A new near-IR window of low extinction in the Galactic plane

Abstract

Aims. The windows of low extinction in the Milky Way (MW) plane are rare but important because they enable us to place structural constraints on the opposite side of the Galaxy, which has hitherto been done rarely. Methods. We use the near-infrared (near-IR) images of the VISTA Variables in the Vía Láctea (VVV) Survey to build extinction maps and to identify low extinction windows towards the Southern Galactic plane. Here we report the discovery of VVV WIN 1713−3939, a very interesting window with relatively uniform and low extinction conveniently placed very close to the Galactic plane. Results. The new window of roughly 30 arcmin diameter is located at Galactic coordinates (l, b) = (347.4, −0.4) deg. We analyse the VVV near-IR colour-magnitude diagrams in this window. The mean total near-IR extinction and reddening values measured for this window are A K s = 0.46 and E(J − K s ) = 0.95. The red clump giants within the window show a bimodal magnitude distribution in the K s band, with peaks at K s = 14.1 and 14.8 mag, corresponding to mean distances of D = 11.0 ± 2.4 and 14.8 ± 3.6 kpc, respectively. We discuss the origin of these red clump overdensities within the context of the MW disk structure.

VVV WIN 1733−3349: a low extinction window to probe the far side of the Milky Way bulge

“…The slope of the reddening vector is flatter than A K s = 0.725 × E(J − K s ) from Schlegel et al (1998), but steeper than A K s = 0.528 × E(J − K s ) from Nishiyama et al (2009). These values are much steeper than the slope in Alonso-García et al (2017) and Minniti et al (2018), where spectively. The use of a different extinction law causes the distance scale to shrink/expand.…”

The structure behind the Galactic bar traced by red clump stars in the VVV survey

“…The applications of this reddening map range from the study of stellar populations such as age determinations via turn-off fitting, structure from the construction of the LF and fitting of the RC, as well as photometric first guess stellar parameters for spectroscopic abundance analysis. It can also be used to identify and explore new regions of low reddening in the VVV area (Minniti et al 2018). Here we identify a new low-reddening window in the Galactic plane located at (l, b) = (−5.2 • , −0.3 • ) (see Fig.…”

Milky Way demographics with the VVV survey

“…The area surveyed in the disk is located at very low Galactic latitudes (|b| < 2 • .25). Although our new PSF photometry allows the identification of new low-extinction windows (Minniti et al 2018), these low latitudes imply that most of the CMDs suffer the effect of heavy extinction. The small range in Galactic latitude and large range in longitude covered (see Fig.…”

“…RC stars in the disk have proven to be a useful way in tracing its shape. Using the RC stars found with our new PSF photometry in the newly discovered low-extinction Dante's window, Minniti et al (2018) has been able to trace different components of the spiral arms, while Minniti et al (2011) trace the edge of the Galactic disk following the rapid decline and termination of the RC sequence along different lines of sight on the UKIDSS and VVV fields, using for these last ones a first implementation of our PSF photometry. Finally, the sequence of the K and M dwarfs from the thin disk is clearly distinct at J − K s ∼ 0.85 and 14 < K s < 16, in a similar position as shown in the left panel of Fig.…”