Kartik Sheth - Academia.edu (original) (raw)

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David Trethewey

Attila Kovács

Bruno Altieri

A. Cava

A. Cava

University of Geneva, Switzerland

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Papers by Kartik Sheth

Research paper thumbnail of Molecular gas in a z ˜ 2.5 triply-imaged, sub-mJy submillimetre galaxy typical of the cosmic far-infrared background

Astronomy & Astrophysics, 2005

We present the results of observations from the IRAM array of the submm galaxy SMMJ16359+6612 lyi... more We present the results of observations from the IRAM array of the submm galaxy SMMJ16359+6612 lying at z=2.516 behind the massive cluster A2218. The foreground gravitational lens produces 3 images with a total mag. of 45 of this faint submm galaxy, which has an intrinsic submm flux of f_850mic=0.8mJy placing it below the confusion limit of blank-field surveys. The substantial magnification provides a rare opportunity to probe the nature of a distant sub-mJy submm-selected galaxy, part of the population which produces the bulk of the submm cosmic far-infrared background. Our observations detect the CO(3-2) line in all 3 images, as well as the CO(7-6) line and the dust continuum at 1.3mm for the brightest image. The CO(3-2) velocity profile displays a double-peak profile which is well fit by two Gaussians with FWHM of 220km/s and separated by 280km/s. We estimate the dynamical mass of the system to be ~1.5 10^10 M_sun and an H2 gas mass of 2.6 10^9 M_sun. We identify a spatial offset of ~1'' between the two CO(3-2) velocity components, modeling of which indicates that the offset corresponds to just ~3kpc in projection at z=2.5. The spatial and velocity properties of these two components are closely related to features detected in previously published Halpha spectroscopy. We conclude that this source is likely to be a compact merger of 2 fairly typical Ly-break galaxies with a maximal separation between the two nuclei of ~3kpc. This system is much less luminous and massive than other high-z submm galaxies studied to date, but it bears a close similarity to similarly luminous, dusty starburst resulting from lower-mass mergers in the local Universe.

Research paper thumbnail of Detection of CO from SMM J16359+6612, the Multiply Imaged Submillimeter Galaxy behind A2218

Astrophysical Journal, 2004

We report the detection of CO ($J$=3$\to$2) line emission from all three multiple images (A,B and... more We report the detection of CO ($J$=3$\to$2) line emission from all three multiple images (A,B and C) of the intrinsically faint ($\simeq$ 0.8 mJy) submillimeter-selected galaxy SMM J16359+6612. The brightest source of the submm continuum emission (B) also corresponds to the brightest CO emission, which is centered at zzz=2.5168, consistent with the pre-existing redshift derived from \Ha. The observed CO flux in the A, B and C images is 1.2, 3.5 and 1.6 Jy \kms respectively, with a linewidth of 500pm100500\pm 100500pm100 \kms. After correcting for the lensing amplification, the CO flux corresponds to a molecular gas mass of sim2times1010h71−2\sim 2\times 10 ^{10} h_{71}^{-2}sim2times1010h71−2 \Msun, while the extent of the CO emission indicates that the dynamical mass of the system sim9times1010\sim9\times10^{10}sim9times1010 \Msun. Two velocity components are seen in the CO spectra; these could arise from either a rotating compact ring or disk of gas, or merging substructure. The star formation rate in this galaxy was previously derived to be sim\simsim100--500 \Msun \yr. If all the CO emission arises from the inner few kpc of the galaxy and the galactic CO-to-H$_2$ conversion factor holds, then the gas consumption timescale is a relatively short 40 Myr, and so the submm emission from SMM J16359+6612 may be produced by a powerful, but short-lived circumnuclear starburst event in an otherwise normal and representative high-redshift galaxy.

Research paper thumbnail of Molecular gas in a z ˜ 2.5 triply-imaged, sub-mJy submillimetre galaxy typical of the cosmic far-infrared background

Astronomy & Astrophysics, 2005

We present the results of observations from the IRAM array of the submm galaxy SMMJ16359+6612 lyi... more We present the results of observations from the IRAM array of the submm galaxy SMMJ16359+6612 lying at z=2.516 behind the massive cluster A2218. The foreground gravitational lens produces 3 images with a total mag. of 45 of this faint submm galaxy, which has an intrinsic submm flux of f_850mic=0.8mJy placing it below the confusion limit of blank-field surveys. The substantial magnification provides a rare opportunity to probe the nature of a distant sub-mJy submm-selected galaxy, part of the population which produces the bulk of the submm cosmic far-infrared background. Our observations detect the CO(3-2) line in all 3 images, as well as the CO(7-6) line and the dust continuum at 1.3mm for the brightest image. The CO(3-2) velocity profile displays a double-peak profile which is well fit by two Gaussians with FWHM of 220km/s and separated by 280km/s. We estimate the dynamical mass of the system to be ~1.5 10^10 M_sun and an H2 gas mass of 2.6 10^9 M_sun. We identify a spatial offset of ~1'' between the two CO(3-2) velocity components, modeling of which indicates that the offset corresponds to just ~3kpc in projection at z=2.5. The spatial and velocity properties of these two components are closely related to features detected in previously published Halpha spectroscopy. We conclude that this source is likely to be a compact merger of 2 fairly typical Ly-break galaxies with a maximal separation between the two nuclei of ~3kpc. This system is much less luminous and massive than other high-z submm galaxies studied to date, but it bears a close similarity to similarly luminous, dusty starburst resulting from lower-mass mergers in the local Universe.

Research paper thumbnail of Detection of CO from SMM J16359+6612, the Multiply Imaged Submillimeter Galaxy behind A2218

Astrophysical Journal, 2004

We report the detection of CO ($J$=3$\to$2) line emission from all three multiple images (A,B and... more We report the detection of CO ($J$=3$\to$2) line emission from all three multiple images (A,B and C) of the intrinsically faint ($\simeq$ 0.8 mJy) submillimeter-selected galaxy SMM J16359+6612. The brightest source of the submm continuum emission (B) also corresponds to the brightest CO emission, which is centered at zzz=2.5168, consistent with the pre-existing redshift derived from \Ha. The observed CO flux in the A, B and C images is 1.2, 3.5 and 1.6 Jy \kms respectively, with a linewidth of 500pm100500\pm 100500pm100 \kms. After correcting for the lensing amplification, the CO flux corresponds to a molecular gas mass of sim2times1010h71−2\sim 2\times 10 ^{10} h_{71}^{-2}sim2times1010h71−2 \Msun, while the extent of the CO emission indicates that the dynamical mass of the system sim9times1010\sim9\times10^{10}sim9times1010 \Msun. Two velocity components are seen in the CO spectra; these could arise from either a rotating compact ring or disk of gas, or merging substructure. The star formation rate in this galaxy was previously derived to be sim\simsim100--500 \Msun \yr. If all the CO emission arises from the inner few kpc of the galaxy and the galactic CO-to-H$_2$ conversion factor holds, then the gas consumption timescale is a relatively short 40 Myr, and so the submm emission from SMM J16359+6612 may be produced by a powerful, but short-lived circumnuclear starburst event in an otherwise normal and representative high-redshift galaxy.

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