Adam Ginsburg's blog

Articles by Adam Ginsburg

• Deokkeun An: The Galactic Center: Not an active galactic nucleus

  

  Focus on infrared

  • high gas surface density
  • cloud-cloud collisions

  Spitzer IRS survey of CMZ

  • 107 candidates
  • 35 YSOs discovered
  • half of observing time spent on background
    • 428 total spectra on ISM lines of sight
  • NeII, SII, SiII maps
  • parameter maps:
    • ionization state
    • electron density
    • rad field hardness

  Comparison to IRS observations of other galaxies

  • SINGS comparison + NeIII/NeII ratio vs O/H abundance + Galactic center is moderately inconsistent with AGN
  • Other line ratios (FeII/NeII vs SiII/SIII) - GC offset from AGNagain + Most CMZ points look like "normal" star forming regions + lots of scatter, but trend with longitude
  • photoionization by hot stars & shocks explain colors

  Questions

  • Q: Is there any significance to the idea that high-latitude are most similar to AGN?
  • A: ...didn't understand question... talked about oxygen abundance determinations and statistical significance
  • Q: Is there any physical significance to the high-latitude points having AGN colors? Could it be from AGN being "turned off" years ago?
  • A: you tell me. Could be X-ray binaries, wolf-rayet stars. No clear evidence that Sgr A* excited it.
  • Q: Need bright source. XRBs would have to be very bright.
  • A: Our obs don't show much. Distance unknown. Could be foreground.
  • Q Stocke: - detections of Ne V. Couldn't see. How many had Ne V definitely detected? In infrared or diffuse?
  • A: ~12 out of 400 detected. Mostly Ne V in ISM, not in point sources.
  • Q Farhad: What does # of detected YSOs tell you about SFR? How are they distributed in plane?
  • A: Consistent with Schmidt law. Not far from Farhad's measurement. YSOs selected on IR photometry. 50% of sources from near Sgr B. Asymmetry: YSOs on left

---

• Naomi McClure Griffiths: HI Outflows from the Galactic Center (20 + 5 minutes)

  

  Outflows - M82 example

  Our Galaxy

  • 8.3um correlated with radio continuum
  • Fermi bubbles
  • Radio polarization - magnetized bubble
  • ATCA + Parkes HI survey
  • HI data publicly available: http://arxiv.org/abs/1201.2438, http://www.atnf.csiro.au/research/HI/sgps/queryForm.html + 86 high latitude clouds that are completely distinct from the rest + ± 200 km/s + negative velocities at the bottom + size ~15 pc, ~few hundred Msun + 4000K clouds + n~1cm^-3 + not in circular orbits

  Lockman "very dumb simulation"

  • model as outflowing clouds
  • wind velocity, outflow angle
  • min/max velocity plots: look for clouds beyond the min/max vel + wind velocities 150-270 km/s can reproduce population

  Cooper 2008, Melioli 2013

  • simulations predict entrainment of dense gas
  • cold wind is responsible
  • 2 Myr to get clouds to observed height

  Wind dynamics

  • cold clumps entrained in hot outflow total mass ~4x10^4, but completeness loss -> 10^5 msun
  • energy total ~10^52 erg
  • easily supplied by present SFR

  Future

  • can look further in both lat & long + determine lifetime + constrain opening angle

  Questions

  • Q: Where does the mass come from? Is it hard to resupply? Where does it go?
  • Q: Do you see any warm gas (H-alpha)?
  • A: looked at WHAM, but resolution too poor. Not clear yet.

  • Q Mitch: 600 km/s. Injected explosively or must go through a sonic point

    with a grav. potential, which would imply that it's coming from a black hole

  • A: OK, great, someone else give me the theoretical explanation

  • Q Stocke: Warm component has been detected in absorption against AGN; velocities consistent.

    Gas goes up to 12 kpc on either side and does not escape. Hot wind requires Chandra, not yet successful.

