PISCES II & PEGASUS III: TWIN SISTERS OR ONLY GOOD FRIENDS?

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1 PISCES II & PEGASUS III: TWIN SISTERS OR ONLY GOOD FRIENDS? ALESSIA GAROFALO 1,2 1-DIPARTIMENTO DI FISICA E ASTRONOMIA-UNIVERSITÀ DI BOLOGNA 2-INAF-OSSERVATORIO ASTRONOMICO DI BOLOGNA!! 1 TEAM WORK: MARIA TANTALO, FELICE CUSANO, GISELLA CLEMENTINI 2 AND TATIANA MURAVEVA! 2! 2 TH FLORENCE JUNE, LBTO USER S MEETING 2017

2 OUTLINE DWARF SPHEROIDAL & ULTRA FAINT DWARF GALAXIES SURROUNDING THE MILKY WAY PISCES II AND PEGASUS III WHY? PISCES II AND PEGASUS III Our observations goals & methods Results & Discussion Future studies

3 DWARF SPHEROIDAL & ULTRA-FAINT DWARF GALAXIES SURROUNDING THE MILKY WAY GAS-FREE SYSTEMS dsphs STRONGLY DARK MATTER DOMINATED NOT ROTATIONALLY SUPPORTED FOUND NEARBY MASSIVE GALAXIES PegasusIII UFD CLEMENTINI 2010 L vs Rh DIAGRAMM OF CLASSICAL AND UFD dsphs AROUND THE MW AND M31

4 DWARF SPHEROIDAL & ULTRA-FAINT DWARF GALAXIES SURROUNDING THE MILKY WAY FA M ILY P O R T R A IT UFDs dsphs LeoT Gaia2 Gaia1 Col1 CetIII CetII UPDATED TO 2017 DISCOVERED 44 UFDs, 27 (61%, from DES, Pan-STARRS, VST ATLAS )

5 DWARF SPHEROIDAL & ULTRA-FAINT DWARF GALAXIES SURROUNDING THE MILKY WAY >> LOW SURFACE BRIGHTNESS μv 28 mag/arcsec 2 >> HOSTING MOSTLY AN ANCIENT STELLAR POPULATION ( 10 Gyr) >> HIGH M/L ( 100) SYSTEMS STRONGLY DARK MATTER DOMINATED >> RR LYRAE STARS PULSATIONAL PROPERTIES >> METAL-POOR [Fe/H] -2, -3 dex >> IRREGULAR/DISTORTED SHAPE MW TIDAL INTERACTIONS

6 VARIABLE STARS & UFDS >> THE MOST COMMON PULSATING VARIABLE STARS IN dsphs and UFDs RR LYRAE STARS MASS FROM 0.6 TO 0.8 MSUN PERIOD FROM 0.3 TO 1 days; AMPLITUDE V mag PRIMARY DISTANCE INDICATORS OLD STELLAR POPULATION TRACERS (t>10 Gyr) >> ACCORDING TO <Pab> (Oosterhoff 1939) (GGCs, HALO FIELDs) Oo-I <Pab>=0.55d fc=0.17 Oo-II <Pab>=0.64d fc=0.44 [Fe/H] ~ -1.5 dex [Fe/H] ~ -2 dex

7 PISCES II & PEGASUS III news from scientific literature MEMBERS (7) X NOT-MEMBERS σ[fe/h] <0.5 dex (4/7) <2rh DISCOVERED BY SDSS DR7 (Belokurov+2010) 13.5Gyr -2.0 Mv = -4.1 ± 0.4 mag rh = 1.09 ± 0.19 (58 ±10 pc) d=183 ± 15 kpc r=4 GC-M92 <[Fe/H]> =-2.45 ± 0.07 dex σv 5.4± km/s <v > ± 2.7 km/s 13.5Gyr Gyr Gyr -1.5 KIRBY+2015 SAND+2012

