- ID:
- ivo://CDS.VizieR/J/AJ/126/3007
- Title:
- Spectroscopy of faint red NLTT dwarfs
- Short Name:
- J/AJ/126/3007
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present low-resolution optical spectroscopy and BVRI photometry of 453 candidate nearby stars drawn from the NLTT (<I/98>) proper-motion catalog. The stars were selected based on optical/near-infrared colors, derived by combining the NLTT photographic data with photometry from the 2MASS Second Incremental Data Release (<II/241>). Based on the derived photometric and spectroscopic parallaxes, we identify 111 stars as lying within 20pc of the Sun, including nine stars with formal distance estimates of less than 10pc. A further 53 stars have distance estimates within 1{sigma} of our 20pc limit. Almost all of those stars are additions to the nearby-star census. In total, our NLTT-based survey has so far identified 496 stars likely to be within 20pc, of which 195 are additions to nearby-star catalogs. Most of the newly identified nearby stars have spectral types between M4 and M8.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1521
- Title:
- Spectroscopy of galaxies around distant QSOs
- Short Name:
- J/ApJ/714/1521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results from a survey of MgII absorbers in the spectra of background quasi-stellar objects (QSOs) that are within close angular distances to a foreground galaxy at z<0.5, using the Magellan Echellette Spectrograph. We have established a spectroscopic sample of 94 galaxies at a median redshift of <z>=0.24 in fields around 70 distant background QSOs (z_QSO_>0.6), 71 of which are in an "isolated" environment with no known companions and located at {rho}<~120h^-1^kpc from the line of sight of a background QSO. The rest-frame absolute B-band magnitudes span a range from M_B_-5logh=-16.4 to M_B_-5logh=-21.4 and rest-frame B_AB_-R_AB_ colors range from B_AB_-R_AB_~0 to B_AB_-R_AB_~1.5. Of these "isolated" galaxies, we find that 47 have corresponding MgII absorbers in the spectra of background QSOs and rest-frame absorption equivalent width W_r_(2796)=0.1-2.34{AA}, and 24 do not give rise to MgII absorption to sensitive upper limits.
- ID:
- ivo://CDS.VizieR/J/AJ/149/79
- Title:
- Spectroscopy of 299 galaxies from NewHa survey
- Short Name:
- J/AJ/149/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a sample of 299 H{alpha}-selected galaxies at z~~0.8, we study the relationship between galaxy stellar mass, gas-phase metallicity, and star formation rate (SFR), and compare to previous results. We use deep optical spectra obtained with the IMACS spectrograph at the Magellan telescope to measure strong oxygen lines. We combine these spectra and metallicities with (1) rest-frame UV-to-optical imaging, which allows us to determine stellar masses and dust attenuation corrections, and (2) H{alpha} narrowband imaging, which provides a robust measurement of the instantaneous SFR. Our sample spans stellar masses of ~10^9^-6x10^11^M_{sun}_, SFRs of 0.4-270M_{sun}_/yr, and metal abundances of 12+log(O/H)~~8.3-9.1(~~0.4-2.6Z_{sun}_). The correlations that we find between the H{alpha}-based SFR and stellar mass (i.e., the star-forming "main sequence") and between the stellar mass and metallicity are both consistent with previous z~1 studies of star-forming galaxies. We then study the relationship between the three properties using various plane-fitting techniques and a curve-fitting projection. In all cases, we exclude strong dependence of the M_{star}_-Z relation on SFR, but are unable to distinguish between moderate and no dependence. Our results are consistent with previous mass-metallicity-SFR studies. We check whether data set limitations may obscure a strong dependence on the SFR by using mock samples drawn from the Sloan Digital Sky Survey. These experiments reveal that the adopted signal-to-noise ratio cuts may have a significant effect on the measured dependence. Further work is needed to investigate these results, and to test whether a "fundamental metallicity relation" or a "fundamental plane" describes star-forming galaxies across cosmic time.
