- ID:
- ivo://CDS.VizieR/J/ApJ/756/79
- Title:
- Optical photometry in 3 Local Group dwarf galaxies
- Short Name:
- J/ApJ/756/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep wide-field photometry of three recently discovered faint Milky Way (MW) satellites: Leo V, Pisces II, and Canes Venatici II. Our main goals are to study the structure and star formation history of these dwarfs; we also search for signs of tidal disturbance. The three satellites have similar half-light radii (~60-90pc) but a wide range of ellipticities. Both Leo V and CVn II show hints of stream-like overdensities at large radii. An analysis of the satellite color-magnitude diagrams shows that all three objects are old (>10Gyr) and metal-poor ([Fe/H]~-2), though neither the models nor the data have sufficient precision to assess when the satellites formed with respect to cosmic reionization. The lack of an observed younger stellar population (<~10Gyr) possibly sets them apart from the other satellites at Galactocentric distances >~150kpc. We present a new compilation of structural data for all MW satellite galaxies and use it to compare the properties of classical dwarfs to the ultra-faints. The ellipticity distribution of the two groups is consistent at the ~2{sigma} level. However, the faintest satellites tend to be more aligned toward the Galactic Center, and those satellites with the highest ellipticity (>~0.4) have orientations ({Delta}{theta}_GC_) in the range 20{deg}<~{Delta}{theta}_GC_<~40{deg}. This latter observation is in rough agreement with predictions from simulations of dwarf galaxies that have lost a significant fraction of their dark matter halos and are being tidally stripped.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/409/857
- Title:
- Optical polarization of 3C 279
- Short Name:
- J/A+A/409/857
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a microvariability polarization study in the violently variable quasar 3C 279. We have resolved the polarization curves in the V band for this object down to timescales of minutes. We found two main components in the evolution of the degree of linear polarization, one consisting of a flicker with timescales of several tens of minutes and other component with far more significant variations on timescales of a few days. The linear polarization descended from ~17% down to ~8% in three nights. The polarization angle underwent a sudden change of more that 10 degrees in a few hours, perhaps indicating the injection of a new shock in the jet. The amplitude of the intranight flickering in the degree of polarization is at the level of ~1%. These are probably the best sampled polarization data ever obtained for this object. We also performed IR observations and we provide a follow-up of the evolution of this source at such energies after the main polarization outburst.
- ID:
- ivo://CDS.VizieR/J/ApJS/170/33
- Title:
- Optical properties of Markarian galaxies
- Short Name:
- J/ApJS/170/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A database for the entire Markarian catalog is presented that combines extensive new measurements of their optical parameters with a literature and database search. The measurements were made using images extracted from the STScI Digitized Sky Survey (DSS) of F_pg_(red) and J_pg_(blue) band photographic sky survey plates obtained by the Palomar and UK Schmidt telescopes. We provide accurate coordinates, morphological type, spectral and activity classes, red and blue apparent magnitudes, apparent diameters, axial ratios, and position angles, as well as number counts of neighboring objects in a circle of radius 50kpc. Special attention was paid to the individual descriptions of the galaxies in the original Markarian lists, which clarified many cases of misidentifications of the objects, particularly among interacting systems, larger galaxies with knots of star formation, possible stars, and cases of stars projected on galaxies. The total number of individual Markarian objects in the database is now 1544.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/1119
- Title:
- Optical properties of radio galaxies at z<0.3
- Short Name:
- J/ApJ/723/1119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extended extragalactic radio sources have traditionally been classified into Fanaroff & Riley (FR) I and II types, based on the ratio r_s_ of the separation S between the brightest regions on either sides of the host galaxy and the total size T of the radio source (r_s_~S/T). In this paper, we examine the distribution of various physical properties as a function of r_s_ of 1040 luminous (L>~L*) extended radio galaxies (RGs) at z<0.3 selected with well-defined criteria from the SDSS (Strauss et al. 2002AJ....124.1810S), NVSS (Condon et al. 1998, Cat. VIII/65), and FIRST (Becker et al. 1995+, Cat. VIII/71) surveys. About 2/3 of the RGs are lobe dominated (LD) and 1/3 have prominent jets. If we follow the original definition of the FR types, i.e., a division based solely on r_s_, FRI and FRII RGs overlap in their host galaxy properties.
