- ID:
- ivo://CDS.VizieR/J/AJ/139/1413
- Title:
- M81 star cluster candidates
- Short Name:
- J/AJ/139/1413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of extended objects in the vicinity of M81 based on a set of 24 Hubble Space Telescope Advanced Camera for Surveys Wide Field Camera F814W (I-band) images. We have found 233 good globular cluster (GC) candidates; 92 candidate HII regions, OB associations, or diffuse open clusters; 489 probable background galaxies; and 1719 unclassified objects. We have color data from ground-based g- and r-band MMT Megacam images for 79 galaxies, 125 GC candidates, 7 HII regions, and 184 unclassified objects. The color-color diagram of GC candidates shows that most fall into the range 0.25<g-r<1.25 and 0.5<r-I<1.25, similar to the color range of Milky Way GCs. Unclassified objects are often blue, suggesting that many of them are likely to be HII regions and open clusters, although a few galaxies and GCs may be among them.
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2342. M 31 Stokes images
- ID:
- ivo://CDS.VizieR/J/A+A/633/A5
- Title:
- M 31 Stokes images
- Short Name:
- J/A+A/633/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetic fields play an important role in the dynamics and evolution of galaxies; however, the amplification and ordering of the initial seed fields are not fully understood. The nearby spiral galaxy M 31 is an ideal laboratory for extensive studies of magnetic fields. Our aim was to measure the intrinsic structure of the magnetic fields in M 31 and compare them with dynamo models of field amplification. The intensity of polarized synchrotron emission and its orientation are used to measure the orientations of the magnetic field components in the plane of the sky. The Faraday rotation measure gives information about the field components along the line of sight. With the Effelsberg 100-m telescope three deep radio continuum surveys of the Andromeda galaxy, M 31, were performed at 2.645, 4.85, and 8.35 GHz (wavelengths of 11.3, 6.2, and 3.6 cm). The {lambda} 3.6 cm survey is the first radio survey of M 31 at such small wavelengths. Maps of the Faraday rotation measures (RMs) are calculated from the distributions of the polarization angle. At all wavelengths the total and polarized emission is concentrated in a ring-like structure of about 7-13 kpc in radius from the centre. Propagation of cosmic rays away from the star-forming regions is evident. The ring of synchrotron emission is wider than the ring of the thermal radio emission, and the radial scale length of synchrotron emission is larger than that of thermal emission. The polarized intensity from the ring in the plane of the sky varies double-periodically with azimuthal angle, indicating that the ordered magnetic field is oriented almost along the ring, with a pitch angle of -14{deg}+/-2{deg} at {lambda}6.2 cm. The RM varies systematically along the ring. The analysis shows a large-scale sinusoidal variation with azimuthal angle, signature of an axisymmetric spiral (ASS) regular magnetic field, plus a superimposed double-periodic variation of a bisymmetric spiral (BSS) regular field with about six times smaller amplitude. The RM amplitude of (118+/-3) rad/m^2^ between {lambda}6.2 cm and {lambda}3.6 cm is about 50% larger than between {lambda}11.3 cm and {lambda}6.2 cm, indicating that Faraday depolarization at {lambda}11.3 cm is stronger (i.e. with a larger Faraday thickness) than at {lambda}6.2 cm and {lambda}3.6 cm. The phase of the sinusoidal RM variation of -7{deg}+/-1{deg} is interpreted as the average spiral pitch angle of the regular field. The average pitch angle of the ordered field, as derived from the intrinsic orientation of the polarized emission (corrected for Faraday rotation), is significantly smaller: -26{deg}+/-3{deg}. The dominating ASS plus the weaker BSS field of M 31 is the most compelling case so far of a field generated by the action of a mean-field dynamo. The difference in pitch angle of the regular and the ordered fields indicates that the ordered field contains a significant fraction of an anisotropic turbulent field that has a different pattern than the regular (ASS + BSS) magnetic field.
- ID:
- ivo://CDS.VizieR/J/ApJ/610/247
- Title:
- M31 supersoft and quasi-soft X-ray sources
- Short Name:
- J/ApJ/610/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on very soft X-ray sources (VSSs) in M31. In a survey that was most sensitive to soft sources in four 8'x8' regions covered by Chandra's ACIS-S S3 CCD, we find 33 VSSs that appear to belong to M31. Fifteen VSSs have spectral characteristics mirroring the supersoft X-ray sources studied in the Magellanic Clouds and Milky Way (kT_eff_<=100eV); we therefore call these "classical" supersoft sources, or simply supersoft sources (SSSs). Eighteen VSSs may have either small (<10%) hard components or slightly higher effective temperatures (but still less than 350eV). We refer to these VSSs as quasi-soft sources (QSSs).