8 PISCES II & PEGASUS III news from scientific literature DISCOVERED BY SDSS DR10 - CONFIRMED WITH DECam (Kim+2015) X Mv = -3.4 ± 0.4 mag rh = 0.85 ± 0.22 (53 ±14 pc) 10 x Gyr Gyr -1.1 KIM+2015 d=215 ± 12 kpc! <[Fe/H]> =-2.55 ± 0.15 dex σv 5.4± ! km/s <v > ± 2.6 km/s AMBIGOUS (1) MEMBERS (7) NOT-MEMBERS (4) <3rh KIM+2016

9 PISCES II & PEGASUS III PEG III and PSC II SHARE SIMILAR PROPERTIES Our proposal G.CLEMENTINI ASK TO OBTAIN B and V time-series TO: PEG III + PSC II + 10 fields a.derive PROPERTIES (AGES METALLICITIES, DISTANCE MODULI, Oo-TYPE, SPATIAL DISTRIBUTION) OBSERVABLES PegIII SAND+2012 PULSATING VARIABLES FOUND IN THE UFDS COLOR-MAGNITUDE DIAGRAM (CMD) OF THE RESOLVED STELLAR POPULATIONS GC b.investigate SIGNATURES OF A PHYSICAL CONNECTION BETWEEN PEG III and PSC II (SIMILAR DISTANCE FROM US, 8 APART IN THE SKY)

10 PISCES II rh = 1.09 ± 0.19 (58 ±10 pc) RRab RRab/AC? MEMBERS (Kirby+2015) SXPhe SXPhe? DATES N FILTER TEXP SEEING OCTOBER-DECEMBER B - 26 V 180s V2 SX Phe? rh V4 RRab/AC? 2rh 3rh P=0.722/ d not calibrated PSF PHOTOMETRY DAOPHOT-ALLSTAR-ALLFRAME LIGHT CURVE CLASSIFICATION AND STUDY GRATIS 1RRAB 1SXPHE? 1SXPHE 1RRAB/AC? <rh <3rh >3rh V4 IS 0.25 mag BRIGHTER THAN V1

11 PISCES II RRLs/AC KIRBY+2015 SXPhe

12 PISCES II <2rh (m-m) = ± 0.14 mag 0 d = 175± 11 kpc d=183 ± 15 kpc E(B-V) = ± mag E(B-V) RR = ± mag (Piersimoni+02)

13 PISCES II <2rh 13Gyr Gyr Gyr Gyr Gyr -1.5 (m-m) = ± 0.14 mag 0 d = 175± 11 kpc d=183 ± 15 kpc E(B-V) = ± mag E(B-V) RR = ± mag (Piersimoni+02) HB + RGB stars best matched: stellar population 12 Gyr old with [Fe/H] =-1.8 /-1.7 dex RIDGE LINES FROM CMD 2.7 (Bressan+12)

14 PISCES II <2rh 13Gyr Gyr Gyr Gyr Gyr -1.5

15 PISCES II PEGIII MS+RGB stars 23 x 23 HB MS+RGB PEGIII HB stars ISODENSITY CONTOURS REVEAL A SIMMETRICAL AND REGULAR SHAPE

16 DATES N FILTER TEXP SEEING PEGASUS III OCTOBER-DECEMBER B - 28 V 180s RRAB 1RRAB/AC? <5rh 10rh 4 AUXILIARY PHASE-POINTS FROM SDSS DATA V2 IS 0.20 mag BRIGHTER THAN V1 V2 RRab? (as V4 in PSC II) RRab RRab/AC MEMBERS (Kim+2016) AMBIGOUS V2 AC? rh 2rh rh = 0.85 ± 0.22 (53 ±14 pc) 10rh 3rh 5rh DURING PEG III OBSERVATIONS

17 DATES N FILTER TEXP SEEING PEGASUS III OCTOBER-DECEMBER B - 28 V 180s RRAB 1RRAB/AC? <5rh 10rh 4 AUXILIARY PHASE-POINTS FROM SDSS DATA V2 IS 0.20 mag BRIGHTER THAN V1 V2 RRab? (as V4 in PSC II) RRab RRab/AC MEMBERS (Kim+2016) AMBIGOUS V2 AC? rh rh 2rh 3rh ZOOMING OUT 10rh 5rh UNREQUESTED ROTATION OF LBT!!!

