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arXiv · 2607.17776

Structural and dynamical properties of Tidal dwarf galaxies in the tails and bridge of the Guitar galaxy Arp 105

Jyoti Prakash·Kanak Saha
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Abstract

We present a multi-wavelength (far-ultraviolet to infrared) analysis of two tidal dwarf galaxy (TDG) candidates and a tidal bridge in the interacting system Arp 105 at $z = 0.029$ in the Abell 1185 cluster. Far-ultraviolet observations obtained with the Ultraviolet Imaging Telescope onboard AstroSat reveal strong FUV emission from the tidal galaxies Arp~105N and Arp~105S, indicating recent star formation. In Arp~105N, strong nebular emission lines and large equivalent widths $EW(H\alpha)=77.6\pm1.3$ $\overset{\circ}{\mathrm {A}}$ and $EW(H\beta)=15.8\pm1.7$ $\overset{\circ}{\mathrm {A}}$ imply a dominant starburst age of $\sim$6 - 10~Myr under an instantaneous-burst assumption, while the FUV emission suggests star formation sustained over the past $\sim100 - 200$~Myr. The relatively high metallicity, $\sim2/3,Z_\odot$ (based on the strong-line method), is consistent with expectations for a tidal dwarf galaxy formed from material inherited from the host galaxy. Together, these results suggest that Arp~105N hosts a composite stellar population, consisting of older stars stripped from the host galaxy and younger stars formed in situ. Spectral energy distribution modeling yields stellar masses of $5.75\times10^{9}$, $0.8\times10^{9}$, and $6.8\times10^{9},\rm M_\odot$ for Arp~105N, Arp~105S, and the tidal bridge, respectively. Based on the dynamical mass estimate from VLA HI measurements for Arp~105N and based on CFHT H$\alpha$ kinematics for A105S, they have a dynamical-to-baryonic mass ratio of $\sim1.95$ and $\sim1.30$, respectively, indicating a deficiency of dark matter. Further observations, particularly integral field spectroscopy and high-resolution 21~cm observations, may provide better constraints into the kinematics and improve understanding of TDG formation.

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Jyoti Prakash, Kanak Saha. 2026-07-20. Structural and dynamical properties of Tidal dwarf galaxies in the tails and bridge of the Guitar galaxy Arp 105. https://doi.org/10.1093/mnras%2Fstag1373

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