Lateral Interactions and Receptive Field Structure of Lobula Plate Tangential Cells in the Blowfly

As a fly flies around in the world the visual scene moves constantly across its eyes. Depending on its path, this elicits a particular large-field motion pattern called ‘flow field’. Since the flow-fields are characteristic for particular flight trajectories they can be used to guide behavior, in particular to control the course of the fly. In the blowfly, these visual motion cues are mediated by a set of 60 motion-sensitive neurons called lobula plate tangential cells (LPTCs). The directionally selective response of the LPTCs has been ascribed to the integration of local motion information across their extensive dendritic trees. As the lobula plate is organized retinotopically the receptive fields of the tangential cells ought to be determined by their dendritic architecture. This appears not always to be the case. Recent experiments have revealed many lateral connections among tangential cells that appear to mediate their often complex receptive fields. Here single cells were ablated in order to determine which lateral connections are functionally important. I found that the ablation of a single cell, or class of cells revealed that the lateral connections among LPTCs can be the source of their local motion input, or augment the feedfoward input from local motion elements through either dendro-dendritic and axonal-axonal connections. Other connections between LPTCs were found to have no discernable functional significance and suggest that the lobula plate circuitry is yet to be fully revealed. The specific projects are outlined below. Input Circuitry to the HS- and CH-cells A single class of the lobula plate tangential cells the CH (centrifugal horizontal) neurons, play an important role in two pathways: figure-ground discrimination and flow-field selectivity. As was recently found, the dendrites of CH-cells are electrically coupled to the dendritic tree of another class of neurons sensitive to horizontal image motion, the horizontal system cells (HS). However, whether motion information arrives independently at both of these cells or is passed from one to the other is not known. Here I examine the ipsilateral input circuitry to HS and CH neurons by selective laser ablation of individual interneurons. I find that the response of CH neurons to motion presented in front of the ipsilateral eye is entirely abolished after the ablation of HS-cells. In contrast the motion response of HS-cells persists after the ablation of CH-cells. I conclude that HS-cells receive direct motion input from local motion elements, whereas CH-cells do not; their motion response is driven by HS-cells. This connection scheme is discussed with reference as to how the dendritic networks involved in figure-ground detection and flow-field selectivity might operate. Rotational Flow-Field Selectivity The group of neurons that processes horizontal motion forms a symmetric bilateral network that is able to combine information about motion presented in front of both eyes. Here I consider a group of 16 neurons whose connections have been explicitly identified. Each of these neurons has a large dendritic tree receiving information about ipsilateral local motion events that is spatially pooled to produce a directionally selective response. In addition, some of the lobula plate neurons are also sensitive to motion cues in front of the other eye. This information is carried by the spiking neurons H1, H2 and Hu that send their axons to the other side of the brain, where the H1- and H2-cells synapse onto 2 of the 3 HS-cells, and all three contralaterally projecting cell provide input to both CH-cells. The CH-cells are known to provide inhibitory input to the H1- and H2-cells. These network interactions appear to amplify the response to rotational stimuli and reduce the response to translation. I ablate either single HS-cells or both CH-cells in order to break the path whereby information about the opposite eye reaches the H1- and H2-cell. I did not find that these ablations affected the flow-field selectivity of either H1- and H2-cells. Network modeling showed that although the described circuitry does support rotational flow-field selectivity for the HS- and CH-cells, the model H2-cell does not show the expected flow-field selectivity. This suggests that the circuitry or cellular mechanisms underlying the response properties of the H2-cell are not completely understood. Basis of the Broad Receptive Field of VS-cells As the lobula plate is organized retinotopically the receptive fields of the tangential cells ought to be determined by their dendritic architecture. This appears not always to be the case. One compelling example is the exceptionally wide receptive fields of the vertical system (VS) tangential cells. Using dual intracellular recordings Haag and Borst (2004) found VS-cells to be mutually coupled in such a way that each VS-cell is connected exclusively to its immediate neighbours. This coupling may form the basis of the broad receptive fields of VS-cells. Here I tested this hypothesis directly by photo-ablating individual VS-cells. The receptive field width of VS-cells indeed narrowed after the ablation of single VS-cells, specifically depending on whether the receptive field of the ablated cell was more frontal or more posterior to the recorded cell. In particular, the responses changed as if the neuron lost access to visual information from the ablated neuron and those VS-cells more distal than it from the recorded neuron. These experiments provide compelling evidence that the lateral connections amongst VS-cells are a crucial component in the mechanism underlying their complex receptive fields, augmenting the direct columnar input to their dendrites. Vertical-Horizontal Interactions Two heterolaterally spiking cells, the H1- and H2-cells have been shown to be sensitive to vertical motion presented in the frontal portion of their receptive fields. Receptive field measurements performed here show that the H1-, VS1- and VS2-cells all respond to vertical downward motion across an almost completely overlapping portion of the frontal visual field. Using dual intracellular recordings Haag and Borst (2003) demonstrated that the VS1-cell but not the VS2-cell supplies input to both these cells. Through current injections into different compartments of the VS1-and VS2-cells I have provided physiological evidence that the output of VS1-cell near its dendritic arbors is the likely site of its input to the H1-cell. This coupling may form the basis of the vertical sensitivity of the H1- and H2-cell. I tested this hypothesis directly by recording the sensitivity of the H1-cell to horizontal and vertical motion in the frontal visual field both before and after the ablation of single VS1-cells. After the ablation of the VS1-cell the response of the H1-cell to vertical motion disappeared but its response to horizontal motion remained robust. These experiments demonstrate that the VS1-cell provides the input to the H1-cell that makes it sensitive to vertical motion in the frontal visual field likely through connections in their dendritic trees

