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A Sequoia in the Garden: a Dwarf Galaxy Or a Giant Globular Cluster Hidden in the Bulge?

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A Sequoia in the Garden: a Dwarf Galaxy Or a Giant Globular Cluster Hidden in the Bulge? A sequoia in the garden: a dwarf galaxy or a giant globular cluster 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 universe, describing both heaven and Earth. In Astrophysics, the term is beginning to be used to describe attempts to determine the large-scale matter distribution and kinematics of the observable universe (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 Astronomy, relevant are: VVV, UKIDDS, Glimpse, WISE, DECaPS, SkyMapper, PANSTARRS, Herschel, etc. ● Gaia DR2 is opening a Pandora’s Box, and transforming our knowledge about the Milky Way structure. ● Tens of large scale new structures discovered. DECaPS ● Dark Energy Camera Galactic Plane 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. �������� ������������ /*" &!�J��� ��� ���������� � � ������������ /*" &!J1��$%�� ������ �!�"��������� � � /*" &!J-+!* � �� ����#�������������� � � /*" &!J-+!* ����� ���$$$�% ���& 01"�KF=G 9��:? �"-�A:> 01"�KFF? �"-�A:: � � VVV Window – Minniti et al 2018, A&A, 616, A26 ........., o.O 1 Q) '"d 0 L......J ..Q - 1 E(J -Ks ) 2 ........., o.O 1 Q) '"d 0 L......J ..Q - 1 - 2 35 0 345 34 0 335 33 0 325 1 [ deg] 3 1.44 0 2.5 1.20 ........., 2 0.96 o.O ---~ U) Q) U) '"d ::.::: L......J ~ 1.5 0.72 ~ '----" ..Q - 0.5 ~ 1 0.48 0.5 0.24 0 0.00 - 1 348.5 348 347 346.5 VVV Window – Minniti et al 2018, A&A, 616, A26 ------ .,,,,... .... -- / / / I ' I ' \ I \ I \ I \ I \ ,-..._ u I I I I ~ o I I >- I I \ I \ I \ I \ I \ I I ' / / ' / ' ' .,,/ ' ..... --- --- -,,... 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 Sun 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). /*" &! � � /*" &! � � '�(� )�* /*" &! '����� �+������,�"��) � � /*" &!�J�777N *���������1�)��������� ������� &��$���������)���������������� �1����$%����8OAF�?�2'8O>�H= "�$% ����������01"�KK?:)� 01"�KK:K /�O�AA�=�J<'�A�>�(%� /� ��O�F�G�(%������6�O�'G=>�%� "�$ %����������#F)�#AF P4�<�Q�O�'A�=�J<'�>�F���� � � 1 � ;��� $��J�@1 * � &#�%���)����������� RS�O�':�H=�$ �< RT�O�:�==�$ �< � " �� �'1 �������� ���,:>AH.� ���� ����������������������������1 � ;�� %��%����������A::U��������� � ��� ����� �� � =���' ���� ���C&V�O�>�KH?�� � @����������++�W�$�� �'%����1" � /�O�A>�A�J<'�A�>�(%� � � 1 � ;��� $��J�@1 * � � /*" &! � 8���;��%������)��'� �� "����� ������F;�J<'�>�:; 9�� ��� ������?=;�J<'�A:; ���O�A>�J<'�A�%� ���O�A=>�J<'�?>�%� � "������� ������������A�: 9�%�� �����1"� � �$���������#��C�'H�= � 7������������)���$�� ����� �$�� �"�� � � 1 � ;��� $� 1/�:�&#������������ �������� ������������� ��� ����������$�� ��&#� �1�� ��������� ��� �������������������� �(� � � @�����1"��������� �� 4!��AG=H 01"�KFH> "�$% �����������1"�������� �� � 01"�KFH>)���% � �����>�HD)�����$����$�� �'�����P4�<�Q�O�'>�H����)�������$�� � ����������������� ���� � 9���:)���% � �����A�?D)� � ���P4�<�Q�O�'>�G)��������/�O�H�:�(%�� � � Conclusions Large, distinctive stellar structure identified in DECaPS, VVVX images, and GDR2 data. CMDs produced with DECaPS and VVVX photometry 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 dwarf galaxy (Scorpius). .
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