arXiv subjects

Manuel Aravena

Publications and source records attributed to Manuel Aravena.

166 records · Page 10Linked to original sources

arXiv2010

Cold molecular gas in massive disk galaxies at z=1.5

We report the detection of the CO J=1-0 emission line in three near-infrared selected star-forming galaxies at z~1.5 with the Very Large Array (VLA) and the Green Bank telescope (GBT). These observations directly trace the bulk of molecular gas in these galaxies. We find H_2 gas masses of 8.3 \pm 1.9 x 10^{10} M_sun, 5.6 \pm 1.4 x 10^{10} M_sun and 1.23 \pm 0.34 x 10^{11} M_sun for BzK-4171, BzK-21000 and BzK-16000, respectively, assuming a conversion alpha_CO=3.6 M_sun (K km s^{-1} pc^{2})^{-1}. We combined our observations with previous CO 2-1 detections of these galaxies to study the properties of their molecular gas. We find brightness temperature ratios between the CO 2-1 and CO 1-0 emission lines of 0.80_{-0.22}^{+0.35}, 1.22_{-0.36}^{+0.61} and 0.41_{-0.13}^{+0.23} for BzK-4171, BzK-21000 and BzK-16000, respectively. At the depth of our observations it is not possible to discern between thermodynamic equilibrium or sub-thermal excitation of the molecular gas at J=2. However, the low temperature ratio found for BzK-16000 suggests sub-thermal excitation of CO already at J=2. For BzK-21000, a Large Velocity Gradient model of its CO emission confirms previous results of the low-excitation of the molecular gas at J=3. From a stacked map of the CO 1-0 images, we measure a CO 2-1 to CO 1-0 brightness temperature ratio of 0.92_{-0.19}^{+0.28}. This suggests that, on average, the gas in these galaxies is thermalized up to J=2, has star-formation efficiencies of ~100 L_sun (K km s^{-1} pc^2)^{-1} and gas consumption timescales of ~0.4 Gyr, unlike SMGs and QSOs at high redshifts.

astro-ph.CO↗

arXiv2009

Environment of MAMBO galaxies in the COSMOS field

Submillimeter galaxies (SMG) represent a dust-obscured high-redshift population undergoing massive star formation activity. Their properties and space density have suggested that they may evolve into spheroidal galaxies residing in galaxy clusters. In this paper, we report the discovery of compact (~10"-20") galaxy overdensities centered at the position of three SMGs detected with the Max-Planck Millimeter Bolometer camera (MAMBO) in the COSMOS field. These associations are statistically significant. The photometric redshifts of galaxies in these structures are consistent with their associated SMGs; all of them are between z=1.4-2.5, implying projected physical sizes of ~170 kpc for the overdensities. Our results suggest that about 30% of the radio-identified bright SMGs in that redshift range form in galaxy density peaks in the crucial epoch when most stars formed.

astro-ph.CO↗

arXiv2009

Imaging Atomic and Highly Excited Molecular Gas in a z=6.42 Quasar Host Galaxy: Copious Fuel for an Eddington-Limited Starburst at the End of Cosmic Reionization

We have imaged CO(J=7-6) and CI(3P2-3P1) emission in the host galaxy of the z=6.42 quasar SDSS J114816.64+525150.3 (hereafter: J1148+5251) through observations with the Plateau de Bure Interferometer. The region showing CO(J=7-6) emission is spatially resolved, and its size of 5 kpc is in good agreement with earlier CO(J=3-2) observations. In combination with a revised model of the collisional line excitation in this source, this indicates that the highly excited molecular gas traced by the CO J=7-6 line is subthermally excited (showing only 58+/-8% of the CO J=3-2 luminosity), but not more centrally concentrated. We also detect CI(3P2-3P1) emission in the host galaxy of J1148+5251, but the line is too faint to enable a reliable size measurement. From the CI(3P2-3P1) line flux, we derive a total atomic carbon mass of M_CI=1.1x10^7 M_sun, which corresponds to ~5x10^-4 times the total molecular gas mass. We also searched for H2O(J_KaKc=2_12-1_01) emission, and obtained a sensitive line luminosity limit of L'_H2O<4.4x10^9 K kms pc^2, i.e., <15% of the CO(J=3-2) luminosity. The warm, highly excited molecular gas, atomic gas and dust in this quasar host at the end of cosmic reionization maintain an intense starburst that reaches surface densities as high as predicted by (dust opacity) Eddington limited star formation over kiloparsec scales.

astro-ph.CO↗

arXiv2008

Properties of the molecular gas in a starbursting QSO at z=1.83 in the COSMOS field

Using the IRAM 30m telescope, we have detected the CO J=2-1, 4-3, 5-4, and 6-5 emission lines in the millimeter-bright, blank-field selected AGN COSMOS J100038+020822 at redshift z=1.8275. The sub-local thermodynamic equilibrium (LTE) excitation of the J=4 level implies that the gas is less excited than that in typical nearby starburst galaxies such as NGC253, and in the high-redshift quasars studied to date, such as J1148+5251 or BR1202-0725. Large velocity gradient (LVG) modeling of the CO line spectral energy distribution (CO SED; flux density vs. rotational quantum number) yields H2 densities in the range 10^{3.5}--10^{4.0} cm-3, and kinetic temperatures between 50 K and 200 K. The H2 mass of (3.6 - 5.4) x 10^{10} M_sun implied by the line intensities compares well with our estimate of the dynamical mass within the inner 1.5 kpc of the object. Fitting a two-component gray body spectrum, we find a dust mass of 1.2 x 10^{9} M_sun, and cold and hot dust temperatures of 42+/-5 K and 160+/-25 K, respectively. The broad MgII line allows us to estimate the mass of the central black hole as 1.7 x 10^{9} M_sun. Although the optical spectrum and multi-wavelength SED matches those of an average QSO, the molecular gas content and dust properties resemble those of known submillimeter galaxies (SMGs). The optical morphology of this source shows tidal tails that suggest a recent interaction or merger. Since it shares properties of both starburst and AGN, this object appears to be in a transition from a strongly starforming submillimeter galaxy to a QSO.

astro-ph↗