Blas;ng Away a Dwarf Galaxy: The Tail of ESO 324- G024

Transcription

1 Blas;ng Away a Dwarf Galaxy: The Tail of ESO 324- G024 Megan Johnson PHISCC Workshop March 2015 CSIRO ASTRONOMY AND SPACE SCIENCE, ATNF

2 Collaborators Bärbel Koribalski Peter Kamphuis Jing Wang Sebas9an Hann Alex Hill Julie Banfield Amy Kimball Paolo Serra Ron Ekers Shane O Sullivan UNAM Se- Heon Oh ICRAR, UWA CSIRO Astronomy and Space Science

3 Outline ² Introduction to ESO 324-G024 and NGC 5128 ² Data suite ² ² Radio spectral line, continuum IR, Optical, UV photometry ² Results

4 Outline ² Introduction to ESO 324-G024 and NGC 5128 ² Data suite ² ² Radio spectral line, continuum IR, Optical, UV photometry ² Results

5 Centaurus A Galaxy Group

6 NGC 5128 and ESO 324- G024

7 Outline ² Introduction to ESO 324-G024 and NGC 5128 ² Data suite ² ² Radio spectral line, continuum IR, Optical, UV photometry ² Results

8 Cen A Radio 1.4 GHz Con;nuum Data Shane O Sullivan: Ø Polarized Intensity Map Ø Rotation Measure Map O Sullivan+ 13

9 Cen A Radio 5 GHz Con;nuum Data Shane O Sullivan: Ø Polarized Intensity Map Ø Fractional Polarized Intensity Map % Polarized Junkes+ 93

10 Fornax A and NGC 1310 Images courtesy Shivanish Kochhar via Brian Gaensler via Ron Ekers PHISCC Mee9ng 2015 Megan Johnson

11 ESO 324- G024 IR, Op;cal, UV Data Jing Wang: SFRFUV+22μm = 1.14(±0.17) x 10-2 M yr- 1 SFRHα = 1.9 x 10-2 M yr- 1 (Lee+ 09) ΣSFRHα = 5-9 x 10-3 M yr- 1 kpc- 1 Hα Equivalent Width = 44 ± 11 Å (Kennicuh+ 08) τgas = Total Gas Mass / SFR = ~13 Gyr è (Weak?) Starburst dirr galaxy! PHISCC Mee9ng 2015 Megan Johnson

12 ESO 324- G024 Magne;c Field Strength LMC has a total magnetic field strength, B T = 4.3 µg (Gaensler+ 05) Thus, it is likely that if ESO 324-G024 were in front of or inside the northern radio lobe of NGC 5128, we would see depolarization in the lobe. We see no depolarization and therefore, conclude that ESO 324-G024 must be behind the lobe. ESO 324-G024 ~ 5-ish µg Chyży+ 11

13 ESO 324- G024 and Possible Orienta;on for Northern Radio Lobe of NGC 5128

14 Outline ² Introduction to ESO 324-G024 and NGC 5128 ² Data suite ² ² Radio spectral line, continuum IR, Optical, UV photometry ² Results

15 The Effects of Cen A s radio lobe on ESO 324- G024 Seb Haan: Tidal Forces are likely not the dominant stripping mechanism in ESO 324-G024 r T = 11 kpc (compared to maximum radius 6 kpc) No stellar tidal feature observed No counter HI tail Binney & Tremaine (1987): R = 125 kpc = distance from ESO 324-G024 to center of NGC 5128 m = 2.5 x 10 9 M = total dynamical mass of ESO 324-G024 M = 1.3 x M = total dynamical mass of NGC 5128 (Woodley+ 07)

16 The Effects of Cen A s radio lobe on ESO 324- G024 Seb Haan: Ram pressure is the most probable mechanism responsible for the creation of the HI tail in ESO 324-G024 min p ram = 16 (km/s) 2 cm -3 min ρ IGM = 10-3 cm -3 This density may not be unreasonable for the shell edges of the northern radio lobe, although O Sullivan+ 13 find a volume averaged density inside the lobe of 10-4 cm -3 Σ gas = cm -2 = gas surface density v rot = 54 km/s = rotation velocity R HI = 6 kpc = radius of HI disk ρ IGM = density of the intergalactic medium (IGM) v gal = 114 km/s = velocity of galaxy through IGM, taken to be the average velocity dispersion of the galaxy group (van den Bergh 00)

17 Results Ø There is no depolariza9on signature in the 1.4 or 5 GHz con9nuum data of the northern radio lobe of Cen A at the loca9on of ESO 324- G024 Ø ESO 324- G024 has a SFR and other characteris9cs common to starburst dirr galaxies, implying that there is a supply of magneto- ionic material to cause a depolariza9on signature if it were in front of or inside the lobe Ø ESO 324- G024 is most likely behind the northern radio lobe of Cen A Ø Tidal forces alone are likely not enough to cause the HI tail in ESO 324- G024 Ø Ram pressure stripping appears to be the most probable mechanism for crea9ng the HI tail in ESO 324- G024

18 Thank you CASS Megan Johnson OCE Postdoctoral Fellow t e megan.johnson@csiro.au w CSIRO ASTRONOMY AND SPACE SCIENCE/ATNF

19 ESO 324- G024 RM Dispersion Alex Hill/Julie Banfield: Minimum rota9on measure dispersion for ESO 324- G024 = σ RM < 9 rad m - 2 L = linearly polarized intensity λ = wavelength p = depolarization factor

20 ESO 324- G024 Radio 20 cm HI Spectral Line Data Local Volume HI Survey (LVHIS) Data: Bärbel Koribalski

21 ESO 324- G024 3D HI Gas Kinema;cs Peter Kamphuis (see Kamphuis+ 2015, in prep): Tilted-Ring Fitting Code (TiRiFiC) Models motions of the HI gas in a rotating disk galaxy in three dimensions Model 1: Made using all of the HI intensity, including the HI tail Model 2: Made without using the HI tail

22 ESO 324- G024 2D HI Gas Kinema;cs Se-Heon Oh: Double Gaussian Decomposition Separates non-circular from circular motions in a rotating disk galaxy PHISCC Mee9ng 2015 Megan Johnson

23 ESO 324- G024 Rota;on Curve and Mass Models <V max >= 54 km/s