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Scientific Results in Press

HCN J = 5-4 Emission in APM 08279+5255 at z = 3.91

Wagg J.$(^{1,2})$, Wilner D.J.$(^{1})$, Neri R.$(^{3})$, Downes D.$(^{3})$, Wiklind, T.$(^{4})$
$(^{1})$Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, $(^{2})$Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Apartado Postal 51 y 216, Puebla, Mexico, $(^{3})$IRAM, Saint Martin d'Hères, F-38406, France, $(^{4})$ESA Space Telescope Division, STScI, 3700 San Martin Drive, Baltimore, MD 21218.

We detect HCN J=5-4 emission from the ultraluminous quasar APM 08279+5255 at $z=3.911$ using the IRAM Plateau de Bure Interferometer. This object is strongly gravitationally lensed, yet still thought to be one of the most intrinsically luminous objects in the universe. The new data imply a line luminosity $L'_{HCN(J=5-4)}=(4.0\pm0.5)\times 10^{10}$ K km s$^{-1}$ pc$^2$. The $\sim 440$ km s$^{-1}$ FWHM of the HCN $J=5-4$ line matches that of the previously observed high-J CO lines in this object and suggests that the emission from both species emerges from the same region: a warm, dense circumnuclear disk. Simple radiative transfer models suggest an enhanced abundance of HCN relative to CO in the nuclear region of APM 08279+5255, perhaps due to increased ionization, or possibly the selective depletion of oxygen. The ratio of far-infrared luminosity to HCN luminosity is at the high end of the range found for nearby star-forming galaxies, but is comparable to that observed in the few high-redshift objects detected in the HCN $J=1-0$ line. This is the first clear detection of high-J HCN emission redshifted into the 3 mm atmospheric window.

Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Appeared in: ApJ 634, L13

Detection of a hot core in the intermediate-mass Class 0 protostar NGC 7129-FIRS 2

Fuente A., Neri R., Caselli P.
Affiliation: $(^{1})$OAN (IGN), Campus Universitario, Apdo. 112, 28803 Alcalá de Henares (Madrid), Spain, $(^{2})$IRAM, 300 rue de la Piscine, 38406 St. Martin d'Hères, France, $(^{3})$INAF - Osservatorio Astrofisico de Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy

We report high angular resolution (HPBW $\sim 0.6\hbox{$^{\prime\prime}$}\times 0.5\hbox{$^{\prime\prime}$}$ at 1.3 mm) observations of the Class 0 intermediate-mass (IM) protostar NGC 7129-FIRS 2 using the Plateau de Bure Interferometer. Our observations show the existence of an intense unresolved source in the continuum at 1.3 mm and 3 mm at the position of the Class 0 object. In addition, compact CH$_3$CN emission is detected at this position. The high rotational temperature derived from the CH$_3$CN lines ( $T_{rot} \approx 50$ K), as well as the enhanced CH$_3$CN fractional abundance (X(CH$_3$CN) $\sim
7.0\times 10^{-9}$), shows the existence of a hot core in this IM young stellar object. This is to our knowledge the first IM hot core detected so far. Interferometric maps of the region in the CH$_3$OH $5_{kk'}\rightarrow 4_{kk'}$ and D$_2$CO $4_{04}\rightarrow 3_{03}$ lines are also presented in this paper. The methanol emission presents two condensations, one associated with the hot core, which was very intense in the high upper state energy lines (E$_u > 100$ K), and the other associated with the bipolar outflow which dominates the emission in the low excitation lines. Enhanced CH$_3$OH abundances (X(CH$_3$OH) $3\times 10^{-8}$ - a few $10^{-7}$) were measured in both components. While intense D$_2$CO $4_{04}\rightarrow 3_{03}$ emission was detected towards the hot core, the N$_2$D $^{+} 3\rightarrow 2$ line was not detected in our interferometric observations. The different behaviors of D$_2$CO and N$_2$D$^{+}$ emissions suggest different formation mechanisms for the two species and different deuteration processes for H$_2$CO and N$_2$H$^{+}$ (surface and gas-phase chemistry, respectively). Finally, the spectrum of the large bandwidth correlator shows a forest of lines at the hot core position, revealing that this object is extraordinarily rich in complex molecules. For deeper insight into the chemistry of complex molecules, we compared the fractional abundances of the complex O- and N- bearing species in FIRS 2 with those in hot corinos and massive hot cores. Within the large uncertainty involved in fractional abundance estimates towards hot cores, we did not detect any variation in the relative abundances of O- and N-bearing molecules ([ CH$_3$CN] /[ CH$_3$OH] ) with the hot core luminosity. However, the O-bearing species H$_2$CO and HCOOH seemed to be more abundant in low and intermediate mass stars than in massive star-forming regions. We propose that this could be the consequence of a different grain mantle composition in low and massive star-forming regions.

