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Register a new userThe H$alpha$ Dots Survey. II. A Second List of Faint Emission-Line Objects
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We present the second catalog of serendipitously discovered compact extragalactic emission-line sources -- H$alpha$ Dots. These objects have been discovered in searches of moderately deep narrow-band images acquired for the ALFALFA H$alpha$ project (Van Sistine et al. 2016). In addition to cataloging 119 new H$alpha$ Dots, we also present follow-up spectral data for the full sample. These spectra allow us to confirm the nature of these objects as true extragalactic emission-line objects, to classify them in terms of activity type (star forming or AGN), and to identify the emission line via which they were discovered. We tabulate photometric and spectroscopic data for the all objects, and present an overview of the properties of the full H$alpha$ Dot sample. The H$alpha$ Dots represent a broad range of star-forming and active galaxies detected via several different emission lines over a wide range of redshifts. The sample includes H$alpha$-detected blue compact dwarf galaxies at low redshift, [ion{O}{3}]-detected Seyfert 2 and Green Pea-like galaxies at intermediate redshifts, and QSOs detected via one of several UV emission lines, including Ly$alpha$. Despite the heterogeneous appearance of the resulting catalog of objects, we show that our selection method leads to well-defined samples of specific classes of emission-line objects with properties that allow for statistical studies of each class.
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We present the fourth catalog of serendipitously discovered compact extragalactic emission-line sources -- H$alpha$ Dots. A total of 454 newly discovered objects are included in the current survey list. These objects have been detected in searches of moderately deep narrow-band images acquired for the ALFALFA H$alpha$ project (Van Sistine et al. 2016). The catalog of H-alpha Dots presented in the current paper was derived from searches carried out using ALFALFA H$alpha$ images obtained with the KPNO 2.1 m telescope. This results in a substantially deeper sample of Dots compared to our previous lists, which were all discovered in images taken with the WIYN 0.9 m telescope. The median R-band magnitude of the current catalog is 21.59, more than 1.6 magnitudes fainter than the median for the 0.9~m sample (factor of 4.4x fainter). Likewise, the median emission-line flux of the detected sources is a factor of 4.3x fainter. The line-flux completeness limit of the current sample is approximately 3 x 10$^{-16}$ erg/s/cm$^2$. We present accurate coordinates, apparent magnitudes and narrow-band line fluxes for each object in the sample. Unlike our previous lists of H$alpha$ Dots, the current sample does not include follow-up spectroscopy.
We take advantage of the capability of the OTELO survey to obtain the H$alpha$ luminosity function (LF) at ${rm z}sim0.40$. Because of the deepest coverage of OTELO, we are able to determine the faint end of the LF, and thus better constrain the star formation rate and the number of galaxies at low luminosities. The AGN contribution to this LF is estimated as well. We make use of the multi-wavelength catalogue of objects in the field compiled by the OTELO survey, which is unique in terms of minimum flux and equivalent width. We also take advantage of the pseudo-spectra built for each source, which allow the identification of emission lines and the discrimination of different types of objects. The H$alpha$ luminosity function at $zsim0.40$ is obtained, which extends the current faint end by almost 1 dex, reaching minimal luminosities of $log_{10}L_{rm lim}=38.5$ erg s$^{-1}$ (or $sim0.002, text{M}_odottext{ yr}^{-1})$. The AGN contribution to the total H$alpha$ luminosity is estimated. We find that no AGN should be expected below a luminosity of $log_{10}L=38.6$ erg s$^{-1}$. From the sample of non-AGN (presumably, pure SFG) at $zsim0.40$ we estimated a star formation rate density of $rho_{rm SFR}=0.012pm0.005 {rm text{M}_{odot} yr^{-1} Mpc^{-3}}$.
We present a catalogue of 3,305 H$alpha$ emission-line point sources observed with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) in the vicinity fields of M31 and M33 during September 2011 and January 2016. The catalogue contains 1,487 emission-line stars, 532 emission-line nebulae including 377 likely planetary nebulae (PNe), 83 H~{textsc{ii}} regions candidates and 20 possible supernovae remnants (SNRs) and 1,286 unknown objects. Among them, 24 PN candidates, 19 H~{sc ii} region candidates, 10 SNR candidates and 1 symbiotic star candidate are new discoveries. Radial velocities and fluxes estimated from the H$alpha$ line and those quantities of seven other major emission lines including H$beta$, [O~{textsc{iii}}]~$lambda$4959, [O~{textsc{iii}}]~$lambda$5007, [N~{textsc{ii}}]~$lambda$6548, [N~{textsc{ii}}]~$lambda$6583, [S~{textsc{ii}}]~$lambda$6717 and [S~{textsc{ii}}]~$lambda$6731 lines of all the catalogued sources yielded from the LAMOST spectra are also presented in our catalogue. Our catalogue is an ideal starting point to study the chemistry properties and kinematics of M31 and M33.
We present a catalogue of candidate H{alpha} emission and absorption line sources and blue objects in the Galactic Bulge Survey (GBS) region. We use a point source catalogue of the GBS fields (two strips of (l x b) = (6 x 1) degrees centred at b = 1.5 above and below the Galactic centre), covering the magnitude range 16 < r < 22.5. We utilize (r-i, r-H{alpha}) colour-colour diagrams to select H{alpha} emission and absorption line candidates, and also identify blue objects (compared to field stars) using the r-i colour index. We identify 1337 H{alpha} emission line candidates and 336 H{alpha} absorption line candidates. These catalogues likely contain a plethora of sources, ranging from active (binary) stars, early-type emission line objects, cataclysmic variables (CVs) and low-mass X-ray binaries (LMXBs) to background active galactic nuclei (AGN). The 389 blue objects we identify are likely systems containing a compact object, such as CVs, planetary nebulae and LMXBs. Hot subluminous dwarfs (sdO/B stars) are also expected to be found as blue outliers. Crossmatching our outliers with the GBS X-ray catalogue yields sixteen sources, including seven (magnetic) CVs and one qLMXB candidate among the emission line candidates, and one background AGN for the absorption line candidates. One of the blue outliers is a high state AM CVn system. Spectroscopic observations combined with the multi-wavelength coverage of this area, including X-ray, ultraviolet and (time-resolved) optical and infrared observations, can be used to further constrain the nature of individual sources.
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