18 PEGASUS III (KIM+2016) s members 13Gyr Gyr Gyr Gyr rh (m-m) = ± 0.26 mag 0 d = 174± 21 kpc d=215 ± 12 kpc E(B-V) = 0.13 ± 0.04 mag E(B-V) RR = 0.16 ± 0.05 mag HB + RGB stars best matched: stellar population 13 Gyr old with [Fe/H] =-1.7/-1.6 dex RIDGE LINES FROM CMD 2.9

19 PEGASUS III 23 x23 (KIM+2016) s members 5rh 13Gyr Gyr Gyr Gyr -2.2 MS+RGB stars RIDGE LINES FROM CMD 2.9 FAKE DUE TO LBT ROTATION PSCII

20 PISCES II & PEGASUS III UFDs # RRL <Pab> Oo-Type Pisces II Oo-I Pegasus III Oo-I

21 SUMMARY & RESULTS WE IDENTIFIED IN PSC II AND PEG III 3 AND 2 VARIABLE STARS RESPECTIVELY. WE RE- DEFINED THEIR DISTANCES THE COMPARISON OF THE CMDS WITH STELLAR ISOCHRONES REVEALS THE PRESENCE OF AN OLD STELLAR POPULATION (12-13 Gyr), WITH [Fe/H] >-1.8 dex IN BOTH GALAXIES higher than the spectroscopic estimates, higher than the typical UFDs metallicity WE CLASSIFIED PSC II AND PEG III AS AN OO-I SYSTEMS BASED ON THE PERIOD OF ONLY THE INNER RR LYRAE STAR THE FIRST UFDS OO-I SYSTEMS ISODENSITY CONTOURS DO NOT SEEM TO SHOW EVIDENCE FOR AN IRREGULAR SHAPE WHICH MIGHT HINT TO THE EXISTENCE OF A LINK/STREAM CONNECTING GALAXIES TO BETTER CONSTRAIN UNCERTAIN PERIODS (V4, V2) WE ARE COLLECTING ABOUT NEW 10 PHASE POINTS (JUNE 2017) IMPROVING LIGHT CURVES SAMPLING SEPTEMBER? THIS IS THE INSTRUMENT, THIS IS THE TIME!

22 THANK YOU!

23 ACS OR RRLS? MACs [Fe/H]ACs from 1.8 to 2.2 MSUN > -1.8 dex Fixed MACs and [Fe/H]ACs Fixed PISCES II /PEGASUS III distance a) Adopting EVOLUTIVE TRACKS FROM BASTI (Pietrinferni+2004) NO AC beloging to PISCES II /PEGASUS III AC field (background)? b) Adopting PERIOD-WESENHEIT RELATION for ACs V2 AND V4 are about 0.2 mag BRIGHTER THAN inner RRLs YES, AC beloging to PISCES II /PEGASUS III TOTALLY IN DISAGREEMENT RRL field (foreground)? Oo-II

24 PISCES II RAW 23 x 23 CORRECTION FOR DAOPHOT QUALITY IMAGE PARAMETERS

25 PISCES II CLEAN

26 PISCES II <2rh

27 PISCES II <1rh

28 PISCES II <2rh

29 PISCES II RRLs/AC SXPhe

30 PISCES II KIRBY+2015

31 Togliere

32 Togliere

33 PISCES II 13Gyr -2.3 <2rh (m-m) = ± 0.14 mag 0 d = 175± 11 kpc E(B-V) = ± mag E(B-V) RR = ± mag (Piersimoni+02) RIDGE LINES FROM CMD 2.7 (Bressan+12)

34 PISCES II <2rh 13Gyr Gyr -2.0 RIDGE LINES FROM CMD 2.7 (Bressan+12)

35 PISCES II <2rh 13Gyr Gyr Gyr -1.8 RIDGE LINES FROM CMD 2.7 (Bressan+12)

36 PISCES II <2rh 13Gyr Gyr Gyr Gyr -1.7 RIDGE LINES FROM CMD 2.7 (Bressan+12)