- ID:
- ivo://CDS.VizieR/J/ApJ/733/L47
- Title:
- Galaxy bulge types within 11Mpc
- Short Name:
- J/ApJ/733/L47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an inventory of galaxy bulge types (elliptical galaxy, classical bulge, pseudobulge, and bulgeless galaxy) in a volume-limited sample within the local 11Mpc sphere using Spitzer 3.6um and Hubble Space Telescope data. We find that whether counting by number, star formation rate, or stellar mass, the dominant galaxy type in the local universe has pure disk characteristics (either hosting a pseudobulge or being bulgeless). Galaxies that contain either a pseudobulge or no bulge combine to account for over 80% of the number of galaxies above a stellar mass of 10^9^M_{sun}_. Classical bulges and elliptical galaxies account for ~1/4, and disks for ~3/4 of the stellar mass in the local 11Mpc. About 2/3 of all star formation in the local volume takes place in galaxies with pseudobulges. Looking at the fraction of galaxies with different bulge types as a function of stellar mass, we find that the frequency of classical bulges strongly increases with stellar mass, and comes to dominate above 10^10.5^M_{sun}_. Galaxies with pseudobulges dominate at 10^9.5^-10^10.5^M_{sun}_. Yet lower-mass galaxies are most likely to be bulgeless. If pseudobulges are not a product of mergers, then the frequency of pseudobulges in the local universe poses a challenge for galaxy evolution models.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/755
- Title:
- Galaxy mergers and AGN activity
- Short Name:
- J/MNRAS/470/755
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Active galactic nuclei (AGNs), particularly the most luminous AGNs, are commonly assumed to be triggered through major mergers; however, observational evidence for this scenario is mixed. To investigate any influence of galaxy mergers on AGN triggering and luminosities through cosmic time, we present a sample of 106 luminous X-ray-selected type 1 AGNs from the COSMOS survey. These AGNs occupy a large redshift range (0.5<z<2.2) and two orders of magnitude in X-ray luminosity (~10^43^-10^45^erg/s). AGN hosts are carefully mass and redshift matched to 486 control galaxies. A novel technique for identifying and quantifying merger features in galaxies is developed, subtracting GALFIT galaxy models and quantifying the residuals. Comparison to visual classification confirms this measure reliably picks out disturbance features in galaxies. No enhancement of merger features with increasing AGN luminosity is found with this metric, or by visual inspection. We analyse the redshift evolution of AGNs associated with galaxy mergers and find no merger enhancement in lower redshift bins. Contrarily, in the highest redshift bin (z~2) AGNs are ~4 times more likely to be in galaxies exhibiting evidence of morphological disturbance compared to control galaxies, at 99 per cent confidence level (~2.4{sigma}) from visual inspection. Since only ~15 per cent of these AGNs are found to be in morphologically disturbed galaxies, it is implied that major mergers at high redshift make a noticeable but subdominant contribution to AGN fuelling. At low redshifts, other processes dominate and mergers become a less significant triggering mechanism.
- ID:
- ivo://CDS.VizieR/J/AJ/128/163
- Title:
- Galaxy morphological classification
- Short Name:
- J/AJ/128/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present two new nonparametric methods for quantifying galaxy morphology: the relative distribution of the galaxy pixel flux values (the Gini coefficient or G) and the second-order moment of the brightest 20% of the galaxy's flux (M_20_). We test the robustness of G and M_20_ to decreasing signal-to-noise ratio (S/N) and spatial resolution and find that both measures are reliable to within 10% for images with average S/N per pixel greater than 2 and resolutions better than 1000 and 500pc, respectively. We have measured G and M_20_, as well as concentration (C), asymmetry (A), and clumpiness (S) in the rest-frame near-ultraviolet/optical wavelengths for 148 bright local "normal" Hubble-type galaxies (E-Sd) galaxies, 22 dwarf irregulars, and 73 0.05<z<0.25 ultraluminous infrared galaxies (ULIRGs).
- ID:
- ivo://CDS.VizieR/J/ApJ/539/577
- Title:
- Galaxy morphologies in Cl 1358+62
- Short Name:
- J/ApJ/539/577
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the morphological composition of a sample of 518 galaxies in the field of Cl 1358+62 at z=0.33, drawn from a large Hubble Space Telescope mosaic covering 53 square arcminutes. The sample is complete to I=22, corresponding to M_V_=-18.5 in the rest frame. The galaxy morphologies have been independently classified by the authors of this paper and by Alan Dressler. Dressler's classifications place our work in context with the previous MORPHS study and allow us to estimate the scatter between different sets of visual classifications. We restrict most of our analysis to the brighter part of the sample, I<21 (M_V_<-19.5), where the scatter between the two sets of classifications is 1 in morphological type.
