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Home , FSR 1758, Galactic astronomy, Milky Way (mythology)

A sequoia in the garden: a dwarf or a giant hidden in the bulge?

Rodolfo H. Barbá

Universidad de La Serena Chile

Modern Cosmography: Playing the game of big panchromatic all-sky surveys

Cosmography is the science that maps the general features of the cosmos or , describing both heaven and Earth.

In , the term is beginning to be used to describe attempts to determine the large-scale matter distribution and kinematics of the (Wikipedia)

In collaboration with:

Dante Minniti (UNAB) Doug Geisler (ULS-UdeC) Javier Alonso-García (UA) Maren Hempel (UNAB) Antonela Monachesi (ULS) Julia Arias (ULS) Facundo Gómez (ULS)

Motivation

● Large multi-frequency, synoptic, and all-sky surveys are opening new horizons in the heaven exploration.

● For Galactic , relevant are: VVV, UKIDDS, Glimpse, WISE, DECaPS, SkyMapper, PANSTARRS, Herschel, etc.

● DR2 is opening a Pandora’s Box, and transforming our knowledge about the structure.

● Tens of large scale new structures discovered.

DECaPS

● Dark Energy Camera Survey http://decaps.skymaps.info

● DECAM: 520 mpix, 4-m Blanco Telescope, CTIO (Chile)

● Southern GP, 1000 sq-deg (|b| < 4º).

● Very deep, limits g~23.7, r~22.8, i~22.2, z~21.8, and Y~21.0

● Details in Schlafly et al. 2018.

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0 I [deg] 10 0 -10 X (kpc) Fig. 2. ill maps at different velocities for the inner Galactic plane, for 342.6 < l < 353.4 and -1.4 < b < 1.4. Top: ill emission for velocities Fig. 6. Schematic map of the MW adapted from Vallee (2014) indicat­ between - 15 to - 20 kmfs. Middle: Same for velocities between -3 0 to ing the position of the and the line of sight through the window. -42 km/s. The location of the low extinction window is indicated with We adopted a distance to the Galactic centre of R0 = 8 kpc. According the circle. Bottom: Same for velocities between -150 to -185 km/s. to this picture, the line of sight should pass through the Sagittarius arm and the end of the long bar, and the far side of the Norma and Scutum­ Centaurus arms. Red circles mark corresponding distances for the main peaks using AKs = 0.484 x E(J - Ks). Using AKs = 0.725 x E(J - Ks) the distances are systematically shorter (black diamonds).

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Large, distinctive stellar structure identified in DECaPS, VVVX images, and GDR2 data.

CMDs produced with DECaPS and VVVX show clear signature of a large metal-poor cluster, with prominent RGB and extended blue BHB.

Estimated heliocentric distance of about 11.0 kpc, Dgal = 3.7 kpc, z = -0.75 kpc (from RRab, BHB-RGBb)

Metal-poor [Fe/H] = -1.5 +/- 0.3

Rc = 10 +/- 1 pc, Rt = 150 +/- 40 pc, c = 1.2 (typical for GCs)

GDR2 PM selected stars show a extended tidal tail.

FSR 1758 is not related to other GC in the area.

Luminosity, i-band Mi < -8.5, large size competing with ω Cen → very bright GC or ().