Appeared in: A&A 444, 481

SIMBA Observations of the Keyhole Nebula

Brooks K.J.$(^{1})$, Garay G.$(^{2})$, Nielbock M.$(^{3})$, Smith N.$(^{4})$, Cox P.$(^{5})$
$(^{1})$ATNF, P.O. Box 76, Epping NSW 1710, Australia, $(^{2})$Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile, $(^{3})$Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstraße 150, D-44780 Bochum, Germany, $(^{4})$Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309, $(^{5})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France

We report observations made with the SIMBA bolometer at SEST to measure the 1.2 mm continuum emission toward the Keyhole nebula. We have detected 1.2 mm emission toward the ionized gas filaments of the Car II radio source that is attributed to thermal free-free emission. Several compact 1.2 mm emission sources have also been identified and found to correspond to bright-rimmed molecular globules. Under the assumption that for these sources the 1.2 mm emission corresponds to dust, we find mass estimates in the range $3-19\mbox{M$_\odot$}$, which are consistent with previous molecular line measurements. The data also yield new 1.2 mm flux measurements at two different epochs during the cyclic brightness variation of $\eta$ Carinae. No emission was detected toward the trademark dark keyhole of the nebula, consistent with it being cool molecular gas situated at the outskirts of the H II region.

Appeared in: ApJ 634, 436

Continuum emission in NGC 1068 and NGC 3147: indications for a turnover in the core spectra

Krips M.$(^{1})$, Eckart A.$(^{1})$, Neri R.$(^{2})$, Schödel R.$(^{1})$, Leon S.$(^{3})$, Downes D.$(^{2})$, García-Burillo S.$(^{4})$, Combes, F.$(^{5})$
$(^{1})$I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany, $(^{2})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France, $(^{3})$Instituto de Astrofísica de Andalucía (CSIC), C/ Camino Bajo de Huétor,24, Apartado 3004, 18080 Granada, Spain, $(^{4})$Observatorio Astronómico Nacional (OAN)-Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain, $(^{5})$Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France

We present new interferometric observations of the continuum emission at mm wavelengths in the Seyfert galaxies NGC 1068 and NGC 3147. Three mm continuum peaks are detected in NGC 1068, one centered on the core, one associated with the jet and the third one with the counter-jet. This is the first significant detection of the radio jet and counter-jet at mm wavelengths in NGC 1068. While the fluxes of the jet components agree with a steep spectral index extrapolated from cm-wavelengths, the core fluxes indicate a turnover of the inverted cm- into a steep mm-spectrum at roughly $\sim 50$ GHz which is most likely caused by electron-scattered synchrotron emission. As in NGC 1068, the spectrum of the pointlike continuum source in NGC 3147 also shows a turnover between cm and mm-wavelengths at $\sim 25$ GHz resulting from synchrotron self-absorption different to NGC 1068. This strongly resembles the spectrum of Sgr A*, the weakly active nucleus of our own galaxy, and M 81*, a link between Sgr A* and Seyfert galaxies in terms of activity sequence, which may display a similar turnover.

Appeared in: A&A 446, 113

Probing isotopic ratios at redshift z=0.89: molecular line absorption toward PKS 1830-211

Muller S.$(^{1})$, Guélin M.$(^{2})$, Dumke M.$(^{3})$, Lucas R.$(^{2})$
$(^{1})$Institute of Astronomy and Astrophysics, Academia Sinica, 128 Section 2, PO Box 1-87, Nankang, Taipei 115, Taiwan $(^{2})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France $(^{3})$ESO, Alonso de Cordova 3107, Vitacura, Santiago, Chile