The First Stage of Cardinal Direction Selectivity Is Localized to the Dendrites of Retinal Ganglion Cells

SummaryInferring the direction of image motion is a fundamental component of visual computation and essential for visually guided behavior. In the retina, the direction of image motion is computed in four cardinal directions, but it is not known at which circuit location along the flow of visual information the cardinal direction selectivity first appears. We recorded the concerted activity of the neuronal circuit elements of single direction-selective (DS) retinal ganglion cells at subcellular resolution by combining GCaMP3-functionalized transsynaptic viral tracing and two-photon imaging. While the visually evoked activity of the dendritic segments of the DS cells were direction selective, direction-selective activity was absent in the axon terminals of bipolar cells. Furthermore, the glutamate input to DS cells, recorded using a genetically encoded glutamate sensor, also lacked direction selectivity. Therefore, the first stage in which extraction of a cardinal motion direction occurs is the dendrites of DS cells

Unbiased Cosmological Parameter Estimation from Emission Line Surveys with Interlopers

The galaxy catalogs generated from low-resolution emission line surveys often contain both foreground and background interlopers due to line misidentification, which can bias the cosmological parameter estimation. In this paper, we present a method for correcting the interloper bias by using the joint-analysis of auto- and cross-power spectra of the main and the interloper samples. In particular, we can measure the interloper fractions from the cross-correlation between the interlopers and survey galaxies, because the true cross-correlation must be negligibly small. The estimated interloper fractions, in turn, remove the interloper bias in the cosmological parameter estimation. For example, in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) low-redshift ($z<0.5$) [O II] $\lambda3727${\AA} emitters contaminate high-redshift ($1.9<z<3.5$) Lyman-$\alpha$ line emitters. We demonstrate that the joint-analysis method yields a high signal-to-noise ratio measurement of the interloper fractions while only marginally increasing the uncertainties in the cosmological parameters relative to the case without interlopers. We also show the same is true for the high-latitude spectroscopic survey of Wide-Field Infrared Survey Telescope (WFIRST) mission where contamination occurs between the Balmer-$\alpha$ line emitters at lower redshifts ($1.1<z<1.9$) and Oxygen ([O III] $\lambda5007${\AA}) line emitters at higher redshifts ($1.7<z<2.8$).Comment: 36 pages, 26 figure

Using Dark Energy Explorers and Machine Learning to Enhance the Hobby-Eberly Telescope Dark Energy Experiment

