15 research outputs found

    An Hα\alpha Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40%\% ALFALFA \ion{H}{1} Survey

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    We present the observed Hα\alpha flux and derived star formation rates (SFRs) for a fall sample of low−-surface−-brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40%\% ALFALFA {\ion{H}{1}} survey −- SDSS DR7 photometric data, and all the HαH\alpha images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and HαH\alpha flux was measured in 92 of them. Though almost all the LSBGs in our sample are {\ion{H}{1}}−-rich, their SFRs derived from the extinction and filter−-transmission−-corrected HαH\alpha flux, are less than 1M_{\sun}yr−1yr^{-1}. LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities, but LSBGs have much lower SFRs and SFR surface densities than star−-forming galaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt law significantly, which indicate that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support the previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers during their star formation histories

    An Hα\alpha Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40%\% ALFALFA \ion{H}{1} Survey

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    We present the observed Hα\alpha flux and derived star formation rates (SFRs) for a fall sample of low−-surface−-brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40%\% ALFALFA {\ion{H}{1}} survey −- SDSS DR7 photometric data, and all the HαH\alpha images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and HαH\alpha flux was measured in 92 of them. Though almost all the LSBGs in our sample are {\ion{H}{1}}−-rich, their SFRs derived from the extinction and filter−-transmission−-corrected HαH\alpha flux, are less than 1M_{\sun}yr−1yr^{-1}. LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities, but LSBGs have much lower SFRs and SFR surface densities than star−-forming galaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt law significantly, which indicate that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support the previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers during their star formation histories

    Cavity-birefringence-dependent vector pure-quartic soliton fiber laser

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    Pure-quartic soliton (PQS) fiber lasers provide a promising avenue for exploring novel soliton interaction dynamics and generating high-energy pulses. Here, we present the numerical observation of vector PQSs generation and the evolution dynamics in a mode-locked fiber laser, using the coupled Ginzburg-Landau equations. We investigate the buildup dynamics of vector PQSs in a mode-locked laser with birefringent fibers, passing through three stages: energy amplification, energy pulsation owing to the cross-phase modulation (XPM) effect, and finally stabilization. Depending on the strength of the cavity-birefringence, the evolution of PQSs in non-polarization-maintaining fibers reveals that both the elliptical-polarization vector PQSs and near-linear-polarization vector PQSs can be formed by the energy conservation and balance between the two orthogonal directions. Additionally, we observe the transition process from vector PQSs to scalar PQSs with higher cavity-birefringence, resulting from the failure compensation of the walk-off via the soliton trapping effect between the two orthogonal components. These results provide valuable insights into the ultrafast transient process of vector solitons and enhance the understanding of PQS generation in fiber lasers

    Buildup and synchronization regimes of a vector pure-quartic soliton molecule in a fiber laser cavity

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    Pure-quartic solitons (PQSs) have recently received increasing attention due to their energy-width scaling over the traditional soliton, which has expanded our understanding of soliton dynamics with high-order dispersion in nonlinear systems. Here, we numerically reveal the asynchronization and synchronization processes of the sub-pulse within the vector PQS molecule in a mode-locked fiber laser by solving the coupled Ginzburg-Landau equations. During the establishment of a vector PQS molecule, the repulsion, attraction, and finally stabilization processes have been observed. Specifically, sub-pulse disappearance, regeneration, and finally synchronization with the other pulses are also investigated. Our analysis of the pulse energy, time interval, and relative phase evolution dynamics with the round trip indicates that the asynchronization and synchronization within the vector PQS molecule associate tightly with the gain competition and the cross-phase modulation. Our findings provide insights into the internal mutual dynamics within the vector soliton molecule and offer guidance for the applications of PQS.</p
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