J/A+A/Accepted for publication (Vioque+, 2020) Reference number: AA/2020/37731 ======================================================================================================== Catalogue of new Herbig Ae/Be and classical Be stars. A machine learning approach to Gaia DR2 Vioque M., Oudmaijer R.D., Schreiner M., Mendigutia I., Baines D., Mowlavi N., Perez-Martinez R. ======================================================================================================== Keywords: Catalogs - Hertzsprung-Russell and C-M diagrams - Stars: emission-line, Be - Stars: formation - Stars: pre-main sequence - Stars: variables: T Tauri, Herbig Ae/Be Abstract: Context. The intermediate-mass pre-main sequence (PMS) Herbig Ae/Be stars are key to understanding the differences in formation mechanisms between low- and high-mass stars. The study of the general properties of these objects is hampered by the lack of a well-defined, homogeneous sample, and because few and mostly serendipitously discovered sources are known. Aims. Our goal is to identify new Herbig Ae/Be candidates to create a homogeneous and well defined catalogue of these objects. Methods. We have applied machine learning techniques to 4,150,983 sources with data from Gaia DR2, 2MASS, WISE, and IPHAS or VPHAS+. Several observables were chosen to identify new Herbig Ae/Be candidates based on our current knowledge of this class, which is characterised by infrared excesses, photometric variabilities, and Halpha emission lines. Classical techniques are not efficient for identifying new Herbig Ae/Be stars mainly because of their similarity with classical Be stars (CBe), with which they share many characteristics. By focusing on disentangling these two types of objects, our algorithm has also identified new classical Be stars. Results. We have obtained a large catalogue of 8470 new pre-main sequence candidates and another catalogue of 693 new classical Be candidates with a completeness of 78.8+/-1.4% and 85.5+/-1.2%, respectively. Of the catalogue of pre-main sequence candidates, at least 1361 sources are potentially new Herbig Ae/Be candidates according to their position in the Hertzsprung-Russell diagram. In this study we present the methodology used, evaluate the quality of the catalogues, and perform an analysis of their flaws and biases. For this assessment, we make use of observables that have not been accounted for by the algorithm and hence are selection-independent, such as coordinates and parallax based distances. The catalogue of new Herbig Ae/Be stars that we present here increases the number of known objects of the class by an order of magnitude. Description: File Summary: ----------------------------------------------------------------------------------------------------------------------------------------------------------- FileName #Rows #Columns Explanations ----------------------------------------------------------------------------------------------------------------------------------------------------------- ReadMe PMS_candidates 8470 74 Table D.1 - pre-main sequence candidates - The 'HAeBe' column indicates the Herbig Ae/Be candidates. CBe_candidates 693 72 Table D.2 - classical Be candidates Either_PMS_or_CBe_candidates 1309 72 Sources that have a probability p(PMS) + p(CBe) > 50% but p(PMS) < 50%, and p(CBe) < 50%. Discussed in section 5.3 of the paper. Sample_of_Study_with _probabilities 4150983 70 All sources considered in this study with assigned probabilities of belonging to each of the three categories (PMS, CBe, and other). Discussed in section 4 of the paper. Catalogue warning flags: -HAeBe: Herbig Ae/Be candidate. Selected as those PMS candidates with M_G<6, re-normalised unit weight error (RUWE)<1.4 and Parallax/Parallax_error>=10. -Flag G_UMAP: Possible evolved star contaminant. Identified through UMAP visualisation. Discussed in Appx. C. -Flag ID AllW: Source with an AllWISE name repeated in the Sample_of_Study_with _probabilities.txt table. Discussed in Sect. 5.2, point 3. -Flag ID IPH/VPH: Source with an IPHAS or VPHAS+ name repeated in the Sample_of_Study_with _probabilities.txt table. Discussed in Sect. 5.2, point 3. -Flag PN: Possible Planetary Nebula or 'unclassified B[e]' contaminant. Defined as those candidates with r-Halpha>=1.3. Discussed in Sect. 5.2, point 5. -Flag Var: Photometrically variable PMS candidate. Defined as those PMS candidates with G_var>=10. Discussed in Sect. 4.4. -Flag W3W4: Source which extended source flag of AllWISE catalogue is different of 0. Discussed in Sect. 5.2, point 2. -Flag X-mtch: Likely false candidate because of incorrect cross-match with IPHAS or VPHAS+. Discussed in Sect. 4. We refer to the paper for more details. All tables have the same columns with the following exceptions: - CBe_candidates and Either_PMS_or_CBe_candidates do not have the 'HAeBe' and 'Flag Var' columns. - Sample_of_Study_with _probabilities does not have the 'HAeBe', 'Flag G_UMAP', 'Flag PN', and 'Flag Var' columns. Column description. -------------------------------------------------------------------------------------- Label Explanations Units -------------------------------------------------------------------------------------- Gaia source id Gaia DR2 source identifier RA Right ascension from Gaia DR2 h:m:s DEC Declination from Gaia DR2 deg:m:s Gaia ra Right ascension from Gaia DR2 deg Gaia dec Declination from Gaia DR2 deg l Galactic longitude from Gaia DR2 [180,-180] deg b Galactic latitude from Gaia DR2 deg Probability PMS Probability of belonging to the pre-main sequence class e_Probability