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[show abstract]
[hide abstract]
ABSTRACT: We report the existence of spiral arms in the recently formed gaseous and
dusty disk of the closest giant elliptical, NGC 5128 (Centaurus A), using high
resolution 12CO(2-1) observations of the central 3 arcmin (3 kpc) obtained with
the Submillimeter Array (SMA). This provides evidence that spiral-like features
can develop within ellipticals if enough cold gas exists. We elucidate the
distribution and kinematics of the molecular gas in this region with a
resolution of 4.4 x 1.9 (80 pc x 40 pc). The spiral arms extend from the
circumnuclear gas at a radius of 200 pc to at least 1 kiloparsec. The general
properties of the arms are similar to those in spiral galaxies: they are
trailing, the width is \sim 500 \pm 200 pc, and the pitch angle is 20 degrees.
From independent estimates of the time when the HI-rich galaxy merger occurred,
we infer that the formation of spiral arms happened on a time scale of less
than \sim10^8 yr. The formation of spiral arms increases the gas density and
thus the star formation efficiency in the early stages of the formation of a
disk.
08/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We present the first aperture synthesis unbiased spectral line survey toward an extragalactic object. The survey covered the 40 GHz frequency range between 202 and 242 GHz of the 1.3 mm atmospheric window. We find that 80% of the observed band shows molecular emission, with 73 features identified from 15 molecular species and 6 isotopologues. The 13C isotopic substitutions of HC3N and transitions from H2(18)O, 29SiO, and CH2CO are detected for the first time outside the Galaxy. Within the broad observed band, we estimate that 28% of the total measured flux is due to the molecular line contribution, with CO only contributing 9% to the overall flux. We present maps of the CO emission at a resolution of 2.9"x1.9" which, though not enough to resolve the two nuclei, recover all the single-dish flux. The 40 GHz spectral scan has been modelled assuming LTE conditions and abundances are derived for all identified species. The chemical composition of Arp 220 shows no clear evidence of an AGN impact on the molecular emission but seems indicative of a purely starburst-heated ISM. The overabundance of H2S and the low isotopic ratios observed suggest a chemically enriched environment by consecutive bursts of star formation, with an ongoing burst at an early evolutionary stage. The large abundance of water (~10^-5), derived from the isotopologue H2(18)O, as well as the vibrationally excited emission from HC3N and CH3CN are claimed to be evidence of massive star forming regions within Arp 220. Moreover, the observations put strong constraints on the compactness of the starburst event in Arp 220. We estimate that such emission would require ~2-8x10^6 hot cores, similar to those found in the Sgr B2 region in the Galactic center, concentrated within the central 700 pc of Arp 220. Comment: Accepted for publication in A&A
12/2010;
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D. Espada, A. B. Peck,
S. Matsushita,
K. Sakamoto,
C. Henkel,
D. Iono,
F. P. Israel,
S. Muller,
G. Petitpas,
Y. Pihlström,
G. B. Taylor,
and D. V. Trung
[show abstract]
[hide abstract]
ABSTRACT: We report on atomic gas (H I) and molecular gas (as traced by CO(2-1)) redshifted absorption features toward the nuclear regions of the closest powerful radio galaxy, Centaurus A (NGC 5128). Our H I observations using the Very Long Baseline Array allow us to discern with unprecedented sub-parsec resolution H I absorption profiles toward different positions along the 21 cm continuum jet in the inner 03 (or 5.4 pc). In addition, our CO(2-1) data obtained with the Submillimeter Array probe the bulk of the absorbing molecular gas with little contamination by emission, which was not possible with previous CO single-dish observations. We shed light on the physical properties of the gas in the line of sight with these data, emphasizing the still open debate about the nature of the gas that produces the broad absorption line (~55 km s–1). First, the broad H I line is more prominent toward the central and brightest 21 cm continuum component than toward a region along the jet at a distance ~20 mas (or 0.4 pc) further from the nucleus. This indicates that the broad absorption line arises from gas located close to the nucleus, rather than from diffuse and more distant gas. Second, the different velocity components detected in the CO(2-1) absorption spectrum match well with other molecular lines, such as those of HCO+(1-0), except the broad absorption line that is detected in HCO+(1-0) (and most likely related to that of the H I). Dissociation of molecular hydrogen due to the active galactic nucleus seems to be efficient at distances r 10 pc, which might contribute to the depth of the broad H I and molecular lines.
