- ID:
- ivo://CDS.VizieR/J/A+A/618/A156
- Title:
- Stellar populations of the central region of M31
- Short Name:
- J/A+A/618/A156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We continue the analysis of the data set of our spectroscopic observation campaign of M31, whose ultimate goal is to provide an understanding of the three-dimensional structure of the bulge, its formation history, and composition in terms of a classical bulge, boxy-peanut bulge, and bar contributions. We derive simple stellar population (SSP) properties, such as age metallicity and alpha-element overabundance, from the measurement of Lick/IDS absorption line indices. We describe their two-dimensional maps taking into account the dust distribution in M31. We found 80% of the values of our age measurements are larger than 10Gyr. The central 100-arcsec of M31 are dominated by the stars of the classical bulge of M31. These stars are old (11-13Gyr), metal-rich (as high as [Z/H]~0.35dex) at the center with a negative gradient outward and enhanced in alpha-elements ([alpha/Fe]~0.28+/-0.01dex). The bar stands out in the metallicity map, where an almost solar value of [Z/H] (~0.02+/-0.01dex) with no gradient is observed along the bar position angle (55.7{deg}) out to 600 arcsec from the center. In contrast, no signature of the bar is seen in the age and [alpha/Fe] maps, which are approximately axisymmetric, delivering a mean age and overabundance for the bar and boxy-peanut bulge of 10-13Gyr and 0.25-0.27dex, respectively. The boxy-peanut bulge has almost solar metallicity (-0.04+/-0.01dex). The mass-to-light ratio of the three components is approximately constant at M/LV~4.4-4.7M_{sun}_/L_{sun}_. The disk component at larger distances is made of a mixture of stars, as young as 3-4Gyr, with solar metallicity and smaller M/LV (~3+/-0.1M_{sun}_/L_{sun}_). We propose a two-phase formation scenario for the inner region of M31, where most of the stars of the classical bulge come into place together with a proto-disk, where a bar develops and quickly transforms it into a boxy-peanut bulge. Star formation continues in the bulge region, producing stars younger than 10Gyr, in particular along the bar, thereby enhancing its metallicity. The disk component appears to build up on longer timescales.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/234/35
- Title:
- Stellar population synthesis of clumps
- Short Name:
- J/ApJS/234/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 1027 star-forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star-forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in 8{mu}m observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution of our clumps with the Code Investigating GALaxy Emission using a double exponentially declined star formation history. We derive the star formation rates (SFRs), stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an active galactic nucleus for these clumps. The resolved star formation main sequence holds on 2.5kpc scales, although it does not hold on 1kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that the SFR is enhanced through the disk and in the tidal features relative to normal spirals.
- ID:
- ivo://CDS.VizieR/J/MNRAS/412/423
- Title:
- Stellar population trends in S0 galaxies
- Short Name:
- J/MNRAS/412/423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present stellar population age and metallicity trends for a sample of 59 S0 galaxies based on optical Sloan Digital Sky Survey (SDSS) and near-infrared (NIR) J and H photometry. When combined with optical g and r passband imaging data from the SDSS archive and stellar population models, we obtain radial age and metallicity trends out to at least five effective radii for most of the galaxies in our sample. The sample covers a range in stellar mass and light concentration.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/37
- Title:
- Stellar specific angular momentum & mass relation
- Short Name:
- J/ApJ/860/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the relation between stellar specific angular momentum j*, stellar mass M*, and bulge-to-total light ratio {beta} for The HI Nearby Galaxy Survey, the Calar Alto Legacy Integral Field Area Survey, and Romanowsky & Fall (2012ApJS..203...17R) data sets, exploring the existence of a fundamental plane between these parameters, as first suggested by Obreschkow & Glazebrook (2014ApJ...784...26O). Our best-fit M*-j* relation yields a slope of {alpha}=1.03+/-0.11 with a trivariate fit including {beta}. When ignoring the effect of {beta}, the exponent {alpha}=0.56+/-0.06 is consistent with {alpha}=2/3 that is predicted for dark matter halos. There is a linear {beta}-j*/M* relation for {beta}<~0.4, exhibiting a general trend of increasing {beta} with decreasing j*/M*. Galaxies with {beta}>~0.4 have higher j* than predicted by the relation. Pseudobulge galaxies have preferentially lower {beta} for a given j*/M* than galaxies that contain classical bulges. Pseudobulge galaxies follow a well- defined track in {beta}-j*/M* space, consistent with Obreschkow & Glazebrook, while galaxies with classical bulges do not. These results are consistent with the hypothesis that while growth in either bulge type is linked to a decrease in j*/M*, the mechanisms that build pseudobulges seem to be less efficient at increasing bulge mass per decrease in specific angular momentum than those that build classical bulges.
