GALACTICNUCLEUS: A high-angular-resolution JHK_s imaging survey of the Galactic centre

Abstract

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.

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

“…Finally, we also find that the calculated extinction indices, α JH and α HK s , do not depend on the line-of-sight and can be assumed as constant within the given uncertainties and the analysed regions, which is in agreement with previous works (Nogueras-Lara et al 2019a;Deno Stelter & Eikenberry 2020). For this analysis, we considered all the fields observed in the GALACTICNUCLEUS survey, except for the NSD W because its low quality impeded this study.…”

“…In this paper, we analyse in detail the extinction curve towards the GC in the NIR by applying independent methods based on RC stars. For the first time, we used the whole GALACTICNU-CLEUS survey (Nogueras-Lara et al 2019a) and extended the study of the extinction to a large area of the NSD, the inner bulge, and the transition region between the GC and the inner bulge, covering a total area of ∼6000 pc 2 . For the analysis, we used more than 165 000 stars in the RC feature detected in all three bands, JHK s , of the GALACTICNUCLEUS survey, superseding our previous study by a factor ∼3 (Nogueras-Lara et al 2019b).…”

“…The photometry reaches 5 σ detections for J ∼ 22, H ∼ 21, and K s ∼ 21 mag. The statistical uncertainties are below 0.05 mag at J 21, H 19, and K s 18 mag (Nogueras-Lara et al 2019a). This allows us to properly cover RC stars (e.g.…”

“…This work makes use of the GALACTICNUCLEUS survey (Nogueras-Lara et al 2018a, 2019a carried out using the HAWK-I camera (Kissler-Patig et al 2008) at the ESO VLT unit telescope 4, which includes accurate JHK s photometry of more than 3.3 million stars located in the GC and inner regions of the Galactic bulge. Figure 1 shows the fields included in the GALACTICNUCLEUS survey: three different regions distributed along the GC (Central, NSD East, and NSD West), two regions in the inner Galactic bulge (inner bulge South and inner bulge North), and two transition regions (transition East and West).…”

“…Nishiyama et al 2008;Schödel et al 2010;Nogueras-Lara et al 2018a) that limits the stellar analysis to near-and mid-infrared observations. In this sense, the GALAC-TICNUCLEUS survey (Nogueras-Lara et al 2018a, 2019a constitutes the most complete high-angular resolution (∼0.2 ) catalogue available to properly characterise the stellar population in the GC. This is a near infrared (NIR) multi-wavelength (JHK s ) survey that covers a total area of ∼0.3 square degrees (∼6000 pc 2 ) along the NSD, the inner bulge, and the transition regions between the inner bulge and the NSD (see Fig.…”