The Astrophysical Journal 08/2010; 720(1):666. · 6.02 Impact Factor
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J. D. Younger,
G. G. Fazio,
M. L. N. Ashby,
F. Civano,
M. Elvis,
M. A. Gurwell,
J S Huang,
D. Iono, A. B. Peck,
G. R. Petitpas,
K. S. Scott,
D. J. Wilner,
G W Wilson,
M. S. Yun
[show abstract]
[hide abstract]
ABSTRACT: We present high-resolution 345 GHz interferometric observations of two extreme luminous (L_{IR}>10^{13} L_sun), submillimetre-selected galaxies (SMGs) in the COSMOS field with the Submillimeter Array (SMA). Both targets were previously detected as unresolved point-sources by the SMA in its compact configuration, also at 345 GHz. These new data, which provide a factor of ~3 improvement in resolution, allow us to measure the physical scale of the far-infrared in the submillimetre directly. The visibility functions of both targets show significant evidence for structure on 0.5-1 arcsec scales, which at z=1.5 translates into a physical scale of 5-8 kpc. Our results are consistent with the angular and physical scales of two comparably luminous objects with high-resolution SMA followup, as well as radio continuum and CO sizes. These relatively compact sizes (<5-10 kpc) argue strongly for merger-driven starbursts, rather than extended gas-rich disks, as the preferred channel for forming SMGs. For the most luminous objects, the derived sizes may also have important physical consequences; under a series of simplifying assumptions, we find that these two objects in particular are forming stars close to or at the Eddington limit for a starburst. Comment: 9 pages, 3 Figures, submitted to MNRAS
03/2010;
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B. Hatsukade,
D. Iono,
T. Akiyama,
M. Yoshikawa,
J. S. Dunlop,
R. J. Ivison, A. B. Peck,
S. Ikarashi,
A. Biggs,
H. Ezawa, [......],
S. Matsushita,
K. Nakanishi,
N. Padilla,
G. Petitpas,
Y. Tamura,
J. Wagg,
D. J. Wilner,
G. W. Wilson,
T. Yamada,
and M. S. Yun
[show abstract]
[hide abstract]
ABSTRACT: We present an 880 μm Submillimeter Array (SMA) detection of the submillimeter galaxy SXDF 850.6. SXDF 850.6 is a bright source (S 850 μm = 8 mJy) detected in the SCUBA Half Degree Extragalactic Survey and has multiple possible radio counterparts in its deep radio image obtained at the VLA. Our new SMA detection finds that the submillimeter emission coincides with the brightest radio emission that is found ~8'' north of the coordinates determined from SCUBA. Despite the lack of detectable counterparts in deep UV/optical images, we find a source at the SMA position in near-infrared and longer wavelength images. We perform spectral energy distribution (SED) model fits to UV-optical-IR photometry (u, B, V, R, i', z', J, H, K, 3.6 μm, 4.5 μm, 5.8 μm, and 8.0 μm) and to submillimeter-radio photometry (850 μm, 880 μm, 1100 μm, and 21 cm) independently, and we find both are well described by starburst templates at a redshift of z 2.2 ± 0.3. The best-fit parameters from the UV-optical-IR SED fit are a redshift of z = 1.87+0.15 –0.07, a stellar mass of M = 2.5+2.2 –0.3 × 1011 M ☉, an extinction of AV = 3.0+0.3 –1.0 mag, and an age of 720+1880 –210 Myr. The submillimeter-radio SED fit provides a consistent redshift of z ~ 1.8-2.5, an IR luminosity of L IR = (7-26) ×1012 L ☉, and a star formation rate of 1300-4500 M ☉ yr–1. These results suggest that SXDF 850.6 is a mature system already having a massive amount of old stellar population constructed before its submillimeter bright phase and is experiencing a dusty starburst, possibly induced by major mergers.