- ID:
- ivo://CDS.VizieR/J/MNRAS/390/1437
- Title:
- Stellar streams in Andromeda (M31)
- Short Name:
- J/MNRAS/390/1437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic analysis of five stellar streams ("A", "B", "Cr", "Cp" and "D") as well as the extended star cluster, EC4, which lies within Stream "C", all discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey. These spectroscopic results were initially serendipitous, making use of our existing observations from the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope, and thereby emphasizing the ubiquity of tidal streams that account for ~70 per cent of the M31 halo stars in the targeted fields. Subsequent spectroscopy was then procured in Stream "C" and Stream "D" to trace the velocity gradient along the streams. Nine metal-rich ([Fe/H]~-0.7) stars at v_hel_=-349.5km/s, {sigma}_v,corr_~5.1+/-2.5km/s are proposed as a serendipitous detection of Stream "Cr", with follow-up kinematic identification at a further point along the stream. Seven metal-poor ([Fe/H]~-1.3) stars confined to a narrow, 15km/s velocity bin centred at v_hel_=-285.6, {sigma}_v,corr_=4.3^+1.7^_-1.4_km/s represent a kinematic detection of Stream "Cp", again with follow-up kinematic identification further along the stream. For the cluster EC4, candidate member stars with average [Fe/H]~-1.4, are found at v_hel_=-282 suggesting it could be related to Stream "Cp". No similarly obvious cold kinematic candidate is found for Stream "D", although candidates are proposed in both of two spectroscopic pointings along the stream (both at ~-400km/s). Spectroscopy near the edge of Stream "B" suggests a likely kinematic detection at v_hel_~-330, {sigma}_v,corr_~6.9km/s, while a candidate kinematic detection of Stream "A" is found (plausibly associated to M33 rather than M31) with v_hel_~-170, {sigma}_v,corr_=12.5km/s. The low dispersion of the streams in kinematics, physical thickness and metallicity makes it hard to reconcile with a scenario whereby these stream structures as an ensemble are related to the giant southern stream. We conclude that the M31 stellar halo is largely made up of multiple kinematically cold streams.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A5
- Title:
- Stellar structure models of edge-on galaxies
- Short Name:
- J/A+A/610/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies have made the community aware of the importance of accounting for scattered light when examining low-surface-brightness galaxy features such as thick discs. In our past studies of the thick discs of edge-on galaxies in the Spitzer Survey of Stellar Structure in Galaxies - the S4G - we modelled the point spread function as a Gaussian. In this paper we re- examine our results using a revised point spread function model that accounts for extended wings out to more than 2.5arcmin. We study the 3.6micron images of 141 edge-on galaxies from the S4G and its early-type galaxy extension. Thus, we more than double the samples examined in our past studies. We decompose the surface-brightness profiles of the galaxies perpendicular to their mid-planes assuming that discs are made of two stellar discs in hydrostatic equilibrium. We decompose the axial surface- brightness profiles of galaxies to model the central mass concentration - described by a Sersic function - and the disc - described by a broken exponential disc seen edge-on. Our improved treatment fully confirms the ubiquitous occurrence of thick discs. The main difference between our current fits and those presented in our previous papers is that now the scattered light from the thin disc dominates the surface brightness at levels below ~26mag/arcsec^2^. We stress that those extended thin disc tails are not physical, but pure scattered light. This change, however, does not drastically affect any of our previously presented results: 1) Thick discs are nearly ubiquitous. They are not an artefact caused by scattered light as has been suggested elsewhere. 2) Thick discs have masses comparable to those of thin discs in low-mass galaxies - with circular velocities vc<120km/s - whereas they are typically less massive than the thin discs in high-mass galaxies. 3) Thick discs and central mass concentrations seem to have formed at the same epoch from a common material reservoir. 4) Approximately 50% of the up-bending breaks in face-on galaxies are caused by the superposition of a thin and a thick disc where the scale-length of the latter is the largest.
