centre

2020 ◽  
Vol 641 ◽  
pp. A141
Author(s):  
F. Nogueras-Lara ◽  
R. Schödel ◽  
N. Neumayer ◽  
E. Gallego-Cano ◽  
B. Shahzamanian ◽  
...  
Keyword(s):  
Stellar Population ◽  
Near Infrared ◽  
Angular Resolution ◽  
Interstellar Extinction ◽  
Extinction Curve ◽  
Line Of Sight ◽  
Galactic Centre ◽  
High Angular Resolution ◽  
The Galaxy ◽  
Red Clump

Context. The characterisation of the extinction curve in the near-infrared (NIR) is fundamental to analysing the structure and stellar population of the Galactic centre (GC), whose analysis is hampered by the extreme interstellar extinction (AV ~ 30 mag) that varies on arc-second scales. Recent studies indicate that the behaviour of the extinction curve might be more complex than previously assumed, pointing towards a variation of the extinction curve as a function of wavelength. Aims. We aim to analyse the variations of the extinction index, α, with wavelength, line-of-sight, and absolute extinction, extending previous analyses to a larger area of the innermost regions of the Galaxy. Methods. We analysed the whole GALACTICNUCLEUS survey, a high-angular resolution (~0.2″) JHKs NIR survey specially designed to observe the GC in unprecedented detail. It covers a region of ~6000 pc2, comprising fields in the nuclear stellar disc, the inner bulge, and the transition region between them. We applied two independent methods based on red clump (RC) stars to constrain the extinction curve and analysed its variation superseding previous studies. Results. We used more than 165 000 RC stars and increased the size of the regions analysed significantly to confirm that the extinction curve varies with the wavelength. We estimated a difference Δα = 0.21 ± 0.07 between the obtained extinction indices, αJH = 2.44 ± 0.05 and αHKs = 2.23 ± 0.05. We also concluded that there is no significant variation of the extinction curve with wavelength, with the line-of-sight or the absolute extinction. Finally, we computed the ratios between extinctions, AJ∕AH = 1.87 ± 0.03 and AH/AKs = 1.84 ± 0.03, consistent with all the regions of the GALACTICNUCLEUS catalogue.

scholarly journals Strömgren Photometry of Stars in Baade's Window

1995 ◽  
Vol 164 ◽  
pp. 410-410
Author(s):  
Alex Ruelas-Mayorga ◽  
Gabriel García-Ruíz
Keyword(s):  
Stellar Population ◽  
Solar Neighbourhood ◽  
Galactic Centre ◽  
Galactic Bulge ◽  
Galactic Disc

Baade's Window (BW) has long been observed because of its low absorption and its position near the galactic centre. These characteristics permit the observation of many stars which are presumably members of the galactic bulge; although it is not possible to exclude contamination of this field by stars belonging to the galactic disc. Geometric arguments as well as galactic models allow to see that most of the stars are located far away from the solar neighbourhood. Based on this fact alone, many astronomers have assumed that the entire stellar population observed in BW consists of bulge stars.

scholarly journals The IR stellar population around the Galactic Centre

1993 ◽  
Vol 153 ◽  
pp. 329-330
Author(s):  
A. Ruelas-Mayorga ◽  
P. Teague
Keyword(s):  
Stellar Population ◽  
Galactic Centre ◽  
Disc Model ◽  
The Galaxy

We present K-counts for a number of stars with K ≤ +9.0 in 3 clear regions near the galactic centre. They are located approximately at l∼0.0 and b ∼ −3.5, −4.0 and −4.5. Their Cumulative Counts Functions (CCF's) are formed, and with the aid of an exponential disc model for the Galaxy are separated into disc and bulge CCF. As for the case in Baade's Window (BW) (Ruelas-Mayorga and Teague, 1992a) the disc is dominant at bright magnitudes whereas the bulge dominates at fainter ones. The slope of the bulge CCF is steeper than that for the disc in all cases corroborating the result obtained for BW. The two colour JHK and the K vs J-K diagrams show that the stellar population in these areas is similar to that studied in BW by us and by Frogel and Whitford (1987). An average E(J-K) ∼0.42 mag for the reddening is obtained. At K ≤ +9.0, the disc may be accounted for by those sources with J-K ≤ +1.6 whereas the bulge population presents values for J-K in excess of +1.6.

scholarly journals GALACTICNUCLEUS: A high-angular-resolution JHKs imaging survey of the Galactic centre