The Astrophysical Journal 02/2010; 711(2):974. · 6.02 Impact Factor
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B. Hatsukade,
D. Iono,
T Yoshikawa,
M Akiyama,
J. S. Dunlop,
R. J. Ivison, A. B. Peck,
S. Ikarashi,
A. Biggs,
H. Ezawa, [......],
S Matsushita,
K Nakanishi,
N. Padilla,
G. Petitpas,
Y Tamura,
J. Wagg,
D. J. Wilner,
G W Wilson,
T Yamada,
M. S. Yun
[show abstract]
[hide abstract]
ABSTRACT: We present an 880 micron Submillimeter Array (SMA) detection of the submillimeter galaxy SXDF850.6. SXDF850.6 is a bright source (S(850 micron) = 8 mJy) detected in the SCUBA Half Degree Extragalactic Survey (SHADES), and has multiple possible radio counterparts in its deep radio image obtained at the VLA. Our new SMA detection finds that the submm emission coincides with the brightest radio emission that is found ~8" north of the coordinates determined from SCUBA. Despite the lack of detectable counterparts in deep UV/optical images, we find a source at the SMA position in near-infrared and longer wavelength images. We perform SED model fits to UV-optical-IR photometry (u, B, V, R, i', z', J, H, K, 3.6 micron, 4.5 micron, 5.8 micron, and 8.0 micron) and to submm-radio photometry (850 micron, 880 micron, 1100 micron, and 21 cm) independently, and we find both are well described by starburst templates at a redshift of z ~= 2.2 (+/- 0.3). The best-fit parameters from the UV-optical-IR SED fit are a redshift of z = 1.87 (+0.15/-0.07), a stellar mass of M_star = 2.5 +2.2/-0.3 x 10^11 M_sun, an extinction of A_V = 3.0 (+0.3/-1.0) mag, and an age of 720 (+1880/-210) Myr. The submm-radio SED fit provides a consistent redshift of z ~ 1.8-2.5, an IR luminosity of L_IR = (7-26) x 10^12 L_sun, and a star formation rate of 1300-4500 M_sun/yr. These results suggest that SXDF850.6 is a mature system already having a massive amount of old stellar population constructed before its submm bright phase and is experiencing a dusty starburst, possibly induced by major mergers. Comment: 7 pages, 5 figures, Accepted for publication in Astrophysical Journal
01/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present ~2'' resolution submillimeter observations of the submillimeter luminous giant Lyα blob (LAB1) in the SSA 22 protocluster at redshift z = 3.1 with the Submillimeter Array (SMA). Although the expected submillimeter flux density is 16 mJy at 880 μm, no emission is detected with the 2.4'' × 1.9'' (18 × 14 kpc) beam at the 3 σ level of 4.2 mJy beam-1 in the SMA field of view of 35''. This is in contrast to the previous lower angular resolution (15'') observations where a bright (17 mJy) unresolved submillimeter source was detected at 850 μm toward the LAB1 using the Submillimeter Common-User Bolometer Array on the James Clerk Maxwell Telescope. The SMA nondetection suggests that the spatial extent of the submillimeter emission of LAB1 should be larger than 4'' (>30 kpc). The most likely interpretation of the spatially extended submillimeter emission is that starbursts occur throughout the large area in LAB1. Some part of the submillimeter emission may come from spatially extended dust expelled from starburst regions by galactic superwind. The spatial extent of the submillimeter emission of LAB1 is similar to those of high-redshift radio galaxies rather than submillimeter galaxies.
The Astrophysical Journal 12/2008; 667(2):667. · 6.02 Impact Factor
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D. Iono, A. B. Peck,
A. Pope,
C. Borys,
D. Scott,
D. J. Wilner,
M. Gurwell,
P. T. P. Ho,
M. S. Yun,
S. Matsushita,
G. R. Petitpas,
J. S. Dunlop,
M. Elvis,
A. Blain,
and E. Le Floc'h
[show abstract]
[hide abstract]
ABSTRACT: We present high-resolution 890 μm images of two 20 mJy submillimeter galaxies, SMM J123711+622212 and MIPS J142824.0+352619, obtained using the Submillimeter Array (SMA). Using submillimeter interferometric observations with an angular resolution of 25, the coordinates of these high-redshift sources are determined with an accuracy of 02. The new SMA data on SMM J123711+622212 reveal an unresolved submillimeter source offset to the east by 08 from an optical galaxy found in deep HST images, suggesting either a large galaxy with a dusty central region or an interacting galaxy system. The SMA image of hyperluminous (LFIR = 3.2 × 1013 L☉) source MIPS J142824.0+352619 provides a firm upper limit to the source size of 12. This constraint provides evidence that the foreground lens is only weakly affecting the observed high far-infrared luminosity.
