Arcsec Aperture Research Articles

HELP: a catalogue of 170 million objects, selected at 0.36–4.5 μm, from 1270 deg2 of prime extragalactic fields

ABSTRACT We present an optical to near-infrared (NIR) selected astronomical catalogue covering 1270 deg2. This is the first attempt to systematically combine data from 23 of the premier extragalactic survey fields – the product of a vast investment of telescope time. The fields are those imaged by the Herschel Space Observatory that form the Herschel Extragalactic Legacy Project (HELP). Our catalogue of 170 million objects is constructed by a positional cross-match of 51 public surveys. This high-resolution optical, NIR, and mid-infrared catalogue is designed for photometric redshift estimation, extraction of fluxes in lower resolution far-infrared maps, and spectral energy distribution modelling. It collates, standardizes, and provides value added derived quantities including corrected aperture magnitudes and astrometry correction over the Herschel extragalactic wide fields for the first time. $grizy$ fluxes are available on all fields with g-band data reaching $5\sigma$ point-source depths in a 2 arcsec aperture of 23.5, 24.4, and 24.6 (AB) mag at the 25th, 50th, and 75th percentiles, by area covered, across all HELP fields. It has K or $K_s$ coverage over 1146 deg2 with depth percentiles of 20.2, 20.4, and 21.0 mag, respectively. The IRAC Ch 1 band is available over 273 deg2 with depth percentiles of 17.7, 21.4, and 22.2 mag, respectively. This paper defines the ‘masterlist’ objects for the first data release (DR1) of HELP. This large sample of standardized total and corrected aperture fluxes, uniform quality flags, and completeness measures provides large well-understood statistical samples over the full Herschel extragalactic sky.

The GALEX Ultraviolet Virgo Cluster Survey (GUViCS)

Context. At low redshift, early-type galaxies often exhibit a rising flux with decreasing wavelength in the 1000–2500 Å range, called “UV upturn”. The origin of this phenomenon is debated, and its evolution with redshift is poorly constrained. The observed GALEX FUV-NUV color can be used to probe the UV upturn approximately to redshift 0.5.Aim. We provide constraints on the existence of the UV upturn up to redshift ~0.4 in the brightest cluster galaxies (BCG) located behind the Virgo cluster, using data from the GUViCS survey.Methods. We estimate the GALEX far-UV (FUV) and near-UV (NUV) observed magnitudes for BCGs from the maxBCG catalog in the GUViCS fields. We increase the number of nonlocal galaxies identified as BCGs with GALEX photometry from a few tens of galaxies to 166 (64 when restricting this sample to relatively small error bars). We also estimate a central color within a 20 arcsec aperture. By using the r-band luminosity from the maxBCG catalog, we can separate blue FUV-NUV due to recent star formation and candidate upturn cases. We use Lick indices to verify their similarity to redshift 0 upturn cases.Results. We clearly detect a population of blue FUV-NUV BCGs in the redshift range 0.10–0.35, vastly improving the existing constraints at these epochs by increasing the number of galaxies studied, and by exploring a redshift range with no previous data (beyond 0.2), spanning one more Gyr in the past. These galaxies bring new constraints that can help distinguish between assumptions concerning the stellar populations causing the UV upturn phenomenon. The existence of a large number of UV upturns around redshift 0.25 favors the existence of a binary channel among the sources proposed in the literature.

The third data release of the Kilo-Degree Survey and associated data products

The Kilo-Degree Survey (KiDS) is an ongoing optical wide-field imaging survey with the OmegaCAM camera at the VLT Survey Telescope. It aims to image 1500 square degrees in four filters (ugri). The core science driver is mapping the large-scale matter distribution in the Universe, using weak lensing shear and photometric redshift measurements. Further science cases include galaxy evolution, Milky Way structure, detection of high-redshift clusters, and finding rare sources such as strong lenses and quasars. Here we present the third public data release (DR3) and several associated data products, adding further area, homogenized photometric calibration, photometric redshifts and weak lensing shear measurements to the first two releases. A dedicated pipeline embedded in the Astro-WISE information system is used for the production of the main release. Modifications with respect to earlier releases are described in detail. Photometric redshifts have been derived using both Bayesian template fitting, and machine-learning techniques. For the weak lensing measurements, optimized procedures based on the THELI data reduction and lensfit shear measurement packages are used. In DR3 stacked ugri images, weight maps, masks, and source lists for 292 new survey tiles (~300 sq.deg) are made available. The multi-band catalogue, including homogenized photometry and photometric redshifts, covers the combined DR1, DR2 and DR3 footprint of 440 survey tiles (447 sq.deg). Limiting magnitudes are typically 24.3, 25.1, 24.9, 23.8 (5 sigma in a 2 arcsec aperture) in ugri, respectively, and the typical r-band PSF size is less than 0.7 arcsec. The photometric homogenization scheme ensures accurate colors and an absolute calibration stable to ~2% for gri and ~3% in u. Separately released are a weak lensing shear catalogue and photometric redshifts based on two different machine-learning techniques.