- ID:
- ivo://CDS.VizieR/J/ApJS/100/105
- Title:
- Stellar velocity dispersions. II.
- Short Name:
- J/ApJS/100/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalog of central velocity dispersion measurements is presented, current through 1993 September. The catalog includes 2474 measurements of 1563 (*) galaxies. A standard set of 86 galaxies is defined, consisting of galaxies with at least three reliable concordant measurements. It is suggested that future studies observe some of these standard galaxies so that different studies can be normalised to a consistent system. All measurements are reduced to a normalized system using these standards. (*) Actually 1562 galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/146/209
- Title:
- STIS emission-line galaxies observations
- Short Name:
- J/ApJS/146/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the first 3 years of operation the Space Telescope Imaging Spectrograph (STIS) obtained slitless spectra of ~2500 fields in parallel to prime Hubble Space Telescope (HST) observations as part of the STIS parallel survey (SPS). The archive contains ~300 fields at high Galactic latitude (|b|>30{deg}) with spectroscopic exposure times greater than 3000s. This sample contains 219 fields (excluding special regions and requiring a consistent grating angle) observed between 1997 June 6 and 2000 September 21, with a total survey area of ~160-arcmin^2^. At this depth, the SPS detects an average of one emission-line galaxy per three fields. We present the analysis of these data and the identification of 131 low- to intermediate-redshift galaxies detected by optical emission lines. The sample contains 78 objects with emission lines that we infer to be redshifted [O II] {lambda}3727 emission at 0.43<z<1.7. The comoving number density of these objects is comparable to that of H{alpha}-emitting galaxies in the NICMOS parallel observations. One quasar and three probable Seyfert galaxies are detected. Many of the emission-line objects show morphologies suggestive of mergers or interactions. The reduced data are available upon request from the authors.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/1442
- Title:
- 78 Stripe82 galaxies masses
- Short Name:
- J/MNRAS/478/1442
- Date:
- 19 Jan 2022 11:53:49
- Publisher:
- CDS
- Description:
- We present a cross-calibration of CO- and dust-based molecular gas masses at z<=0.2. Our results are based on a survey with the IRAM 30-m telescope collecting CO(1-0) measurements of 78 massive (logM*/M_{sun}_>10) galaxies with known gas-phase metallicities and with IR photometric coverage from Wide-field Infrared Survey Explorer(WISE; 22um) and Herschel Spectral and Photometric Imaging Receiver (SPIRE; 250, 350, 500um). We find a tight relation (~0.17dex scatter) between the gas masses inferred from CO and dust continuum emission, with a minor systematic offset of 0.05dex. The two methods can be brought into agreement by applying a metallicity-dependent adjustment factor (~0.13dex scatter). We illustrate that the observed offset is consistent with a scenario in which dust traces not only molecular gas but also part of the HI reservoir, residing in the H_2_-dominated region of the galaxy. Observations of the CO(2-1) to CO(1-0) line ratio for two-thirds of the sample indicate a narrow range in excitation properties, with a median ratio of luminosities <R_21_>~0.64. Finally, we find dynamical mass constraints from spectral line profile fitting to agree well with the anticipated mass budget enclosed within an effective radius, once all mass components (stars, gas, and dark matter) are accounted for.
- ID:
- ivo://org.gavo.dc/annisred/q/cone
- Title:
- Stripe 82 Photometric Redshifts from SDSS Coadditions
- Short Name:
- s82 coadd cone
- Date:
- 27 Dec 2024 08:31:03
- Publisher:
- The GAVO DC team
- Description:
- This survey gives photometric redshifts of objects within 275 deg² (−50◦ < α < 60◦ and −1.◦25 < δ < +1.◦25) centered on the Celestial Equator. Each piece of sky has ∼20 runs of repeated scanning by the SDSS camera contributing and thus reaches ∼2 mag fainter than the SDSS single pass data, i.e., to r ∼ 23.5 for galaxies.
