Maite Beltr

1
The intringuing hot molecular core G31.410.31
Maite Beltrán Osservatorio Astrofisico di Arcetri
2
The HMC G31.410.31

• G31.41 is located at a distance of 7.9 kpc,
• LIRAS 3x105 L? ? consistent with an embedded
  star of 25 M?

• G31.41 is a hot core (without UCHII) at a
  distance of 7.9 kpc
• G31.41 luminosity, 3 105 L?, suggests that it
  harbors O-type (proto)stars

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Glycolaldehyde in G31.410.31

• Glycolaldehyde, the simplest of the
  monosaccharide sugars that reacts with propenal
  to form ribose was detected for the first time
  towards a HMC OUTSIDE the Galactic Center in
  G31.410.31.

Plateau de Bure
1.4 mm
2.1 mm
2.9 mm

• Very compact emission (1.3, 10,000 AU) unlike
  in Sgr B2.
• Estimated abundance of the order of 10-8. Only
  small amounts of CO need to be processed on
  grains to reproduce the observed column densities
  with the HMC model of Viti et al. (2004).

Beltrán et al. (2009)
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Glycolaldehyde in HMCs
contours CH3CN greyscale glyco
Beltrán et al. (in preparation)
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A rotating toroid in G31.410.31

• G31.41 is a rotating toroid with R 8000 AU,
  Mcore 490 M?, Mdyn 87 M?, and Vrot 2.10
  km/s (Beltrán et al. 2004, 2005 Girart, MTB et
  al. 2009 Cesaroni, MTB et al. 2011)
• Mcore ??6 x Mdyn ? core unstable and undergoing
  collapse.
• The two white dots denote the free-free
  continuum sources (radio jets) detected by
  Cesaroni et al. (2010).

Cesaroni, Beltrán et al. (2011)
CH3OH
Girart, Beltrán et al. (2009)
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Magnetic field in G31.410.31
dust polarized emission velocity
gradient

• Hot core elongated in NE-SW direction
• Dust polarization observations have revealed
  dust linearly polarized emission mainly along the
  major axis of the HMC B lines perpendicular to
  the major axis of the HMC, in the direction of
  rotation or accretion, with a clear pinched
  morphology (Girart, Beltrán et al. 2009).
• The dust polarization pattern suggests an
  hourglass shape morphology, similar to the one
  found in low-mass regions (e.g NGC1333 IRAS4A
  Girart et al. 2006) but the scale and mass
  involved are much larger.

CH3OH
870 ?m
Girart, Beltrán et al. (2009)

• B-field strength 10 mG
• ?0.350.29/0.20 ? Emagnetic gt Eturbulent
• Mass-to-flux ratio (wrt critical value) 2.7
  (supercritical)

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Magnetic field in G31.410.31

• The more compact transitions show a shorter
  velocity range, that is a smaller rotation
  velocity
• Rotation and radius have been measured from the
  Half Maximum contour of different methanol
  transitions in the zero and first order maps of
  the integrated emission.
• The measured spin velocity of the hot core
  decreases with decreasing radius
• Therefore the angular momentum is not conserved
  Magnetic braking. Theoretical models of magnetic
  braking predict a spin down (Basu Mouschovias
  1994 Mellon Li 2008)
• Magnetic fields might play an important role in
  the formation of massive stars and could control
  the dynamical evolution (gravitational collapse)
  of the cores.

Girart, Beltrán et al. (2009)
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Inverse P-Cygni profiles in G31.410.31

• There is a clear inverse P-Cygni in C34S (7-6),
  H2CO (31,2-21,1), and CN (2-1) profiles that
  suggests infalling gas.
• Red-shifted absorption observed against the
  bright continuum emission of a very hot compact
  dust component.
• VinfVLSR-Vred3.1 km/s
• Accretion rate W/4p 3x10-3 3x10-2 M?/yr
  for (4080-12640 AU)

Girart, Beltrán et al. (2009)
C34S (7-6)
CN (2-1)
absorption
emission
Frau et al. (in preparation)
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Outflows in G31.410.31

• CO observations reveal a complex outflow
  emission (Cesaroni, Beltrán et al. 2011)
• at high velocities E-W outflow
• at systemic velocities 2 outflows?
• NE-SW wide-angle outflow? (CH3OH Araya et al.
  2008)

Can CH3CN (and CO) trace a NE-SW bipolar ouflow?