PROBING THE PHYSICS OF NARROW LINE REGIONS IN ACTIVE GALAXIES. II. THE SIDING SPRING SOUTHERN SEYFERT SPECTROSCOPIC SNAPSHOT SURVEY (S7)

Here we describe the \emph{Siding Spring Southern Seyfert Spectroscopic Snapshot Survey} (S7) and present results on 64 galaxies drawn from the first data release. The S7 uses the Wide Field Spectrograph (WiFeS) mounted on the ANU 2.3m telescope located at the Siding Spring Observatory to deliver an integral field of $38\times25$~ arcsec at a spectral resolution of $R=7000$ in the red ($530-710$nm), and $R=3000$ in the blue ($340-560$nm). {From these data cubes we have extracted the Narrow Line Region (NLR) spectra from a 4 arc sec aperture centred on the nucleus. We also determine the H$\beta$ and [OIII]~$\lambda$5007 fluxes in the narrow lines, the nuclear reddening, the reddening-corrected relative intensities of the observed emission lines, and the H$\beta$ and \lOIII\ luminosities {determined from spectra for which the stellar continuum has been removed.} We present a set of images of the galaxies in [OIII]~$\lambda$5007, [NII]~$\lambda$6584 and H$\alpha$ which serve to delineate the spatial extent of the extended narrow line region (ENLR) and {\bf also to} reveal the structure and morphology of the surrounding \HII\ regions. Finally, we provide a preliminary discussion of those Seyfert~1 and Seyfert~2 galaxies which display coronal emission lines in order to explore the origin of these lines.

OUTBURST DUST PRODUCTION OF COMET 29P/SCHWASSMANN-WACHMANN 1

Multi-aperture photometry of Comet 29P/Schwassmann-Wachmann 1 was conducted on Johnson-Cousins R-band observations spanning 2011 May 1-9 and 2012 June 6-July 3. The comet was observed in outburst on 2011 May 3 and 2012 July 1, during which its brightness increased by 2.2 and 2.1 mag, respectively, as measured through a 10 arcsec aperture. Dust production before and after each outburst is calculated using the parameter Af ρ, which is converted to a lower limit on the dust production rate based on dust models and derived nuclear properties from other studies. Both outbursts are accompanied by large increases in dust production, Af ρ by a factor of ~6.5-7 and dust production rate by a factor of ~18-23. In addition, variations in the dust brightness profile of the coma are examined during the events. The profile is observed to steepen significantly at the beginning of each outburst and then slowly return to pre-outburst values, mirroring the behavior of Af ρ. The start of an outbound ripple of dust in the profile might be observed as the comet returns to its pre-outburst state, although this cannot be confirmed. Using a simple model of the 2011 May 3 outburst, an estimated lower limit of (2.6 ± 0.7) × 108 kg of dust was released during the event. If this is representative of a typical outburst of 29P, then it is estimated that outbursts account for a lower limit of 80 of the total material ejected by the comet per year.

Differences between the two types Seyfert 2 galaxies – With and without polarized broad lines