2344. MSX galaxy observations
- ID:
- ivo://CDS.VizieR/J/AJ/124/2990
- Title:
- MSX galaxy observations
- Short Name:
- J/AJ/124/2990
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have imaged eight nearby spiral galaxies with the SPIRIT III infrared telescope on the Midcourse Space Experiment (MSX) satellite in the mid-infrared at 18" resolution at 8.3, 12.1, 14.7, and 21.3{mu}m. Each of the eight shows interesting structure not previously detected with older, lower resolution infrared data sets, such as a resolved nucleus or spiral structure. The MSX data are compared with existing data sets at ultraviolet, optical, and infrared wavelengths, including recent observations from the Infrared Space Observatory. The infrared structures in M83 and NGC 5055 show a striking similarity to the ultraviolet emission but are less similar to the optical emission. Several point sources with no identified counterparts at other wavelengths are found near M31, NGC 4945, M83, and M101. Over 200 previously known objects are also detected at 8{mu}m.
- ID:
- ivo://CDS.VizieR/J/MNRAS/432/1178
- Title:
- 2MTF. HI observations of 303 southern galaxies
- Short Name:
- J/MNRAS/432/1178
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new 21-cm neutral hydrogen (HI) observations of spiral galaxies for the 2MASS Tully-Fisher (2MTF) survey. Using the 64-m Parkes radio telescope multibeam system we obtain 152 high signal to noise ratio HI spectra from which we extract 148 high-accuracy (<5% error) velocity widths and derive reliable rotation velocities. The observed sample consists of 303 southern ({delta}<-40{deg}) galaxies selected from the 2MASS Redshift Survey with Ks<11.25mag, cz<10000km/s and axis ratio b/a<0.5. The HI observations reported in this paper will be combined with new HI spectra from the Green Bank and Arecibo telescopes, together producing the most uniform Tully-Fisher survey ever constructed (in terms of sky coverage). In particular, due to its near-infrared selection, 2MTF will be significantly more complete at low Galactic latitude (|b|<15{deg}) and will provide a more reliable map of peculiar velocities in the local Universe.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A123
- Title:
- M51 total intensity image at 333MHz
- Short Name:
- J/A+A/592/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cosmic ray electrons (CREs) are a crucial part of the ISM and are observed via synchrotron emission. While much modelling has been carried out on the CRE distribution and propagation of the Milky Way, little has been done on normal external star-forming galaxies. Recent spectral data from a new generation of radio telescopes enable us to find more robust estimations of the CRE propagation To model the synchrotron spectral index of M51 using the diffusion energy-loss equation and to compare the model results with the observed spectral index determined from recent low-frequency observations with LOFAR. We solve the time-dependent diffusion energy-loss equation for CREs in M51. This is the first time that this model for CRE propagation has been solved for a realistic distribution of CRE sources, which we derive from the observed star formation rate, in an external galaxy. The radial variation of the synchrotron spectral index and scale-length produced by the model are compared to recent LOFAR and older VLA observational data and also to new observations of M51 at 325MHz obtained with the GMRT. We find that propagation of CREs by diffusion alone is sufficient to reproduce the observed spectral index distribution in M51. An isotropic diffusion coefficient with a value of 6.6+/-0.2Dunits is found to fit best and is similar to what is seen in the Milky Way. We estimate an escape time of 11Myr from the central galaxy to 88Myr in the extended disk. It is found that an energy dependence of the diffusion coefficient is not important for CRE energies in the range 0.01GeV-3GeV. We are able to reproduce the dependence of the observed synchrotron scale-lengths on frequency, with l{propto}{nu}^-1/4^ in the outer disk and l{propto}{nu}^-1/8^ in the inner disk.
2347. M31 UBVR photometry
- ID:
- ivo://CDS.VizieR/J/ApJ/324/172
- Title:
- M31 UBVR photometry
- Short Name:
- J/ApJ/324/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report deep UBVR CCD photometry of stars in a portion of an arm of M 31, 20kpc southwest of the nucleus. The color-magnitude diagram shows a main sequence that reaches from Mv=-0.7 (at our photometric limit) to Mv=-6.2 and a well-populated giant region. The R, B-R diagram separates the stars rather clearly into three groups, the main sequence, intermediate-color stars (which include the brighter foreground stars), and the red giants. Reddening is found to average E(B-V)=0.13+/-0.04. To determine a reliable luminosity function, we have eliminated foreground contamination and have evaluated our sample completeness, using a large number of artificial stars in the DAOPHOT reduction routine. The corrected luminosity function, which extends from Mv=-5 to -1, has a logarithmic slope of 0.57+/-0.07 for all stars and 0.53+/-0.06 for main-sequence stars only. This value is similar to that reported for galaxies in general (Freedman 1985ApJ...299...74F and 1986, IAUS 116, 61).
