### Abstract

A primary goal of integral field spectroscopic (IFS) surveys is to provide a statistical census of galaxies classified by their internal kinematics. As a result, the observational spin parameter, lambda(R), has become one of the most popular methods of quantifying the relative importance of velocity dispersion and rotation in supporting a galaxy's inner structure. The goal of this paper is to examine the relationship between the observationally deduced lambda(R) and one of the most commonly used theoretical spin parameters in the literature, the Bullock et al. lambda'. Using a set of N-body realizations of galaxies from which we construct mock IFS observations, we measure lambda(R) as an observer would, incorporating the effects of beam smearing and seeing conditions. Assuming parameters typical of current IFS surveys, we confirm that there are strong positive correlations between lambda(R) and measurement radius, and strong negative correlations between lambda(R) and size of the PSF, for late-type galaxies; these biases can be reduced using a recently proposed empirical correction. Once observational biases are corrected for, we find that lambda(R) provides a good approximation to similar to root 3/2 lambda' (R-eff), where lambda' is evaluated for the galactic stellar component within 1 R-eff.

Original language | English |
---|---|

Pages (from-to) | 249-262 |

Number of pages | 14 |

Journal | Monthly Notices of the Royal Astronomical Society |

Volume | 483 |

Issue number | 1 |

DOIs | |

Publication status | Published - Feb 2019 |

### Cite this

*Monthly Notices of the Royal Astronomical Society*,

*483*(1), 249-262. https://doi.org/10.1093/mnras/sty3120

}

*Monthly Notices of the Royal Astronomical Society*, vol. 483, no. 1, pp. 249-262. https://doi.org/10.1093/mnras/sty3120

**A numerical twist on the spin parameter, lambda (R).** / Harborne, K. E.; Power, C.; Robotham, A. S. G.; Cortese, L.; Taranu, D. S.

Research output: Contribution to journal › Article

TY - JOUR

T1 - A numerical twist on the spin parameter, lambda (R)

AU - Harborne, K. E.

AU - Power, C.

AU - Robotham, A. S. G.

AU - Cortese, L.

AU - Taranu, D. S.

PY - 2019/2

Y1 - 2019/2

N2 - A primary goal of integral field spectroscopic (IFS) surveys is to provide a statistical census of galaxies classified by their internal kinematics. As a result, the observational spin parameter, lambda(R), has become one of the most popular methods of quantifying the relative importance of velocity dispersion and rotation in supporting a galaxy's inner structure. The goal of this paper is to examine the relationship between the observationally deduced lambda(R) and one of the most commonly used theoretical spin parameters in the literature, the Bullock et al. lambda'. Using a set of N-body realizations of galaxies from which we construct mock IFS observations, we measure lambda(R) as an observer would, incorporating the effects of beam smearing and seeing conditions. Assuming parameters typical of current IFS surveys, we confirm that there are strong positive correlations between lambda(R) and measurement radius, and strong negative correlations between lambda(R) and size of the PSF, for late-type galaxies; these biases can be reduced using a recently proposed empirical correction. Once observational biases are corrected for, we find that lambda(R) provides a good approximation to similar to root 3/2 lambda' (R-eff), where lambda' is evaluated for the galactic stellar component within 1 R-eff.

AB - A primary goal of integral field spectroscopic (IFS) surveys is to provide a statistical census of galaxies classified by their internal kinematics. As a result, the observational spin parameter, lambda(R), has become one of the most popular methods of quantifying the relative importance of velocity dispersion and rotation in supporting a galaxy's inner structure. The goal of this paper is to examine the relationship between the observationally deduced lambda(R) and one of the most commonly used theoretical spin parameters in the literature, the Bullock et al. lambda'. Using a set of N-body realizations of galaxies from which we construct mock IFS observations, we measure lambda(R) as an observer would, incorporating the effects of beam smearing and seeing conditions. Assuming parameters typical of current IFS surveys, we confirm that there are strong positive correlations between lambda(R) and measurement radius, and strong negative correlations between lambda(R) and size of the PSF, for late-type galaxies; these biases can be reduced using a recently proposed empirical correction. Once observational biases are corrected for, we find that lambda(R) provides a good approximation to similar to root 3/2 lambda' (R-eff), where lambda' is evaluated for the galactic stellar component within 1 R-eff.

KW - Galaxy: evolution

KW - galaxies: kinematics and dynamics

KW - SAMI GALAXY SURVEY

KW - STELLAR ANGULAR-MOMENTUM

KW - SDSS-IV MANGA

KW - SAURON PROJECT

KW - SLOW ROTATORS

KW - MATTER

KW - DARK

KW - MASS

KW - KINEMATICS

KW - EVOLUTION

U2 - 10.1093/mnras/sty3120

DO - 10.1093/mnras/sty3120

M3 - Article

VL - 483

SP - 249

EP - 262

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 1

ER -