Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Hideaki Takemura
Fumitaka Nakamura
Héctor G. Arce
Nicola Schneider
Volker Ossenkopf-Okada
Shuo Kong
Shun Ishii
Kazuhito Dobashi
Tomomi Shimoikura
Patricio Sanhueza
Takashi Tsukagoshi
Paolo Padoan
Ralf S. Klessen
Paul. F. Goldsmith
Blakesley Burkhart
Dariusz C. Lis Álvaro Sánchez-Monge
Yoshito Shimajiri
Ryohei Kawabe
Abstract： The mass distribution of dense cores is a potential key to understand the process of star formation. Applying dendrogram analysis to the CARMA-NRO Orion C$^{18}$O ($J$=1--0) data, we identify 2342 dense cores, about 22 \% of which have virial ratios smaller than 2, and can be classified as gravitationally bound cores. The derived core mass function (CMF) for bound starless cores which are not associate with protostars has a slope similar to Salpeter's initial mass function (IMF) for the mass range above 1 $M_\odot$, with a peak at $\sim$ 0.1 $M_\odot$. We divide the cloud into four parts based on the declination, OMC-1/2/3, OMC-4/5, L1641N/V380 Ori, and L1641C, and derive the CMFs in these regions. We find that starless cores with masses greater than 10 $M_\odot$ exist only in OMC-1/2/3, whereas the CMFs in OMC-4/5, L1641N, and L1641C are truncated at around 5--10 $M_\odot$. From the number ratio of bound starless cores and Class II objects in each subregion, the lifetime of bound starless cores is estimated to be 5--30 free-fall times, consistent with previous studies for other regions. In addition, we discuss core growth by mass accretion from the surrounding cloud material to explain the coincidence of peak masses between IMFs and CMFs. The mass accretion rate required for doubling the core mass within a core lifetime is larger than that of Bondi-Hoyle accretion by a factor of order 2. This implies that more dynamical accretion processes are required to grow cores.
Peer Review Status:
Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Shuo Huang
Hideki Umehata
Ryohei Kawabe
Kotaro Kohno
Minju Lee
Yoichi Tamura
Bunyo Hatsukade
Ken Mawatari
Abstract： We report the physical characterization of four CO emitters detected near the bright submillimeter galaxy (SMG) SSA22-AzTEC26. We analyze the data from ALMA band 3, 4, and 7 observations of the SSA22-AzTEC26 field. In addition to the targeted SMG, we detect four line emitters with SNR$>5.2$ in the cube smoothed with 300 km s$^{-1}$ FWHM Gaussian filter. All four sources have near-infrared (NIR) counterparts within 1 arcsec. We perform ultraviolet to far-infrared spectral energy distribution (SED) modeling to derive the photometric redshift and physical properties. Based on photometric redshift, we reveal that two of them are CO(2-1) at a redshift of 1.113 and 1.146, and one is CO(3-2) at $z=2.124$. The three sources are massive galaxies with a stellar mass $\gtrsim10^{10.5}M_\odot$, but have different levels of star formation. Two lie within the scatter of the main sequence (MS) of star-forming galaxies at $z\sim1-2$, and the most massive galaxy lies significantly below the MS. However, all three sources have a gas fraction within the scatter of the MS scaling relation. This shows that a blind CO line search can detect massive galaxies with low specific star formation rates that still host large gas reservoirs and complements targeted surveys, suggesting later gas acquisition and the need for other mechanisms in addition to gas consumption to suppress the star formation.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Akio Taniguchi
Tom J. L. C. Bakx
Jochem J. A. Baselmans
Robert Huiting
Kenichi Karatsu
Nuria Llombart
Matus Rybak
Tatsuya Takekoshi
Yoichi Tamura
Hiroki Akamatsu
Stefanie Brackenhoff
Juan Bueno
Bruno T. Buijtendorp
Shahab Dabironezare
Anne-Kee Doing
Yasunori Fujii
Kazuyuki Fujita
Matthijs Gouwerok
Sebastian Hähnle
Tsuyoshi Ishida
Abstract： Integrated superconducting spectrometer (ISS) technology will enable ultra-wideband, integral-field spectroscopy for (sub)millimeter-wave astronomy, in particular, for uncovering the dust-obscured cosmic star formation and galaxy evolution over cosmic time. Here we present the development of DESHIMA 2.0, an ISS for ultra-wideband spectroscopy toward high-redshift galaxies. DESHIMA 2.0 is designed to observe the 220-440 GHz band in a single shot, corresponding to a redshift range of $z$=3.3-7.6 for the ionized carbon emission ([C II] 158 $\mu$m). The first-light experiment of DESHIMA 1.0, using the 332-377 GHz band, has shown an excellent agreement among the on-sky measurements, the lab measurements, and the design. As a successor to DESHIMA 1.0, we plan the commissioning and the scientific observation campaign of DESHIMA 2.0 on the ASTE 10-m telescope in 2023. Ongoing upgrades for the full octave-bandwidth system include the wideband 347-channel chip design and the wideband quasi-optical system. For efficient measurements, we also develop the observation strategy using the mechanical fast sky-position chopper and the sky-noise removal technique based on a novel data-scientific approach. In the paper, we show the recent status of the upgrades and the plans for the scientific observation campaign.
Peer Review Status:Awaiting Review
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