- ID:
- ivo://CDS.VizieR/J/A+A/641/A129
- Title:
- Multi-band photometry catalogue of 185 DSFGs
- Short Name:
- J/A+A/641/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dusty high-z galaxies are extreme objects with high star formation rates (SFRs) and luminosities. Characterising the properties of this population and analysing their evolution over cosmic time is key to understanding galaxy evolution in the early Universe. We select a sample of high-z dusty star-forming galaxies (DSFGs) and evaluate their position on the main sequence (MS) of star-forming galaxies, the well-known correlation between stellar mass and SFR. We aim to understand the causes of their high star formation and quantify the percentage of DSFGs that lie above the MS. We adopted a multi-wavelength approach with data from optical to submillimetre wavelengths from surveys at the North Ecliptic Pole (NEP) to study a submillimetre sample of high-redshift galaxies. Two submillimetre selection methods were used, including: sources selected at 850um with the Sub-millimetre Common-User Bolometer Array 2) SCUBA-2 instrument and Herschel-Spectral and Photometric Imaging Receiver (SPIRE) selected sources (colour-colour diagrams and 500um risers), finding that 185 have good multi-wavelength coverage. The resulting sample of 185 high-z candidates was further studied by spectral energy distribution (SED) fitting with the CIGALE fitting code. We derived photometric redshifts, stellar masses, SFRs, and additional physical parameters, such as the infrared luminosity and active galactic nuclei (AGN) contribution. We find that the Herschel-SPIRE selected DSFGs generally have higher redshifts (z=2.57^+0.08^_-0.09_) than sources that are selected solely by the SCUBA-2 method (z=1.45^+0.21^_-0.06_). We find moderate SFRs (797^+108^_-50_M_{sun}/yr}), which are typically lower than those found in other studies. We find that the different results in the literature are, only in part, due to selection effects, as even in the most extreme cases, SFRs are still lower than a few thousand solar masses per year. The difference in measured SFRs affects the position of DSFGs on the MS of galaxies; most of the DSFGs lie on the MS (60%). Finally, we find that the star formation efficiency (SFE) depends on the epoch and intensity of the star formation burst in the galaxy; the later the burst, the more intense the star formation. We discuss whether the higher SFEs in DSFGs could be due to mergers.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A10
- Title:
- Multiband surface photometry of 21 BCGs
- Short Name:
- J/A+A/556/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep surface photometry of a volume-limited sample of 21 UM emission line galaxies in broadband optical UBVRI and near infra-red (NIR) HKs filters. The sample comprises 19 blue compact galaxies (BCGs) and two spirals. For some targets the exposure times are the deepest to date. For the BCG UM462 we observe a previously undetected second disk component beyond a surface brightness level of mu_B_=26mag/arcsec^2^. This is a true low surface brightness component with central surface brightness mu_0_=24.1mag/arcsec^2^ and scale length h_r_=1.5kpc. All BCGs are dwarfs, with M_B_>=-18, and very compact, with an average scale length of h_r_~1kpc. We separate the burst and host populations for each galaxy and compare them to stellar evolutionary models with and without nebular emission contribution. We also measure the A_180_ asymmetry in all filters and detect a shift from optical to NIR in the average asymmetry of the sample. This shift seems to be correlated with the morphological class of the BCGs. Using the color-asymmetry relation, we identify five BCGs in the sample as mergers, which is confirmed by their morphological class. Though clearly separated from normal galaxies in the concentration-asymmetry parameter space, we find that it is not possible to distinguish luminous starbursting BCGs from the merely star forming low luminosity BCGs.
- ID:
- ivo://CDS.VizieR/J/AJ/122/1718
- Title:
- Multicolor photometry in Abell 2634
- Short Name:
- J/AJ/122/1718
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An optical photometric observation with the Beijing-Arizona-Taipei-Connecticut multicolor system is carried out for the central region of the nearby cluster of galaxies Abell 2634. From the 2Kx2K CCD images with 14 filters, which cover a range of wavelength from 3600 to 10000{AA}, 5572 sources are detected down to V~20mag in a field of 56'x56' centered on this regular cluster of galaxies. As a result, we achieved the spectral energy distributions (SEDs) of all sources detected. There are 178 previously known galaxies included in our observations, 147 of which have known radial velocities in the literature. After excluding the foreground and background galaxies, a sample of 124 known members is formed for an investigation of the SED properties. The comparison of observed SEDs of the early-type member galaxies with the template SEDs demonstrates the accuracy and reliability of our photometric measurements.
