- ID:
- ivo://CDS.VizieR/J/ApJ/735/71
- Title:
- Oxygen abundances in outlying HII regions
- Short Name:
- J/ApJ/735/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a search for outlying HII regions in the extended gaseous outskirts of nearby (D<40Mpc) galaxies and subsequent multi-slit spectroscopy used to obtain the HII region nebular oxygen abundances. The galaxies in our sample have extended HI disks and/or interaction-related HI features that extend well beyond their primary stellar components. We report oxygen abundance gradients out to 2.5 times the optical radius for these galaxies which span a range of morphologies and masses. We analyze the underlying stellar and neutral HI gas distributions in the vicinity of the HII regions to understand the physical processes that give rise to the observed metal distributions in galaxies. These measurements, for the first time, convincingly show flat abundance distributions out to large radii in a wide variety of systems and have broad implications for galaxy chemodynamical evolution.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/892/23
- Title:
- Pa-beta, Ha and attenuation in NGC5194 & NGC6946
- Short Name:
- J/ApJ/892/23
- Date:
- 19 Jan 2022 08:58:18
- Publisher:
- CDS
- Description:
- We combine Hubble Space Telescope Paschen {beta} (Pa{beta}) imaging with ground-based, previously published H{alpha} maps to estimate the attenuation affecting H{alpha}, A(H{alpha}), across the nearby, face-on galaxies NGC 5194 and NGC 6946. We estimate A(H{alpha}) in ~2000 independent 2" ~75pc diameter apertures in each galaxy, spanning out to a galactocentric radius of almost 10kpc. In both galaxies, A(H{alpha}) drops with radius, with a bright, high-attenuation inner region, though in detail the profiles differ between the two galaxies. Regions with the highest attenuation-corrected H{alpha} luminosity show the highest attenuation, but the observed H{alpha} luminosity of a region is not a good predictor of attenuation in our data. Consistent with much previous work, the IR-to-H{alpha} color does a good job of predicting A(H{alpha}). We calculate the best-fit empirical coefficients for use combining H{alpha} with 8, 12, 24, 70, or 100{mu}m to correct for attenuation. These agree well with previous work, but we also measure significant scatter around each of these linear relations. The local atomic plus molecular gas column density, N(H), also predicts A(H{alpha}) well. We show that a screen with magnitude ~0.2 times that expected for a Milky Way gas-to-dust value does a reasonable job of explaining A(H{alpha}) as a function of N(H). This could be expected if only ~40% of gas and dust directly overlap regions of H{alpha} emission.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A188
- Title:
- PHANGS-MUSE sample HII regions catalog
- Short Name:
- J/A+A/658/A188
- Date:
- 02 Mar 2022 06:10:18
- Publisher:
- CDS
- Description:
- We use an unprecedented sample of about 23000 HII regions detected at an average physical resolution of 67pc in the PHANGS-MUSE sample to study the extragalactic HII region H{alpha} luminosity function (LF). Our observations probe the star-forming disk of 19 nearby spiral galaxies with low inclination and located close to the star formation main sequence at z=0. The mean LF slope in our sample is =1.73 with a {sigma} of 0.15. We find that {alpha} decreases with the galaxy's star formation rate surface density {SIGMA}_SFR_ and argue that this is driven by an enhanced clustering of young stars at high gas surface densities. Looking at the HII regions within single galaxies we find that no significant variations occur between the LF of the inner and outer part of the star-forming disk, whereas the LF in the spiral arm areas is shallower than in the inter-arm areas for six out of the 13 galaxies with clearly visible spiral arms. We attribute these variations to the spiral arms increasing the molecular clouds arm-inter-arm mass contrast and find suggestive evidence that they are more evident for galaxies with stronger spiral arms. Furthermore, we find systematic variations in {alpha} between samples of HII regions with high and low ionization parameter q and argue that they are driven by the aging of HII regions.
- ID:
- ivo://CDS.VizieR/J/A+A/483/209
- Title:
- Photometry of a stellar cluster near IRAS 07141-092
- Short Name:
- J/A+A/483/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution optical UBVRI and H{alpha} images obtained with ALFOSC mounted on the Nordic Optical Telescope (NOT), near-infrared JHK_S_ images obtained with NOTCam at the Nordic Optical Telescope, and VLT/ISAAC images obtained through the H_2_ (2.12{mu}m) filter were all used to make photometric and morphological studies of the point sources and the nebula seen towards Sh2-294. Identification of PMS members was done using three different methods: comparison with isochrones in optical colour-magnitude diagrams and detection of either near-IR excess or H{alpha} emission.