Molecular absorption lines in the line of sight to distant quasars are an extremely powerful tool to probe the dense interstellar medium and its chemical composition in intervening galaxies from low to high redshifts. The absorption line measurements of different isotopomers even allow us to study isotopic ratios, which can be interpreted as the signature of past nucleosynthesis activity, and put some constraints on the chemical evolution this paper, we present the study of molecular absorption lines in front of the quasar PKS 1830-211. The absorption is due to an intervening galaxy at $z=0.89$ which is identified as a nearly face-on spiral galaxy. We have carried out a survey of absorption lines of various HCO$^+$, HCN, HNC, and CS isotopomers with the plateau de bure interferometer and derived for the first time the C, N, O, and S isotopic ratios in such a distant object.this $z=0.89$ absorption system offers an unique opportunity to study the chemical composition in the disk of a spiral galaxy only a few gyr old. Our results show significantly different isotopic ratios as compared to those measured in the solar system or in the local ISM, indicating a poorly enhanced abundance of material processed by intermediate and low mass stars.

Appeared in: Probing Galaxies through Quasar Absorption Lines, Proc. IAU 199, March 14-18 2005, Shanghai, Eds. P.R. Williams, Ch.-G. Shu and B. Menard. Cambridge Univ. Press 2005, p.313

On the density of EKOs and related objects

Altenhoff W.J.$(^{1})$, Bertoldi F.$(^{1,2})$, Menten K.M.$(^{1})$, Thum C.
$(^{1})$MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany, $(^{2})$Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany, $(^{3})$IRAM, 300 rue de la Piscine, 38406 St. Martin d'Hères, France

Recently published mass determinations of EKO binaries, combined with photometric size determinations, allow to derive a mean density of the distant minor planets of $\approx 0.2$ g cm$^{-3}$. This agrees well with the nuclear density of 1P/Halley of 0.26 g cm$^{-3}$, determined in the Giotto mission, and it suggests that these low density objects are essentially undifferentiated planetesimals.

Appeared in: A&A 441, L5

Observing Procedures at Millimeter and Sub-millimeter Wavelengths: Imaging an Astronomical Object

Michel Guélin$(^{1})$
$(^{1})$IRAM, 300 rue de la Piscine, 38406 St. Martin d'Hères, France

This lecture, presented at the 2004 IAOC International Workshop The Cool Universe: Observing Cosmic Dawn, held in October 2004 at Valparaiso, is a 24 page introduction to radio imaging at millimeter and sub-millimeter wavelengths. The emission from interstellar sources and the absorption by the Earth's atmosphere are briefly discussed. The basic concepts of instrumental transfer function, visibility, noise and image deconvolution are presented.

Appeared in: ``The Cool Universe: Observing Cosmic Dawn'' Eds. C.Lidman and D.Alloin, ASP Conf. Series 344, 3

Molecular gas in the Andromeda galaxy

Ch. Nieten$(^{1})$, N. Neininger$(^{1,2,3})$, M. Guélin$(^{3})$, H. Ungerechts$(^{4})$, R. Lucas$(^{3})$, E. M. Berkhuijsen$(^{1})$, R. Beck$(^{1})$, R. Wielebinski$(^{1})$
$(^{1})$MPIfR, Bonn, Germany, $(^{2})$Radioastronomisches Institut, Univ. Bonn, Germany, $(^{3})$IRAM, Grenoble, France, $(^{4})$IRAM, Granada, Spain