?if CH3CN indicates rotation, where is the
perpendicular outflow? ? the PV plot of the 12CO
emission in the direction of the CH3CN velocity
gradient is consistent with the Hubble-law
expansion observed in molecular outflows ?
CH313CN outflow parameters too high (Mout290
M?, P 1200 M?km/s, F0.3 M?km/s/yr, Lbol 6
106 L?) ? the velocity gradient would involve the
whole core not only gas emitting in the wings.
Most CH3CN affected by the velocity gradient ?
dynamical timescale (4x103 yr) too short to form
hot core species (Charnley et al. 2002) ? not
compatible with the hourglass-shaped morphology
of the magnetic field
Cesaroni, Beltrán et al. (2011)
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Outflows in G31.410.31
Can CH3CN (and CO) trace a NE-SW bipolar ouflow?

?if CH3CN indicates rotation, where is the
perpendicular outflow? ? the PV plot of the 12CO
emission in the direction of the CH3CN velocity
gradient is consistent with the Hubble-law
expansion observed in molecular outflows ?
CH313CN outflow parameters too high (Mout290
M?, P 1200 M?km/s, F0.3 M?km/s/yr, Lbol 6
106 L?) ? the velocity gradient would involve the
whole core not only gas emitting in the wings.
Most CH3CN affected by the velocity gradient ?
dynamical timescale (4x103 yr) too short to form
hot core species (Charnley et al. 2002) ? not
compatible with the hourglass-shaped morphology
of the magnetic field
Cesaroni, Beltrán et al. (2011)
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Maser jet in G31.410.31
H2O

• H2O and CH3OH maser VLBI observations have
  revealed an extremely compact and highly
  collimated jet (Moscadelli et al. 2012)
• the spots outline an elliptical pattern with
  major axis oriented roughly N-S and centered in
  one of the two cm sources detected towards the
  center (Cesaroni et al. 2010)
• Major and minor axes are 1.4 and 0.24 (11000
  and 1900 AU) with PA 8, and maser average
  expansion velocity 20 km/s.
• Jet dynamical timescale is 1300 yr
• Jet momentum rate is 0.1M?/yr consistent with a
  powering source of L gt 104 L?

CH3CN
Moscadelli et al. (2011)
H2O
CH3OH
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Maser jet in G31.410.31
H2O

• H2O and CH3OH maser VLBI observations have
  revealed an extremely compact and highly
  collimated jet (Moscadelli et al. 2012)
• the spots outline an elliptical pattern with
  major axis oriented roughly N-S and centered in
  one of the two cm sources detected towards the
  center (Cesaroni et al. 2010)
• Major and minor axes are 1.4 and 0.24 (11000
  and 1900 AU) with PA 8, and maser average
  expansion velocity 20 km/s.
• Jet dynamical timescale is 1300 yr
• Jet momentum rate is 0.1M?/yr consistent with a
  powering source of L gt 104 L?

CH3CN
Moscadelli et al. (2011)
Where is the large-scale bipolar outflow?
H2O
CH3OH
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Molecular jet in G31.410.31

• SMA observations at 345 GHz and 0.8 reveal two
  possible jets (outflows)
• E-W (PA90o) south of the HMC center
• N-S (PA15o) associated with maser jet
• Alternative explanation NE-SW wide-angle jet
  (PA68o) less convincing

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ALMA and G31.410.31(and HMCs)
OPEN QUESTIONS

• Keplerian circumstellar disk in G31.410.31
• ALMA should be sensitive enough to detect a disk
  up to distances of 20 kpc (Cesaroni 2008)
• Angular resolution of 0.1 (790 AU) should detect
  an embedded disk in G31 (if it exists)
• Jets and outflows in G31.410.31
• ALMA SiO observations at 0.1-0.2 resolution
  (separation of the two cm sources and minor axis
  of maser distribution) ? information on the jet
  ejection process on scales lt 1000 AU and on the
  interaction between the ejected material and the
  surrounding entrained gas in G31
• Distribution and abundance of glycolaldehyde in
  G31.410.31
• ALMA will resolve G31 and map the distribution of
  glycolaldehyde on scales smaller than 1000 AU.
• ALMA (8 GHz BW) will allow simultaneous
  observations of several transitions of
  glycolaldehyde with different line strengths and
  energies (excitation conditions) ? temperature,
  column density and abundance to further constrain
  the formation routes (e.g. Woods et al. 2012).
• Magnetic field in G31.410.31
• ALMA polarization capabilities will allow to
  study the morphology of the magnetic field at a
  scale similar to the separation of the cm sources
  (0.2)