General model of vertical distribution of stars in the Milky Way using complete Jeans equations

Sarkar, S.; Jog, Chanda J.

doi:10.1093/mnras/stz3512

Cited by 4 publications

(1 citation statement)

References 21 publications

(34 reference statements)

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“…Further, using the stellar and the HI surface density, along with the dark matter mass models, we solve the two-component Jeans equation for modeling the vertical stellar dispersion as a function of radius. We use the observed stellar scaleheight and the limits on the HI velocity dispersion and the HI scaleheight as constraints on the two-component Jeans equation (Narayan & Jog 2002;Banerjee et al 2010;Sarkar & Jog 2020, 2019bPatra 2020bPatra ,a, 2018.…”

Section: Introductionmentioning

confidence: 99%

HI 21 cm observation and mass models of the extremely thin galaxy FGC 1440

Aditya,

Kamphuis,

Banerjee

et al. 2021

Preprint

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We present observations and models of the kinematics and distribution of neutral hydrogen (HI) in the superthin galaxy FGC 1440 with an optical axial ratio a/b = 20.4. Using the Giant Meterwave Radio telescope (GMRT), we imaged the galaxy with a spectral resolution of 1.7 km s −1 and a spatial resolution of 15. 9 × 13. 5. We find that FGC 1440 has an asymptotic rotational velocity of 141.8 km s −1 . The structure of the HI disc in FGC 1440 is that of a typical thin disc warped along the line of sight, but we can not rule out the presence of a central thick HI disc. We find that the dark matter halo in FGC 1440 could be modeled by a pseudo-isothermal (PIS) profile with R c /R d < 2, where R c is the core radius of the PIS halo and R d the exponential stellar disc scale length. We note that in spite of the unusually large axial ratio of FGC 1440, the ratio of the rotational velocity to stellar vertical velocity dispersion, V Rot σ z ∼ 5 − 8, which is comparable to other superthins. Interestingly, unlike previously studied superthin galaxies which are outliers in the log 10 ( j * ) − log 10 (M * ) relation for ordinary bulgeless disc galaxies, FGC 1440 is found to comply with the same. The values of j for the stars, gas and the baryons in FGC 1440 are consistent with those of normal spiral galaxies with similar mass.

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Section: Introductionmentioning

confidence: 99%

HI 21 cm observation and mass models of the extremely thin galaxy FGC 1440

Aditya,

Kamphuis,

Banerjee

et al. 2021

Preprint

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Vertical stellar density distribution in a non-isothermal galactic disc

Sarkar

Jog

2020

Monthly Notices of the Royal Astronomical Society

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The vertical density distribution of stars in a galactic disc is traditionally obtained by assuming an isothermal vertical velocity dispersion of stars. Recent observations from SDSS, LAMOST, RAVE, Gaia etc show that this dispersion increases with height from the mid-plane. Here we study the dynamical effect of such non-isothermal dispersion on the self-consistent vertical density distribution for the thin disc stars in the Galaxy, obtained by solving together the Poisson equation and the equation of hydrostatic equilibrium. We find that in the non-isothermal case the mid-plane density is lower, and the scale height is higher than the corresponding values for the isothermal distribution, due to higher vertical pressure, hence the distribution is vertically more extended. The change is $\sim 35 \%$ at the solar radius for a stars-alone disc for the typical observed linear gradient of +6.7 km s−1kpc−1 and becomes even higher with increasing radii and increasing gradients explored. The distribution shows a wing at high z, in agreement with observations, and is fitted well by a double $\operatorname{sech}^{2}$, which could be mis-interpreted as the existence of a second, thicker disc, specially in external galaxies. We also consider a more realistic disc consisting of gravitationally coupled stars and gas in the field of dark matter halo. The results show the same trend but the effect of non-isothermal dispersion is reduced due to the opposite, constraining effect of the gas and halo gravity. Further, the non-isothermal dispersion lowers the theoretical estimate of the total mid-plane density i.e, Oort limit value, by 16%.

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H i 21 cm observation and mass models of the extremely thin galaxy FGC 1440

Aditya

Kamphuis

Banerjee

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present observations and models of the kinematics and distribution of neutral hydrogen (H i) in the superthin galaxy FGC 1440 with an optical axial ratio a/b = 20.4. Using the Giant Meterwave Radio telescope (GMRT), we imaged the galaxy with a spectral resolution of 1.7 km s−1 and a spatial resolution of 15${^{\prime \prime }_{.}}$9 × 13${^{\prime \prime }_{.}}$5. We find that FGC 1440 has an asymptotic rotational velocity of 141.8 km s−1. The structure of the H i disc in FGC 1440 is that of a typical thin disc warped along the line of sight, but we can${^{\prime \prime }_{.}}$ not rule out the presence of a central thick H i disc. We find that the dark matter halo in FGC 1440 could be modeled by a pseudo- isothermal (PIS) profile with $\rm R_{c}/ R_{d} <2$, where Rc is the core radius of the PIS halo and Rd the exponential stellar disc scale length. We note that in spite of the unusually large axial ratio of FGC 1440, the ratio of the rotational velocity to stellar vertical velocity dispersion, $\frac{V_{Rot}}{\sigma _{z}} \sim 5 - 8$, which is comparable to other superthins. Interestingly, unlike previously studied superthin galaxies which are outliers in the log10(j*) − log10(M*) relation for ordinary bulgeless disc galaxies, FGC 1440 is found to comply with the same. The values of j for the stars, gas and the baryons in FGC 1440 are consistent with those of normal spiral galaxies with similar mass.

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General model of vertical distribution of stars in the Milky Way using complete Jeans equations

Cited by 4 publications

References 21 publications

HI 21 cm observation and mass models of the extremely thin galaxy FGC 1440

HI 21 cm observation and mass models of the extremely thin galaxy FGC 1440

Vertical stellar density distribution in a non-isothermal galactic disc

H i 21 cm observation and mass models of the extremely thin galaxy FGC 1440

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