The Astrophysical Journal 12/2008; 640(1):L1. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present Submillimeter Array observations of the z = 3.91 gravitationally lensed broad absorption line quasar APM 08279+5255 which spatially resolve the 1.0 mm (200 μm rest frame) dust continuum emission. At 0.4'' resolution, the emission is separated into two components, a stronger, extended one to the northeast (46 ± 5 mJy) and a weaker, compact one to the southwest (15 ± 2 mJy). We have carried out simulations of the gravitational lensing effect responsible for the two submillimeter components in order to constrain the intrinsic size of the submillimeter continuum emission. Using an elliptical lens potential, the best-fit lensing model yields an intrinsic (projected) diameter of ~80 pc, which is not as compact as the optical/near-infrared (NIR) emission and agrees with previous size estimates of the gas and dust emission in APM 08279+5255. Based on our estimate, we favor a scenario in which the 200 μm (rest frame) emission originates from a warm dust component (Td = 150-220 K) that is mainly heated by the AGN rather than by a starburst. The flux is boosted by a factor of ~90 in our model, consistent with recent estimates for APM 08279+5255.
The Astrophysical Journal 12/2008; 671(1):L5. · 6.02 Impact Factor
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J. D. Younger,
J. S. Dunlop, A. B. Peck,
R. J. Ivison,
A. D. Biggs,
E. L. Chapin,
D. L. Clements,
S. Dye,
T. R. Greve,
D. H. Hughes,
D. Iono,
I. Smail,
M. Krips,
G. R. Petitpas,
D. Wilner,
A. M. Schael,
C. D. Wilson
[show abstract]
[hide abstract]
ABSTRACT: We present high-resolution interferometric imaging of LH 850.02, the brightest 850- and 1200-μm submillimetre (submm) galaxy in the Lockman Hole. Our observations were made at 890 μm with the Submillimetre Array (SMA). Our high-resolution submm imaging detects LH 850.02 at ≳6σ as a single compact (size ≲1 arcsec or ≲8 kpc) point source and yields its absolute position to ∼0.2-arcsec accuracy. LH 850.02 has two alternative radio counterparts within the Submillimetre Common User Bolometer Array (SCUBA) beam (LH 850.02N and LH 850.02S), both of which are statistically very unlikely to be so close to the SCUBA source position by chance. However, the precise astrometry from the SMA shows that the submm emission arises entirely from LH 850.02N, and is not associated with LH 850.02S (by far the brighter of the two alternative identifications at 24 μm). Fits to the optical–infrared (IR) multicolour photometry of LH 850.02N and LH 850.02S indicate that both lie at z≈ 3.3, and are therefore likely to be physically associated. At these redshifts, the 24-μm-to-submm flux density ratios suggest that LH 850.02N has an Arp 220-type starburst-dominated far-IR spectral energy distribution (SED), while LH 850.02S is more similar to Mrk 231, with less dust enshrouded star formation activity, but a significant contribution at 24 μm (rest frame 5–6 μm) from an active nucleus. This complex mix of star formation and active galactic nucleus (AGN) activity in multicomponent sources may be common in the high-redshift ultraluminous galaxy population, and highlights the need for precise astrometry from high-resolution interferometric imaging for a more complete understanding.
