the extremely high gas content of galaxy ugc8802 chang rui-xiang hou jin-liang shen shi-yin
TRANSCRIPT
![Page 1: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/1.jpg)
The extremely high gas content of galaxy UGC8802
Chang Rui-xiang
Hou Jin-liang
Shen Shi-yin
![Page 2: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/2.jpg)
• Understanding the content and distribution of cold gas in galaxies is an important step to understand the formation and evolution of galaxies.
• The GALEX Arecibo SDSS Survey (GASS):
to gather high quality HI-line spectra using the Arecibo radio telescope for ~1000 galaxies selected from SDSS and GALEX:
M* >1010M⊙
0.025 < z < 0.05
![Page 3: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/3.jpg)
Moran et al.(2010, ApJ, 720,1126)
![Page 4: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/4.jpg)
UGC8802 is an interesting target:
• z=0.0411
• M*=2*1010M ⊙
• HI mass: 2.1*1010M⊙
CO observations:
• H2 mass: 1.45*109M⊙
Long-slit spectroscopy: • SFR• D4000• metallicity
Moran et al.(2010, ApJ, 720,1126)
![Page 5: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/5.jpg)
Milky Way M31 UGC8802
Stellar mass (1010M⊙) 5.0 5.9~8.7 2
Disk scale-length (kpc) 2.3 4.8 5.8
HI mass (1010M⊙) 0.4 0.5 2.1
H2 mass (1010M⊙) 0.11 0.02~0.04 0.14
Gas fraction 0.09 0.08 0.5
Total SFR (M⊙ yr-1) 1~5 0.4~1.0 3.7
Abundance gradient
(dex kpc-1) -0.04~-0.07 -0.18~-0.027 -0.04
![Page 6: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/6.jpg)
The origin and the fate of the gas in UGC8802:
• Scenarios that the gas was acquired in a recent merging event are disfavored because of the regular kinematics of the disk.
• Further investigations are required to answer this question.
Our motivations:• to construct a simple model and test if the continuous ga
s-infall model can be viable for UGC8802• to further understand the origin and evolution of cold gas
in UGC8802
![Page 7: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/7.jpg)
Main assumptions of our model:
• The disk is sheet-like and composed by a set of independent rings.
• The disk origins and grows by continuous gas infall.• The radial profile of stellar mass surface density is expon
ential in the present day.
![Page 8: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/8.jpg)
Main ingredients of the model:
• gas infall rate:
• modified K-S star formation law:
• gas outflow rate:
22 2/)()(),( pttin erAtrf
),(),( trSFRbtrf outout
4.1)(),( gasrtr
free parameters: )(),( rrt p
![Page 9: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/9.jpg)
• Chang et al.(2010,ApJ,722,380) showed that later infall-peak time or lower SFE predicts bluer color, higher gas fraction, lower metallicity and higher SFR density.
• The predicted SFR surface density are more sensitive to the SFE.
• Our best-fitting model:
It is adopted that the infall-peak time increases while the SFE decreases from the inner disk to the outer parts
![Page 10: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/10.jpg)
![Page 11: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/11.jpg)
The predicted evolution of gas surface density at three different Regions, 1rd (dot line), 3rd (solid line), and 5rd (dash line).
1rd
3rd
5rd
![Page 12: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/12.jpg)
• The model adopts late infall-peak time and low SFE in the outer disk results in high gas surface density in outer disk, which can explain the observed high gas fraction of UGC8802.
• Our results show that the continuous gas-infall model is also viable for UGC8802. This suggests that the cold gas in UGC8802 may be originated from continue gas-infall from the dark matter halo.
![Page 13: The extremely high gas content of galaxy UGC8802 Chang Rui-xiang Hou Jin-liang Shen Shi-yin](https://reader036.vdocuments.site/reader036/viewer/2022081518/551c1df9550346b24f8b5a4d/html5/thumbnails/13.jpg)
next steps:
• H2 mass: new star formation law