We present analysis using a citizen science campaign to improve the cosmological measures from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). The goal of HETDEX is to measure the Hubble expansion rate, $H(z)$, and angular diameter distance, $D_A(z)$, at $z =$ 2.4, each to percent-level accuracy. This accuracy is determined primarily from the total number of detected Lyman-$\alpha$ emitters (LAEs), the false positive rate due to noise, and the contamination due to [O II] emitting galaxies. This paper presents the citizen science project, Dark Energy Explorers, with the goal of increasing the number of LAEs, decreasing the number of false positives due to noise and the [O II] galaxies. Initial analysis shows that citizen science is an efficient and effective tool for classification most accurately done by the human eye, especially in combination with unsupervised machine learning. Three aspects from the citizen science campaign that have the most impact are 1) identifying individual problems with detections, 2) providing a clean sample with 100% visual identification above a signal-to-noise cut, and 3) providing labels for machine learning efforts. Since the end of 2022, Dark Energy Explorers has collected over three and a half million classifications by 11,000 volunteers in over 85 different countries around the world. By incorporating the results of the Dark Energy Explorers we expect to improve the accuracy on the $D_A(z)$ and $H(z)$ parameters at $z =$ 2.4 by 10 - 30%. While the primary goal is to improve on HETDEX, Dark Energy Explorers has already proven to be a uniquely powerful tool for science advancement and increasing accessibility to science worldwide.Comment: 14 pages, 6 figures, accepted for publication in The Astrophysical Journa

Searching for Supernovae in HETDEX Data Release 3

We have extracted 636 spectra taken at the positions of 583 transient sources from the third data release of the Hobby-Eberly Telescope Dark Energy eXperiment (HETDEX). The transients were discovered by the Zwicky Transient Facility (ZTF) during 2018-2022. The HETDEX spectra provide a potential means to obtain classifications for a large number of objects found by photometric surveys for free. We attempt to explore and classify the spectra by utilizing several template-matching techniques. We have identified two transient sources, ZTF20aatpoos = AT 2020fiz and ZTF19abdkelq, as supernova (SN) candidates. We classify AT 2020fiz as a Type IIP SN observed ∼10 days after explosion, and we propose ZTF19abdkelq as a likely Type Ia SN caught ∼40 days after maximum light. ZTF photometry of these two sources are consistent with their classifications as SNe. Beside these two objects, we have confirmed several ZTF transients as variable active galactic nuclei based on their spectral appearance, and determined the host galaxy types of several other ZTF transients

Cosmological-scale Lyα Forest Absorption around Galaxies and AGNs Probed with the HETDEX and SDSS Spectroscopic Data

We present cosmological-scale three-dimensional neutral hydrogen (H i) tomographic maps at z = 2-3 over a total of 837 deg2 in two blank fields that are developed with Lyα forest absorptions of 14,736 background Sloan Digital Sky Survey (SDSS) quasars at z = 2.08-3.67. Using the tomographic maps, we investigate the large-scale (≳10 h −1 cMpc) average H i radial profiles and two-direction profiles of the line-of-sight (LOS) and transverse directions around galaxies and active galactic nuclei (AGNs) at z = 2-3 identified by the Hobby-Eberly Telescope Dark Energy eXperiment survey and SDSS, respectively. The peak of the H i radial profile around galaxies is lower than the one around AGNs, suggesting that the dark matter halos of galaxies are less massive on average than those of AGNs. The LOS profile of AGNs is narrower than the transverse profile, indicating the Kaiser effect. There exist weak absorption outskirts at ≳30 h −1 cMpc beyond H i structures of galaxies and AGNs found in the LOS profiles that can be explained by the H i gas at ≳30 h −1 cMpc falling toward the source position. Our findings indicate that the H i radial profile of AGNs has transitions from proximity zones (≲a few h −1 cMpc) to the H i structures (∼1-30 h −1 cMpc) and the weak absorption outskirts (≳30 h −1 cMpc). Although there is no significant dependence of AGN types (type 1 vs. type 2) on the H i profiles, the peaks of the radial profiles anticorrelate with AGN luminosities, suggesting that AGNs’ ionization effects are stronger than the gas mass differences

The Active Galactic Nuclei in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX). III. A Red Quasar with Extremely High Equivalent Widths Showing Powerful Outflows