- ID:
- ivo://CDS.VizieR/J/AJ/154/251
- Title:
- Spectroscopy of galaxies in z=0.2-0.9 clusters
- Short Name:
- J/AJ/154/251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of stellar populations in passive galaxies in seven massive X-ray clusters at z=0.19-0.89. Based on absorption-line strengths measured from our high signal-to-noise spectra, the data support primarily passive evolution of the galaxies. We use the scaling relations between velocity dispersions and the absorption-line strengths to determine representative mean line strengths for the clusters. From the age determinations based on the line strengths (and stellar population models), we find a formation redshift of z_form_=1.96_-0.19_^+0.24^. Based on line strength measurements from high signal-to-noise composite spectra of our data, we establish the relations between velocity dispersions, ages, metallicities [M/H], and abundance ratios [{alpha}/Fe] as a function of redshift. The [M/H]-velocity dispersion and [{alpha}/Fe]-velocity dispersion relations are steep and tight. The age-velocity dispersion relation is flat, with zero-point changes reflecting passive evolution. The scatter in all three parameters is within 0.08-0.15 dex at fixed velocity dispersions, indicating a large degree of synchronization in the evolution of the galaxies. We find an indication of cluster-to-cluster differences in metallicities and abundance ratios. However, variations in stellar populations with the cluster environment can only account for a very small fraction of the intrinsic scatter in the scaling relations. Thus, within these very massive clusters, the main driver of the properties of the stellar populations in passive galaxies appears to be the galaxy velocity dispersion.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/98
- Title:
- Spectroscopy of galaxy clusters to find LCBGs
- Short Name:
- J/ApJ/741/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the DEIMOS spectrograph on the Keck II Telescope to obtain spectra of galaxies in the fields of five distant, rich galaxy clusters over the redshift range 0.5<z<0.9 in a search for luminous compact blue galaxies (LCBGs). Unlike traditional studies of galaxy clusters, we preferentially targeted blue cluster members identified via multi-band photometric pre-selection based on imaging data from the WIYN telescope. Of the 1288 sources that we targeted, we determined secure spectroscopic redshifts for 848 sources, yielding a total success rate of 66%. Our redshift measurements are in good agreement with those previously reported in the literature, except for 11 targets which we believe were previously in error. Within our sample, we confirm the presence of 53 LCBGs in the five galaxy clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/144/8
- Title:
- Spectroscopy of ~100 G/K/M-type Sco-Cen complex members
- Short Name:
- J/AJ/144/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have spectroscopically identified ~100 G-, K-, and M-type members of the Scorpius-Centaurus complex. To deduce the age of these young stars we compare their Li {lambda}6708 absorption line strengths against those of stars in the TW Hydrae association and {beta} Pictoris moving group. These line strengths indicate that Sco-Cen stars are younger than {beta} Pic stars whose ages of ~12Myr have previously been derived from a kinematic traceback analysis. Our derived age, ~10Myr, for stars in the Lower Centaurus Crux and Upper Centaurus Lupus subgroups of ScoCen is younger than previously published ages based on the moving cluster method and upper main-sequence fitting. The discrepant ages are likely due to an incorrect (or lack of) cross-calibration between model-dependent and model-independent age-dating methods.
