- ID:
- ivo://CDS.VizieR/J/ApJ/685/235
- Title:
- Host and companion galaxies in the SDSS
- Short Name:
- J/ApJ/685/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the number of companions per galaxy (N_c_) as a function of r-band absolute magnitude for both the Sloan Digital Sky Survey (DR5) and the Croton and coworkers semianalytic catalog, 2006MNRAS.365...11C, applied to the Millennium Run simulation (Springel et al., 2005Natur.435..629S). For close pairs with projected separations of 5-20kpc/h, velocity differences less than 500km/s, and luminosity ratios between 1:2 and 2:1, we find good agreement between the observations and simulations, with N_c_ consistently close to 0.02 over the range -22<M_r_<-18. For larger pair separations, N_c_(M_r_) instead becomes increasingly steep toward the faint end, implying that luminosity-dependent clustering plays an important role on small scales. Using the simulations to assess and correct for projection effects, we infer that the real-space N_c_(M_r_) for close pairs peaks at about M^*^ and declines by at least a factor of 2 as M_r_ becomes fainter. Conversely, by measuring the number density of close companions, we estimate that at least 90% of all major mergers occur between galaxies which are fainter than L^*^. Finally, measurements of the luminosity density of close companions indicate that L^*^ galaxies likely dominate in terms of the overall importance of major mergers in the evolution of galaxy populations at low redshift.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/830/13
- Title:
- Host-galaxy NUV-NIR data of 32 superluminous SNe
- Short Name:
- J/ApJ/830/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ultraviolet through near-infrared photometry and spectroscopy of the host galaxies of all superluminous supernovae (SLSNe) discovered by the Palomar Transient Factory prior to 2013 and derive measurements of their luminosities, star formation rates, stellar masses, and gas-phase metallicities. We find that Type I (hydrogen-poor) SLSNe (SLSNe I) are found almost exclusively in low-mass (M_*_<2x10^9^M_{sun}_) and metal-poor (12+log_10_[O/H]<8.4) galaxies. We compare the mass and metallicity distributions of our sample to nearby galaxy catalogs in detail and conclude that the rate of SLSNe I as a fraction of all SNe is heavily suppressed in galaxies with metallicities >~0.5Z_{sun}_. Extremely low metallicities are not required and indeed provide no further increase in the relative SLSN rate. Several SLSN I hosts are undergoing vigorous starbursts, but this may simply be a side effect of metallicity dependence: dwarf galaxies tend to have bursty star formation histories. Type II (hydrogen-rich) SLSNe (SLSNe II) are found over the entire range of galaxy masses and metallicities, and their integrated properties do not suggest a strong preference for (or against) low-mass/low-metallicity galaxies. Two hosts exhibit unusual properties: PTF 10uhf is an SLSN I in a massive, luminous infrared galaxy at redshift z=0.29, while PTF 10tpz is an SLSN II located in the nucleus of an early-type host at z=0.04.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A160
- Title:
- Hot aminoacetonitrile in Sgr B2
- Short Name:
- J/A+A/641/A160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aminoacetonitrile, a molecule detected in the interstellar medium only towards the star-forming region Sagittarius B2 (Sgr B2) thus far, is considered an important prebiotic species; in particular it is a possible precursor of the simplest amino acid glycine. To date, observations were limited to ground state emission lines, whereas transitions from within vibrationally excited states remained undetected. We wanted to accurately determine the energies of the low-lying vibrational states of aminoacetonitrile, which are expected to be populated in Sgr B2(N1), the main hot core of Sgr B2(N). This step is fundamental in order to properly evaluate the vibration-rotation partition function of aminoacetonitrile as well as the line strengths of the rotational transitions of its vibrationally excited states. This is necessary to derive accurate column densities and secure the identification of these transitions in astronomical spectra. The far-infrared ro-vibrational spectrum of aminoacetonitrile has been recorded in absorption against a synchrotron source of continuum emission. Three bands, corresponding to the lowest vibrational modes of aminoacetonitrile, were observed in the frequency region below 500cm^-1^. The combined analysis of ro-vibrational and pure rotational data allowed us to prepare new spectral line catalogs for all the states under investigation. We used the imaging spectral line survey ReMoCA performed with ALMA to search for vibrationally excited aminoacetonitrile toward Sgr B2(N1). The astronomical spectra were analyzed under the local thermodynamic equilibrium (LTE) approximation. Almost 11000 lines have been assigned during the analysis of the laboratory spectrum of aminoacetonitrile, thanks to which the vibrational energies of the v_11_=1, v_18_=1, and v_17_=1 states have been determined. The whole dataset, which includes high J and Ka transitions, is well reproduced within the experimental accuracy. Reliable spectral predictions of pure rotational lines can now be produced up to the THz region. On the basis of these spectroscopic predictions, we report the interstellar detection of aminoacetonitrile in its v_11_=1 and v_18_=1 vibrational states toward Sgr B2(N1) in addition to emission in its vibrational ground state. The intensities of the identified v_11_=1 and v_18_=1 lines are consistent with the detected v=0 lines under LTE at a temperature of 200K for an aminoacetonitrile column density of 1.1x10^17^/cm^2^. This work shows the strong interplay between laboratory spectroscopy exploiting (sub)millimeter and synchrotron far-infrared techniques, and observational spectral surveys to detect complex organic molecules in space and quantify their abundances.