We report an active galactic nucleus (AGN) with an extremely high equivalent width (EW), EWLyα+N V,rest ≳921 Å, in the rest frame, at z ∼ 2.24 in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX), as a representative case of the high-EW AGN population. The continuum level is a nondetection in the HETDEX spectrum; thus the measured EW is a lower limit. The source is detected with significant emission lines (>7σ) at Lyα + N v λ1241, C iv λ1549, and a moderate emission line (∼4σ) at He ii λ1640 within the wavelength coverage of HETDEX (3500-5500 Å). The r-band magnitude is 24.57 from the Hyper Suprime-Cam-HETDEX joint survey with a detection limit of r = 25.12 at 5σ. The Lyα emission line spans a clearly resolved region of ∼10″ (85 kpc) in diameter. The Lyα line profile is strongly double peaked. The spectral decomposed blue gas and red gas Lyα emission are separated by ∼1.″2 (10.1 kpc) with a line-of-sight velocity offset of ∼1100 km s−1. This source is probably an obscured AGN with powerful winds

The Stars of the HETDEX Survey. I. Radial Velocities and Metal-Poor Stars from Low-Resolution Stellar Spectra

The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is an unbiased, massively multiplexed spectroscopic survey, designed to measure the expansion history of the universe through low-resolution (R∼750) spectra of Lyman-Alpha Emitters. In its search for these galaxies, HETDEX will also observe a few 105 stars. In this paper, we present the first stellar value-added catalog within the internal second data release of the HETDEX Survey (HDR2). The new catalog contains 120,571 low-resolution spectra for 98,736 unique stars between 10∘) Galactic latitudes. With these spectra, we measure radial velocities (RVs) for ∼42,000 unique FGK-type stars in the catalog and show that the HETDEX spectra are sufficient to constrain these RVs with a 1σ precision of 28.0 km/s and bias of 3.5 km/s with respect to the LAMOST surveys and 1σ precision of 27.5 km/s and bias of 14.0 km/s compared to the SEGUE survey. Since these RVs are for faint (G≥16) stars, they will be complementary to Gaia. Using t-Distributed Stochastic Neighbor Embedding (t-SNE), we also demonstrate that the HETDEX spectra can be used to determine a star's Teff, and log g and its [Fe/H]. With the t-SNE projection of the FGK-type stars with HETDEX spectra we also identify 416 new candidate metal-poor ([Fe/H] <−1~dex) stars for future study. These encouraging results illustrate the utility of future low-resolution stellar spectroscopic surveys

The Pre-explosion Environments and The Progenitor of SN 2023ixf from the Hobby Eberly Telescope Dark Energy Experiment (HETDEX)

Supernova (SN) 2023ixf was discovered on May 19th, 2023. The host galaxy, M101, was observed by the Hobby Eberly Telescope Dark Energy Experiment (HETDEX) collaboration over the period April 30, 2020 -- July 10, 2020, using the Visible Integral-field Replicable Unit Spectrograph (VIRUS; $3470\lesssim\lambda\lesssim5540$ \r{A}) on the 10-m Hobby-Eberly Telescope (HET). The fiber filling factor within $\pm$ 30 arcsec of SN 2023ixf is 80% with a spatial resolution of 1 arcsec. The r<5.5 arcsec surroundings are 100% covered. This allows us to analyze the spatially resolved pre-explosion local environments of SN 2023ixf with nebular emission lines. The 2-dimensional (2D) maps of the extinction and the star-formation rate (SFR) surface density ($\Sigma_{\rm SFR}$) show weak increasing trends in the radial distributions within the r<5.5 arcsec regions, suggesting lower values of extinction and SFR in the vicinity of the progenitor of SN 2023ixf. The median extinction and that of the surface density of SFR within r<3 arcsec are $E(B-V)=0.06\pm0.14$, and $\Sigma_{\rm SFR}=10^{-5.44\pm0.66}~\rm M_{\odot}\cdot yr^{-1}\cdot arcsec^{-2}$. There is no significant change in extinction before and after the explosion. The gas metallicity does not change significantly with the separation from SN 2023ixf. The metal-rich branch of the $R_{23}$ calculations indicates that the gas metallicity around SN 2023ixf is similar to the solar metallicity ($\sim Z_{\odot}$). The archival deep images from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) show a clear detection of the progenitor of SN 2023ixf in the $z$-band at $22.778\pm0.063$ mag, but non-detections in the remaining four bands of CFHTLS ($u,g,r,i$). The results suggest a massive progenitor of $\approx$ 22 $M_\odot$.Comment: 11 pages, 5 figures, Accepted by ApJ