- ID:
- ivo://CDS.VizieR/II/25
- Title:
- Photometry of orange-red CaI triplet in Late-Type Stars
- Short Name:
- II/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Calcium absorption lines were measured using narrow-band photometry on 296 high and low velocity G8-K5 stars of all luminosity classes. Because the blue-violet region of the stellar spectra is too crowded for narrow-band photometry, this investigation of abundance involved measurements of the orange-red CaI triplet 4(3)P-5(3)S, with wavelengths 6102.7, 6122.2 and 6162.2{AA}. "Calcium triplet ratio" is defined as "the measured light intensity ratios, comparison/central regions, calibrated in terms of a standard lamp as described in previous Cambridge papers". The catalog (table I of paper) includes HD number, (B-V) color index, Mg b ratio, H{alpha} ratio, Calcium triplet ratio, and a running number.
- ID:
- ivo://CDS.VizieR/J/AJ/154/268
- Title:
- Point & compact H{alpha} sources in the inner of M33
- Short Name:
- J/AJ/154/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A variety of interesting objects such as Wolf-Rayet stars, tight OB associations, planetary nebulae, X-ray binaries, etc., can be discovered as point or compact sources in H{alpha} surveys. How these objects distribute through a galaxy sheds light on the galaxy star formation rate and history, mass distribution, and dynamics. The nearby galaxy M33 is an excellent place to study the distribution of H{alpha}-bright point sources in a flocculant spiral galaxy. We have reprocessed an archived WIYN continuum-subtracted H{alpha} image of the inner 6.5'x6.5' of M33 and, employing both eye and machine searches, have tabulated sources with a flux greater than approximately 10^-15^ erg/cm^2^/s. We have effectively recovered previously mapped H II regions and have identified 152 unresolved point sources and 122 marginally resolved compact sources, of which 39 have not been previously identified in any archive. An additional 99 H{alpha} sources were found to have sufficient archival flux values to generate a Spectral Energy Distribution. Using the SED, flux values, H{alpha} flux value, and compactness, we classified 67 of these sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/31
- Title:
- Post-merger cluster A2255 membership
- Short Name:
- J/ApJ/794/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The effects of dense environments on normal field galaxies are still up for debate despite much study since Abell published his catalog of nearby clusters in 1958 (1958ApJS....3..211A). There are changes in color, morphology, and star formation properties when galaxies fall into groups and clusters, but the specifics of how and where these modifications occur are not fully understood. To look for answers, we focused on star-forming galaxies in A2255, an unrelaxed cluster thought to have recently experienced a merger with another cluster or large group. We used H{alpha}, MIPS 24 {mu}m, and WISE 22 {mu}m to estimate total star formation rates (SFRs) and Sloan Digital Sky Survey photometry to find stellar masses (M_*_) for galaxies out to ~5 r_200_. We compared the star-forming cluster galaxies with the field SFR-mass distribution and found no enhancement or suppression of star formation in currently star-forming galaxies of high mass (log(M_*_/M_{sun}_)>~10). This conclusion holds out to very large distances from the cluster center. However, the core (r_proj_<3 Mpc) has a much lower fraction of star-forming galaxies than anywhere else in the cluster. These results indicate that for the mass range studied here, the majority of the star formation suppression occurs in the core on relatively short timescales, without any enhancement prior to entering the central region. If any significant enhancement or quenching of star formation occurs, it will be in galaxies of lower mass (log(M_*_/M_{sun}_)<10).