PMS Error of the Probability PMS Probability CBe Probability of belonging to the classical Be class e_Probability CBe Error of the Probability CBe Probability Other Probability of belonging to the 'other objects' class e_Probability Other Error of the Probability Other V_htg Heterogeneous variability (Equation 2) G_var G band variability proxy (Equation 1) G_BP Gaia DR2 blue band (0.50 microns) mag G Gaia DR2 G (white) band (0.59 microns) mag G_RP Gaia DR2 red band (0.77 microns) mag IPHAS/VPHAS name IPHAS or VPHAS+ catalogue name r IPHAS or VPHAS+ r band (0.62 microns) mag e_r Error of IPHAS or VPHAS+ r band mag i IPHAS or VPHAS+ i band (0.77 microns) mag e_i Error of IPHAS or VPHAS+ i band mag Halpha IPHAS or VPHAS+ Halpha band mag (0.66 microns) e_Halpha Error of IPHAS or VPHAS+ Halpha band mag a10point 'a10point' quality flag from IPHAS or 'clean' quality flag from VPHAS+ angDist_IPHAS_VPHAS Angular distance from the IPHAS or as VPHAS+ source to the Gaia source AllWISE name AllWISE catalogue name Jmag 2MASS J band from AllWISE (1.24 microns) mag e_Jmag Error of 2MASS J band from AllWISE mag Hmag 2MASS H band from AllWISE (1.66 microns) mag e_Hmag Error of 2MASS H band from AllWISE mag Kmag 2MASS Ks band from AllWISE (2.16 microns) mag e_Kmag Error of 2MASS Ks band from AllWISE mag W1mag WISE W1 band from AllWISE (3.4 microns) mag e_W1mag Error of WISE W1 band from AllWISE mag W2mag WISE W2 band from AllWISE (4.6 microns) mag e_W2mag Error of WISE W2 band from AllWISE mag W3mag WISE W3 band from AllWISE (12 microns) mag e_W3mag Error of WISE W3 band from AllWISE mag W4mag WISE W4 band from AllWISE (22 microns) mag e_W4mag Error of WISE W4 band from AllWISE mag ccf AllWISE contamination and confusion flag ex AllWISE extended source flag var AllWISE variability flag qph AllWISE photometric quality flag angDist_AllWISE Angular distance from the AllWISE as source to the Gaia source RUWE Re-normalised unit weight error from Gaia DR2 Parallax Parallax from Gaia DR2. mas Parallax_error Parallax uncertainty from Gaia DR2. mas Distance Distance from parallax pc (see below for reference) E_Distance Upper error on the Distance pc e_Distance Lower error on the Distance pc A_G_intst Interstellar extinction in the G band mag (see below for reference) M_G Absolute G magnitude corrected from mag interstellar extinction using A_G_intst. G_BP_G_RP G_BP - G_RP colour corrected from mag interstellar extinction using A_G_intst. HAeBe 'Yes' if Herbig Ae/Be candidate, defined as those PMS candidates with M_G<6, RUWE<1.4, and Parallax/Parallax_error>=10, nothing otherwise Flag G_UMAP 'G_UMAP' if possible evolve star contaminant, nothing otherwise Flag ID AllW 'ID AllW' if this source have the same AllWISE name than other source in the Sample_of_Study_with _probabilities.txt table, nothing otherwise Flag ID IPH/VPH 'ID IPH/VPH' if this source have the same IPHAS or VPHAS+ name than other source in the Sample_of_Study_with _probabilities.txt table, nothing otherwise Flag PN 'PN' if possible Planetary Nebula or 'unclassified B[e]' contaminant. Defined as those with r-Halpha>=1.3, nothing otherwise Flag Var 'Var' if photometrically variable PMS candidate. Defined as those with G_var>=10, nothing otherwise Flag W3W4 'W3W4' if extended source flag of AllWISE catalogue is different of 0, nothing otherwise Flag X-mtch 'X-mtch' if likely false candidate because of incorrect cross-match with IPHAS or VPHAS+, nothing otherwise. pmra Proper motion in right ascension from Gaia DR2 mas/year pmra_error Error of pmra from Gaia DR2 mas/year pmdec Proper motion in declination from Gaia DR2 mas/year pmdec_error Error of pmdec from Gaia DR2 mas/year phot_g_mean_flux_error Error of G band in flux from Gaia DR2 e-/s phot_bp_mean_flux_error Error of G_BP band in flux from Gaia DR2 e-/s phot_rp_mean_flux_error Error of G_RP band in flux from Gaia DR2 e-/s phot_bp_rp_excess_factor Gaia DR2 colour excess factor quality flag radial_velocity Spectroscopic radial velocity from Gaia DR2 km/s radial_velocity_error Error of radial_velocity from Gaia DR2 km/s ---------------------------------------------------------------------------------------------------------------------------------------------------------------- Note: A_G_intst, M_G, and G_BP_G_RP values are only presented for sources with RUWE<1.4 and Parallax/Parallax_error>=5. Note: By construction the indicated Herbig Ae/Be candidates have RUWE<1.4 and Parallax/Parallax_error>=10. These constraints can be relaxed to obtain more Herbig Ae/Be candidates. Note: 57 out of 693 classical Be candidates have a 'X-mtch' flag and hence they are likely false candidates because of an incorrect cross-match with IPHAS or VPHAS+. This especially affects the ones with higher 'Probability CBe' values as derived from the artificial neural network. ---------------------------------------------------------------------------------------------------------------------------------------------------------------- References: Distances were taken from Bailer-Jones, C. A. L., Rybizki, J., Fouesneau, M., Mantelet, G., & Andrae, R. 2018, AJ, 156, 58 Interstellar extinction was derived using the dust map of Lallement, R., Babusiaux, C., Vergely, J. L., et al. 2019, A&A, 625, A135 We refer to the paper for the complete list of references. ================================================================================ Acknowledgements: Miguel Vioque, pymvdl(at)leeds.ac.uk ================================================================================ (End) Miguel Vioque [University of Leeds, UK] 27-Apr-2020