The Role of Gas in Galaxy Dynamics October 3 rd , Malta H I clouds near the Galactic Center: Possible tracers for a Milky-Way nuclear wind? Enrico Di Teodoro Enrico Di Teodoro Enrico Di Teodoro Research School of Astronomy and Astrophysics Research School of Astronomy and Astrophysics Research School of Astronomy and Astrophysics Australian National University Australian National University Australian National University Collaborators: Naomi McClure-Griffiths (RSAA), Felix J. Lockman (NRAO-GBT) Gas in Galaxies - Malta Gas in Galaxies - Malta
Galactic Wind In The Milky Way Galactic Wind In The Milky Way Our Galaxy has its own wind! Giant lobes extending to 8-10 kpc Ackermann et al., 2014 Bi-conical outflow generated a few 10 6 years ago by either SF (Crocker+11) or SMBH (Yang+12) Fermi Bubbles ATCA H I Data Wind model McClure-Griffiths+13 found 86 clouds at the GC not following rotation Entrained in a wind at ~200 km/s Gas in Galaxies - Malta Gas in Galaxies - Malta
A new Green Bank Telescope survey A new Green Bank Telescope survey -10 -5 0 5 10 A new survey with 100 m GBT Galactic Latitude (deg) single-dish telescope to widen McClure-Griffiths+13 work ATCA GBT High sensitivity -10 -5 0 5 10 Galactic Longitude (deg) ATCA-GC GASS (HI4PI) GBT (McClureGriffiths+13) (McClureGriffiths+09) (Di Teodoro+, subm.) (l,b) region ± 4º All sky ± 10º Velocity range (km/s) ± 250 ± 450 ± 650 Spatial resolution (arcmin) 2.4 15.9 9.1 Channel width (km/s) 1.00 0.82 0.90 Sensitivity (Kelvin) 0.700 0.057 0.025 Gas in Galaxies - Malta Gas in Galaxies - Malta
Masking the MW disk emission Masking the MW disk emission GOAL: detecting and studying anomalous clouds above and below the GC Masking the MW disk by modelling it! Clouds not in the disk -20 -10 0 10 20 -20 -10 0 10 20 V LSR = -130 km/s V LSR = 200 km/s Galactic Latitude (degree) Galactic Latitude (degree) -20 -10 0 10 20 -20 -10 0 10 20 Galactic Longitude (degree) Galactic Longitude (degree) GALACTIC DISK ROTATION GALACTIC DISK ROTATION ANOMALOUS CLOUDS ANOMALOUS CLOUDS Gas in Galaxies - Malta Gas in Galaxies - Malta
Results: source detection Results: source detection GC GC 106 anomalous clouds covering ~ 130 deg 2 Gas in Galaxies - Malta Gas in Galaxies - Malta
Results: property distributions Results: property distributions |VLSR| < 350 km/s Δv ~ 5 - 30 km/s R < ~ 40 pc N HI ~ 5x10 18 - 10 20 No correlation between FHWM, R or N HI with latitude (height) Gas in Galaxies - Malta Gas in Galaxies - Malta
Wind kinematic model Wind kinematic model V w ≡ V w (r) Describing observed cloud kinematic with a simple a galactic wind model CLOUD A cloud in (R, z, θ) with V = V(r) can be easily z D r mapped into the (l, b, V LSR ) system: R d ϕ b y x l θ GC R 0 SUN Simplest model defined by 2 parameters: - wind velocity V w = const - opening angle α = π - 2φ Gas in Galaxies - Malta Gas in Galaxies - Malta
Wind best model Wind best model Simulating winds with different velocities and opening angles ` 300 km/s < V w < 400 km/s α > 140º Best model V w = 330 km/s Gas in Galaxies - Malta Gas in Galaxies - Malta
Derived wind properties Derived wind properties Model-dependent derived properties for a wind with V w = 330 km/s and α = 140º ` - Total HI mass in clouds: 1 x 10 6 Msun Challenge for theory. Destruction - Cloud lifetimes: ~ few x 10 6 years timescales are generally lower - Cold mass loading rate: ~ 0.1 Msun/yr Similar to SFR in the CMZ Can be supplied by GC with - Wind kinetic power: > 3 x 10 39 erg/s SFR~0.1-0.2 Ms/yr (Crocker12) Clouds likely represent the cold gas component entrained in a hot, starburst-driven nuclear wind Gas in Galaxies - Malta Gas in Galaxies - Malta
Conclusions Conclusions - A population of anomalous clouds definitely exists at the GC They can be used to trace the properties of MW wind - Our new GBT survey revealed 106 clouds with kinematics compatible with being entrained in a wind with 300 km/s < V w < 400 km/s and α > 140º Future developments Future developments - Refine kinematic model with more reliable V w (r) (e.g., Zhang+17) - Run HD simulations of MW wind and compare to cloud observed property distributions (e.g., N HI , Δv ). - Follow-up interferometric observations of a few clouds to resolve their morpho-kinematics and compare to simulations Gas in Galaxies - Malta Gas in Galaxies - Malta
Thank you for your kind attention Thank you for your kind attention Gas in Galaxies - Malta Gas in Galaxies - Malta
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