- ID:
- ivo://CDS.VizieR/J/AJ/160/221
- Title:
- Predicted planetary yields of gap transitional disks
- Short Name:
- J/AJ/160/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a massive accreting gap planet model that ensures large gaps in transitional disks are kept dust free by the scattering action of three coplanar quasi-circular planets in a 1:2:4 mean motion resonance (MMR). This model uses the constraint of the observed gap size, and the dust-free nature of the gap, to determine within ~10% the possible orbits for three massive planets in an MMR. Calculated orbits are consistent with the observed orbits and H{alpha} emission (the brightest line to observe these planets) for LkCa15b, PDS70b, and PDS70c within observational errors. Moreover, the model suggests that the scarcity of detected H{alpha} planets is likely a selection effect of the current limitations of non-coronagraphic, low (<10%) Strehl, H{alpha} imaging with adaptive optics (AO) systems used in past H{alpha} surveys. We predict that as higher Strehl AO systems (with high- performance custom coronagraphs; like the 6.5m Magellan Telescope MagAO-X system) are utilized at H{alpha}, the number of detected gap planets will substantially increase by more than tenfold. For example, we show that >25{+/-}5 new H{alpha} "gap planets" are potentially discoverable by a survey of the best 19 transitional disks with MagAO-X. Detections of these accreting protoplanets will significantly improve our understanding of planet formation, planet growth and accretion, solar system architectures, and planet-disk interactions.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A53
- Title:
- R Aqr SPHERE/ZIMPOL narrow-H{alpha} image
- Short Name:
- J/A+A/602/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- R Aqr is a symbiotic binary system consisting of a mira variable, a hot companion with a spectacular jet outflow, and an extended emission line nebula. Because of its proximity to the Sun, this object has been studied in much detail with many types of high resolution imaging and interferometric techniques. We have used R Aqr as test target for the visual camera subsystem ZIMPOL, which is part of the new extreme adaptive optics (AO) instrument SPHERE at the Very Large Telescope (VLT). We describe SPHERE/ZIMPOL test observations of the R Aqr system taken in H{alpha} and other filters in order to demonstrate the exceptional performance of this high resolution instrument. We compare our observations with data from the Hubble Space Telescope (HST) and illustrate the complementarity of the two instruments. We use our data for a detailed characterization of the inner jet region of R Aqr. We analyze the high resolution ~=25mas images from SPHERE/ZIMPOL and determine from the H{alpha} emission the position, size, geometric structure, and line fluxes of the jet source and the clouds in the innermost region <2"(<400AU) of R Aqr. The data are compared to simultaneous HST line filter observations. The H{alpha} fluxes and the measured sizes of the clouds yield H{alpha} emissivities for many clouds from which one can derive the mean density, mass, recombination time scale, and other cloud parameters. Our H{alpha} data resolve for the first time the R Aqr binary and we measure for the jet source a relative position 45 mas West (position angle -89.5{deg}) of the mira. The central jet source is the strongest H{alpha} component with a flux of about 2.5x10^-12^erg/cm^2^/s. North east and south west from the central source there are many clouds with very diverse structures. Within 0.5" (100AU) we see in the SW a string of bright clouds arranged in a zig-zag pattern and, further out, at 1"-2", fainter and more extended bubbles. In the N and NE we see a bright, very elongated filamentary structure between 0.2"-0.7" and faint perpendicular "wisps" further out. Some jet clouds are also detected in the ZIMPOL [OI] and HeI filters, as well as in the HST-WFC3 line filters for H{alpha}, [OIII], [NII], and [OI]. We determine jet cloud parameters and find a very well defined correlation Ne{prop.to}r^-1.3^ between cloud density and distance to the central binary. Densities are very high with typical values of Ne~=3x10^5^cm^-3^ for the "outer" clouds around 300AU, Ne~=3x10^6^cm^-3^ for the "inner" clouds around 50AU, and even higher for the central jet source. The high Ne of the clouds implies short recombination or variability timescales of a year or shorter. H{alpha} high resolution data provide a lot of diagnostic information for the ionized jet gas in R Aqr. Future H{alpha} observations will provide the orientation of the orbital plane of the binary and allow detailed hydrodynamical investigations of this jet outflow and its interaction with the wind of the red giant companion.
- ID:
- ivo://CDS.VizieR/J/AJ/161/277
- Title:
- Sample of 45 H{alpha}EW outliers
- Short Name:
- J/AJ/161/277
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- In this work, we calibrate the relationship between H{alpha} emission and M-dwarf ages. We compile a sample of 892 M-dwarfs with H{alpha} equivalent width (H{alpha}EW) measurements from the literature that are either comoving with a white dwarf of known age (21 stars) or in a known young association (871 stars). In this sample we identify 7 M-dwarfs that are new candidate members of known associations. By dividing the stars into active and inactive categories according to their H{alpha}EW and spectral type (SpT), we find that the fraction of active dwarfs decreases with increasing age, and the form of the decline depends on SpT. Using the compiled sample of age calibrators, we find that H{alpha} EW and fractional H{alpha} luminosity (L_H{alpha}_/L_bol_) decrease with increasing age. H{alpha}EW for SpT<~M7 decreases gradually up until ~1Gyr. For older ages, we found only two early M dwarfs that are both inactive and seem to continue the gradual decrease. We also found 14 mid-type M-dwarfs, out of which 11 are inactive and present a significant decrease in H{alpha}EW, suggesting that the magnetic activity decreases rapidly after ~1Gyr. We fit L_H{alpha}_/L_bol_ versus age with a broken power law and find an index of -0.11_-0.01_^+0.02^ for ages <~776Myr. The index becomes much steeper at older ages, but a lack of field age-calibrators (>>1Gyr) leaves this part of the relation far less constrained. Finally, from repeated independent measurements for the same stars, we find that 94% of them have a level of H{alpha}EW variability <~5{AA} at young ages (<1Gyr).
