J/MNRAS/442/3544 Kinematic tracers in Umbrella galaxy (NGC4651) (Foster+, 2014) ================================================================================ Kinematics and simulations of the stellar stream in the halo of the Umbrella galaxy. Foster C., Lux H., Romanowsky A.J., Martinez-Delgado D., Zibetti S., Arnold J.A., Brodie J.P., Ciardullo R., Gabany R.J., Merrifield M.R., Singh N., Strader J. =2014MNRAS.442.3544F ================================================================================ ADC_Keywords: Galaxies, photometry ; Clusters, globular ; H II regions ; Planetary nebulae ; Photometry, SDSS Keywords: galaxies: individual: NGC 4651 - galaxies: interactions - galaxies: kinematics and dynamics Abstract: We study the dynamics of faint stellar substructures around the Umbrella Galaxy, NGC 4651, which hosts a dramatic system of streams and shells formed through the tidal disruption of a nucleated dwarf elliptical galaxy. We elucidate the basic characteristics of the system (colours, luminosities, stellar masses) using multiband Subaru/Suprime-Cam images. The implied stellar mass ratio of the ongoing merger event is ~1:50. We identify candidate kinematic tracers (globular clusters, planetary nebulae, HII regions) and follow up a subset with Keck/DEIMOS (DEep Imaging Multi-object Spectrograph) spectroscopy to obtain velocities. We find that 15 of the tracers are likely associated with halo substructures, including the probable stream progenitor nucleus. These objects delineate a kinematically cold feature in position-velocity phase space. We model the stream using single test particle orbits, plus a rescaled pre-existing N-body simulation. We infer a very eccentric orbit with a period of ~0.35Gyr and turning points at ~2-4 and ~40kpc, implying a recent passage of the satellite through the disc, which may have provoked the visible disturbances in the host galaxy. This work confirms that the kinematics of low surface brightness substructures can be recovered and modelled using discrete tracers - a breakthrough that opens up a fresh avenue for unravelling the detailed physics of minor merging. Description: In an effort to better define the properties of the faint substructures, new images were obtained on the nights of 2011 January 3 and 4 in photometric conditions using the Suprime-Cam wide-field camera (34x27arcmin^2^ field of view) on the 8.2m Subaru telescope. NGC 4651 was imaged under 0.9, 0.6 and 0.9 arcsec seeing in the g'-band (1300s), r'-band (500s) and i'-band (505s) filters, respectively, using a preset dithering pattern that offset successive images in order to compensate for gaps between Suprime-Cam's 10 CCDs (laid out in a 5x2 xrid). An [OIII] narrow-band image (4860s) was also acquired for HII region and PN candidate selection, under 1.2-arcsec seeing. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 91 810 Catalog of photometrically selected globular cluster candidates table3.dat 91 64 Catalog of photometrically selected HII region candidates table4.dat 91 39 Catalog of photometrically selected planetary nebula candidates table5.dat 100 46 Summary of measured kinematic tracers -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat table3.dat table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Name Candidate name 11 A1 --- n_Name [*] * for spectroscopically confirmed 13- 14 I2 h RAh Right ascension (J2000) 16- 17 I2 min RAm Right ascension (J2000) 19- 24 F6.3 s RAs Right ascension (J2000) 26 A1 --- DE- Declination sign (J2000) 27- 28 I2 deg DEd Declination (J2000) 30- 31 I2 arcmin DEm Declination (J2000) 33- 38 F6.3 arcsec DEs Declination (J2000) 40- 45 F6.3 mag gmag ?=- Subaru/Suprime g magnitude (not for PN) 47- 52 F6.3 mag e_gmag ?=- rms uncertainty on gmag 54- 59 F6.3 mag rmag ?=- Subaru/Suprime r magnitude (not for PN) 61- 65 F5.3 mag e_rmag ?=- rms uncertainty on rmag 67- 72 F6.3 mag imag ?=- Subaru/Suprime i magnitude (not for PN) 74- 78 F5.3 mag e_imag ?=- rms uncertainty on imag 80- 85 F6.3 mag m5007 [21/29]?=- Subaru/Suprime [OIII] (5007{AA}) magnitude 87- 91 F5.3 mag e_m5007 ?=- rms uncertainty on m5007 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 A6 --- Type Type (Nuclei, PNe, HII or GCs) 8- 18 A11 --- Name Name 20- 21 I2 h RAh Right ascension (J2000) 23- 24 I2 min RAm Right ascension (J2000) 26- 30 F5.2 s RAs Right ascension (J2000) 32 A1 --- DE- Declination sign (J2000) 33- 34 I2 deg DEd Declination (J2000) 36- 37 I2 arcmin DEm Declination (J2000) 39- 42 F4.1 arcsec DEs Declination (J2000) 44- 47 I4 km/s Vobs Observed heliocentric corrected recession velocity 49- 50 I2 km/s e_Vobs rms uncertainty on Vobs 51 A1 --- n_Vobs [a] a: measured from the higher resolution long-slit spectrum (1) 52- 56 F5.2 mag gmag ?=- Subaru/Suprime-Cam foreground extinction corrected g' magnitude 58- 61 F4.2 mag e_gmag ?=- rms uncertainty on gmag 62 A1 --- n_gmag [c] c: photometry affected by crowding (1) 64- 68 F5.2 mag rmag ?=- Subaru/Suprime-Cam foreground extinction corrected r' magnitude 70- 73 F4.2 mag e_rmag ?=- rms uncertainty on rmag 74 A1 --- n_rmag [c] c: photometry affected by crowding (1) 76- 80 F5.2 mag imag ?=- Subaru/Suprime-Cam foreground extinction corrected i' magnitude 82- 85 F4.2 mag e_imag ?=- rms uncertainty on imag 86 A1 --- n_imag [c] c: photometry affected by crowding (1) 88- 91 F4.1 mag m5007 ?=- Subaru/Suprime-Cam foreground extinction corrected [OIII] (5007{AA}) magnitude 93- 95 F3.1 mag e_m5007 ? rms uncertainty on m5007 96 A1 --- n_m5007 [b] identified by eye on image (1) 98-100 A3 --- Disc [Yes/No] whether or not the kinematics are consistent with the disc of NGC 4651 -------------------------------------------------------------------------------- Note (1): Notes as follows: a = measured from the higher resolution long-slit spectrum b = identified by eye on image c = photometry affected by crowding -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Patricia Vannier [CDS] 05-Mar-2015