Based on spectropolarimetric observations Seyfert 2 (Sy2) galaxies are generally divided into two populations. Some Sy2s show polarized broad emission lines (PBLs) which is an evidence for the hypothesis of the Unified model while others do not. In order to determine the properties of these two apparently different populations we compiled a sample of 66 Sy2 objects with and without detected PBLs. We used a ( J − H) − ( H − K s) diagram based on 2MASS J, H, K s magnitudes in 14 arcsec aperture, the F [OIII] emission line flux and the infrared emission flux F K s using the K s filter. From the ( J − H) − ( H − K s) diagram we determined that one third of the Sy2 objects with PBLs have a power-law infrared component which could be a result of both a non-thermal AGN component scattered by free electrons (or dust) and emission from hot dust near its sublimation temperature. The rest of the objects (with PBLs) are significantly dominated by a dust thermal re-emission. The Sy2s without PBLs show infrared emission dominated by a host galaxy stellar component and also by thermal dust re-emission. The Sy2s with PBLs tend to have a few times larger L [OIII] luminosities than those without. Following the median values of F [ OIII ] / F K s , it seems that this ratio is sensitive enough to separate our sample of Sy2 galaxies into two types – with and without PBLs. There are no Sy2s with PBLs having Eddington ratio below 10 −3 which confirms the results of Nicastro et al. (2003).

AN ULTRAVIOLET SPECTROSCOPIC ATLAS OF LOCAL STARBURSTS AND STAR-FORMING GALAXIES: THE LEGACY OF FOS AND GHRS

We present 46 rest-frame ultraviolet (UV) spectra of 28 local starburst and star-forming galaxies which were observed with the Faint Object Spectrograph (FOS) and the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) at a spectral resolution of a few 100 km/s. We compare the HST spectra with lower resolution International Ultraviolet Explorer (IUE) spectra of the same galaxies and find systematic differences: the bright star clusters targeted in HST's ~1 arcsec apertures provide about 15% of the starburst luminosity traced by IUE's 10 arcsec by 20 arcsec aperture; they are bluer and have stronger stellar-wind features suggesting that the HST apertures have preferentially been placed on the youngest areas of the burst. In contrast, lines arising from the interstellar medium (ISM) show similar equivalent widths in both the large and small aperture observations, suggesting similar ISM properties from larger to smaller scales. In order to quantify the UV spectral morphology of star-forming galaxies, we created a set of UV line indices similar to the standard optical Lick indices. We discuss the relation between the UV spectral morphology and the properties of the galaxy host. We present our atlas of FOS and GHRS spectra both in print and electronically. The data set is useful as a baseline for comparisons with observations of the rest-frame UV spectra of star-forming galaxies at high redshift.

Far Ultraviolet Emission from NGC 7009

The high-excitation planetary nebula NGC 7009 and its central star were observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) through a 30 $\,{\times}\,$ 30 arcsec (LWRS) aperture, and with the HIRS narrow slit (1.25 $\,{\times}\,$ 20 arcsec) to isolate the inner and outer parts of the nebula from the central star. The high-resolution (15 km/s) nebular spectra (910-1187 A) show strong emission from C III] and permitted transitions of He II N II, N III, S III, S IV, S VI and O VI, with stronger emission closer to the central star. In this paper we present results obtained on the spatial variation of these tracers of highly ionized gas. The hot central star of NGC 7009 is discussed in a separate paper by Sonneborn et al.

The rotational temperature and column density of H 3+ in Uranus

H 3 + emission from Uranus has been observed repeatedly for over a decade. However, the details of the emission mechanisms are still poorly understood. In this paper, we discuss our findings from the observations we made in September 2000 and September 2001. The spectrum of Uranus was recorded at the NASA Infrared Telescope Facility using the SpeX instrument between 3 and 5 μm , with a resolving power of 1000. The 3.4– 4.1 μm range permits a determination of both the H 3 + column density and its rotational temperature. The H 3 + emission, measured at 3.986 μm in the 0.8×3.7 arcsec aperture, was 0.031 Jy in September 2000 and 0.053 Jy in September 2001. The rotational temperature was found to be 560±40 K and 640±40 K in 2000 and 2001 respectively, with corresponding column densities of 5.1 (+3.2,−1.4) 10 11 and 4.0 (+1.8,−1.0) 10 11 cm −2 . These results extend the baseline for the variability study of the H 3 + emission (Astrophys. J. 524 (1999) 1059). Previous observations between 1992 and 1998 seemed to indicate a correlation between the H 3 + intensity and the solar cycle. The current data for 2000 and 2001 appear to be consistent with this general tendency.