Monthly Notices of the Royal Astronomical Society 06/2008; 387(2):707 - 712. · 4.90 Impact Factor
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J. D. Younger,
J. S. Dunlop, A. B. Peck,
R. J. Ivison,
A. D. Biggs,
E. L. Chapin,
D. L. Clements,
S. Dye,
T. R. Greve,
D. H. Hughes,
D. Iono,
I. Smail,
M. Krips,
G. R. Petitpas,
D. Wilner,
A. M. Schael,
C. D. Wilson
[show abstract]
[hide abstract]
ABSTRACT: We present high-resolution interferometric imaging of LH850.02, the brightest 850- and 1200-micron submillimetre (submm) galaxy in the Lockman Hole. Our observations were made at 890 micron with the Submillimetre Array (SMA). Our high-resolution submm imaging detects LH850.02 at >6-sigma as a single compact (size < 1 arcsec or < 8 kpc) point source and yields its absolute position to ~0.2-arcsec accuracy. LH850.02 has two alternative radio counterparts within the SCUBA beam (LH850.02N & S), both of which are statistically very unlikely to be so close to the SCUBA source position by chance. However, the precise astrometry from the SMA shows that the submm emission arises entirely from LH850.02N, and is not associated with LH850.02S (by far the brighter of the two alternative identifications at 24-micron). Fits to the optical-infrared multi-colour photometry of LH850.02N & S indicate that both lie at z~3.3, and are therefore likely to be physically associated. At these redshifts, the 24 micron--to--submm flux density ratios suggest that LH850.02N has an Arp220-type starburst-dominated far-IR SED, while LH850.02S is more similar to Mrk231, with less dust-enshrouded star-formation activity, but a significant contribution at 24-micron (rest-frame ~5-6 micron) from an active nucleus. This complex mix of star-formation and AGN activity in multi-component sources may be common in the high redshift ultraluminous galaxy population, and highlights the need for precise astrometry from high resolution interferometric imaging for a more complete understanding. Comment: MNRAS, in press
01/2008;
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[show abstract]
[hide abstract]
ABSTRACT: We present Submillimeter Array observations of the z=3.91 gravitationally lensed broad absorption line quasar APM08279+5255 which spatially resolve the 1.0mm (0.2mm rest-frame) dust continuum emission. At 0.4" resolution, the emission is separated into two components, a stronger, extended one to the northeast (46+/-5mJy) and a weaker, compact one to the southwest (15+/-2mJy). We have carried out simulations of the gravitational lensing effect responsible for the two submm components in order to constrain the intrinsic size of the submm continuum emission. Using an elliptical lens potential, the best fit lensing model yields an intrinsic (projected) diameter of ~80pc, which is not as compact as the optical/near-infrared (NIR) emission and agrees with previous size estimates of the gas and dust emission in APM08279+5255. Based on our estimate, we favor a scenario in which the 0.2mm (rest-frame) emission originates from a warm dust component (T_d=150-220K) that is mainly heated by the AGN rather than by a starburst (SB). The flux is boosted by a factor of ~90 in our model, consistent with recent estimates for APM08279+5255. Comment: 6 pages, 2 figures, accepted for publication in ApJL, in emulateApJ format
10/2007;
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[show abstract]
[hide abstract]
ABSTRACT: One of the biggest challenges facing submillimeter wavelength
interferometry is correcting for short timescale atmospheric phase
fluctuations during the observations. Quasars sufficiently bright to
use as calibrators for current submillimeter facilities are scarce,
particularly at frequencies higher than 300 GHz. We present results of
an ongoing monitoring program to determine the fluxes and variability of
quasars at 230 and 345 GHz. The data are being collected at the
Submillimeter Array (SMA) on Mauna Kea and reduced using MIR data
reduction software. Results are updated regularly and are available in a
searchable format at http://sma1.sma.hawaii.edu/callist.html.
09/2007; 375:234.