- ID:
- ivo://CDS.VizieR/J/ApJS/231/1
- Title:
- Hot DA white dwarfs grid of synthetic spectra
- Short Name:
- J/ApJS/231/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work we present a grid of LTE and non-LTE synthetic spectra of hot DA white dwarfs (WDs). In addition to its usefulness for the determination of fundamental stellar parameters of isolated WDs and in binaries, this grid will be of interest for the construction of theoretical libraries for stellar studies from integrated light. The spectral grid covers both a wide temperature and gravity range, with 17000K<=Teff<=100000K and 7.0<=log(g)<=9.5. The stellar models are built for pure hydrogen and the spectra cover a wavelength range from 900{AA} to 2.5um. Additionally, we derive synthetic HST/ACS, HST/WFC3, Bessel UBVRI, and SDSS magnitudes. The grid was also used to model integrated spectral energy distributions of simple stellar populations and our modeling suggests that DAs might be detectable in ultraviolet bands for populations older than ~8Gyr.
- ID:
- ivo://CDS.VizieR/J/AJ/162/188
- Title:
- Hot degenerates in the MCT survey. III.
- Short Name:
- J/AJ/162/188
- Date:
- 21 Mar 2022 00:13:43
- Publisher:
- CDS
- Description:
- We present optical spectra of 144 white dwarfs detected in the Montreal-Cambridge-Tololo colorimetric survey, including 120 DA, 12 DB, 4 DO, 1 DQ, and 7 DC stars. We also perform a model atmosphere analysis of all objects in our sample using the so-called spectroscopic technique, or the photometric technique in the case of DC white dwarfs. The main objective of this paper is to contribute to the ongoing effort of confirming spectroscopically all white dwarf candidates in the Gaia survey, in particular in the southern hemisphere. All our spectra are made available in the Montreal White Dwarf Database.
- ID:
- ivo://CDS.VizieR/J/ApJ/757/46
- Title:
- Hot methane (CH4) line list
- Short Name:
- J/ApJ/757/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present comprehensive experimental line lists of methane (CH_4_) at high temperatures obtained by recording Fourier transform infrared emission spectra. Calibrated line lists are presented for the temperatures 300-1400{deg}C at twelve 100{deg}C intervals spanning the 960-5000/cm (2.0-10.4{mu}m) region of the infrared. This range encompasses the dyad, pentad, and octad regions, i.e., all fundamental vibrational modes along with a number of combination, overtone and hot bands. Using our CH_4_ spectra, we have estimated empirical lower state energies (E_low_ in cm^-1^) and our values have been incorporated into the line lists along with line positions ({nu} in cm^-1^) and calibrated line intensities (S' in cm/molecule). We expect our hot CH_4_ line lists to find direct application in the modeling of planetary atmospheres and brown dwarfs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/425/355
- Title:
- Hot stars in LMC UKST H{alpha} survey
- Short Name:
- J/MNRAS/425/355
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new, accurate positions, spectral classifications, radial and rotational velocities, H{alpha} fluxes, equivalent widths and B, V, I, R magnitudes for 579 hot emission-line stars (classes B0-F9) in the Large Magellanic Cloud (LMC) which include 469 new discoveries. Candidate emission-line stars were discovered using a deep, high-resolution H{alpha} map of the central 25 degree^2^ of the LMC obtained by median stacking a dozen 2h H{alpha} exposures taken with the UK Schmidt Telescope (UKST). Spectroscopic follow-up observations on the Anglo-Australian Telescope, the UKST, the Very Large Telescope, the South African Astronomical Observatory 1.9m and the 2.3-m telescope at Siding Spring Observatory have established the identity of these faint sources down to magnitude R_equiv_~23 for H{alpha} (4.5x10^-17^ergs/cm^2^/s/{AA}).