Dim galaxies and outer halos of galaxies missed by 2MASS? The near–infrared luminosity function and density

By using high–resolution and deep Ks band observations of early–type galaxies of the nearby Universe and of a cluster at we show that the two luminosity functions (LFs) of the local universe derived from 2MASS data miss a fair fraction of the flux of the galaxies (more than 20 to 30%) and a whole population of galaxies of central brightness fainter than the isophote used for detection, but bright enough to be included in the published LFs. In particular, the fraction of lost flux increases as the galaxy surface brightness become fainter. Therefore, the so far derived LF slopes and characteristic luminosity as well as luminosity density are underestimated. Other published near–infrared LFs miss flux in general, including the LF of the distant field computed in a 3 arcsec aperture.

Near-IR spectral evolution of dusty starburst galaxies

We propose a multicomponent analysis of starburst galaxies, based on a model that takes into account the young and evolved stellar components and the gas emission, with their respective extinction, in the frame of a coherent dust distribution pattern. Near-IR signatures are preferentially investigated, in order to penetrate as deep as possible into the dusty starburst cores. We computed the 1.4-2.5 μm spectra of synthetic stellar populations evolving through strong, short timescale bursts of star formation (continuum and lines, R ≃ 500). The evolution model is specifically sensitive to cool stellar populations (AGB and red supergiant stars). It takes advantage of the stellar library of Lançon & Rocca-Volmerange (1992) [A&ASS, 96, 593], observed with the same instrument (FTS/CFHT) as the analysed galaxy sample, so that the instrumental effects are minimised. The main near-IR observable constraints are the molecular signatures of CO and H2O and the slope of the continuum, observed over a range exceptionally broad for spectroscopic data. The H - K colour determined from the spectra measures the intrinsic stellar energy distribution but also differential extinction, which is further constrained by optical emission line ratios. Other observational constraints are the near-IR emission lines (Brγ, He I 2.06 μm, [Fe II] 1.64 μm, H2 2.12 μm) and the far-IR luminosity. The coherence of the results relies on the interpretation in terms of stellar populations from which all observable properties are derived, so that the link between the various wavelength ranges is secured. The luminosity LK is used for the absolute calibration.We apply this approach to the typical spectrum of the core of NGC 1614. Consistent solutions for the starburst characteristics (star-formation rate, IMF, burst age, morphology) are found and the role of each observational constraint in deriving satisfactory models is extensively discussed. The acceptable contamination of the K band light by the underlying population amounts ≥ 15% even through a 5 arcsec aperture. The model leads to a limit on the direct absorption of Lyman continuum photons by dust situated inside the ionised areas, which in turn, with standard gas-to-dust ratios, translates into small characteristic sizes for the individual coexisting H II regions of the massive starburst area (clusters containing ∼ 102 ionising stars). We show that room is left for IMFs extending to 120 M⊙, rather than truncated at ∼ 60 M⊙ as most conservative studies conclude. High internal velocity dispersions (≥ 20 km s−1) are then needed for the H II regions. An original feature of this work is to base the analysis of near-infrared spectral galaxy observations on a large wavelength range, using models constructed with spectral stellar data observed with the same instrument. However a broader use of this spectral evolution model on other spectral or photometric data samples is possible if the spectral resolution of the model is adapted to observations or if colours are derived from the energy distributions.Catherine J. Cesarsky

Luminous infrared galaxies - Sizes at 10-32 microns

We have made estimates of the sizes of 19 infrared galaxies drawn from the highest luminosity galaxies detected by the IRAS survey. The techniques we used were to make multiaperture photometric measurements on the ground-based IR Telescope Facility and to compare these flux densities with the much broader beam measurements obtained by the IRAS survey. Our primary result is that most, but not all, of the galaxies in our sample are extended at 10-25 microns, with characteristic radii of a few hundred parsecs. This result directly supports the widely held assumption that the bulk of the infrared luminosity in these galaxies comes from a central starburst region rather than from the whole disk of the galaxy or from a compact nucleus. The compact nature of Arp 220 is confirmed by direct scans with a 2.9 arcsec aperture at 32 microns.