  • Q: for Stocke - How much gas in hot wind?
  • A: Not detected
  • Q: Could this be inflow?
  • A: We don't see this around other parts of the galaxy except around superbubbles. No conspiracy accreting towards CMZ
  • Q Farhad: We've looked at RRLs in inner degree. Don't see any high-velocity ionized gas. Must be accelerated away from disk.
  • Q Namir Kassim: High energy emission from cosmic rays impacting these clouds?
  • A: Possibly, we'd like to look at that more

---

• Mathieu de Naurois: TeV Observations of GC and Starburst Systems

  

  TeV observations

  • scintillation in air (Cherenkov)
  • Hadron detection
  • watching for light showers
  • HESS camera is huge: 1.5m across (fast photometers)
  • HESS, VERITAS, MAGIC dominate

  Galactic Center

  • high energy density (100 eV cm^-3)
  • dense GMCs & starburst activity
  • HESS CMZ good...
  • VERITAS CMZ 18-sigma in 46h
  • HESS, mol clds trace similar areas
  • Local excess of 10 TeV -> requires local source of CRs
  • Correlation between mol clds great in Sgr B, Sgr A, but poor in Sgr D + no TeV emission at |l|>1 degree + Propagation from central source? not enough propagation time + Maybe CRs directly accelerated?

  Central Source

  • Could be Sgr A*, Sgr A East SNR, or other
  • best fit position is 6"rms around Sgr A* + Sgr A East ruled out with CCD-guiding based observations
  • No variability detected
  • in general, only middle part of SED variable
  • Pulsar Wind Nebula ruled out with Chandra?

  Dark Matter search

  • exclude central region with diffuse CR-driven emission
  • search at |b|>0.5
  • no positive detection; see Friday talks

  Testing SFR

  • TeV detections of M82 (Veritas), NGC 253 (HESS)
  • NGC 253 approximately pointlike + 0.5% crab + Linear from gamma ray to TeV + hard spectrum + 3 orders of magnitude more luminous than CMZ + 2x10^38 vs 10^35
  • M82 VERITAS + 0.9% crab + more luminous: 2x10^39 ergs
  • Why brighter? + Higher B-field? Higher CR density?
  • Starburst could be calorimetric; Sgr A cannot be + [Unclear - does that mean CRs escape in the Galaxy?]

  HESS II

  • bigger telescopes
  • lower energy threshold
  • better res & sens
  • 10m+ optical dish

  Sgr A* with HESS II

  • 3 hrs so far...
  • lines up with Fermi spectrum

  Questions

  • Can you model with no pulsar wind nebula (all emission in black hole)?
  • A: PWN can explain GeV but not TeV. PWN not needed for TeV. But, PWN could still account for some GeV emission.
  • GeV and TeV could be different. Which has worse resolution?
  • Similar resolution. Fermi around 200 MeV ~ HESS 100 GeV. Both have better resolution at higher energy.
  • Consistent with Sgr A*...
  • Fermi problem is the diffuse background; HESS doesn't have that problem
  • Q Farhad: What is the energy density of CRs for diffuse TeV emission?
  • about 100 eV cm^-3, maybe
  • Q Stocke: How much loss is there between us and CMZ due to electron/positron? For TeV rays?
  • <10%. Main absorber is CMB?
  • Maybe more photons from CMZ -> greater absorption than CMZ
  • ~5% loss at highest energy only

---

• Fred Baganoff: X-ray Visionary Project: SgrA*

  

  High-res x-ray spectra of Sgr A* & surrounding emission

  • Radio pol obs: most accreting matter doesn't reach event horizon
  • 3 Ms exposure
  • specific roll-angles required because Chandra has no slit
  • detected 6.67 keV Helium-like Fe K-alpha + hi-res rules out 6.4 keV emission model

  What mechanism drives Sgr A* flares?

  • what x-ray emission mechanism? Thermal? Compton? Synchro? etc.
  • X-ray/NIR variable
  • mm/radio events weaker, longer timescale, optically thick
  • do mm/radio lead or lag?
  • What determines flare cycle?
  • What triggers flares?

  Observations

  • Backgrounds are a big problem
  • Details about order sorting, etc.