- ID:
- ivo://CDS.VizieR/J/ApJ/818/202
- Title:
- Hot subdwarf stars in LAMOST DR1
- Short Name:
- J/ApJ/818/202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 166 spectroscopically identified hot subdwarf stars from LAMOST DR1, 44 of which show the characteristics of cool companions in their optical spectra. Atmospheric parameters of 122 subdwarf stars with non-composite spectra were measured by fitting the profiles of hydrogen (H) and helium (He) lines with synthetic spectra from non-LTE model atmospheres. A unique property of our sample is that it covers a large range in apparent magnitude and galactic latitude, therefore it contains a mix of stars from different populations and galactic environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/63
- Title:
- How to constrain your M dwarf. II. Nearby binaries
- Short Name:
- J/ApJ/871/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass-luminosity relation for late-type stars has long been a critical tool for estimating stellar masses. However, there is growing need for both a higher-precision relation and a better understanding of systematic effects (e.g., metallicity). Here we present an empirical relationship between M_Ks_ and M_*_ spanning 0.075M_{sun}_<M_*_<0.70M_{sun}_. The relation is derived from 62 nearby binaries, whose orbits we determine using a combination of near infra-red (Keck/NIRC2) imaging, archival adaptive optics data, and literature astrometry. From their orbital parameters, we determine the total mass of each system, with a precision better than 1% in the best cases. We use these total masses, in combination with resolved Ks magnitudes and system parallaxes, to calibrate the M_Ks_-M_*_ relation. The resulting posteriors can be used to determine masses of single stars with a precision of 2%-3%, which we confirm by testing the relation on stars with individual dynamical masses from the literature. The precision is limited by scatter around the best-fit relation beyond measured M_*_ uncertainties, perhaps driven by intrinsic variation in the M_Ks_-M_*_ relation or underestimated uncertainties in the input parallaxes. We find that the effect of [Fe/H] on the M_Ks_-M_*_ relation is likely negligible for metallicities in the solar neighborhood (0.0%{+/-}2.2% change in mass per dex change in [Fe/H]). This weak effect is consistent with predictions from the Dartmouth Stellar Evolution Database, but inconsistent with those from modules for experiments in stellar astrophysics (MESA) Isochrones and Stellar Tracks (MIST) (at 5{sigma}). A sample of binaries with a wider range of abundances will be required to discern the importance of metallicity in extreme populations (e.g., in the Galactic halo or thick disk).
- ID:
- ivo://CDS.VizieR/J/AJ/160/259
- Title:
- HPF RVs and TESS photometry of TOI-1266
- Short Name:
- J/AJ/160/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the validation of two planets orbiting the nearby (36pc) M2 dwarf TOI-1266 observed by the TESS mission. This system is one of a few M dwarf multiplanet systems with close-in planets where the inner planet is substantially larger than the outer planet. The inner planet is sub-Neptune-sized (R=2.46{+/-}0.08R{Earth}) with an orbital period of 10.9days, while the outer planet has a radius of 1.67_-0.11_^+0.09^R{Earth} and resides in the exoplanet radius valley-the transition region between rocky and gaseous planets. With an orbital period of 18.8days, the outer planet receives an insolation flux of 2.4 times that of Earth, similar to the insolation of Venus. Using precision near-infrared radial velocities with the Habitable-zone Planet Finder Spectrograph, we place upper mass limits of 15.9 and 6.4M{Earth} at 95% confidence for the inner and outer planet, respectively. A more precise mass constraint of both planets, achievable with current radial velocity instruments given the host star brightness (V=12.9, J=9.7), will yield further insights into the dominant processes sculpting the exoplanet radius valley.