Two micron spectroscopy of the nucleus of M32

The 3.6 m Canada-France-Hawaii Telescope has been used to study the near- infrared spectrum of the Local Group elliptical M32. The data, which were recorded through a 12 arcsec aperture centered on the galaxy nucleus, span the wavelength range 1.6-2.4 micron with a resolution λ/{DELTA}λ~230 at 2 micron. The strongest features have been identified as absorption bands of CO, CN, and H20. The 1.8 micron Ballik- Ramsey C_2_ band head is not conspicuous, suggesting that carbon stars are relatively rare in the nucleus of M32. A suite of model spectra have been constructed using a library of stellar observations, based on evolutionary sequences summarized in The Revised Yale Isochrones and Luminosity Functions (Green et al. 1987). The model spectra consistently underestimate the strengths of the CO bands for a wide range of plausible mass functions, indicating that M32 must contain a population of cool, evolved stars in addition to those evolving on the red giant branch. In an effort to improve the fit to the observations and investigate the nature of the "missing" component, the model spectra were modified by adding spectra of various late-type stars in quantities sufficient to match the strength of the {DELTA}v = (2,0) band head of CO. The results imply that the additional component must be dominated by stars later than spectral-type K, which is suggestive of evolution on the asymptotic giant branch (AGB) rather than the horizontal branch. Moreover, it is found that this component must contribute at least 50% of the 2 micron flux, regardless of the assumed stellar content. The model which produces the best fit to the observations, based on the sum of the squares of the residuals, has a relatively steep mass function, and an AGB dominated by late-type M giants and carbon stars, which together produce 60% of the 2 micron flux. This contribution is twice that predicted for an old coeval population, so it is concluded that M32 must contain an intermediate-age population. Finally, the possibility of using near-infrared spectra to study the low-mass dwarf content of M32 and other galaxies is also discussed.

Nova Ophiuchi 1988: 0.9–1.35 μm Spectroscopy

Near IR grating spectrophotometric observations (λ / Δλ ≃ 400 ) of Nova Ophiuchi 1988 between 0.9 and 1.35 μm on September 22.2, 1988 UT (J.D. = 2447426.7) are reported. We observed the nova with the Lick Observatory 3–meter Shane telescope using the Aerospace cooled grating spectrometer. A 7.5 arc sec aperture was used. The detector was a germanium photodiode, cooled to 77 K and used in conjunction with a charge integrating amplifier. These are the first IR observations ever made of a slow nova.Figure 1 shows the spectrum which contains Paschen emission lines β, γ δ, ε, ζ, η, He I λ1.083 μm, and a very weak continuum, all consistent with a post-maximum, early nebular phase. Figure 1 also shows a number of possible weak lines including [ Fe II ] and He I as well as an unidentified feature at 1.01 μm in the far red wing of Paδ. The line to continuum ratio for He I λ1.083 is about 300. The emission lines are resolved in the stronger features ( Paδ Paζ, Paβ, and He I λ1.083) and show a mean FWHM of 900 ± 150 km/sec.

Optical Spectrophotometry of Nova PW Vulpeculae

PW Vul (Nowa Vul 1984 #1) was a slow classical nova which began its outburst in July 1984 and reached optical maximum in the first week of August 1984. Eight low dispersion spectra (160 A/mm) in the blue spectral range (λλ3400-5100 A) were secured between October 1984 and July 1985, with the CCS spectrograph equipped with 3.5 arcsec aperture image slicer and mounted on 90 cm Schmidt-Cassegrain telescope at Toruń Observatory. Kodak IIa-O plates were used. In addition two moderate dispersion (40 A/mm) spectra in the Hγ-Hβ range were obtained on 28 October and 3 November 1984, using the same instrumentation. Standard stars were observed on each night to remove the influence of spectral sensitivity of the photographic emulssion and atmospheric extinction. The calibration of the absolute flux scale was performed by comparing synthetic B magnitudes calculated from our spectra with published B photometry of PW Vul (Voloshina 1985, Noskova et al. 1985, Kolotilov and Noskova 1986). The accuracy of the flux calibration is ±0.1 mag.

The Early Outburst Spectra of Nova V1500 Cygni

Nova Cygni 1975 (V1500 Cyg) was outstanding in several respects. It was the most luminous galactic nova ever observed, had the largest outburst amplitude, and had the fastest evolution with time.The spectra, with dispersion 28 A/mm and in spectral range λλ3560-5055 A, were obtained with the CCS spectrograph on 90 cm reflector at Toruń Observatory by the research group supervised by prof. A. WoszczyK. The CCS spectrograph was equipped with the 3.5 arcsec aperture Richardson’s image slicer and stars with known spectral energy distributions were observed on each night, so we were able to derive absolute energy distributions for the V1500 Cyg spectra. The calibration of the energy scale was performed by comparing synthetic B magnitudes calculated from our spectra with numerous published B photometry of the nova. The first spectra were obtained about 3h later than spectra reported by Boyarchuk (1977) and about 6h earlier than spectra discussed by Duerbeck and Wolf (1977); thus they are among the earliest spectra of the nova available. Simultaneously, the spectra correspond to the earliest state of spectral evolution of a nova ouburst yet observed. The pre-maximum spectral evolution of Nova V1500 Cyg is extremely fast. The spectra (Figures 1 and 2) secured on JD 2442654 are characterized by a very strong continuum and broad blueshifted absorption lines of OII, NII and CII of unusual strengths, as well as the Balmer series and Hel.