  Questions

  • Farhad: Discovered a lot of X-ray binaries. Find any sources within 1'?
  • Found the old recurrent ones. Magnetar is new. No new bright ones, searching for faint ones. Vast population of faint variables.
  • Q: Underlying physical mechanism still unknown. Where are we going? How do we figure it out?
  • A: NuStar will help. Very narrow window; can't see optical or UV. This campaign gives more examples.
  • Cornelia: Is anyone working on the diffuse? Nonthermal filament sticks out brightly
  • Yes. Sgr E & F sources. Studying with NuStar team.
  • Q: Can you create images with 3Ms spectra?
  • A: Not much better; the grating reduces raw sensitivity.
  • Q: Dismissed possibility of periodicity. Have you carefully looked? Lomb-Scargle?
  • A: Lots of times with no flaring obvious. But, maybe a lot missed below the noise of the DC signal. Brightest peaks are not periodic. Peaks put into Lomb-Scargle, but not enough data for that. Will look at power spectrum though.

---

• Woong-Tae Kim: Star Formation in Nuclear Rings

  

  Nuclear Rings

  • Form by resonant interactions with barred potentials + but bar torque is low near inner lindbland resonances + resonance is very long timescale
  • claim that bar strength controls bar substructure
  • bar potential modeled by "Ferrers Prolates"
  • Q_B is the "controlling parameter" + Q_B = 0.23 yields really cool looking models
  • stronger bar leads to smaller radius ring + pushes more gas inward
  • range of SFR + age gradient within nuclear rings

  Two models of ring SF

  • popcorn model + randomly distributed + no age gradient
  • pearls-on-a-string model + SF at contact point + age gradient
  • age gradient <-> lower SFR
  • simulation generating 10^5 msun clusters

  Sim results

  • presence or absence of age gradient depends on SFR + no age gradient if SFR > 1 Myr + corresponds to maximum SFR at a contact point
  • prolonged SF requires prolonged feeding + HVCs (accretion of primordial gas) + ang mom dissipation by spiral arms + Galactic fountains
  • If corotation radius at large R, can feed spiral arms into ring

  Questions

  • Q: Sims are pure hydro. Speculate on B-fields. Chuckle.
  • A: Ring would be smaller
  • Q: Typical velocity of gas along bar in model?
  • A: 50-100 km/s
  • Q: Do you mean no need for x2 orbit?
  • A: no, need X2 to form ring. Formation mechanism of ring is not related to resonance.
  • Q: Ring on x2 orbit?
  • A: yes
  • Q: is there observation evidence of age gradients in nuclear rings?
  • A: Yes, Mazzuca '08 shows gradient in H-alpha EQW
  • Q Farhad: Can you form the circumnuclear disk (2pc) with the same mechanism?
  • A: Can't answer now. Need to run the simulation with the right size-scale
  • Q: Would the bar be unstable to bending instabilities in 3D?
  • A: We ran 3D, and didn't see any difference. But, with different initial conditions, may see dynamical difference..
  • Q: Have you modeled where the bar meets the arm?
  • A: No, couldn't do that, only treated stellar.

---

• Fiona Harrison: NuSTAR Results: From the Galactic Center to Local Starbursts

  

  NuStar

  • Explorer class
  • PI-led
  • Will have guest investigator program
  • First focusing telescope in high-energy X-ray band
  • 100x improvement in 3-79 keV
  • Previous telescopes: detector was larger than collecting area of telescope
  • ~18" resolution, 12.5' fov

  Our CMZ: Multicolor cmz vs INTEGRAL

  • NUstar FOV = Integral resolution
  • Survey Muno field (CMZ surey covering negative longitudes)

  Sgr A*

  • Flares show it obviously
  • ~1hr/day
  • detection of flare at >10 keV

  Gamma ray pulse in Galactic Center

  • enhanced X-ray emission
  • pulsations detected
  • 3.7 second pulsations
  • 3" distant magnetar: SGR J1745-29
  • Associated with disk of massive stars near Sgr A*?