- ID:
- ivo://CDS.VizieR/J/ApJ/616/71
- Title:
- Optical properties of SCUBA galaxies
- Short Name:
- J/ApJ/616/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and near-infrared photometry for a sample of 96 dusty, far-infrared luminous galaxies. We have precise spectroscopic redshifts for all these galaxies, yielding a median redshift of <z>=2.2. The majority, 78, are submillimeter-detected galaxies lying at z=0.2-3.6, while the remaining 18 are optically faint {mu}Jy radio galaxies at z=0.9-3.4 that are proposed to be similarly luminous, dusty galaxies whose dust emission is too hot to be detected in the submillimeter waveband.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/25
- Title:
- Optical properties of WISE galaxies
- Short Name:
- J/ApJ/758/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), covering a 4deg^2^ region of a deep imaging survey, the Deep Lens Survey (DLS), to study the optical spectral properties of Wide-field Infrared Survey Explorer (WISE) 22{mu}m selected galaxies. Among 507 WISE 22{mu}m selected sources with (S/N)_22{mu}m_>=3 ({approx}S_22{mu}m_>~2.5mJy), we identify the optical counterparts of 481 sources (~98%) at R<25.2 in the very deep, DLS R-band source catalog. Among them, 337 galaxies at R<21 have SHELS spectroscopic data. Most of these objects are at z<0.8. The infrared (IR) luminosities are in the range 4.5x10^8^(L_{sun}_)<~L_IR_<~5.4x10^12^(L_{sun}_). Most 22{mu}m selected galaxies are dusty star-forming galaxies with a small (<1.5) 4000{AA} break. The stacked spectra of the 22 {mu}m selected galaxies binned in IR luminosity show that the strength of the [O III] line relative to H{beta} grows with increasing IR luminosity. The optical spectra of the 22{mu}m selected galaxies also show that there are some (~2.8%) unusual galaxies with very strong [Ne III] {lambda}3869, 3968 emission lines that require hard ionizing radiation such as active galactic nuclei (AGNs) or extremely young massive stars. The specific star formation rates (sSFRs) derived from the 3.6 and 22{mu}m flux densities are enhanced if the 22{mu}m selected galaxies have close late-type neighbors. The sSFR distribution of the 22{mu}m selected galaxies containing AGNs is similar to the distribution for star-forming galaxies without AGNs. We identify 48 dust-obscured galaxy candidates with large (>~1000) mid-IR to optical flux density ratio. The combination of deep photometric and spectroscopic data with WISE data suggests that WISE can probe the universe to z~2.
- ID:
- ivo://CDS.VizieR/J/A+A/495/379
- Title:
- Optical radial velocities in A85
- Short Name:
- J/A+A/495/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this series of papers we explore the evolution of late-type galaxies in the rich cluster Abell 85. In this first paper we revisit the complex dynamical state of A 85 by using independent methods. First, we analyze the galaxy redshift distribution towards A 85 in the whole range 0-40000km/s, and determine the mean redshifts of the background clusters A 87 and A 89, very close in projection to A 85. Then we search for substructures in A 85 by considering the 2D galaxy distribution of its members (13000-20000km/s) and by applying the kinematical 3D {Delta}-test to both projected positions and radial velocities.