- ID:
- ivo://CDS.VizieR/J/ApJ/892/137
- Title:
- Spectroscopy of Grus II, Tuc IV and Tuc V
- Short Name:
- J/ApJ/892/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Magellan/IMACS spectroscopy of three recently discovered ultra-faint Milky Way satellites, Grus II, Tucana IV, and Tucana V. We measure systemic velocities of v_hel_=-110.0+/-0.5km/s, v_hel_=15.9_-1.7_^+1.8^km/s, and v_hel_=-36.2_-2.2_^+2.5^km/s for the three objects, respectively. Their large relative velocities demonstrate that the satellites are unrelated despite their close physical proximity. We determine a velocity dispersion for Tuc IV of {sigma}=4.3_-1.0_^+1.7^km/s, but we cannot resolve the velocity dispersions of the other two systems. For Gru II, we place an upper limit (90% confidence) on the dispersion of {sigma}<1.9km/s, and for Tuc V, we do not obtain any useful limits. All three satellites have metallicities below [Fe/H]=-2.1, but none has a detectable metallicity spread. We determine proper motions for each satellite based on Gaia astrometry and compute their orbits around the Milky Way. Gru II is on a tightly bound orbit with a pericenter of 25_-7_^+6^kpc and orbital eccentricity of 0.45_-0.05_^+0.08^. Tuc V likely has an apocenter beyond 100kpc and could be approaching the Milky Way for the first time. The current orbit of Tuc IV is similar to that of Gru II, with a pericenter of 25_-8_^+11^kpc and an eccentricity of 0.36_-0.06_^+0.13^. However, a backward integration of the position of Tuc IV demonstrates that it collided with the Large Magellanic Cloud at an impact parameter of 4kpc ~120Myr ago, deflecting its trajectory and possibly altering its internal kinematics. Based on their sizes, masses, and metallicities, we classify Gru II and Tuc IV as likely dwarf galaxies, but the nature of Tuc V remains uncertain.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/140
- Title:
- Spectroscopy of Herschel-SPIRE galaxies
- Short Name:
- J/ApJ/761/140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Keck spectroscopic observations and redshifts for a sample of 767 Herschel-SPIRE selected galaxies (HSGs) at 250, 350, and 500{mu}m, taken with the Keck I Low Resolution Imaging Spectrometer and the Keck II DEep Imaging Multi-Object Spectrograph. The redshift distribution of these SPIRE sources from the Herschel Multitiered Extragalactic Survey (HerMES) peaks at z=0.85, with 731 sources at z<2 and a tail of sources out to z~5. We measure more significant disagreement between photometric and spectroscopic redshifts (<{Delta}z/(1+z_spec_)>=0.29) than is seen in non-infrared selected samples, likely due to enhanced star formation rates and dust obscuration in infrared-selected galaxies. The infrared data are used to directly measure integrated infrared luminosities and dust temperatures independent of radio or 24{mu}m flux densities. By probing the dust spectral energy distribution (SED) at its peak, we estimate that the vast majority (72%-83%) of z<2 Herschel-selected galaxies would drop out of traditional submillimeter surveys at 0.85-1mm. This work significantly increased the number of spectroscopically confirmed infrared-luminous galaxies at z{Gt}0 and demonstrates the growing importance of dusty starbursts for galaxy evolution studies and the build-up of stellar mass throughout cosmic time.
- ID:
- ivo://CDS.VizieR/J/AJ/117/2329
- Title:
- Spectroscopy of hot stars in the halo. III
- Short Name:
- J/AJ/117/2329
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from an analysis of medium-resolution spectroscopy and UBV photometry for a sample of 1121 A-type stars in the halo (and disk) of the Galaxy. A previously developed calibration technique is used to assign estimates of effective temperature, surface gravity, and stellar metal abundance, as parametrized by [Fe/H]. Radial velocities are reported with an accuracy of {~}10 km.s^-1^. Distance estimates are obtained for the stars with well-determined luminosity classes. Note that although we refer to "A-type" stars, which dominate the present sample, the present data set includes roughly 100 stars of later spectral types, as a result of the temperature range we have chosen to explore in this paper (6000 K {<=} T_eff_ {<=} 10,000 K).
- ID:
- ivo://CDS.VizieR/J/ApJ/657/241
- Title:
- Spectroscopy of Leo I red giants
- Short Name:
- J/ApJ/657/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present low-resolution spectroscopy of 120 red giants in the Galactic satellite dwarf spheroidal (dSph) Leo I, obtained with GeminiN GMOS and Keck DEIMOS. We find stars with velocities consistent with membership of Leo I out to 1.3 King tidal radii. By measuring accurate radial velocities with a median measurement error of 4.6km/s, we find a mean systemic velocity of 284.2km/s with a global velocity dispersion of 9.9km/s. The dispersion profile is consistent with being flat out to the last data point.