  HESS J1640-465

  • being observed right now
  • TeV source
  • possible evidence from NuStar for a pulsar

  Nearby Starburst Galaxies

  • Observations coordinated with Chandra
  • NGC 253, Arp 299, M82, NGC 3310, NGC 3256
  • AGN may only be visible at high energies b/c of absorption at lower energies
  • sampling range in mass, sfr

  NGC 253

  • Lehmer et al 2013
  • Where is the nucleus? Crowded core, hard to determine
  • Chandra obscured X-ray source "off-center" compared to Radio
  • dynamical center determined; Chandra sees one source near it + variability driven by that source + nustar spectrum by assuming all variability associated with it + classical ULX source: binary star + BH + Either IMBH or super-eddington accretion
  • nuclear emission overestimated due to ULXs

  Arp 299

  • Only "B" nucleus visible at high X-ray energies
  • Only one nucleus currently active

  Questions:

  • Farhad: Will Nu-Star look at gamma-ray bubble?
  • A: Two problems: 1. too extended, too much time, can't contribute much
  • Is there a possibility of other magnetars not yet detected?
  • A: Various types of magnetars. Undetectable in quiescence. Difficult to constrain overall population. Raises questions: unlikely by chance; do we not understand magnetar population
  • What is the diffuse emission detected with INTEGRAL? In Sgr E?
  • A: We don't see hard x-ray emission coincident with INTEGRAL source. Centroid of INTEGRAL source offset from diffuse emission

---

• Susanne Aalto: Physical Conditions and Chemistry of Molecular Gas in Galactic Centers

  Physical conditions & chemistry

  Astrochemistry as a diagnostic...

  • 50+ molecules detected exgalactically
  • CO n>10^2, HCN n>10^4
  • temperature NH3, H2CO
  • Only works if molecules excited by collisions
  • 12CO/13CO increases towards GC because more diffuse gas [my q: integrated?]

  "Raisin Roll" view:

  • Mol massin dense clumps, HI diffuse throughout
  • HCO+, H3O+, HNC, HC3N, CN, SiO, H2O

  General Trends

  • HNC 1-0 anticorrelated with HCN+ 1-0
  • C2H ubiquitous

  "Hot Cores"

  • Arp 220
  • Drive outflows
  • "Boring" NGC 1377 (optically) + has very deep SiO absorption + molecular outflow M~10^7 Msun + 860um optically thick core
  • NGC 4418 "Ugly Duckling" galaxy + optically thick "atmosphere" dust core surrounded by molecular disk + N~10^25 cm^-2 + inner temp ~200-300K + molecular "disk" ~50K
  • unclear how common optically thick cores are + can be studied with vibrationally excited molecules
  • NGC 4418 + Global spectrum dominated by vibrationally excited HC3N
  • Mrk231 + HCN outflow, 1000 km/s + vibrationally excited HCN in core
  • vibrationally excited lines trace warped disk
  • Arp 220W: amplified IR-pumped HNC

  ALMA NGC 4418 "spectral scan"

  • dominated by vibrational lines

  SMA spectral scanning in Arp 220

  • problematic: wide lines
  • vibrational lines are the new standard

  Less obscured galaxies

  • NGC 253, IC 342, Maffei 2, NGC 1068...
  • same chemistry can trace outflows or star formation
  • HNC, HCN, HCO+ correlated with 3mm continuum: trace SF
  • HNCO, CH3OH, SiO anti-correlated with SF: probably trace outflows
  • N2H+ - "warm gas" and "warm dust". Not the same in our galaxy & others

  NGC 1068

  • PdBI Spirals around center
  • ALMA bar + spirals + central cirumnuclear disk
  • complicated chemistry towards true center
  • noncircular motions

  More results:

  • ALMA + ATCA towards Cen A
  • NGC 1097
  • HC3N in Mrk 231
  • HCN in wind... extreme hcn abundance

  Questions:

  • Inner NGC 1068 ring - what resolution can you get with ALMA? Can you see kinematics?
  • A: Yes, can see kinematics. 0.1", can do ~10x better eventually. 400 km/s
  • Draw attention to MOPRA MALT-90: good comparison survey for galaxies
  • Thanks

---

• John Bally - Hi-Gal CMZ

  

  Summary of Hi-Gal:

  • 900hrs,
  • inner ±60 deg, then outer ±60 deg, then full 360 deg.
  • Release scheduled late in 2013.
  • 0.5 million band-merged sources

  The CMZ:

  • we live in a mildly barred galaxy
  • NGC 1097 as an analog
  • our CMZ less symmetric

  Multiwave comparison:

  • asymmetry: 24, 70 right; gas left
  • snrs, evolved stars, nonthermal filaments, arched filaments...