2019 ◽  
Vol 631 ◽  
pp. A20 ◽  
Author(s):  
F. Nogueras-Lara ◽  
R. Schödel ◽  
A. T. Gallego-Calvente ◽  
H. Dong ◽  
E. Gallego-Cano ◽  
...  
Keyword(s):  
Stellar Population ◽  
Near Infrared ◽  
Milky Way ◽  
Angular Resolution ◽  
State Of The Art ◽  
Zero Point ◽  
Uncertainty Estimation ◽  
Galactic Centre ◽  
High Angular Resolution ◽  
Central Regions

Context. The high extinction and extreme source crowding of the central regions of the Milky Way are serious obstacles to the study of the structure and stellar population of the Galactic centre (GC). Existing surveys that cover the GC region (2MASS, UKIDSS, VVV, SIRIUS) do not have the necessary high angular resolution. Therefore, a high-angular-resolution survey in the near infrared is crucial to improve the state of the art. Aims. Here, we present the GALACTICNUCLEUS catalogue, a near infrared JHKs high-angular-resolution (0.2″) survey of the nuclear bulge of the Milky Way. Methods. We explain in detail the data reduction, data analysis, calibration, and uncertainty estimation of the GALACTICNUCLEUS survey. We assess the data quality comparing our results with previous surveys. Results. We obtained accurate JHKs photometry for ∼3.3 × 106 stars in the GC detecting around 20% in J, 65% in H, and 90% in Ks. The survey covers a total area of ∼0.3 deg2, which corresponds to ∼6000 pc2. The GALACTICNUCLEUS survey reaches 5σ detections for J ∼ 22 mag, H ∼ 21 mag, and Ks ∼ 21 mag. The uncertainties are below 0.05 mag at J ∼ 21 mag, H ∼ 19 mag, and Ks ∼ 18 mag. The zero point systematic uncertainty is ≲0.04 mag in all three bands. We present colour–magnitude diagrams for the different regions covered by the survey.

scholarly journals Probability of simultaneous parallax detection for free-floating planet microlensing events near Galactic Centre

2020 ◽  
Vol 494 (3) ◽  
pp. 3235-3252 ◽  
Author(s):  
M Ban
Keyword(s):  
Interstellar Dust ◽  
Stellar Population ◽  
Event Rate ◽  
Galactic Centre ◽  
Signal To Noise ◽  
Nearby Star ◽  
Mass Estimation ◽  
Galactic Model ◽  
Noise Limit ◽  
Stellar Background

ABSTRACT The event rate and the efficiency of mass estimation for free-floating planet (FFP) microlensing events were determined from the simulation of the simultaneous parallax observations by Euclid, WFIRST, and LSST. The stellar population from the Besançon Galactic model toward (l, b) = (1°, −1.°75) was applied to our 3D microlensing model, and 30 000 parallax observations were simulated for each following FFP lens masses: Jupiter mass, Neptune mass, and Earth mass assuming the population of one FFP per star. The interstellar dust, unresolved stellar background, nearby star blending was modelled. A signal-to-noise limit considering a finite source effect determined the event detectability. The Euclid–WFIRST combination yielded 30.7 Jupiter-mass FFPs during two 30-d periods per year in parallax observation. The parallax event rate decreases to 3.9 FFPs for Earth-mass planets. The mass estimation from the parallax light curve allowed recovery of FFP masses to within a factor of 2 for 20–26 per cent of cases. The Euclid–LSST combination yielded 34.5 Jupiter-mass FFPs down to 0.5 Earth-mass FFPs for the same periods and the mass is recovered to within a factor of 2 in 20–40 per cent of cases. The event rate will be normalized by the unknown FFP abundance to recover the number of expected detections.

Spectroscopic Studies of the Stellar Population in Baade’s Window

1983 ◽  
Vol 5 (2) ◽  
pp. 214-217
Author(s):  
R. A. Ruelas-Mayorga ◽  
A. R. Hyland
Keyword(s):  
Stellar Population ◽  
Spectroscopic Studies ◽  
Galactic Centre ◽  
Galactic Bulge ◽  
General Direction

Baade (1963) pointed out three regions of low obscuration in the general direction of the galactic centre, wherein a stellar population assumed to be characteristic of the galactic bulge could be studied.

Statistical criteria of stellar population types

1966 ◽  
Vol 24 ◽  
pp. 101-110
Author(s):  
W. Iwanowska
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Spectrophotometric Study ◽  
Physical And Chemical Properties ◽  
Population Type ◽  
The Galaxy ◽  
Distribution Parameters ◽  
Physical And Chemical ◽  
Statistical Criteria ◽  
And Chemical Properties

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.

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