分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present updated measurements of the [O III] 88 $\mu$m, [C II] 158 $\mu$m,
and dust continuum emission from a star-forming galaxy at $z=7.212$,
SXDF-NB1006-2, by utilizing Atacama Large Millimeter/submillimeter Array (ALMA)
archival data sets analysed in previous studies and data sets that have not
been analysed before. The follow-up ALMA observations with higher angular
resolution and sensitivity reveal a clumpy structure of the [O III] emission on
a scale of $0.32-0.85\,\rm{kpc}$. We also combined all the ALMA [O III] ([C
II]) data sets and updated the [O III] ([C II]) detection to $5.9\sigma$
($3.6\sigma-4.5\sigma$). The non-detection of [C II] with data from the REBELS
large program implies the incompleteness of spectral-scan surveys using [C II]
to detect galaxies with high star formation rates (SFRs) but marginal [C II]
emission at high-$z$. The dust continuum at 90 $\mu$m and 160 $\mu$m remains
undetected, indicating little dust content of
$<3.9\times10^{6}\,M_\odot\,(3\sigma)$, and we obtained a more stringent
constraint on the total infrared luminosity. We updated the [O III]/[C II]
luminosity ratios to $10.2\pm4.7~(6.1\pm3.5$) and $20\pm12~(9.6\pm6.1$) for
$4.5\sigma$ and $3.6\sigma$ [C II] detections, respectively, where the ratios
in the parentheses are corrected for the surface brightness dimming effect on
the extended [C II] emission. We also found a strong [C II] deficit ($0.6-1.3$
dex) between SXDF-NB1006-2 and the mean $L_{\rm{[CII]}}-\rm{SFR}$ relation of
galaxies at $0
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We conduct a $^{12}$C$^{16}$O($J$=1-0) (hereafter CO) mapping survey of 64 galaxies in the Fornax cluster using the ALMA Morita array in cycle 5. CO emission is detected from 23 out of the 64 galaxies. Our sample includes dwarf, spiral and elliptical galaxies with stellar masses of $M_{\rm star}\sim10^{6.3-11.6}$~M$_\odot$. The achieved beam size and sensitivity are $15''\times8''$ and $\sim12$~mJy~beam$^{-1}$ at the velocity resolution of $\sim10$~km~s$^{-1}$, respectively. We study the cold-gas (molecular- and atomic-gas) properties of 38 subsamples with $M_{\rm star}>10^9$~M$_\odot$ combined with literature HI data. We find that: (1) the low star-formation (SF) activity in the Fornax galaxies is caused by the decrease in the cold-gas mass fraction with respect to stellar mass (hereafter, gas fraction) rather than the decrease of the SF efficiency from the cold gas; (2) the atomic-gas fraction is more heavily reduced than the molecular-gas fraction of such galaxies with low SF activity. A comparison between the cold-gas properties of the Fornax galaxies and their environmental properties suggests that the atomic gas is stripped tidally and by the ram pressure, which leads to the molecular gas depletion with an aid of the strangulation and consequently SF quenching. Pre-processes in the group environment would also play a role in reducing cold-gas reservoirs in some Fornax galaxies.