  The Gas:

  • 10^7 Msun

  • CMZ clouds more massive, more turbulent

  • Cold gas to the left of Sgr B2, warmer to the right

  • Column density somewhat flat from l=1.5 to l=0 + "Optically thick as a brick"

  • Molinari "ring" - column density, some evidence from velocities + vertical oscillation = 2x circular speed + offset... + predicts Sgr B2 at tangent of ring

    • velocity of Sgr B2 too slow
    • Sgr B2 has significant proper motion: 80 km/s

    • Molinari ring falsified: must extend to larger long

  • Few point sources in the Arched Filaments

  Sofue-Handa ('84) lobe:

  • brightest super-bubble in galaxy
  • powered by AGN or starburst?
  • Warning: Lots of foreground towards CMZ. + Sco-Cen group + radio emission associated with wall of scocen

  Sgr B2 spectroscopy:

  • Two temperature components in Sgr B2
  • PACS sees 300K CO

  Sgr C mention

  Bania's clump

  • 200 km/s linewidth

  The Brick

  • most extreme IRDC
  • 24, 70 opaque
  • HCO+ cubes

  Dust

  • Are dust grains different?
  • Temperature differs between gas and dust

  Questions:

  • COMMENT: NGC 1068 has 100 pc molecular ring, will mention later in discussion
  • Lang: Sources in arched filaments - are they aligned with filament?
  • A: Yes, 50-60 in filament. SEDs look like protostars.
  • Jerry (?): Note - hard to avoid conical wind from Sgr A* dynamically.
  • Bally: Yes. High-latitude CO gas off-plane: entrained. Starburst likely, AGN unlikely to entrain it.
  • Jay Gallagher: M82 energy density ~100x higher than in MW, driving wind out of smaller potential. Galaxy requires huge pressure change.
  • Bally: Yes, wimpy nucleus
  • Michael: Evidence for bar from cobe & spitzer. Is it related to gas bar?
  • Bally: Related. Gas bar 20 ±3 from line of sight, but infrared stellar bar more like 45 degrees. Why offset? controversial. Generically related.

---

• My favorite Splatalogue queries

  I tend to be most interested in low-energy molecular lines: CO, NH₃, and H₂CO being the main candidates.

  Note: Splatalogue has made some recent changes to their returned tables, partly per my recommendations. The code below has been update to reflect these changes.

  >>> from astropy import units as u
  >>> from astroquery.splatalogue import Splatalogue
  >>> S = Splatalogue(energy_max=500,
  ...    energy_type='eu_k',energy_levels=['el4'],
  ...    line_strengths=['ls4'],
  ...    only_NRAO_recommended=True,noHFS=True)
  >>> def trimmed_query(*args,**kwargs):
  ...     columns = ('Species','Chemical Name','Resolved QNs','Freq-GHz',
  ...                'Meas Freq-GHz','Log<sub>10</sub> (A<sub>ij</sub>)',
  ...                'E_U (K)')
  ...     table = S.query_lines(*args, **kwargs)[columns]
  ...     table.rename_column('Log<sub>10</sub> (A<sub>ij</sub>)','log10(Aij)')
  ...     table.rename_column('E_U (K)','EU_K')
  ...     table.rename_column('Resolved QNs','QNs')
  ...     table.sort('EU_K')
  ...     return table
  >>> trimmed_query(1*u.GHz,30*u.GHz,
  ...     chemical_name='(H2.*Formaldehyde)|( HDCO )',
  ...     energy_max=50).pprint()
  Species Chemical Name      QNs      Freq-GHz Meas Freq-GHz log10(Aij)   EU_K
  ------- ------------- ------------- -------- ------------- ---------- --------
     HDCO  Formaldehyde 1(1,0)-1(1,1)       --       5.34614   -8.31616 11.18287
   H2C18O  Formaldehyde 1(1,0)-1(1,1)   4.3888        4.3888   -8.22052 15.30187
   H213CO  Formaldehyde 1(1,0)-1(1,1)       --       4.59309   -8.51332 15.34693
     H2CO  Formaldehyde 1(1,0)-1(1,1)  4.82966            --   -8.44801 15.39497
     HDCO  Formaldehyde 2(1,1)-2(1,2)       --      16.03787   -7.36194 17.62746
   H2C18O  Formaldehyde 2(1,1)-2(1,2) 13.16596      13.16596   -6.86839 22.17455
   H213CO  Formaldehyde 2(1,1)-2(1,2)       --       13.7788   -7.55919 22.38424
     H2CO  Formaldehyde 2(1,1)-2(1,2) 14.48848            --   -7.49383 22.61771
   H2C18O  Formaldehyde 3(1,2)-3(1,3) 26.33012      26.33014   -6.03008 32.48204
   H213CO  Formaldehyde 3(1,2)-3(1,3)       --      27.55567   -6.95712  32.9381
     H2CO  Formaldehyde 3(1,2)-3(1,3)       --       28.9748   -6.89179 33.44949
  