Interferometric CO-18 observations of DR 21(OH) and L1551 IRS 5 at lambda = 1.4 millimeters

High-resolution (3 arcsec) aperture synthesis maps in the J = 2 to 1 transition of CO-18 have been obtained for the star formation regions DR 21(OH) and L1551 IRS 5. Two compact sources, separated by 7 arcsec, have been discovered at the centers of H2O maser activity associated with DR 21(OH). Mass estimates from the 1.4 mm continuum and CO-18 line emission are similar to the 110 solar masses required for a bound system with the observed 4 km/s radial velocity difference, suggesting that a massive multiple star system is forming. The CO-18 emission from L1551 IRS 5 is extended in an elongated structure of radius 700 AU and mass of 0.1 solar masses. 17 refs.

Velocity-Resolved Spectra of Brαand Brγon IRS16 SW and NE

The source IRS16 has been observed with the FTS at the Canada-France -Hawaii Telescope, in July 1987 and May 1988, in an attempt of spectral resolution associated with spatial resolution. Three positions were observed with a 2.5 arcsec aperture, centered on the sub-structures SW, NE and NW. Brαand Brγspectra were obtained at respective velocity resolutions of 210 and 140 km s−1, allowing resolution of the line profiles. The detection of hydrogen emission was marginal on NW, and strong on SW and NE, showing a net velocity difference of the gas of 160 km s−1. The Brαline on SW has very extended wings suggesting two components of different origin. These observations imply a difference of physical nature of the objects located in the vicinity of Sgr A∗.

ONE-MICRON CN OBSERVATIONS OF COMET HALLEY

ABSTRACT Three spectra of Comet Halley in the 0.86 to 1.37-micron wavelength region have been obtained. On December 4, 1985, the 0-0, 1-1, 1-0, and 2-1 transitions of the red system of CN were detected using a 13 arcsec aperture centered on the nucleus of the comet. The 0-0 and 1-1 transitions were also observed in the coma at positions 20 arcsec from the nucleus. A line to continuum ratio of 0.25 was observed for the 0-0 transition at the position of the nucleus of the comet. A ratio of 1.5 was observed at the off-nucleus positions. On April 28, 1986, an upper limit to the strength of the 0-0 transition was obtained.

On the ratio of forbidden N II/H-alpha in the nucleus of M33 and in the nuclei of other galaxies

view Abstract Citations (26) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Ratio of [N ii]/H alpha in the Nucleus of M33 and in the Nuclei of Other Galaxies Rubin, V. C. ; Ford, K. W., Jr. Abstract Spectra of the inner 1.77 arcsec (radial distance less than 4 pc) of M33 are unique in showing H-alpha in deep sharp absorption and forbidden N II 6548 and 6583 in emission. Just beyond the nucleus, strong disk H-alpha and forbidden N II emission are present. Hence if M33 were located at a distance several times as great, a spectrum through the 1.77 arcsec aperture would show H-alpha and forbidden N II in emission, as the contamination from the disk emission overwhelms the nuclear H-alpha absorption. For galaxies at greater distances, the measured forbidden N II/H-alpha ratio in the central region is a complex function of nuclear and disk light which enters the aperture. Publication: The Astrophysical Journal Pub Date: June 1986 DOI: 10.1086/184680 Bibcode: 1986ApJ...305L..35R Keywords: Absorption Spectra; Galactic Nuclei; H Alpha Line; Spiral Galaxies; Astronomical Spectroscopy; Disk Galaxies; Hydrogen Clouds; Line Of Sight; Astrophysics; ABUNDANCES; GALAXIES: GENERAL; GALAXIES: INDIVIDUAL MESSIER NUMBER: M33 full text sources ADS | data products NED (6) SIMBAD (2)