- ID:
- ivo://CDS.VizieR/J/ApJ/631/85
- Title:
- Galaxy morphologies in the Hubble UDF
- Short Name:
- J/ApJ/631/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxies in the Hubble Ultra Deep Field (UDF) larger than 10 pixels (0.3") have been classified according to morphology, and their photometric properties are presented. There are 269 spiral, 100 elliptical, 114 chain, 126 double-clump, 97 tadpole, and 178 clump-cluster galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/134/1508
- Title:
- Galaxy morphology catalog
- Short Name:
- J/AJ/134/1508
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Careful inspection of large-scale photographs of Shapley-Ames galaxies seems to show a smooth transition between the morphological characteristics of galaxies located on the narrow red and on the broad blue sequences in the galaxian color-magnitude diagram. In other words, there does not appear to be a dichotomy between blue and red galaxies. Both the colors and the morphologies of galaxies are found to correlate strongly with their environments. Red and early-type Shapley-Ames galaxies are dominant in clusters, whereas blue late-type star-forming objects dominate the general field. Interestingly, the colors and morphologies of galaxies in small groups resemble the field and differ from those in clusters. As noted by Baade, the presence of dust and star formation are very closely correlated, except in a few galaxies that probably had unusual evolutionary histories. Over the entire range from S0 to Sc there is no significant difference between the integrated colors of normal and barred objects, suggesting that the formation of a bar does not significantly affect the stellar evolutionary history of a galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/506/1071
- Title:
- Galaxy morphology in 5 medium redshift clusters
- Short Name:
- J/A+A/506/1071
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following the study presented in our previous paper, based on the Nordic Optical Telescope (NOT) sample, which consists of five clusters of galaxies within the redshift range 0.18<=z<=0.25 imaged in the central 0.5-2Mpc in very good seeing conditions, we have studied the quantitative morphology of their bright galaxy population. We analyzed the surface brightness profiles of the galaxy population in those clusters, after performing simulations in order to check the reliability of the fits. We also derived a quantitative morphological classification.
- ID:
- ivo://CDS.VizieR/J/AJ/122/621
- Title:
- Galaxy morphology in the CFRS
- Short Name:
- J/AJ/122/621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The images of 229 galaxies in the Canada-France Redshift Survey have been classified on the DDO system. These observations were combined with previous classifications of galaxies with known redshifts in the Hubble Deep Field. The combined sample provides homogeneous morphological classifications for 425 galaxies of known redshift. The fraction of all galaxies that are of type E, S0, or E/S0 appears to remain approximately constant at ~17% over the redshift range 0.25<z<1.2. Over the same range, the fraction of irregular (Ir) galaxies increases from ~5% to ~12%. Part of this increase may be due to mild luminosity evolution of Ir galaxies. The frequency of mergers is found to rise by a factor of 2 or 3 over the redshift range covered by the present survey. These results are in qualitative agreement with those obtained previously by Brinchmann et al. (Cat. <J/ApJ/499/112>) using a coarser galaxy classification system.
- ID:
- ivo://CDS.VizieR/J/ApJ/791/18
- Title:
- Galaxy samples rest-frame ultraviolet structure
- Short Name:
- J/ApJ/791/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the rest-frame UV wavelength dependence of the Petrosian-like half-light radius (r_50_), and the concentration parameter for a sample of 198 star-forming galaxies at 0.5 < z < 1.5. We find a ~5% decrease in r_50_ from 1500 {AA} to 3000 {AA}, with half-light radii at 3000 {AA} ranging from 0.6 kpc to 6 kpc. We also find a decrease in concentration of ~0.07 (1.9 < C_3000_< 3.9). The lack of a strong relationship between r_50_and wavelength is consistent with a model in which clumpy star formation is distributed over length scales comparable to the galaxy's rest-frame optical light. While the wavelength dependence of r_50_is independent of size at all redshifts, concentration decreases more sharply in the far-UV (~1500 {AA}) for large galaxies at z ~ 1. This decrease in concentration is caused by a flattening of the inner ~20% of the light profile in disk-like galaxies, indicating that the central regions have different UV colors than the rest of the galaxy. We interpret this as a bulge component with older stellar populations and/or more dust. The size-dependent decrease in concentration is less dramatic at z ~ 2, suggesting that bulges are less dusty, younger, and/or less massive than the rest of the galaxy at higher redshifts.
- ID:
- ivo://CDS.VizieR/J/ApJ/782/64
- Title:
- Galaxy structural parameters from 3.6um images
- Short Name:
- J/ApJ/782/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed two-dimensional multicomponent decomposition of 144 local barred spiral galaxies using 3.6{mu}m images from the Spitzer Survey of Stellar Structure in Galaxies. Our model fit includes up to four components (bulge, disk, bar, and a point source) and, most importantly, takes into account disk breaks. We find that ignoring the disk break and using a single disk scale length in the model fit for Type II (down-bending) disk galaxies can lead to differences of 40% in the disk scale length, 10% in bulge-to-total luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We find that for galaxies with B/T>=0.1, the break radius to bar radius, r_br_/R_bar_, varies between 1 and 3, but as a function of B/T the ratio remains roughly constant. This suggests that in bulge-dominated galaxies the disk break is likely related to the outer Lindblad resonance of the bar and thus moves outward as the bar grows. For galaxies with small bulges, B/T<0.1, r_br_/R_bar_ spans a wide range from 1 to 6. This suggests that the mechanism that produces the break in these galaxies may be different from that in galaxies with more massive bulges. Consistent with previous studies, we conclude that disk breaks in galaxies with small bulges may originate from bar resonances that may be also coupled with the spiral arms, or be related to star formation thresholds.