  
  >>> trimmed_query(100*u.GHz,400*u.GHz,
  ...     chemical_name='Carbon Monoxide',
  ...     energy_max=50).pprint()
  Species  Chemical Name   QNs   Freq-GHz Meas Freq-GHz log10(Aij)   EU_K
  ------- --------------- ----- --------- ------------- ---------- --------
     C18O Carbon Monoxide   1-0 109.78218     109.78218   -7.20058  5.26868
  13COv=0 Carbon Monoxide   1-0 110.20135            --   -7.49946   5.2888
     C17O Carbon Monoxide J=1-0 112.35928     112.35928   -7.17404  5.39236
    COv=0 Carbon Monoxide   1-0  115.2712      115.2712   -7.14236  5.53211
     C18O Carbon Monoxide   2-1 219.56036     219.56036   -6.21833 15.80595
  13COv=0 Carbon Monoxide   2-1 220.39868            --   -6.51752 15.86618
     C17O Carbon Monoxide J=2-1 224.71437     224.71439   -6.19179 16.17703
    COv=0 Carbon Monoxide   2-1   230.538       230.538   -6.16011 16.59608
     C18O Carbon Monoxide   3-2 329.33055     329.33055   -5.66014  31.6116
  13COv=0 Carbon Monoxide   3-2 330.58797            --   -5.95976 31.73179
     C17O Carbon Monoxide J=3-2  337.0611     337.06113    -5.6336  32.3538
    COv=0 Carbon Monoxide   3-2 345.79599     345.79599   -5.60192 33.19169
  
  >>> trimmed_query(1*u.MHz,2*u.GHz,
  ...     chemical_name=' H2CO .*Formaldehyde',energy_max=75,
  ...     energy_type='eu_k').pprint()
  Species Chemical Name      QNs      Freq-GHz Meas Freq-GHz log10(Aij)   EU_K
  ------- ------------- ------------- -------- ------------- ---------- --------
     H2CO  Formaldehyde 2(2,0)-2(2,1)       --       0.07114  -13.81846   57.612
     H2CO  Formaldehyde 3(2,1)-3(2,2)       --       0.35557  -12.02319 68.11082
  