- ID:
- ivo://CDS.VizieR/J/MNRAS/459/220
- Title:
- Optical redshifts of OH- and HI-emitting galaxies
- Short Name:
- J/MNRAS/459/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- OH megamasers (OHMs) are rare, luminous molecular masers that are typically observed in (ultra) luminous infrared galaxies and serve as markers of major galaxy mergers. In blind emission line surveys such as the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFALFA) survey for neutral hydrogen (HI), OHMs at z~0.2 can mimic z~0.05 HI lines. We present the results of optical spectroscopy of ambiguous HI detections in the ALFALFA 40 per cent data release detected by the Wide Field Infrared Survey Explorer (WISE) but with uncertain optical counterparts. The optical redshifts, obtained from observations at the Apache Point Observatory, revealed five new OHMs and identified 129 HI optical counterparts. 60 candidates remain ambiguous. The new OHMs are the first detected in a blind spectral line survey. The number of OHMs in ALFALFA is consistent with predictions from the OH luminosity function. Additionally, the mid-infrared magnitudes and colours of the OHM host galaxies found in a blind survey do not seem to differ from those found in previous targeted surveys. This validates the methods used in previous IR-selected OHM surveys and indicates there is no previously unknown OHM-producing population at z~0.2. We also provide a method for future surveys to separate OH megamasers from 99 per cent of HI line emitters without optical spectroscopy by using WISE infrared colours and magnitudes. Since the fraction of OHMs found in flux-limited HI surveys is expected to increase with the survey's redshift, this selection method can be applied to future flux-limited high-redshift hydrogen surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/85
- Title:
- Optical search for SNRs in NGC6946 with WIYN & GMOS
- Short Name:
- J/ApJ/875/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relatively nearby spiral galaxy NGC 6946 is one of the most actively star-forming galaxies in the local universe. Ten supernovae (SNe) have been observed since 1917, and hence NGC 6946 surely contains a large number of supernova remnants (SNRs). Here we report a new optical search for these SNRs using narrowband images obtained with the WIYN telescope. We identify 147 emission nebulae as likely SNRs, based on elevated [SII]:H{alpha} ratios compared to HII regions. We have obtained spectra of 102 of these nebulae with Gemini North-GMOS; of these, 89 have [SII]:H{alpha} ratios greater than 0.4, the canonical optical criterion for identifying SNRs. There is very little overlap between our sample and the SNR candidates identified by Lacey+ (1997ApJS..109..417L) from radio data. Also, very few of our SNR candidates are known X-ray sources, unlike the situation in some other galaxies such as M33 and M83. The emission-line ratios, e.g., [NII]:H{alpha}, of the candidates in NGC 6946 are typical of those observed in SNR samples from other galaxies with comparable metallicity. None of the candidates observed in our low-resolution spectra show evidence of anomalous abundances or significant velocity broadening. A search for emission at the sites of all the historical SNe in NGC 6946 resulted in detections for only two: SN 1980K and SN 2004et. Spectra of both show very broad, asymmetric line profiles, consistent with the interaction between SN ejecta and the progenitor star's circumstellar material, as seen in late spectra from other core-collapse SNe of similar age.
- ID:
- ivo://CDS.VizieR/J/ApJS/203/8
- Title:
- Optical SNR candidates in M83
- Short Name:
- J/ApJS/203/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new optical imaging survey of supernova remnants (SNRs) in M83 (NGC 5236), using data obtained with the Magellan I 6.5m telescope and IMACS instrument under conditions of excellent seeing. Using the criterion of strong [SII] emission relative to H{alpha}, we confirm all but three of the 71 SNR candidates listed in our previous survey, and expand the SNR candidate list to 225 objects, more than tripling the earlier sample. Comparing the optical survey with a new deep X-ray survey of M83 with Chandra, we find that 61 of these SNR candidates have X-ray counterparts. We also identify an additional list of 46 [OIII]-selected nebulae for follow-up as potential ejecta-dominated remnants, seven of which have associated X-ray emission that makes them strong candidates. Some of the other [OIII]-bright objects could also be normal interstellar medium (ISM) dominated SNRs with shocks fast enough to doubly ionize oxygen, but with H{alpha} and [SII] emission faint enough to have been missed. A few of these objects may also be HII regions with abnormally high [OIII] emission compared with the majority of M83 HII regions, compact nebulae excited by young Wolf-Rayet stars, or even background active galactic nuclei. The SNR H{alpha} luminosity function in M83 is shifted by a factor of ~4.5 times higher than for M33 SNRs, indicative of a higher mean ISM density in M83. We describe the search technique used to identify the SNR candidates and provide basic information and finder charts for the objects.