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[show abstract]
[hide abstract]
ABSTRACT: We present ~2" resolution submillimeter observations of the submillimeter luminous giant Ly-alpha blob (LAB1) in the SSA 22 protocluster at redshift z=3.1 with the Submillimeter Array (SMA). Although the expected submillimeter flux density is 16 mJy at 880 micron, no emission is detected with the 2".4 x 1".9 (18 x 14 kpc) beam at the 3 sigma level of 4.2 mJy beam^{-1} in the SMA field of view of 35". This is in contrast to the previous lower angular resolution (15") observations where a bright (17 mJy) unresolved submillimeter source was detected at 850 micron toward the LAB1 using the Submillimeter Common-User Bolometer Array on the James Clerk Maxwell Telescope. The SMA non-detection suggests that the spatial extent of the submillimeter emission of LAB1 should be larger than 4" (>30 kpc). The most likely interpretation of the spatially extended submillimeter emission is that starbursts occur throughout the large area in LAB1. Some part of the submillimeter emission may come from spatially extended dust expelled from starburst regions by galactic superwind. The spatial extent of the submillimeter emission of LAB1 is similar to those of high redshift radio galaxies rather than submillimeter galaxies. Comment: 7 pages, 5 figures, accepted for publication in ApJ
07/2007;
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D. Iono, A. B. Peck,
A. Pope,
C. Borys,
D Scott,
D. J. Wilner,
M. Gurwell,
P. T. P. Ho,
M. S. Yun,
S Matsushita,
G. R. Petitpas,
J. S. Dunlop,
M. Elvis,
A. Blain,
E. Le Floc'h
[show abstract]
[hide abstract]
ABSTRACT: We present high resolution 890 micron images of two 20 mJy submillimeter galaxies, SMMJ123711+622212 and MIPS~J142824.0+352619, obtained using the Submillimeter Array (SMA). Using submillimeter interferometric observations with an angular resolution of 2.5", the coordinates of these high redshift sources are determined with an accuracy of 0.2". The new SMA data on SMMJ123711+622212 reveal an unresolved submm source offset to the east by 0.8" from an optical galaxy found in deep HST images, suggesting either a large galaxy with a dusty central region, or an interacting galaxy system. The SMA image of hyper-luminous (LFIR = 3.2 x 10^{13} Lsun) source MIPS~J142824.0+352619 provides a firm upper limit to the source size of < 1.2. This constraint provides evidence that the foreground lens is only weakly affecting the observed high FIR luminosity. Comment: 11 pages, 2 figures, ApJL accepted
02/2006;
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[show abstract]
[hide abstract]
ABSTRACT: We present high resolution 12CO, 13CO,
C18O J=2-1, and 12CO J=3-2 observations of the
nearby galaxies NGC 2903, NGC 3627, NGC 6574, and NGC 7331 made with the
Submillimeter Array. Our 1.5'' - 3'' resolution observations show the
warm, optically thin gas in the nuclei and spiral arms of these galaxies
exhibits structure and dynamics not detectable in the lower resolution
CO J=1-0 BIMA SONG and NRO-OVRO survey data. We discuss the effects of
the physical conditions in the molecular gas on the nuclear structure
and activity in these galaxies. These data highlight the need to study
the warm ISM at high angular and spectral resolution when trying to
understand gas inflow in barred and spiral galaxies.
The Submillimeter Array is a joint project between the Smithsonian
Astrophysical Observatory and the Academia Sinica Institute of Astronomy
and Astrophysics, and is funded by the Smithsonian Institution and the
Academia Sinica.
11/2005; 37:1258.
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S Matsushita,
K. Sakamoto,
C. -Y. Kuo,
P. -Y. Hsieh,
Dinh-V-Trung,
R. -Q. Mao,
D. Iono, A. B. Peck,
M. C. Wiedner,
S. -Y. Liu,
N. Ohashi,
J. Lim
[show abstract]
[hide abstract]
ABSTRACT: We present the first interferometric CO(J=3-2) observations (beam size of 3.9"x1.6" or 160pc x 65pc) with the Submillimeter Array (SMA) toward the center of the Seyfert 2 galaxy M51. The image shows a strong concentration at the nucleus and weak emission from the spiral arm to the northwest. The integrated intensity of the central component in CO(J=3-2) is almost twice as high as that in CO(J=1-0), indicating that the molecular gas within an ~80 pc radius of the nucleus is warm (>~100 K) and dense (~10^4 cm^-3). Similar intensity ratios are seen in shocked regions in our Galaxy, suggesting that these gas properties may be related to AGN or starburst activity. The central component shows a linear velocity gradient (~1.4 km/s/pc) perpendicular to the radio continuum jet, similar to that seen in previous observations and interpreted as a circumnuclear molecular disk/torus around the Seyfert 2 nucleus. In addition, we identify a linear velocity gradient (~0.7 km/s/pc) along the jet. Judging from the energetics, the velocity gradient can be explained by supernova explosions or energy and momentum transfer from the jet to the molecular gas via interaction, which is consistent with the high intensity ratio. Comment: 12 pages, 3 figures, accepted for publication in ApJL
07/2004;