  
  >>> trimmed_query(20*u.MHz,25*u.GHz,chemical_name=' NH3 ').pprint()
  Species Chemical Name      QNs       Freq-GHz Meas Freq-GHz log10(Aij)    EU_K
  ------- ------------- -------------- -------- ------------- ---------- ---------
   NH3v=0       Ammonia  1(1)0a-1(1)0s 23.69447       23.6945   -6.43769  24.40492
   NH3v=0       Ammonia  2(2)0a-2(2)0s  23.7226      23.72263   -6.31125   65.5867
   NH3v=0       Ammonia  2(1)0a-2(1)0s 23.09885      23.09881   -6.94808   81.5904
   NH3v=0       Ammonia 3(3)0a-3(-3)0s 23.87008      23.87013   -6.25203 124.68113
   NH3v=0       Ammonia  3(2)0a-3(2)0s 22.83422      22.83418     -6.662 151.33353
   NH3v=0       Ammonia  3(1)0a-3(1)0s 22.23456       22.2345   -7.29889 167.29666
   NH3v=0       Ammonia  4(4)0a-4(4)0s 24.13935      24.13942   -6.20938 201.67106
   NH3v=0       Ammonia 4(3)0a-4(-3)0s 22.68835      22.68831   -6.54002 238.96192
   NH3v=0       Ammonia  4(2)0a-4(2)0s 21.70341      21.70336   -6.95001 265.52612
   NH3v=0       Ammonia  4(1)0a-4(1)0s 21.13434      21.13431   -7.58659 281.43749
   NH3v=0       Ammonia  5(5)0a-5(5)0s 24.53292      24.53299    -6.1706 296.53357
   NH3v=0       Ammonia  5(4)0a-5(4)0s 22.65307      22.65302   -6.46829 344.46226
   NH3v=0       Ammonia 5(3)0a-5(-3)0s 21.28532      21.28528   -6.79928  381.6003
   NH3v=0       Ammonia  5(2)0a-5(2)0s 20.37145      20.37145   -7.20859 408.05568
   NH3v=0       Ammonia  5(1)0a-5(1)0s 19.83833      19.83835   -7.84539 423.90259
   NH3v=0       Ammonia  6(5)0a-6(5)0s 22.73249      22.73243   -6.41603 467.80451
  

---

• PPVI Talk 13: Steve Longmore

  THE FORMATION AND EARLY EVOLUTION OF YOUNG MASSIVE CLUSTERS

  S. Longmore (Astrophysics Research Institute, Liverpool John Moores University, United Kingdom), J. Alves (University of Vienna), J. Bally (University of Boulder), N. Bastian (Liverpool John Moores University, United Kingdom), E. Bressert (CSIRO Astronomy and Space Science), J. Dale (LMU, Germany), D. Kruijssen (MPA, Germany), J. Rathborne (CSIRO Astronomy and Space Science), L. Testi (ESO, Germany), A. Stolte (University of Bonn, Argelander Institut, Bonn, Germany)

  We review the formation and early evolution of the most massive (and dense) young stellar clusters in our Galaxy, and the role this can play in our understanding of star and planet formation as a whole. We start by reviewing the global properties and environmental conditions of the known young massive clusters (YMCs) and their progenitor gas clouds. We then focus on the observed embedded dense core and (proto)stellar populations within these clusters, and discuss how such large stellar systems can potentially simultaneously distinguish between competing cluster formation models and provide the strongest constraints on the physical origin of the stellar initial mass function. After reviewing the current theoretical framework for the formation and evolution of YMCs, we summarise the debate on two key open questions: infant (im)mortality and the evidence for/against significant age spreads within YMCs. We then discuss which fraction of all stars and planets, including our own solar system, may have formed in extreme environmental conditions (proximity to high-mass stars, high (proto)stellar densities etc) similar to those found in these clusters, rather than the more benign conditions found in local, low-mass star formation regions. Finally, we review how the most massive and dense young clusters can be used as a bridge linking what we learn about star and planet formation in the nearest-by regions, to starburst systems in the Local Universe, globular cluster formation and star/planet formation at the earliest epochs of the universe.

  Intro

  We understand low-mass sf; it is atypical

  local SF is atypical

  • 50% of SF in most massive clusters (Lee, Murray, Rahman 2012)
  • peak SFR at z=2-3
  • most MW stars older than a few Gyr

  How universal is the SF process?

  • Does SF care about environment?

  What are YMCs?

  • as big as globulars but currently forming

  Carina: Trumpler 14

  • association surrounding YMC. Not YMCAs

  Why good laboratory?

  • How do lives differ in isolation vs cluster?

  Ideal probes because they probe extremal SF

  Theory: How do they form?