We present a new $^{12}$CO(J=1-0)-line survey of the Andromeda galaxy, M31, with the highest resolution to date ( $23\hbox{$^{\prime\prime}$}$, or 85 pc along the major axis), observed On-the-Fly with the IRAM 30-m telescope. We mapped an area of about $2\degr\times 0.5\degr$ which was tightly sampled on a grid of $9\hbox{$^{\prime\prime}$}$ with a velocity resolution of $2.6$ km s$^{-1}$. The r.m.s. noise in the velocity-integrated map is around $0.35$ K km s$^{-1}$ on the $T_{\rm mb}$-scale.
Emission from the $^{12}$CO(1-0) line is detected from galactocentric radius $R=3$kpc to $R=16$kpc, but peaks in intensity at $R\sim 10$kpc. Some clouds are visible beyond $R=16$kpc, the farthest of them at $R=19.4$kpc.
The molecular gas traced by the (1-0) line is concentrated in narrow arm-like filaments, which often coincide with the dark dust lanes visible at optical wavelengths. The HI arms are broader and smoother than the molecular arms. Between $R=4$kpc and $R=12$kpc the brightest CO filaments and the darkest dust lanes define a two-armed spiral pattern that is well described by two logarithmic spirals with a constant pitch angle of 7$^\circ $-8$^\circ $. Except for some bridge-like structures between the arms, the interarm regions and the central bulge are free of emission at our sensitivity. The arm-interarm brightness ratio averaged over a length of 15 kpc along the western arms reaches about 20 compared to 4 for HI at an angular resolution of $45\hbox{$^{\prime\prime}$}$.
In several selected regions we also observed the $^{12}$CO(2-1)-line on a finer grid. Towards the bright CO emission in our survey we find normal ratios of the (2-1)-to-(1-0) line intensities which are consistent with optically thick lines and thermal excitation of CO.
We compare the (velocity-integrated) intensity distribution of CO with those of HI, FIR at $175\,\mu$m and radio continuum, and interpret the CO data in terms of molecular gas column densities. For a constant conversion factor $X_{\rm {CO}}$, the molecular fraction of the neutral gas is enhanced in the spiral arms and decreases radially from 0.6 on the inner arms to 0.3 on the arms at $R\simeq 10$ kpc. We also compare the distributions of HI, H$_2$ and total gas with that of the cold (16K) dust traced at $\lambda = 175\,\mu$m. The ratios $N(HI)/I_{175}$ and $(N(HI)+2N({\rm H}_2))/I_{175}$ increase by a factor of $\sim20$ between the centre and $R\simeq 14$ kpc, whereas the ratio $2N(\rm {H}_2)/I_{175}$ only increases by a factor of 4. For a constant value of $X_{\rm {CO}}$, this means that either the atomic and total gas-to-dust ratios increase by a factor of $\sim20$ or that the dust becomes colder towards larger radii. A strong variation of $X_\mathrm{CO}$ with radius seems unlikely. The observed gradients affect the cross-correlations between gas and dust. In the radial range $R=8$-14 kpc total gas and cold dust are well correlated; molecular gas is better correlated with cold dust than atomic gas. At smaller radii no significant correlations between gas and dust are found.
The mass of the molecular gas in M31 within a radius of 18 kpc is $M (\mbox{H}_2) = 3.6\times 10^8\, \mbox{M$_\odot$}$ at the adopted distance of 780 kpc. This is 12% of the total neutral gas mass within this radius and 7% of the total neutral gas mass in M31.

Appeared in: A&A 443, 841

The trans-neptunian object UB$_{313}$ is larger than Pluto

F. Bertoldi$(^{1,2})$, W. Altenhoff$(^{2})$, A. Weiss$(^{2})$, K.M. Menten$(^{2})$ and C. Thum$(^{3})$
$(^{1})$Argelander Institute for Astronomy, University of Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany, $(^{2})$MPIfR, Auf dem Hügel 69, D-53121 Bonn, Germany, $(^{3})$IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France

The most distant known object in the Solar System, 2003 UB$_{313}$ (97 AU from the Sun), was recently discovered near its aphelion. Its high eccentricity and inclination to the ecliptic plane, along with its perihelion near the orbit of Neptune, identify it as a member of the `scattered disk'. This disk of bodies probably originates in the Kuiper belt objects, which orbit near the ecliptic plane in circular orbits between 30 and 50 AU, and may include Pluto as a member. The optical brightness of 2003 UB$_{313}$, if adjusted to Pluto's distance, is greater than that of Pluto, which suggested that it might be larger than Pluto. The actual size, however, could not be determined from the optical measurements because the surface reflectivity (albedo) was unknown. Here we report observations of the thermal emission of 2003 UB$_{313}$ at a wavelength of 1.2 mm, which in combination with the measured optical brightness leads to a diameter of $3000 \pm 300 \pm 100$ km. Here the first error reflects measurement uncertainties, while the second derives from the unknown object orientation. This makes 2003 UB$_{313}$ the largest known trans-neptunian object, even larger than Pluto (2300 km). The albedo is $0.60 \pm 0.10 \pm 0.05$, which is strikingly similar to that of Pluto, suggesting that the methane seen in the optical spectrum causes a highly reflective icy surface.

Appeared in: Nature 439, 563

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Up: IRAM Newsletter 65 (February 2006) Previous: New Control System (NCS)