  • many processes: too many to simulate
  • gass collapse, but feedback important
  • density essential - determines whether bound or not
  • need to understand initial conditions: mass as a function of size scale early

  

  Observations

  What do we expect to see?

  • mass-radius diagram
  • need v_esc > c_II

  • How dense? YMC at given mass, radius

    • Collapse of single cloud?
    • Cloud-cloud collision?

  Scenarios:

  • Initial radius same as final stellar radius * "in situ"
  • Initial radius >> final radius; shrinks * requires convergence; "conveyor belt" * P-cygni profiles, collision signatures
  • Mass, radius when there are no progenitors
  • Can do YMC progenitors out to 10's of MPC with ALMA

  Status in Jan 2012: G0.253 biggest.

  Inner 200 pc:

  • Molinari Ring, reference to John's talk
  • Masses from Herschel column maps
  • 1pc, 3pc apertures (related to tidal radius)
  • Sgr B2, Sgr C star forming, others are not

  First quadrant:

  • All massive things are prodigiously star forming

  Fourth quadrant:

  • ATLASGAL 4th quadrant - Urquhart 2013. 6 candidates
  • MALT 90 Contreras - a couple candidates
  • Sarolta Zahorecz 1B040

  How do you form YMCs?

  • Where are YMCs? Where are star-forming things?
  • Only fair comparison if present-day gas clouds will produce same stellar population as now
  • Only works if cluster disruption unimportant
  • fair enough samples (10%, 30% area)
  • Only very young clusters so they weren't disrupted
  • same number of star-forming clouds, same number of clusters
  • LOTS of starless in CMZ, NONE in 1st quadrant
  • Galactic Center = in situ mode, 1st quad = conveyor belt mode

  W43, W49 invoked as YMC progenitors [yikes ... W49, W51 actually]

  • W49 fed by filaments on 60 pc scales
  • plenty of regions show similar features
  • looking for evidence of "inflow" or "convergence" onto massive clusters * conveyor belt makes sense

  Back to the CMZ:

  • Dense gas only on the left
  • Mass in boxes same, density is changing
  • Sgr A* is not at the center of the ring * Low density in the back * high density in the front * Sgr A* close to the front * Sgr A* compresses the gas? (interacting with 20, 50 km/s clds)

  Predictions:

  • strongest shocks just after Sgr A*
  • Elongated

  Kruijssen+, Lucas+, Clark+

  • comparison with observations....
  • Exciting because following IMF as a function of absolute time * know orbit around Center * know downstream is older than upstream

  Summary

  • Different modes of YMC formation * None starless * "would be exciting if someone found that" [not for me]
  • Galactic center is different * most extreme SF environment where we can resolve stars
  • Can follow assembly as a function of time
  • Can extrapolate Milky Way to other galaxies (Kruijssen & Longmore)

  ALMA data

  • PI Rathborne
  • Crystal Brogan helped a lot
  • Banana!
  • HNCO movie
  • SiO movie

  

  Questions

  • Q: Battersby - "in situ" idea. Short lifetime. CMZ should not be forming stars.
  • A: SF is slower according to Kruijssen. Once the turbulence dissipates, stars will form anyway.
  • Q: Battersby - What does the previous state of the gas look like for in situ?
  • A: Thor HI envelopes will tell you about kinematics. We don't know initial conditions for things in the disk.
  • Q Hans: Continuum image of brick. High density. No stars formed. Cries out as the initial conditions of SF. Is THIS the initial conditions for SPH codes?
  • A: Surprisingly small clumps. Most massive is ~few hundred Msun
  • Hans: can form more massive stars later
  • Q McKee: What fraction of YMC has already formed in disk?
  • A: High Q (lyman continuum luminosity). Don't know
  • Q Henrik: Help a little with the interpretation. Do the data help say something about shocks, anything?

  • A: A lot of potential answers... simulations of gas cloud at Sgr C, whiz by Sgr A.

    (we will be able to say things...)

  • Q: Klessen - in Alma data, do you have OI? [No] Clarke and Glover predict OI prominent and bright. Could distinguish between UV and CR flux.
  • A: Different gas temperature. Wish we had OI. Shock or CR heating. SOFIA only thing that can do it

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